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Magnetron Sputtering

Magnetron Sputtering

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Magnetron sputtering is a physical vapor deposition technique used to deposit thin films on substrates. It utilizes a magnetron to generate a plasma, which ejects atoms from a target material, allowing them to condense onto the substrate surface, forming a uniform coating.
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Magnetron sputtering is a physical vapor deposition technique used to deposit thin films on substrates. It utilizes a magnetron to generate a plasma, which ejects atoms from a target material, allowing them to condense onto the substrate surface, forming a uniform coating.
Raman spectroscopy on amorphous carbon films
by Sven Ulrich

1996, Journal of Applied Physics

The origin and interpretation of the Raman features of amorphous ͑hydrogenated͒ carbon films deposited at room temperature in the region of 1000-1700 cm Ϫ1 is discussed in this paper. Possible interpretations of the linewidths, positions... more
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TCO and light trapping in silicon thin film solar cells
by Milan Vanecek

2004, Solar Energy

For thin film silicon solar cells and modules incorporating amorphous (a-Si:H) or microcrystalline (lc-Si:H) silicon as absorber materials, light trapping, i.e. increasing the path length of incoming light, plays a decisive role for... more
Fig. 3. SEM images of two typical surfaces of CVD-grown SnO,:F (Asahi Glass Co., type U) and rf magnetron-sputtered and texture-etched ZnO.
Fig. 10. Simulated quantum efficiency of a micromorph tan- dem cell with an intermediate reflector using optimized layers as described in the text. Assuming realistic values for fill factor (73%) and open circuit voltage (1.43 V) of the tandem structure yields an efficiency of 15%. The thickness of a-Si top and j1c-Si bottom cell is 190 nm and 1.8 um, respectively. Main losses (in mA/cm?’) are listed in the upper right corner of the figure (numbers in brackets). R: total reflection; ZnO: front TCO; p*: front doped layer; BR: back reflector.
Fig. 1. Schematic sketch of the cross section of a silicon thin film p-i—n solar cell (a-Si:H and/or pic-Si:H) with rough inter- faces. Thicknesses of the individual layers are typical values. The concept of light trapping is illustrated by the arrows rep- resenting incoming and scattered sun light. Different light paths and scattering events are sketched.
Internal reflectance for the a-Si/BR structure at 600 nm (Rgo9) and the pc-Si/BR structure at 800 nm (Rgo9, BR = back reflector) cal- culated by using Fresnel’s equations Last two columns: Experimentally determined current losses Aj, in a-Si:H and jc-Si:H cells, respectively, with different types of back reflectors as compared to the ZnO/Ag back reflector.
Fig. 2. (a) Absorption coefficient of amorphous (circles), microcrystalline (triangles) and crystalline (dashed line) silicon. (b) Light trapping spectral region for a typical amorphous (i-layer thickness 300 nm) and microcrystalline (2000 nm) sili- con solar cell, with the maximum current value achievable in this region.
Fig. 4. Quantum efficiency QE and (1 — R) curves of pc-Si pin solar cells (i-layer thickness 1.2 um, ZnO/Ag back reflector) on thin texture-etched (dashed lines) and smooth ZnO (solid lines). Resulting short-circuit densities are 20.8 and 15.3 mA/cm? respectively. R = total cell reflectance. Optical transparency and electrical conductivity of front TCO are usually closely related. Both thinner TCO layers and lower free carrier concentration n reduce absorption in the visible (VIS)/IR region, but at the same time the sheet resistance R,, often increases. This is illustrated in Fig. 5 where the absorption coefficients of doped ZnO:Al (n = 4-6x 10° cm-3) and undoped ZnO
Fig. 6. Quantum efficiency QE and (1 — R) curves of c-Si pin solar cells (i-layer thickness 1.2 um, ZnO/Ag back reflector) for front ZnO with different thickness: 330 nm (dashed lines), 870 nm (dotted) and 1370 nm (solid). R = total cell reflectance. (n ~ 5x10'8 cm~) films are plotted. To study the effect of thickness experimentally, c-Si cells were deposited on ZnO of three different initial thicknesses yielding films with 330, 870 and 1370 nm final thickness and similar surface roughness after 30 s of etching in HCl (Fig. 6). The thick substrate has a lower Rsq, which in- creases FF due to reduced series resistance losses (Table 1). However, lower optical transparency leads to lower
Fig. 5. Absorption coefficient of highly conductive Al-doped front contact ZnO, rf-sputtered from a ZnO:Al,O; target (p = 3-5x 10-4 Qem, n= 46x10 cm-3, 4 = 30-40 cm7/Vs, solid line) and of less conductive undoped ZnO as used for the interlayer (p = 0.2 Qcem, n = 3-7x 108 cm-3, w = 5-10 cm’/Vs, dashed line). In the UV region doping shifts the absorption edge to a higher energy due to Burstein—Moss shift, in the red/ IR region the absorption is increased in the doped sample by free carrier absorption. The optical data shown in Fig. 5 were used in the calculations.
Fig. 7. Quantum efficiency QE and (1 — R) curves of a-Si (a) and jc-Si (b) pin solar cells (i-layer thickness 350 nm and 1.2 um, respectively) for different back reflectors: ZnO/Ag (solid lines), Ag (open circles), ZnO/AI (dotted line) and Al (dashed line). R = total cell reflectance.
Fig. 8. Absorbance A of a smooth (solid line) and rough (da- shed line) ZnO(30 nm)/Ag/ZnO back reflector measured by photothermal deflection spectroscopy (PDS) as a function of wavelength (lower scale) or light energy (upper scale). The 30 nm thick ZnO layer is only used to protect the underlying Ag from oxidation and samples were measured from the ZnO(30 nm) side. Error bars for the PDS measurement are also in- cluded.
Fig. 9. Experimental and model data for the external quantum efficiency QE and total reflectance R of an amorphous/micro- crystalline silicon p—i-n tandem solar cell with internal reflector. QE of the top a-Si:H and bottom j1c-Si:H cell was measured separately using red and blue bias light illumination, respec- tively. Optical absorption losses A in each layer were computed with the help of the model.
Short circuit current density j,, and fill factor FF of c-Si pin solar cells (i-layer thickness 1.2 um, ZnO/Ag back reflector) for front ZnO with different thickness (values after 30 s of etching) QE and j,,. Comparing the thin and the thick substrate, optical losses are mostly in the red/IR region (A > 600 nm) due to free carrier absorption in the front ZnO (Fig. 5). In this wavelength region the current density loss A jg as compared to the thin ZnO is ~3 mA/cm’. This is enhanced by multiple passes of scattered light within the solar cell (compare cells with and without light trapping in Fig. 4). Smaller losses (A je = 1 mA/cm?) are observed in the short wavelength region (A < 600 nm). This experiment demonstrates the conflicting requirements of good electrical and optical TCO properties and the necessity of careful optimization with respect to each other.
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Ionized physical vapor deposition (IPVD): A review of technology and applications
by Arutiun Ehiasarian

2006, Thin Solid Films

In plasma-based deposition processing, the importance of low-energy ion bombardment during thin film growth can hardly be exaggerated. Ion bombardment is an important physical tool available to materials scientists in the design of new... more
Therefore it is unlikely that this is the sole reason for the sudden increase in impedance. and the Ar pressure is 3 mTorr (from Ehiasarian et al. [61]]).
3.3.4. Deposition rate 35% of the rates in conventional dc magnetron sputtering discharges at the same average power
Figure 18. The energy distribution for Ar’ and Ti’ ions in a conventional dcMS discharge (from Bohlmark et al. [88]). [he comparison suggests an even higher ion to neutral ratio for the HIPIMS discharge.
Figure 19. Ion energy distributions recorded from a HIPIMS discharge (3 mTorr and 9 J pulse energy) at various time periods during the discharge. (a), (b), and (c) represent the distributions at 0<t< 20 us, 40<t< 60 us, and 140 < t < 160 us respectively (from Bohlmark et al. [88]).
Figure 25. A schematic diagram of a cathode arc source with a 90°-duct filter droplets are emitted most intensely at an angle of 15° from the cathode surface. Thus, the ion path
internal stress at the interface surface may increase tremendously, thus pushing the material closer Bombardment with metal ions is known to provide cleaner interfaces [185]. The reason may
Table II. The reaction rate coefficients for electron impact ionization of a few metal atoms and Ar (after Hopwood [2]]).
resonance, the gyrating electrons rotate in phase with the polarized wave. d the electron cyclotron frequency ®ce = eB/m, within the discharge. Due to this cyclotron from a Ti target in an Ar/N> mixture: (a) Ar’ and (b) Ny" ions (from Liet al. [52]). collisionless heating mechanism. The introduction of a magnetic field leads to a resonance between
with increased microwave power and increased discharge gas pressure. the applied microwave power in an ECR-MS with a cylindrical target. The deposition rate increase
between the target and the substrate. ECR condition in both ECR chambers. Thus, a highly ionized ECR plasma is created in the regior surrents in these coils flow in opposite direction generating a magnetic field of 875 G to satisfy the
discharge is placed parallel to the cathode in the region between the cathode and the anode. sathode target using de or rf power and transit the dense plasma, created by the rf coil, where they plied power [45-47]. In a magnetron sputtering discharge the metal atoms are sputtered from th:
epending on the design the pulses can be generated at the frequency of the mains supply [32], e.s The exact pulse shape is not only determined by the power supply but also by the load, the
of the electron density as modeled by Hopwood [2]
and 40 mTorr is shown in Fig. 4. discharge at different pressures (from Wang et al. [49]). s increased [3, 49]. The ionized flux fraction for Cu versus applied rf power for Ar discharge at 2(
storage capacitor C, is charged through a thyristor switch (T2) from a charging circuit and ¢
Figure 12. The electron density as a function of time following
Figure 15. Temporal evolution of optical emission from a HIPIMS discharge plotted together with
dependent on chamber dimensions and sputtering gas composition. ions originating from the sputtering target. The time delay between the two pulses is consequently location, and (d) the pulse power (from Alami et al. [87]).
1 strong signal from metal ions. After the pulse is shut off, the distributions become narrow anc 3.3.3. Degree of ionization broad distribution extending from 0 to 100 eV during the active phase of the discharge and contain
was performed in Ar using a Ti target (from Bohlmark et al. [64]).
metal can be focused (see section 5.2). In this way, some of the drawback of a lower deposition rate targets: relative deposition rate vs. self-sputtering yield Ss divided with its Ar-sputter yield S\4, show that by applying a magnetic coil between the magnetron target and the substrate, the ionized hat the deposition rate can be optimized by varying the magnetic confinement. Recent results [12
and a magnetic cusp near the target opening acts as an aperture for plasma extraction toward the
films 1 cm down in a trench using conventional dcMS and HIPIMS, respectively. films were grown at room temperature with a substrate bias of -50 V (from Alami et al. [7]).
ionization, whereas for high electron density (n, >> 10°’ m™~) the metal ions are generated by
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Band-Gap Tailoring of Zno by Means of Heavy Al Doping
by B. Sernelius

1988, Physical Review B

Films of ZnO:Al were produced by weakly reactive dual-target magnetron sputtering. Optical band gaps, evaluated from spectrophotometric data, were widened in proportion to the Al doping. The widening could be quantitatively reconciled... more
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Calcium phosphate coatings for bio-implant applications: Materials, performance factors, and methodologies
by Narendra Dahotre

2009, Materials Science and Engineering: R: Reports

FDA requirements for HA coating. Table 6
Fig. 85. Schematic of a PLD setup.
Types of stainless steels in use for medical applications. Table 1
Fig. 45. Figure illustrating (a) a nanohydroxyapatite and poly (t-lactic acid) porous composite scaffold fabricated using a phase separation technique and (b) a porous calcium carbonate coating on Ti-6AI-4V obtained by electrophoresis deposition. (Reprinted from [171] and [163] with permission from Elsevier.)
Essential parameters in plasma spraying. (Reprinted from [199] with permission from Elsevier.). Table 7
Fig. 4. A dental implant. (Reprinted from [22] with permission from source: http:// www.lymebaydentistry.co.uk/Ibd/jsp/dental_implants.jsp.)
Fig. 6. As cast Co-Cr-Mo alloys revealing (a) carbide separation in interdendrites and (b) abnormally long bands of interdendritic carbides near grain boundary. (Reprinted from [35] with permissions from Springer.)
Fig. 113. SEM cross-sectional views of (A) MAO-Ti and HA sol-gel coating on MAO-Ti with sol concentration of (B) 1.5M and (C) 4M. (Reprinted from [274] with permissions from Wiley Inter Science.)
Fig. 66. Graphs illustrating the surface temperatures of HA powder particles. (Reprinted from [205] with permission from Elsevier.)
Fig. 82. The microstructure of the HA deposits at various sintering temperatures: (a) 1000 °C, (b) 1150 °C and (c) 1300 °C. (Reprinted from [217] with permissions from Springer.)
Fig. 62. SEM micrograph of the deposited HA film on Ti-6AI-4V substrate. (Reprinted from [193] with permission from Elsevier.)
Fig. 22. Wear areas of implanted polyethylene cups paired with metal and with ceramic balls respectively and of CoCrMoC metal cups paired with metal balls. (Reprinted from [107] with permissions from Institute of Mechanical Engineers.)
Fig. 24. SEM micrographs of femoral heads worn surfaces, (a) after 100 thousand cycles showing abrasive wear grooves, (b) after 300 thousand cycles showing breakdowns of adhered lubricant film, (c) after 500 thousand cycles showing surface micro pits and (d) surface delaminations. (Reprinted from [112] with permission from Elsevier.)
Fig. 69. Figure illustrating the (a) SEM image and (b) TEM bright field image of the cross-sectioned as sprayed composite coating. (Reprinted from [201] with permission from Elsevier.)
Fig. 9. Microstructure of Ti-6Al-4V (a) under as received and annealed condition and (b) after cold working by equal channel angular pressing (ECA) technique. (Reprint from [55] and [56] with permission from Elsevier.) 1.2.1.3. Titanium and titanium alloys. Titanium as a pure metal was implanted for the first time into laboratory animals in 1940 by Bothe, Beaton, and Davenport [25]. They concluded titanium as a well-tolerated material as compared to stainless steel and Co-Cr- based alloys under in vivo conditions. The two most commercially used specifications for implants are Pure Ti (ASTM F67) and Ti- 6AI-4V (ASTM F136) [15]. These alloys have driven a lot of interest for load bearing implants due to its superior mechanical properties (tensile strength and fatigue strength), chemical stability (corro- sion resistance), and biocompatibility under in vivo conditions
Fig. 76. Scanning electron micrograph of an intraosseous hydroxyapatite-coated Ti- 6AI-7Nb alloy implant after a healing period of 16 weeks in the mandibular bone of a mongrel dog. The bone is originated in the compact and grows in the implant direction (arrow). Original magnification: 17x. (Reprinted from [211] with permissions from Wiley Inter Science.) Fig. 75. Scanning electron micrograph of osteoblasts cultured on hydroxyapatite- coated Ti-6AI-7Nb alloy after 15 days in vitro. The surface of the cell layer is complete, and osteoblasts (arrowhead) and collagen fibers can be identified: 1700x. (Reprinted from [211] with permissions from Wiley Inter Science.)
Fig. 1. Orthopedic Implant devices used for load bearing applications: (a) hip implant (reprinted from [16] with permission from source: www.zimmer.com), (b) knee implant (reprinted from [17] with permission from source: http://thehipkneesurgeon.com/jointKnee.php), (c) shoulder implant (reprinted from [18] with permission from source: http://www.djosurgical.com/products/shoulder/rsp/index.htm) and (d) elbow implant (reprinted from [16] with permission from source: www.zimmer.com).
Fig. 34. Schematic illustration of a contact angle formed by a liquid drop at the solid/ liquid interface and the liquid/vapor interface. If the contact angle is high (>90°) (Fig. 35(a)) then the surface is considered as a nonwetting or a hydrophobic surface. If the contact angle is small (Fig. 35(b)), then the surface is considered as a wetting or a hydrophilic surface. The energy of the surface (ysy) which is directly related to the wettability is also a very useful parameter that can strongly affect the biological interaction. But Ysy cannot be directly obtained from the above equation as we have two unknowns yy, and ys sy can only be calculated by solving simultaneous equations with data collected from liquids of different surface tension.
Fig. 123. X-ray diffraction patterns comparing the phases evolved before, and after immersion in SBF for 48 h.
Fig. 18. Scanning electron micrographs of porous polyetheretherketone- hydroxyapatite (PEEK-HA) composite after implantation for 6 weeks (labeled A) and 16 weeks (labeled B). (Reprinted from [96] with permission from Elsevier.).
Fig. 99. XRD patterns of (a) MAOO, (b) MAO4, (c) MAO8, (d) MAO12 and (e) MAO16 coatings. (Reprinted from [255] with permission from Elsevier.)
Fig. 80. SEM micrograph of (a) green hydroxyapatite deposits on carbon fibers and (b) cross-section of hollow fibers sintered at 1200 °C for 1 h. (Reprinted from [216] with permission from Elsevier.)
Fig. 26. Optical micrographs illustrating the formation of pitting corrosion in medical grade AISI 316L stainless steel following immersion in (a) NaCl, (b) NaCl + albumin, (c) phosphate buffered solution (PBS) and (d) PBS + albumin. (Reprinted from [122] with permission from Elsevier.)
Fig. 86. Variation in film thickness profiles at varying radial angles. (Reprinted from [233] with permissions from American Physical Society (APS).) Socol et al. [237] synthesized nanocrystalline octacalcium phosphate OCP thin films on Ti substrate by PLD technique using a UV KrF Excimer laser source operating at a wavelength of 248 nm. Both deposition and subsequent annealing of the deposited films were carried out in an intense flux of hot water vapors maintained at a constant temperature within the range 2-200 °C. The best results were obtained for a substrate temperature of 150 °C during both deposition and post-deposition treatment. SEM micrographs [237] (Fig. 92) of films deposited by this technique on a Ti substrate heated at 150 °C and post-deposition treatment at 150 °C reveal a droplet-like feature at the surface of the coating (Fig. 92(a)) anda morphologically homogeneous and brush-like layer at the inner structure (Fig. 92(b)). The biocompatibility of the deposited films was carried out by culture of human fetal osteoblast-like cell line hFOB 1.19. Fig. 93 compares the SEM micrographs of hFOB 1.19 cells on control Ti (a) and OCP coating (c). The coatings exhibited strong attachment and proliferation of cells, supporting its good biocompatibility and absence of toxicity. At higher magnification
Fig. 17. Fracture surface of a polyetheretherketone (PEEK) composite with 20 vol% HA, suggesting good dispersion and distribution of HA in the PEEK matrix. It can also be seen that the main fracture mechanism is through-debending of HA from PEEK polymer matrix. (Reprinted from [96] with permission from Elsevier.)
Fig. 122. SEM micrographs revealing the formation of globular apatite like layer following immersion in SBF for 48 h.
Fig. 101. (a) Surface morphologies of the MAO samples formed in the acetate monohydrate and B-glycerophosphate disodium salt pentahydrate containing solution at 500 ind (b) its morphology following immersion in SBF. (Reprinted from [258] with permission from Elsevier.)
Fig. 56. Experimental set up for ion beam assisted deposition using a single ion source. performance of Ca-P coatings in bio-environment produced using these techniques are reviewed in the following sections.
Fig. 94. Schematic representation of micro-arc oxidation setup. (Reprinted from [249] with permission from Elsevier.)
Fig. 61. Microscratch adhesion result for functionally graded hydroxyapatite composite film on silicon. (a) Film delamination occurs at 0.30N; (b) continuous film delamination occurs between 0.30 and 1N; (c) complete film penetration and plastic deformation of substrate occurs at 1N, showing very good integrity of the film. (Reprinted from [192] with permission from Elsevier.)
Fig. 19. A load-elongation curve.
Fig. 90. SEM images showing the morphology of the thin films of (a) OCP, and (b) Mn-CHA deposited by PLD on Ti substrates. (Reprinted from [236] with permission fron Elsevier.)
(x: HA, A: CaCOs, |: Rutile, V: CaTiO;, mi: a-TCP). Fig. 97. XRD spectra of the MAO coatings formed at different applied voltages (A) 400 V (B) 430 V (C) 450 V (D) 480 V treated for 20 min. (Reprinted from [254] with permission from Elsevier.).
Fig. 71. (a) SEM micrograph of a cross-sectioned sample of plasma-sprayed hydroxyapatite coating on the titanium: (HA) hydroxyapatite, (Ti) titanium and (b) an X-ray diffraction pattern taken from the surface of a plasma sprayed hydroxyapatite coating on titanium. (Reprinted from [208] with permissions from Springer.)
Contents knee (Fig. 1(b)) [17], ankle, shoulder (Fig. 1(c)) [18], and elbow joints (Fig. 1(d)) [16]. They also include the fracture fixation devices such as wires, pins, plates, screws, etc. Metals (Ti-6AI-4V, Co-Cr-Mo, stainless steel), polymers (poly(methyl methacrylate) (PMMA), ultrahigh-molecular-weight polyethylene (UHMWPE), and ceramics (alumina, zirconia, hydroxyapatite) are the three classes of materials that are most commonly used for fabricating orthopedic implants. 1. Introduction
Fig. 13. Scanning electron micrograph of the bioactive glass-coated silicone tubing segment in cross section, magnification 65 x. (Reprinted from [75] with permissions from Nature Publishing Group.)
Fig. 84. Cyclic polarization curves in Ringer’s solution of uncoated and HAP-coated type 316LSS at the optimum coating parameters of 60 V and 3 min after sintering at various temperatures in vacuum. (Reprinted from [218] with permission from Elsevier.) TE ANE RESTS SA ES SON TS TEE Bigi and coauthors [236] synthesized octacalcium phosphate (OCP) and Mn?* doped carbonate hydroxyapatite (Mn-CHA) thin films on Ti substrates by PLD process. The PLD was performed
Fig. 112. SEM morphologies of (A) pure Ti, (B) MAO-Ti, and HA sol-gel coating on MAO-Ti with sol concentration of (C) 1.5 M, (D) 2 M, (E) 3 M, and (F) 4 M. (Reprinted from [274] with permissions from Wiley Inter Science.)
Fig. 119. SEM image of the Ca-P coated sample processed at laser fluence of 1006 J cm~? and after immersion in SBF for 1 day. (Reprinted from [7] with permissions from Institute of Physics Publishing (IOP).).
Fig. 5. SEM micrograph of 316L stainless steel wire surface with two different surface chemistries under both in vivo and in vitro conditions (a) 316L wire surface coated with an amorphous oxide layer (AO), and (b) as received 316L stainless steel wire surface (AS). The inset in the upper left hand side in figure (a) reveals a clean and free of pitting damage after anodic polarization test for the (AO) sample, whereas the inset in upper left hand side figure (b) reveals severe pitting degradation for the (AS) sample. Further the inset at the bottom in figure (a) reveals absence of proteins, fibrins and a clean surface for the coils passivated with amorphous oxide film, and the inset in bottom of figure (b) clumps of platelets, red cells, and fibrin under in vivo conditions. (Reprinted from [26] and [34] with permission from Elsevier.)
Fig. 126. Percentage of implant-bone contact for different surface treatments. (Reprinted from [287] with permission from Elsevier.) It is well established that organic components such as proteins and bone-derived growth factors, can serve not only to strengthen the hard tissue but also stabilize its mineral contents. Therefore Ca-P coatings incorporated with non-collagenous proteins and bone-derived growth factors may be an alternate design for the regulation of bone formation, absorption, and fracture healing.
Fig. 129. Schematic representation of the hierarchical organization of bone at different length scales. (Reprinted from [150] with permissions from American Association for the Advancement of Science (AAAS).)
Fig. 57. Experimental set up for a dual ion beam assisted deposition system.
Fig. 63. Immunofluorescent staining image of vinculin. Immunofluorescent staining image of vinculin on titanium (a, d, g), HA (b, e, h), and TCP/HA (c, f, i) at 3 h(a-c), 12 h(d- f), and 24 h (g-i). The number of vinculin-positive adhesions (arrows) on HA and TCP/HA is more than that on titanium at 3 and 12 h (p < 0.05), but there is no significant difference at 24 h(p > 0.05). The number of stained vinculin on TCP/HA is more than that on HA (p < 0.05) at 3 h, but no difference at 12 and 24h (p > 0.05) (bar = 20 wm). (Reprinted from [196] with permission from Elsevier.)
Fig. 106. CLSM images illustrating actin cystoskeleton and vinculin focal contacts on uncoated Ti substrates, as-deposited and heat-treated Si-HA thin films at culture day 4. FITC phalloidin stains the actin sytoskeleton (green) and Texas red stretavidin stains the vinculin focal contacts (red). (Reprinted from [262] with permission from Elsevier.) (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
Fig. 79. FT-IR spectra for HA coatings heat-treated at (a) room temperature; (b) 1150 °C, 2 h; (c) 1200 °C, 2 h; (d) 1250 °C, 2 h and (e) 1300 °C, 2 h. (Reprinted from [215] with permission from Elsevier.) A knowledge of the film thickness profile can be used tc estimate the kinetic energy of the moving species and thereby the temperature of the expanding plasma plume. This in turn may helf us in predicting the phase transformations that take place for < particular set of laser parameters employed for the depositior process. Also as the high energetic species bombard the surface o: the substrate, it may either improve or deteriorate the overal morphology, stoichiometry, and microstructure of the film Knowledge of the film thickness profile can be used to predict the distance between the target and substrate and thereby the energy of the impinging species.
Fig. 131. Schematic representation of interference patterns due to variation in interference angle and thermal conductivity of material. (Reprinted from [297] with permission from Journal of Minerals, Metals and Materials Society (JOM).)
Fig. 130. Schematic setup of laser interferometer. (Reprinted from [297] with permission from Journal of Minerals, Metals and Materials Society (JOM).) In the recent past, however, the “trial-and-error” approach initially taken by the scientists and engineers to develop
Fig. 73. TEM micrograph showing the interface between amorphous calcium phosphate and the titanium substrate: (HA) crystalline hydroxyapatite, (ACP) amorphous calcium phosphate, (Ti) titanium. (Reprinted from [208] with permissions from Springer.)
Fig. 111. Scanning electron micrographs of a freeze-fractured specimen showing that the calcium phosphate film is well-adapted to the Ti-6AI-4V particles (a and b). Bone is observed in direct contact with the HA film (b-d) with numerous osteocytes (b-d). In the sinter neck regions where calcium phosphate film delamination, bone had formec between the film and the underlying Ti alloy substrate (arrows—c and d). (Reprinted from [273] with permission from Elsevier.)
Fig. 78. SEM micrographs of sintered HA coatings: (a) 1150 °C, 2 h; (b) 1200 °C, 2 h; (c) 1250 °C, 2 hand (d) 1300 °C, 2 h. (Reprinted from [215] with permission from Elsevier.
Fig. 127. Mean ultimate interfacial strength of as-deposited CaP, heat-treated CaP, and Ti implants. The error bar represents one standard error. (Reprinted from [288] with permissions from Wiley Inter Science.).
Fig. 72. (a)TEM micrograph taken from hydroxyapatite coatings show crystalline phases within amorphous phase. (b) A selected area diffraction pattern from the crystalline phase showing a ring pattern consistent with a polycrystalline structure. (c) A selected area diffraction pattern taken showing diffuse rings from the amorphous phase. (HA crystalline hydroxyapatite, (ACP) amorphous calcium phosphate. (Reprinted from [208] with permissions from Springer.)
Fig. 128. Histological evaluation of the (a) control Ti implants and (b) Ca-P-coated implant following 12 weeks after implantation. (Reprinted from [288] with permissions from Wiley Inter Science.) Since most of the coating techniques involve a high-temperature deposition process, no biological active molecules can be added simultaneously during the preparation of Ca-P layers. Hence, several alternate biomimetic routes such as dip coating, self-
Fig. 65. Temperature fields inside powder particle before impact and their transformations into crystal phases after rapid solidification and cooling. Oxyhydroxyapatite (OHA and oxyapatite (OA) are the products of the solid-state decomposition of HA (dehydration). (Reprinted from [205] with permission from Elsevier.) Fig. 64. Figure illustrates a schematic setup of a non-transferred arc plasma system.
Fig. 7. Hot isostaic pressed (HIP) and forged Co-Cr based articulating components for hip implants. (Reprinted from [16] with permission from source: www.zimmer.com.)
Fig. 108. Load-displacement curves obtained by nanoindentation at a imposed load of 0.5 mN. (Reprinted from [263] with permission from Elsevier.) coated and uncoated samples are shown in Fig. 112. The pure Ti substrate depicts the machining grooves (Fig. 112(a)) [274] and after MAO treatment at 270 V, a porous oxide layer was formed through out the Ti surface (Fig. 112(b)) [274]. When the MAO-Ti was coated with an HA sol at a concentration of 1.5 M and heat treated at 550 °C, some of the large pores became slightly smaller Fig. 112(c)) [274]. The porosity continuously decreased with increasing HA concentration (Fig. 112(c-f)) [274]. From the cross-sectional views (Fig. 113(a)) [274] it can be observed, that for the MAO treatment at 270 V, a rough oxide layer (2-3 wm thickness) was formed on Ti. When the MAO-Ti was coated with 1.5 M HA sol, a very thin film of HA (100-200 nm) was formed Fig. 113(b) [274]. With the HA coating at highest sol concentration (4M), a much thicker layer (1-1.5 wm) was formed (Fig. 113(c)) [274]. SEM morphologies of the HOS cells proliferated on the specimens during culture for 3 days are shown in Fig. 114. On pure Ti, the cells spread out in an intimate contact with the specimen surface (Fig. 114(a) [274] where as on MAO-Ti the cells appeared to show slightly less extended cell membranes Fig. 114(b)) [274]. On the other hand on HA coated surfaces the cell spread out more actively (Fig. 114(c and d)) [274]. After 5 days of incubation, the cells proliferated on the specimens were counted and presented graphically as shown in Fig. 115. The number of cells on the HA sol-gel coated MAO-Ti substrate was significantly higher as compared to the MAO-Ti without the sol-gel coating and increased with increasing sol concentration. This, therefore, proved the biocompatibility of the sol-gel deposited HA coatings.
Fig. 53. Schematic illustration of the process of surface modification of stainless steel by silane treatment, Ar plasma treatment and UV-induced surface graft polymerizatio. (Reprinted from [176] with permission from Elsevier.) the substrate, low fracture toughness of the ceramic coating, lack of uniformity of the coating, thickness, biodegradation, fatigue and third body wear of the coating [7,188]. The higher coating thickness (>100 p.m) associated with plasma spraying technique poses a major problem as it can cause failure due to fatigue under tensile loading conditions [188]. Also with increasing thickness the providing enhanced fixation. Further, coatings of these biocera- mics on Ti-based alloys also provide the appropriate surface chemistry for tissue compatibility without altering the bulk mechanical properties of the material. Among the above coating methodologies plasma spray deposition is the most commercially used technique for orthopedics and dental implants, but it suffers from certain draw backs such as poor adherence of the coating to
Fig. 3. An intraocular lens. (Reprinted from [20] with permission from Elsevier.) Fig. 2. A replacement heart valve. (Reprinted from [19] with permission from source [19]: www.ascensionortho.com.)
Fig. 23. Detail of a hip joint simulator station, illustrating the holders of the femoral head and the acetabular cup. (Reprinted from [114] with permission from Elsevier.)
Fig. 67. TEM micrographs of HA crystal: (a) bright field, (b) dark field, (c) [2 201] zone selected area diffraction pattern, and (d) indexing of (c). (Reprinted from [206] witl permission from Elsevier.)
Fig. 68. (a) Lattice images of HA crystal showing (1010) plane and surrounding amorphous calcium phosphate, and (b) microdiffraction pattern taken from amorphous calcium phosphate (ACP). (Reprinted from [206] with permission from Elsevier.)
Fig. 107. A white light confocal microscopic image showing the surface aspect of the film grown on TiN/TiAIFe. (Reprinted from [263] with permission from Elsevier.)
Fig. 59. XRD patterns of fully crystallized samples following heat-treatment at 1200 °C. (Reprinted from [191] with permission from Elsevier.) 2.2. Plasma spray deposition
Fig. 21. Fatigue fracture surface morphology of Ti-GAI-4V. ((a) overall fracture surface; (b) crack initiation site taken from area “I”; (c) crack propagation site taken from area “II”; (d) overload site taken from area “III”). (Reprinted from [102] with permission from Elsevier.) Here k is a dimensionless wear coefficient or constant that depends both on the materials in contact and the presence or absence of lubrication, and hardness H is considered as the yield strength of the material being worn. Higher the mutual solid solubility between two materials in contact, higher is the wear. Hence wear is generally higher for similar materials in contact than for dissimilar materials. In contrast, for biomaterials used inside a The first two methods are basically used to screen various materials under high cyclic loading conditions and select materials suitable for implant applications. The third method is used to determine the fatigue behavior in a physiological environment and
Fig. 12. Scanning electron micrograph revealing the (a) pore structure of a 45S5 Bioglass-derived foam sintered at 1000 C for 1 h, and (b) precipitation of an apatite-like phase on the foam structure following immersion in a simulated bio-fluid for 3 days. (Reprinted from [74] with permissions from Elsevier.)
Fig. 39. Shc expressed by serum-starved primary human bone-derived cells (HBDC) cultured for 2 h on titanium alloy (Ti-6AI-4V), titanium alloy modified with zinc ‘Zn-Ti-6Al-4V), magnesium (Mg-Ti-6AI-4V) or alkoxide-derived hydroxy carbonate apatite (CHAP-Ti-6AI-4V). Equal amounts of total proteins were resolved by 10% Tris-HCl polyacrylamide gel electrophoresis and analysed by immunoblotting with anti Shc. Maximum levels of the three isoforms (66, 52, and 46) of Shc expression were found when HBDC were cultured on CHAP-Ti-6AI-4V. (Reprinted from [143] with permission from Elsevier.)
Fig. 110. Scanning electron micrographs depicting the typical appearance of calcium phosphate-coated implants (a = 300x; b = 500x). Higher magnification micrographs o: the calcium phosphate coating in a sinter neck region are shown in (c) at 2000 and (d) 5000~. In these regions the HA film appeared thicker and showed signs o delamination in some regions. (Reprinted from [273] with permission from Elsevier.)
Fig. 36. Surface contact angle of hexamethyldisiloxane surface with different O2- plasma treatment duration. (Reprinted from [140] with permissions from Wiley Inter Science.)
Fig. 103. SEM micrographs of the MG63 cells after culturing for 3, 5 and 7 days on the MAO and heat-treated MAO coatings. (Reprinted from [259] with permission from Elsevier.)
Ion sources for material modification first started with the ion implantation technique in the semiconductor industry in 1970 [189]. In this case, materials were doped in the near surface region by implantation of highly energetic ion beams. Several years later another branch of ion beam technology evolved, where the ion beam is used to coat the surface of a material with thin films. This is referred to as the ion beam assisted deposition process (IBAD) and is useful for depositing films with variety of film properties with respect to their applications. Some featured applications include thin films for optical and electronic devices and corrosion and wear resistant films. IBAD system consists of two main parts: sources for low energy particles which constitute the film to be deposited and sources for simultaneous irradiation with highly energetic ion source. Low energy species are mostly vapor sources where the vapor is generated either by resistive heating or electron beam Fig. 55. Figure illustrating the immobilization of phosphorycholine polymers on to titanium surface controlled by a vinyldimethylsilane (VDMS) monolayer. (Reprinted from [182] with permission from Elsevier.)
Fig. 41. Schematic illustration of the sequential reactions that take place after the implantation of an biomaterial into a living system.
Fig. 44. Bone formation along the SLA surface from the cortical bone to the apex. (Reprinted from [160] with permissions from Institute of Physics Publishing (IOP).)
Ceramics are inorganic compounds of metallic or nonmetallic materials, with interatomic bonding as ionic or covalent and which are generally formed at elevated temperatures. A class of such materials used for skeletal or hard tissue repair are commonly referred to bioceramics. These bioceramics may be bioinert (alumina, zirconia), bioresorbable (tricalcium phosphate), bioac- tive (hydroxyapatite, bioactive glasses, and glass ceramics), or porous for tissue in growth (hydroxyapatite coating, and bioglass coating on metallic materials) [63-65]. Their success depends on their ability to induce bone regeneration and bone in growth at the tissue-implant interface without the intermediate fibrous tissue layer. The featured clinical applications include their use in orthopedics as (a) bone plates and screws, (b) total and partial hip Fig. 8. Microstructure of a hot isostatic pressed (HIP) Co-Cr—-Mo alloy. (Reprinted from [38] with permission from Elsevier.)
Fig. 60. TEM image showing the cross-section of HA film with graded crystallinity on Si substrate. (Reprinted from [192] with permission from Elsevier. Luo et al. [194] studied the morphological and structural evolution of HA crystals in the coating during post-heat-treatment. In this study, they hypothesized that the crystallization tempera- ture of IBAD Ca-P coating on Ti-6Al-4V decreased from 500 to 400 °C through the introduction of water vapor in an ion beam assisted deposition and _ post-heat-treatment process. This decrease in crystallization temperature is attributed to the fact that the crystallization of amorphous calcium phosphate phase into HA is a hydroxyl-diffusion-controlled process. Further recrystallization phenomena also occurred in the coating during heat treatment at 400 °C for different time periods. The driving force for the process was mainly contributed by the high stress field caused by the difference in density between the amorphous Plasma spray involves the spraying of molten or heat-softened material onto a surface to provide coating. Material in the form of powder is injected into a high-temperature plasma flame, where it is rapidly heated and accelerated at a high velocity towards a substrate for coating. It uses an electric arc to ionize the gas and create high-pressure plasma. The temperature at the core region of plasma exceeds 30,000 K. Plasma arcs are of two types, the transferred and the non-transferred arc. In transferred arc the workpiece acts as the anode and the arc is struck between the cooled cathode and the anode. This is mostly employed for welding. For coating applications the non-transferred arc of a plasma gun is most suitable, as it does not create a predominant thermal effect on the substrate [197,198]. Fig. 64 illustrates a schematic setup of a non-transferred arc plasma system. Typically used plasma gasses are He, Ar, Nz, H2 and mixture of these gasses. Argon is usually chosen as the base gas as it ionizes easily and also provides a stable arc at very low operating voltage [197,198]. The most essential parameters that may affect the coating micro- structure and morphology are tabulated in Table 7 [199]. Some of the key applications that can be addressed by plasma spray technique include (1) in-flight melting, (2) densification and spheroidization of powders, (3) atmospheric and vacuum plasma spraying of protective coatings, (4) plasma deposition of near net shape bodies, (5) dc and rf induction plasma deposition of metal matrix composites, and (6) plasma reactive deposition [200]. Among the different coating methodologies applied to obtain hydroxyapatite coatings on various substrates, plasma spray coating is regarded as the most efficient and economical technique [201-205]. As these coatings enter into a human body, proper
Fig. 54. (a) Molecular structure of a PLA-PEG-biotin and (b) Schematic diagram showing the surface engineering of a PLA-PEG-biotin to produce a cell-adhesive surface. (Reprinted from [181] with permissions from American Chemical Society .) residual stresses within the coatings increases and its energy release may promote cracking at the substrate/coating interface [188]. Hence, to address these issues a variety of thin film-based coating techniques such as pulsed laser physical vapor deposition, magnetron sputtering, ion beam assisted deposition, etc. are being employed to deposit Ca—P coatings on metallic substrates [188]. Nonetheless, this and all other techniques listed above and the
Fig. 16. Figure illustrating the use of UHMWPE as a bearing metal for (a) hip joint (reprinted from [89] and [90] with permission from sources: www.devicelink.com and http://www.genesis-tech.ch/company/ respectively) and (b) knee joint prosthesis (reprinted from [91] and [92] with permission from sources: http://tc.engr.wisc.edu/UER/ uer01/author1/content.html and http://www. jri-ltd.co.uk/total_knee_replacement.asp respectively).
Fig. 37. SEM of L929 attached to surfaces with different wettability in 6 and 24 h in low magnification (original: 500) and high magnification (original: 3000x ). (Reprinte from [140] with permissions from Wiley Inter Science.) XPS is widely used to determine the elemental composition of solid surfaces (except H and He). It is capable of providing elemental depth profiles up to 10 nm into the sample. AES can be used for determining both the chemical composition of a solid surface and mapping the spatial distribution of the surface constituents and obtain a depth profile of these constituents into the bulk of the material. FTIR holds the capability for chemical analysis of solids, liquids and gasses. Its other advantages include multicomponent analysis capability, good sensitivity, excellent specificity, speed and simplicity of calibration. It is based on the fact that every molecule has a vibrational spectrum, which is a unique physical property and is a characteristic of the molecule. SIMS is used to determine the surface and near-surface composi- tion in a wide range of solid materials. It is based on the principle that bombardment of a material with a high-energy (1-30 keV) ion beam results in the ejection or sputtering of atoms from the material. Some of these ejected atoms leave as either positively or negatively charged ions and are referred as secondary ions. Collection of these sputtered secondary ions and their analysis by
Fig. 102. The average roughness of the surfaces of the Ti6Al4V, MAO coatings before and after heat treatment. (Reprinted from [259] with permission from Elsevier.) Silicon-substituted hydroxyapatite (Si-HA) as a biomaterial has been reported to promote early bonding at the bone/implant interface. Therefore, Si-HA can be used as a coating material on implant surfaces for load-bearing applications such as artificial hip implants and knee implants. Thian et al. [262] studied the biocompatibility of magnetron co-sputtered silicon-containing hydroxyapatite (Si-HA) coatings on Ti substrate. The film deposition was carried out in a custom-built sputter deposition chamber maintained at room temperature and evacuated to a base pressure lower than 10~” Torr. High-purity argon gas was used as a back-filled gas to bring the work pressure to 5 x 10°? Torr and a constant flow of Ar was supplied into the chamber during the deposition process. Si and HA targets were held onto two water- cooled magnetrons by means of spring clips and the Ti substrate
Fig. 11. Compositional dependence (in wt%) of bone bonding and soft tissue bonding of bioactive glasses and glass—-ceramics. (Reprinted from [63] with permissions from Blackwell Publishing.)
Fig. 48. SEM images of 3D sharp-tip nanotopography samples of silicon. The well-regulated ‘nanopost’ (a—-c) and ‘nanograte’ (d-f) structures were formed by interference lithography and DRIE uniformly on 2 cm x 2 cm silicon substrate, which was then cut into 1 cm x 1 cm samples for the study. While the nanostructure pitch was all kept constant to be 230 nm and tips were all sharpened to be needle- or blade-like, structure heights were varied from ‘low’ (a and d: 50-100 nm high), ‘mid’ (b and e: 200-300 nm high) to ‘high’ (c and f:500-600 nm high) to investigate he exclusive effect of the nanotopographical three-dimensionality to cell behaviors. (Reprinted from [169] with permission from Elsevier.) response to an implant by immobilizing biomolecules representing such molecular cues on the surface of biomaterials. Adsorption, entrapment, and covalent attachment are the three mechanisms by which biomolecules are immobilized on the surface of a biomaterial. The most frequently used biomolecules for immobi- lization include, RGD peptides, heparin and heparin sulfate binding peptides, and purified protein components such as fibronectin, laminin, and collagen. Purified protein components such as collagens from animal tissues are advantageous because of their inherent properties of biological recognition, presentation of receptor binding ligands and susceptibility to cell triggered degradation and remodeling [178]. RGD peptide sequence on the surface of a biomaterial can promote the adhesion of cells through integrin receptors and, therefore, stimulate cell spreading A novel mechanism where the molecular recognition between avidin and biotin is used as a foundation for the immobilization ot RGD peptides to a polymer surface is schematically illustrated ir Fig. 54 [181]. Here a biotinylated biodegradable polymer, PLA-PEG- biotin is initially synthesized as the first step in the process. The structure of such a polymer is shown in Fig. 54(a). The three components in this polymer have their own advantages. PLA is ¢ biodegradable polymer which ensures that the material is eliminated by the body once its function is accomplished. PEG is a hydrophilic, protein-resistive component included to reduce
Fig. 95. XRD patterns of the micro-arc oxidized samples obtained at (A) 250, (B) 350, and (C) 450 V. (Reprinted from [253] with permission from Elsevier.)
Fig. 43. SEM image of human osteoblast on the SLA surface after seven days of incubation at different magnification. (A) 100x and (B) 700x. (Reprinted from [160] with permissions from Institute of Physics Publishing (IOP).) Lu et al. patterned Ti surfaces with micrometer to nanometer features (Fig. 46) [164] utilizing a novel plasma-based dry etching technique. In vitro studies using rat aortic endothelial cell demonstrated enhanced endothelial cell coverage and alignment on nanometer-scale Ti patterns as compared to micrometer-scale Ti patterns and random nanostructured surfaces (Fig. 47) [164]. Choi et al. [169] developed two distinct nanopatterns (posts and grates) (Fig. 48) with varying three-dimensionalities on silicon
Fig. 32. Stereo images of (a) an etched titanium surface, and (b) L929 fibroblast cell cultured on a plastic coated with 8 nm gold/palladium, obtained by a field emissic scanning electron microscope, using a low voltage, high current backscattered electron detector. (Reprinted from [131] with permission from Elsevier.) Ina scanning electron microscope a high energy (typically, 5- 100 keV) electron beam is scanned across the surface of the
Fig. 25. A three-dimensional finite element model for the stress distribution under in vivo conditions across (a) a metallic hip endoprosthesis, and (b) a ceramic ball, used ina hip implant. (Reprinted from [119] with permission from source: http://www.endolab.de/computer/computersimulation_e.htm.) -onditions, cold working, annealing cycles, etc. A summary of the ‘epresentative mechanical properties of three implant grade netallic materials based on its processing conditions is listed in fable 5 [15]. Unfortunately, all of these values are obtained from standard samples with simple and regular geometries and may not ‘epresent the actual stress or loading conditions occurring on a ‘omplex shaped implant under in vivo conditions. Hence, a ‘omputational-based finite element analysis (FEA) is mostly ollowed to solve this problem [15,115-119]. Using a finite element approach the distribution of stresses at various locations of a complex shape implant under in vivo conditions can be easily calculated. Fig. 25 shows the stress distribution across a ceramic head and a hip stem used for hip implant prosthesis obtained by FEA technique [119]. Apart from its use for proper design of a prosthetic device, FEA may also be used to evaluate the stresses occurring across the surrounding tissues upon the insertion of an implant material and thereby its effect on tissue growth, remodeling and degeneration [118].
Fig. 117. SEM images of the hierarchical organization of calcium phosphate tribasic coating on Ti alloy substrate obtained by laser melting using a continuous wave Nd:YA system. (Reprinted from [2] with permission from Elsevier.)
Fig. 30. AFM micrographs of an (a) untreated polyetherurethane surface, (b) O2 treated polyetherurethane surface, (c) Ar treated polyetherurethane surface and (d) N> treate polyetherurethane surface. (Reprinted from [130] with permission from Elsevier.) Wilson et al. [130] used a low-powered gas plasma with Oz, Ar, and Nz as the treatment gasses to modify the surface of a medical Khor et al. [129] used poly(styrene)-block-poly(2-vinylpyrin- dine) diblock copolymer (PS-b-P2VP) and poly(styrene)-block- poly(4-vinylpyrindine) diblock copolymer (PS-b-P4VP) to form surface-induced nanopatterns on mica substrate. Such surfaces were expected to attach mesenchymal stem cells and thereby induce a hierarchy of bone cell population. Diblock copolymers
Fig. 33. Picture of a contact angle goniometer used to measure the measure the contact angle by the static or sessile drop technique (a) (reprinted from [139] with permission from source: http://www.labkorea.com/products/cam/tantec/cammicro.html#specs), digital images of (b) a liquid drop formed on the surface of a sample and, (c) the corresponding contact angle formed by such a drop as measured by the goniometer.
Fig. 46. Scanning electron microscope (SEM) images of Ti patterned surface features of (A) 750 nm, bar = 1 jm; (B) 2 wm, bar=1 wm; (C) 5 wm, bar = 1 wm; (D) 25 wm, bar = 20 wm; (E) 75 wm, bar = 20 pm; and (F) 100 wm, bar = 20 wm. The thin nonuniform bright lines and spots observed in the etched grooves (darker stripes) are artifacts of dry etching process. (Reprinted from [164] with permission from Elsevier.)
Fig. 52. Molecular structure of N-vinyl-2-pyrrolidone and schematic representation of the grafting process. Method A: UV-assisted grafting and Method B: y-ray pre- irradiation grafting. (Reprinted from [175] with permission from Elsevier.)
Fig. 14. Histology of capsules surrounding the (a) uncoated and (b) bioglass coated, catherter segments. (Reprinted from [75] with permissions from Nature Publishin Group.) Polymers are long chain molecules consisting of large number of small repeating units known as monomers. They belong to the family of macromolecules and represent the largest class of biomaterials. Polymers can be derived either from natural sources or from synthetic organic sources. The different types of polymers 10CaCO3 + 6(NH4)2 +2H20 — Ca10(PO4)6(OH)2 + 6(NH4)2CO3 + 4H,CO3
Fig. 118. SEM micrographs of the Ca—P-coated sample processed at a laser fluence of 1006 J cm~?: (a) with a textured topography in the cross-sectioned sample and (b) th inset with multi-scale features at the coating surface. (Reprinted from [7] with permissions from Institute of Physics Publishing (IOP).)
Fig. 50. Schematic illustration of cross-sections of surface-modified layers of titanium specimens with and without calcium-ion-implantation. (Reprinted from [173] with permission from Elsevier.)
Fig. 83. Cyclic polarization curves in Ringer’s solution of uncoated and HAP-coated type 316LSS at the optimum coating parameters of 60 V and 3 min after sintering at various temperatures in air. (Reprinted from [218] with permission from Elsevier.)
Fig. 27. 3D-profiles of (a) titanium alloy surface treated in NaOH 5N and (b) stainless steel surface treated in NaOH 20N, using a mechanical stylus profilometer. (Reprinted from [128] with permissions from Materials Research.)
Fig. 15. Fluorescence microscopy images of U-937 cells cultured on (a and b) TCP, and (c and d) HA, with VD3 and PDBu for 21 days. (Reprinted from [77] with permission fror Elsevier.)
Fig. 88. Cross-section TEM image (a) and the corresponding diffraction pattern (b) of the HA/TiN/Si sample. (Reprinted from [234] with permission from Elsevier.
Fig. 35. Schematic illustration of (a) a hydrophobic or non-wetting surface and (b) hydrophilic or wetting surface. 1.3.3.3. Surface chemistry. Chemical composition of a biomaterial surface can be characterized using X-ray photo electron spectro- scopy (XPS), auger electron spectroscopy (AES), Fourier transfor- mation infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and secondary ion mass spectroscopy (SIMS).
and its exposure, the biomolecules may have different affinities for various surfaces [15]. Further at a microscopic level, a biomaterial surface may have patches, or domains, of different functionality and these patches or domains can interact differently with the biomolecules. For example metallic materials mostly exist in more than one phase. Ti-6Al-4V a commonly used orthopedic implant material consists of two different phases, i.e. the a- and B-phase. Not only these different phases but also the grain boundaries may have a different chemical composition and thereby a different interaction with biomolecules. In polymers, segregation resulting Surface chemical composition and its analysis by the above techniques are important criteria in the design of biomaterials as it determines which functional groups are available for interaction with the biomolecules. Depending on the type of species available
Fig. 98. SEM of the MAO coatings formed at 480 V treated for (A) 1.5 min (B) 3 min (C) 10 min (D) 20 min. (Reprinted from [254] with permission from Elsevier.) concentration on the structure and in vitro bioactivity of the MAO coatings. The HA concentration in the electrolyte was varied as 0, 4, 8, 12, and 16g/l and the MAO samples obtained from such concentrations were labeled as MAOO, MAO4, MAO8, MAO12, and MAO16, respectively. From XRD (Fig. 99) [255] studies it is observed that on the surface of MAOO coating, there is only the presence of anatase with low crystallinity and amorphous phase. Wei and Zhou [259] synthesized TiO2-based coating containing amorphous Ca-P on titanium alloy by MAO and studied its in vitro biocompatibility. The MAO pre-processed sample were heat treated at 400, 600, 700 and 800 °C in air for 1h and the affect
Fig. 51. Scanning electron micrographs of unimplanted titanium (a) and calcium- ion-implanted titanium (b) immersed in Hank’s solution for 30 days. (Reprinted from [173] with permission from Elsevier.)
Mechanical properties and clinical applications of Ti-based metallic materials. Table 2
Fig. 20. S-N curve for four medical grade Ti based alloys. (Reprinted from [102] with permission from Elsevier.)
Fig. 28. Schematic illustration of the working of an AFM. AFM consists of a sharp cantilever tip (aspect ratio >5:1) made from Si3N, or Si with a feed back mechanism that enables a piezo- electric device to maintain the tip at a constant force, or height above the surface of the sample (Fig. 28). As the tip is scanned over the surface, a laser beam focused onto the back of the reflective AFM cantilever, gets deflected onto a photodetector. The photo- detector then measures the variation in light intensities due to the up and down movement of the tip and converts it to a three- dimensional topographical image of the surface. The force between the tip and sample surface is usually in the order of 10~° N. Apart strongly influence the protein adsorption, cell attachment, cell proliferation, contact guidance, and differentiation [125-127]. Hence, it controls the rate and quality of new tissue formation at the interface. The surface roughness or its topography can be
Fig. 29. AFM images of (a) a poly (styrene)-block-poly (2-vinylpyrindine) diblock copolymer (PS-b-P2VP) with a dot like nano-pattern, and (b) poly (styrene)-block-poly (- vinylpyrindine) diblock copolymer (PS-b-P4VP) with a worm like nano-pattern. (Reprinted from [129] with permissions from American Chemical Society (ACS).)
Fig. 31. SEM images of (a) the rough surface of a Ca-P coating on Ti-6Al-4V substrate obtained by direct laser melting technique, and (b) both cuboid and needle-like apatite phase on such coating following immersion in simulated bio fluid for 1 day.
Fig. 40. Osteoblast attachment to PMA and OT SAMs at 90 min (A: MPA, B: OT) and 18 h(C: MPA, D: OT). Bar = 50 wm. Original magnification 180~. (Reprinted from [144] with permissions from Wiley Inter Science.) Zreiqat et al. [143] investigated the effect of surface chemistry modification of Ti-6Al-4V alloy with zinc, magnesium, and alkoxide-derived hydroxy carbonate apatite (CHAP) on the regulation of key intracellular signaling proteins in human bone-derived cells (HBDC) cultured on these modified surfaces. An ion beam implantation technique was used to modify the surface of Ti-6Al-4V with Zn and Mg and a sol gel coating technique was used to deposit alkoxide-derived hydroxy carbo- nate apatite on the surface of Ti-6Al-4V. SEM images (Fig. 38) [143] of HBDC cultured on the three different surfaces for 1, 2, and The various phenomena that may occur at the interface after implantation of a biomaterial into a living system are sequential and is schematically shown in Fig. 41. Initially the proteins respond to the implant surface and form a thin layer of protein film on the
Fig. 42. (A and B) SEM image of a sand blasted and acid etched titanium surface. (Reprinted from [160] with permissions from Institute of Physics Publishing (IOP).)
Fig. 47. Rat aortic endothelial cell (RAEC) cell density after the first day of culture on Ti patterns of (A) 750 nm; (B) 2 um; (C) 5 wm; (D) 75 pm; (E) 100 wm and (F) random nanostructured Ti surfaces. (A-F) bars = 50 wm. Arrows indicate groove alignment direction on patterned samples. (Reprinted from [164] with permission from Elsevier.)
Fig. 49. Cell morphology on 3D sharp-tip nanotopography. To examine fibroblast cells’ morphology, the SEM images were taken at the culture periods of 3 days on nanopost (a: low, b: mid, c: high), and nanograte (d: low, e: mid, f: high) samples. The scale bar in each image indicates 50 wm. Each inset in (a-c) and (d-f) represents the sample’s nanotopography, shown in higher magnification. Each arrow (<——) in (d-f) represents the direction of nanograte patterns on the sample. (Reprinted from [169] with permission from Elsevier.)
Fig. 58. Optical micrographs of coating layer deposited on Si wafer (a) without ion beam bombardments and (b) with Ar ion beam bombardments (120 V, 0.8 A). (Reprinted from [190] with permission from Elsevier.)
Fig. 70. TEM micrographs revealing the nucleation of crystalline HA grains (a) from the amorphous calcium phosphate phase and (b) at the interface of the amorphous and crystalline regions. (Reprinted from [201] with permission from Elsevier.)
Fig. 74. A cross-sectional TEM image of a well-oriented HA splat in a heat-treated HAC (HHT-HAC) (a); (b) shows a typical SAD pattern from the location marked in (a (Reprinted from [210] with permission from Elsevier.) Sintering conditions (such as sintering in air or vacuum) and sintering temperature can strongly affect the stability of electro- phoretically deposited hydroxyapatite coatings in body environ- ment. Sridhar et al. [218] performed potentiodynamic cyclic polarization experiments in Ringer’s solution on two different sets of samples. Fig. 83 [218] represents the polarization curves in Ringer’s solution of uncoated and HA coated 316L stainless steel sintered at various temperatures in air. The E; and E, values of the coated samples decrease with increasing sintering temperature in air. Hence, the corrosion resistance decreases or the corrosion rate increases with increasing sintering temperature. This is attributed
Fig. 77. Schematic illustration of electrophoretic deposition process. (a) Cathodic EPD and (b) anodic EPD. (Reprinted from [213] with permission from Elsevier.) where k is a constant which varies with the pulse width of the laser beam, M is the mass of the plasma plume, z, is the distance at which the substrate is placed with respect to the target and @ is the radial angle and p, is the density of the substrate. The variation in film to the formation of oxides on the base which induces the early initiation of pits and further reduces the adhesion of the coating to the base metal. Fig. 84 [218] represents the polarization curves in Ringer’s solution of uncoated and HA coated 316L stainless steel sintered at various temperatures in vacuum. The E, values of the
Fig. 81. Cross-section SEM micrograph of the electrophoretically deposited HA under the identified optimum suspension condition. (Reprinted from [217] with permissions from Springer.)
Fig. 87. GIXRD spectra (Cu Ka, 4 = 0.154 nm) of the HA thin films without buffer layer (a) and with TiN (b); ZrO2 (c) or Al2O3 and (d) buffer between the HA film and the metallic substrate. (Reprinted from [234] with permission from Elsevier.)
Fig. 89. Confocal ner me sical Ae 5 een of cells attached on HA films deposited on Ti foils using a pulsed laser at various laser processing conditions (a) 3 J/cm? ( 6 J/cm? (c) 9 J/cm? (d) 3 J/cm? annealed (e) 6 J/cm? annealed and (f) 9 J/cm? annealed. (Reprinted from [235] with permission from Elsevier.)
Fig. 91. SEM images of primary osteoblasts on (a and b) Ti, (c and d) OCP coating, and (e and f) Mn-CHA coating. (a, c and e): 7 days of culturing; (b, d and f): 21 days « culturing. (Reprinted from [236] with permission from Elsevier.)
Fig. 92. SEM images showing the morphology of the films deposited by PLD on Ti substrates heated at 150 °C and subjected to post-deposition treatment at 150 °C. (Reprintec from [237] with permission from Elsevier.).
Fig. 93. SEM of hFOB 1.19 cells deposited on bare Ti (a and b), and on OCP coating (c and d). (Reprinted from [237] with permission from Elsevier.
Fig. 96. Surface morphologies of the micro-arc oxidized samples formed at (A) 250 V, (B) 350 V, (C) 450 V, and (D) cross-section view of specimen (B). (Reprinted from [253 with permission from Elsevier.) Sun et al. [254] proposed a novel method to directly deposit HA on Ti-6Al-4V by MAO in Ca- and P-containing electrolytic bath. They proposed that the applied voltage and treatment time were two important factors for HA formation. For the MAO process a pulse power supply was employed, Ti-6AI-4V plate was used as an anode, and a stainless steel cylinder container was used as a cathode. The electrolytic solution used for the process is a mixture Wei et al. [255] developed a micro-arc oxidized TiO2-based coatings containing Ca and P on the titanium alloy. The electrolytes used for the MAO process was a mixture of nano-HA, calcium acetate, calcium dihydrogen phosphate (Ca(H2PO,)2:H20), dis- odium ethylenediaminetetracetate (EDTA-2Na), and sodium hydroxide (NaOH). The authors studied the effects of HA
Fig. 100. SEM micrographs of the surfaces of (a) MAOO, (b) MAO4, (c) MAO8, (d) MAO12 and (e) MAO16 coatings. (Reprinted from [255] with permission from Elsevier.) A magnetron sputtering system works on the principle of applying a specially shaped magnetic field to a diode sputtering of heat treatment on the biocompatibility of the coatings was studied by the culture of MG63 cells. The heat treatment process altered the surface topography of the coating and the average roughness increased with increasing heat treatment temperature (Fig. 102) [259]. SEM micrographs (Fig. 103) [259] of the MG63 cells following culture for 3, 5 and 7 days on the MAO and the MAO modified surfaces demonstrated increased cell proliferation with increasing culture time. After 7 days the cells on the MAO and 400 °C-treated MAO completely covered the surface with a smooth and flat morphology. In contrast, the other heat-treated samples demonstrated less proliferation of the MG63 cells and seem to be not biocompatible. This improved adhesion and proliferation of the MG63 cells on the MAO and 400 °C-treated MAO coatings as compared to the other heat-treated samples were attributed to its
Fig. 104. Schematic of a magnetron sputter deposition system.
Fig. 105. SEM morphology of the as-deposited and heat-treated Si-HA thin films. (Reprinted from [262] with permission from Elsevier.)
The temperature at the surface during heating and cooling can be obtained by substituting z=O in the above two equations. Therefore
Fig. 115. Number of HOS cells proliferated on samples after culturing for 5 days. The error bars represent means + 1 SD; n= 6: p < 0.001 compared to MAO-Ti. (Reprinted from [274] with permissions from Wiley Inter Science.) first level in the hierarchy are the collagen filaments which are Approximately 1mm in diameter. Hydroxyapatite crystals are =mbedded in parallel into these collagen filaments so that the larger dimensions of the crystal are along the long axis of the fiber. These collagen fibrils in turn gets organized into a sheet or woven ‘exture to form the extra-cellular matrix (ECM). Bone cells such as osteocytes resides between these several sheet-like parallel arrays lamellar bone) or are concentrically arranged into a cylindrical structure known as the osteon. These osteons are then grouped ‘together into long bundles known as Haversian bone, a basic uilding block of bone microstructure. Finally, at the macroscopic
Fig. 114. SEM morphology of the HOS cells after culturing for 3 days on (A) pure Ti, (B) MAO-Ti, and HA sol-gel coating on MAO-Ti at sol concentration with (C) 1.5 M and (d) 3 M. (Reprinted from [274] with permissions from Wiley Inter Science.)
Fig. 116. Schematic of a continuous wave Nd:YAG laser used for the coating process Since cells are sensitive to features ranging from the nanoscale to the mesoscale, a key implant design criterion will be to provide appropriate topographical cues that may stimulate cell differ- entiation even without the requirement for an appropriate surface chemistry. A laser-based interference patterning technique may be used to manipulate the surface topography in a periodical way. Interference patterning involves irradiating the surface of the sample with two or more overlapping coherent and linearly polarized laser beams of defined geometry [294-298]. This geometry depends on the wavelength and angles between the
Fig. 120. Schematic of the pulsed Nd:YAG laser system used for the coating process. (Reprinted from [284] with permissions from Institute of Physics Publishing (IOP) where E density is the energy in J/cm?, kis the thermal conductivity in W/m K, T,, is the melting temperature in degrees, t, is the pulse time in seconds, x is the thermal diffusivity in m?/s and z is the
Fig. 121. Figure illustrates (a) a 2-dimensional and (b) 3-dimensional confocal microscopic image of the surface of the Ca—P-coated samples obtained using a pulsed Nd:YAG laser system. (Reprinted from [284,285] with permissions from Maney Publishing.)
Fig. 124. Histological appearance of Ti-CaP/beads implant after (a) 4 weeks and (b) 12 weeks of implantation (bar = 200 wm). (Reprinted from [286] with permission fron Elsevier.) feature size that is assumed to the melt depth in meters. A schematic representation of the interference patterns due to a variation in the interference angle and thermal conductivity of the material is shown in Fig. 131 [297]. Thus, by selecting laser processing parameters in tune with implant material properties, a variety of surface patterns (textures) and microstructures that are suitable for bio-applications can be produced.
Fig. 125. Light micrographs of implant-bone interface 12 weeks after implantation (bar = 300 pm). (Reprinted from [287] with permission from Elsevier.
Chemical name, mineral name, and composition of various Ca-P based ceramics. (Reprinted from [76] with permission from Institute of Mechanical Engineers (I.MechE).). Table 3
Representative mechanical properties of three implant grade metallic materials based on its processing conditions. (Reprinted from [15] with permission from Elsevier. Table 5
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Microstructural comparisons of ultrathin Cu films deposited by ion-beam and dc-magnetron sputtering
by Jonathan D Daniels

2005, Journal of Applied Physics

We report and contrast both the electrical resistance and the microstructure of copper thin films deposited in an oxygen containing atmosphere by ion-beam and dcmagnetron sputtering. For films with thicknesses 5 nm or less, the... more
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Infrared absorption strength and hydrogen content of hydrogenated amorphous silicon
by W. Lanford

1992, Physical review. B, Condensed matter

We have used infrared transmission and nuclear-reaction analysis to determine the ir absorption strength of the Si-H wagging and stretching modes in hydrogenated amorphous silicon (a-Si:H). The films were deposited by plasma-assisted... more
FIG. 7. Correlation between Ny determined from the in- tegrated absorbance of the stretching modes and the wagging mode using the proportionality factors determined in this study. The solid line represents Ny, (stretch) = Ny (wag). absorbance of the wagging and stretching modes using A x99 =(9.0£1.0)X10!? cm~?, A 5499 =(2.240.2) X 10° om *, and A ¢4)=2.1X10!° cm. To check the validity of these proportionality factors, we have analyzed some of the previously published data on stretching and wag- ging modes.° !®!7,21,33.42 These are also shown in Fig. 7. Note that to first order there is reasonably good agree- ment between Nj, determined from the stretching and wagging modes for a wide range of samples.
FIG. 5. Hydrogen content (Ny) from NRA vs the integrated absorbance of the 640-cm~' mode for PACVD (squares) and reactive magnetron-sputtered (circles) films. Least-squares fit to the data yields A 4) =(2.1+0.2) X 10"? cm~?.
TABLE I. Deposition parameters and properties of PACVD and magnetron-sputtered samples used in this study. *Hydrogen content [100Ny /(Ny + Ns;)] from nuclear reactions. >Mass density relative to c-Si from nuclear reations. °Film thickness from stylus profilometry. 4Film thickness from fitting the fringes. *Refractive index from fitting the fringes. ‘Integrated absorbances determined after converting transmission spectra to absorption spectra using exact equations. £Positive and negative numbers, respectively, show the precentage by which the BCC method overestimates and underestimates tl integrated absorbance of the wagging and stretching modes.
The second error in the BCC method leads to a sys- tematic overestimation or underestimation of a@ in many cases even when the baseline is determined correctly. Unless the films are deposited on roughened c-Si sub- strates, ir absorption is determined by coherent multiple reflections in the film. The BCC method, which is de- rived for incoherent reflections, overestimates a by up to FIG. 1. Transmission spectra of glow-discharge-deposited a- Si:H with 7% (upper spectrum) and 24% (lower spectrum) hy- drogen. Substrate absorption has been removed by dividing the sample spectra by that of a bare c-Si substrate and multiplying by 0.54, which is the transmission of c-Si in the nonabsorbing regions. The dashed lines show transmission spectra calculated by taking into account the effects of interference in the film and absorption in the Si-H wagging and stretching modes. The upper spectra have been shifted by 0.1 for clarity.
FIG. 3. The dependence of the number density (Ns, + Ny) on hydrogen content. The horizontal solid line represents Ns; for c-Si. Before presenting the results, we note that hydrogen content is often given as a fraction by dividing Ny by 5X 107", the number of density of c-Si. When quoted as a fraction, it is not clear whether one is referring to the Ny/Ng ratio or the H_ mole fraction, ie., Ny/(Nsg +Ny). Obviously, the two values are very different for high hydrogen content. Several groups have measured the mass density of a-Si:H as a function of the hydrogen content.” !*!%30—34 In Fig. 3 we convert the mass density to number density, Ny+Ns5,, and examine its variation with hydrogen content, N};, determined in- dependently. This figure shows that for a large number of films grown and characterized by several different techniques in different laboratories, the number density has an average value of 5.3 X 107 cm~?, with a rms devi- ation of 10%. This shows that it is reasonable to specify hydrogen content as a fraction by dividing Ny by 5X10”, provided that it is recognized as the mole frac- tion of hydrogen, Ny /(Ny +N; ).
FIG. 2. Thickness dependence of absorption at 640 cm! (circles and solid line) and 2000 cm™! (triangles and dashed line), which is an artifact of the BCC method. The lines are from a calculation and the points show the experimental] data. was deposited by PACVD under identical conditions, at a substrate temperature of 250°C, with the deposition time ranging from 8 to 175 min. Figure 2 shows the thickness dependence of the integrated absorbance of the 640- and 2000-cm™! peaks determined by the BCC method. The solid and dashed lines in the figure show the theoretically predicted variation of the absorption coefficient at these two frequencies. As predicted, the apparent absorption determined by the BCC method increases as the film thickness decreases. The apparent increase in absorption To confirm the predicted dependence of the ir absor- bance on film thickness, a series of films, 0.1—2 zm thick,
FIG. 6. Hydrogen content (Ny) from NRA or thermal evo- lution vs the integrated absorbance of the 640-cm~! mode. The line corresponds to A 64) =2.1 10! cm~?. In short, in view of the discussion in the preceding sec- tion, a +25% uncertainty in the integrated absorbance of the wagging modes is not uncommon if the ir data are an- alyzed by the BCC (Ref. 2) or the Connell-Lewis~’ method. In the absence of a detailed reanalysis of the ir transmission spectra, and given the additional uncertain-
FIG. 4. Absorption spectra of a-Si:H films deposited by PACVD (solid lines) and magnetron sputtering (dashed lines) in the wag- ging, bending, and stretching-mode regions. Spectra are shown in pairs to compare features for samples with hydrogen content as closely matched as possible. From bottom to top, the hydrogen content is 7%, 13%, 20%, and 24% for PACVD and 7%, 14%, 20%, and 30% for magnetron-sputtered films. The correlation between Nj;, the number of hydrogen atoms in the film, measured by NRA, and the integrated absorbance of the 640 cm! mode is shown in Fig. 5 for the sputtered and PACVD films. Within the measure- ment uncertainty, both sets of films show the same trend. A least-squares fit to the data yields a zero intercept and A egg =(2.140.2)X10!9 cm~*. This constitutes the upper limit to A ¢49 since infrared absorption is sensitive only to Si-H bonds while NRA measures this component as well as molecular hydrogen. However, we are not aware of any studies which correlate ir absorbance with the amount of hydrogen bonded to Si determined in- dependently (by NMR, for example). Thus, all estimates of A¢4q to date have been obtained by relating ir absor- bance to the total hydrogen content. The value of A ¢4o obtained in the present study is about 30% larger than the most widely used value of 1.6X10!° cm~? reported by several groups.>*!® It is in very good agreement with the value of 2.010! cm~? reported by Maley et al." and is ~15% smaller than the highest value (2.5 x 10!° cm’), reported by Oguz.’ These discrepancies in A ¢4o can be accounted for by molecular hydrogen provided (i)
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Recent advances of superhard nanocomposite coatings: a review
by sam zhang

2003, Surface & Coatings Technology

In this paper, a review of the present status of the research and technological development in the field of superhard nanocomposite coatings is attempted. Various deposition techniques have been used to prepare nanocomposite coatings.... more
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Production and dispersion stability of nanoparticles in nanofluids
by Soo Kim

2008, Powder Technology

This paper presents an experimental study on the homogeneous dispersion of nanoparticles in nanofluids. In this study, various physical treatment techniques based on two-step method, including stirrer, ultrasonic bath, ultrasonic... more
Fig. 7. (a) TEM image and (b) the size distribution of Ag particles in silicon oil- based nanofluids prepared by the modified magnetron sputtering system (i.e. one-step method). Fig. 8 shows that the zeta potentials of the CB suspensions as a function of pH without and with SDS. These suspensions were prepared with the high-pressure homogenizer. Without SDS addition, the zeta potential of CB suspension was significantly decreased with increasing pH value. However, with the con- trolled-amount addition of SDS, the zeta potential of the CB
Fig. 6. The particle size distributions in nanofluids as a function of the dispersion methods.
Fig. 4. TEM images of CB nanoparticles in water-based nanofluids prepared by two-step methods. (The inserted scale bar is 200 nm).
Fig. 5. TEM images of Ag particles in silicon oil-based nanofluids prepared by two-step methods. (The inserted scale bar is 50 nm).
Fig. 1. SEM images of the tested nanoparticles.
Fig. 3. Schematic diagram of the modified magnetron sputtering system for producing nanofluids.
Fig. 8. The evolution of zeta potentials of the water-based CB nanofluids as a function of pH (a) without SDS and (b) with SDS (1 wt.%).
Fig. 2. Schematic diagram of the high-pressure homogenizer for producing nanofluids. In this study, CB—water and Ag-silicon oil nanofluids were produced by the two-step methods. Also another Ag—silicon oil nanofluid was produced by the one-step method for comparison purpose. The size distribution and zeta potential of nanoparti- cles suspended in nanofluids were measured by an electro- phoretic light scattering (ELS) particle counter (Model No. ELS-8000, Otsuka Electronics Inc.), which consisted of a laser source, a scattering cell, electrodes for applying an electric field, a photomultiplier, and a spectrum analyzer. Operating principle of the ELS is described in detail elsewhere [19,20]. Briefly, the charged particles in the scattering cell were forced to move along the applied electric field. This particle motion resulted in As another two-step method for producing a nanofluid, we employed a high-pressure homogenizer (Model No. M- 110LCE, Microfluidics, Inc.). Fig. 2 presents the schematic diagram of the high-pressure homogenizer, which is consisted of two micro-channels, dividing a liquid stream into two streams.
Test conditions and materials for producing nanofluids Table 1
The methods of producing nanofluids
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Metal-Ion Deposition from Ionized Magnetron Sputtering Discharge
by Stephen Rossnagel

1994, Journal of Vacuum Science & Technology B

Fic. 8. Cross section of high aspect ratio trench which has been lined with TiN at room temperature using ionized magnetron sputter deposition. TiN films were deposited using the present experiment by reactively sputtering a Ti cathode in a combination of Ar and
Fic. 1. Sketch of a cross section of a sputter deposited, layered film onto a medium aspect ratio feature.
Fic, 2. Schematic of the experimental design. A. Relative ionization A dense, inductively coupled rf (RFI) plasma was gener- ated in the region between the sputtering cathode and the sample plane (typically a Si wafer mounted on a holder). The plasma was generated by applying 13.56 MHz power to a multiple turn coil of water-cooled Cu tubing located inside the vacuum chamber. A number of coil designs and locations were explored (Fig. 2). Much of this work utilized two to three turn coils which had a diameter approximately the same as the magnetron cathode and were located ~4 cm from the cathode surface and 2~3 cm from the sample sur- face. Spiral coils were also used on some of the rotating magnet systems. These latter systems required great attention to coil symmetry, as the moving magnetic field coupled weakly into the RFI plasma, causing variations on the scale of the magnet rotation rate.
Fic. 4. Relative ionization for sputtered Al at constant pressure as a function of rf power into the inductively coupled plasma. The cathode used was a 20 cm diam AlCu planar cathode at 36 mTorr pressure.
Fic. 3. Relative ionization level for sputtered Al as a function of chamber pressure for Ar and Ne working gases using a 20 cm diam planar AlCu cathode.
Fic. 6. Optical emission from Ar as a function of increased metal sputtering rate (dc magnetron power). Optical emission from the region above sample location, 10:cm. from the cathode. By using OES and observing both metal neutral and metal ion emission, the relative ionization could be qualitatively extended to higher rf powers. This is shown in Fig. 7, in which the relative ionization inferred from OES is normal- ized to a low power:(200 W) measurement with the electro- static energy analyzer. This indicates that the cooling effect of the metal ion fluxes can be countered somewhat by addi- tional rf power to the RFI plasma.
Fic. 5. Relative ionization for sputtered Al as a function of increasing rf power and increased metal sputtering rate for a 20 cm dis. AlCu cathode.
Fic. 7. Relative ionization level for sputtered Al as a function of rf power tc the RFI plasma. The solid data points to the left-hand side are from Fig. & using the mass-sensitive energy analyzer. The open data points were wkex using OES, comparing the intensity of an ionized Al line to the sum ef the intensity of that ionized line and a nearby Al neutral emission line. The OES data were then normalized to the energy analyzer data at 200 W.
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Modified Thornton model for magnetron sputtered zinc oxide: film structure and etching behaviour
by Jürgen Hüpkes

2003, Thin Solid Films

bstract ZnO:Al films were prepared on glass substrates with different sputter techniques from ceramic ZnO:Al O target as well as 2 3 metallic Zn:Al targets using a wide range of deposition parameters. Independent of the sputter technique,... more
Fig. 1. Pressure dependence of the resistivity for RF and DC ZnO:Al films, sputtered at 7;=150 and 270 °C. All RF and DC sputtered films are deposited in static mode from ceramic ZnO:A1,03 targets or metallic Zn:Al target adding O,. For comparison, data of MF films reactively sputtered in dynamic mode from Zn:A1 targets have been included.
Fig. 5. The modified Thornton model describes the correlation between sputter parameters (sputter pressure and substrate temperature), structural film properties and etching behaviour of RF sputtered ZnO:A1 films on glass substrates. The pressure series at 7; =270 °C shows the systematic influence of the sputter pressure on the surface morphology after etching (see text).
Fig. 2. Pressure dependence of the etching rate of RF and DC ZnO:Al films sputtered at T;=150 and 270 °C. HRSEM- and AFM-measurements reveal systematic correlations between the deposition parameters and the etching behaviour. In the following, we focus on the results obtained for the ZnO:A1 films, which were RF sputtered at T;=270 °C. Fig. 3 shows the influence of the sputter pressure on the surface morphology obtained after 15 s of etching in 0.5% HCl. This series is also included in Figs. 1 and 2. For a quantitative analysis
Fig. 3. Surface morphology, cross-section profiles and depth distribution of RF sputtered ZnO:A1 films (7;=270 °C) on glass obtained after 15 s of etching in 0.5% HCl. The data were generated from the AFM measurements.
Fig. 4. Surface features (opening angle and root mean square rough- ness calculated from AFM data, see text) of RF sputtered ZnO:Al films (T,;=270 °C) shown in Fig. 3.
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TiO2 thin film gas sensor for monitoring ammonia
by Velumani Subramaniam

2007, Materials Characterization

Systematic development and mechanistic studies of sensing materials are critical to the design of higher performance gas sensing elements and arrays. Polycrystalline metal-oxide semiconductors such as SnO 2 and TiO 2 are among the most... more
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Ultra-Low Thermal Conductivity in W/Al2O3 Nanolaminates
by Ruxandra Costescu

2004, Science

Atomic layer deposition and magnetron sputter deposition were used to synthesize thin-film multilayers of W/Al2O3. With individual layers only a few nanometers thick, the high interface density produced a strong impediment to heat... more
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Photocatalytic TiO2 thin film deposited onto glass by DC magnetron sputtering
by salah din

2001, Thin Solid Films

A high performance photocatalytic TiO thin film was successfully obtained by reactive DC magnetron sputtering. The film was 2 deposited onto SiO -coated glass at a substrate temperature of 220ЊC using a titanium metal target in O 100%... more
The sputtering conditions of TiO, thin films Table 1
Fig. 3. Transmission spectra of the films obtained by sol-gel and sputtering method.
Mechanical durability of the sol-gel-derived TiO, thin film and the sputtered TiO, thin film deposited at 7, = 220°C, P = 2.0 Pz Table 2
Fig. 5. 20 X-ray diffraction patterns for the films obtained by sol-gel methods and sputtering methods. Fig. 5 shows the 2© X-ray diffraction patterns of the sol-gel film and the sputtered films. There is no peak for the sputtered film of 7,=r.t., indicating that the film is amorphous. On the other hand, several peaks are clearly observed for the sputtered films of T, = 140 and 220°C although the photocatalytic activity is dif- ferent between them, as shown in Fig. 3. These peaks
Fig. 6. SIMS depth profiles for the films heat-treated at 500°C for 1 h in ‘80, atmosphere.
Fig. 7. Density of states obtained from first-principle calculations based on the density functional theory for (a) perfect model; (b) single oxyge vacancy model; and (c) double oxygen vacancies model. may represent the amount of oxygen vacancies in the film. Namely, the decomposition ability of CH,CHO, the photocatalytic activity, of the film is seen to de- crease with increasing the oxygen vacancies in the film. Fig. 7 shows the density of states (DOS) for (a) perfect model; (b) single oxygen vacancy model; and (c) double oxygen vacancies model obtained from the first-princi- ple calculations. It is found that no energy levels ap- Pilg. O SHOWS We OUVIS GCpul PrOWmes LOT Ue TTS heat-treated in '*O,/N, atmosphere. Before the heat treatment, the secondary ion intensity of '°°Cs'*O* was less than 10? counts for all the films. After the heat treatment, the intensity of '%Cs'*O* increases for all the films although no significant change is observed for the intensity of '°Cs'°O* before and after the heat treatment, indicating that '*O is incor- porated into the films. The amount of incorporated '*O is approximately two orders of magnitude larger than that before the heat treatment. It is found that the amount of incorporated '*O is different among the films, and that the amount of incorporated '8O is larger for the film with lower decomposition ability of CH,CHO than that of the film with higher ability. The incorporation of '*O was not observed for a single crystal of rutile TiO,, which is a stoichiometiric TiO,, indicating that '°O-'%O isotopic exchange reaction is negligible during the heat treatment. These results suggest that the incorporated '*O occupies an oxygen vacancy site, and that the amount of incorporated '°O
Fig. 1. Schematic illustration of experimental apparatus for the mea- surement of photocatalytic activity. The mechanical durability of the films was evaluated by a Taber abrasion tester (Teledyne Taber 503). The tests were carried out using CS-10F abrasion wheels loaded with 500 g. The degree of degradation was evaluated by the change in the haze value. The haze value, H, which is defined by T,/T, x 100% (T,, scat- tered light; 7,, transmitted light). The haze value
Fig. 4. SEM images of the films obtained by sol-gel and sputtering method.
Fig. 2. Change in concentration of CH3;CHO as a function of UV irradiated time by the films obtained by sol-gel and sputtering method.
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The energy balance at substrate surfaces during plasma processing
by Rainer Hippler

2001, Vacuum

A summary is given of different elementary processes influencing the thermal balance and energetic conditions of substrate surfaces during plasma processing. The discussed mechanisms include heat radiation, kinetic and potential energy of... more
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ZnO transparent thin films for gas sensor applications
by Mirela Suchea and 
1 more
Savvas Christoulakis

2006, Thin Solid Films

Zinc oxide (ZnO) transparent thin films were deposited onto silicon and Corning glass substrates by dc magnetron sputtering using metallic and ceramic targets. Surface investigations carried out by Atomic Force Microscopy (AFM) and X-ray... more
The as-deposited ZnO thin films were found to be highly transparent in the visible wavelength region with an average Fig. 3. Photoreduction/oxidation curves for 100 nm films grown from (a) Zn metallic target, (b) ZnO ceramic target. oxygen in the plasma, which could also generate high-energy oxygen neutral atoms. It is generally believed that the formation of grain agglomerations in the film deposited under the introduction of oxygen gas might be due to re-sputtering of high-energy neutral oxygen atoms [10]. As oxygen content in the plasma gas increases, re-sputtering effect by high-energy neutral oxygen atoms can increase. Subsequently it might accelerate grain growth (or aggregation of particles) and thus change the surface topology of the film at the initial stage of the film growth process. For films grown from a ceramic target, the growth rate had a remarkable increase compared with the metallic target case due to the high Ar ion concentration in the plasma. The surface roughness variations of the ZnO thin films deposited at different O2/Ar ratios are shown in Fig. 2b (triangles). The scan area for surface roughness was 5 <5 pm. One can observe that the surface roughness (RMS) generally increased with increasing Ar concentration in the plasma for both target materials.
Fig. 2. (a) Film growth rates versus Ar concentration in plasma, (b) optical band gap (squares) and RMS variations (triangles) versus Ar concentration in plasma.
“ig. 1. AFM 3D images of as-deposited ZnO thin films at room temperature with Ar ratios of respectively (a) 0%, z-range 50 nm/div (b) 27% from Zn metallic target. -range 50 nm/div (c) 100%, z-range 30 nm/div (d) 90% from ZnO ceramic target, z-range 30 nm/div. AFM imaging of the surfaces of ZnO thin films deposited at room temperature from metallic and ceramic targets, under varying Ar-to-O, flow ratios, are shown in Fig. 1. AFM characterization for the films deposited from a metallic target (Fig. la, b) revealed a granular, polycrystalline morphology The deposition of the ZnO films was carried out in an Alcatel dc magnetron sputtering system using 99.999% pure metallic Zn and ZnO ceramic targets under different conditions. The base pressure in the chamber was <5*10 ’ mbar. Films with a thickness of about 100 nm were deposited onto Corning 1737F glass and silicon substrates in an oxygen—argon atmosphere. The deposition constant parameters were the total pressure (8x10 3 mbar), the substrate temperature at 27 °C (RT), and the film thickness. The depositions were done at two different plasma current settings (/=0.44 A and /=0.25 A). The thickness was measured using an Alphastep profilometer. The surface morphology (grain size and surface roughness) was measured with a Nanoscope III atomic force microscope (Digital Co. nstruments, USA) using a normal silicon nitride tip (125 jm) in Tapping Mode scanning the surface with an oscillating tip o its resonant frequency (200—400 kHz). All measurements were made at room temperature (RT). In the present study the RMS roughness of the surface is defined as: RMS (nm)= LY (Zi—Zave)” /Ny'? where z; is the current value of z, Zaye 1S he mean value of z in the scan area, N is the number of points. Grain radius and feature dimensions were evaluated using the Cross Section Analysis Menu facilities of Nano- Scope III Program. The crystal structure of the deposited films was determined by X-ray diffraction (XRD) using a Rigaku diffractometer with CuKa X-rays. The optical
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Magnetization-orientation dependence of the superconducting transition temperature and magnetoresistance in the ferromagnet-superconductor-ferromagnet trilayer system
by Sam Bader

2003, Journal of Applied Physics

The superconducting transition temperature (T c ) of a ferromagnet-superconductor-ferromagnet film system is predicted to exhibit a dependence of the magnetization orientation of the ferromagnetic layers. We have grown CuNi/Nb/CuNi films... more
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A comparative study of reactive direct current magnetron sputtered CrAlN and CrN coatings
by Selvakumar N and 
2 more
Harish C Barshilia, Ph D
B. Deepthi

2006, Surface and Coatings Technology

Approximately 1.5 μm thick CrN and CrAlN coatings were deposited on silicon and mild steel substrates by reactive direct current (DC) magnetron sputtering. The structural and mechanical properties of the coatings were characterized using... more
Assignment of various Raman peaks of as-deposited and heat-treated CrN and CrAIN coatings
Fig. 7. Composite Raman spectra of as-deposited CrAIN and CrAIN coatings heat-treated up to 900 °C in air.
Fig. 1. XRD data of CrN and CrAIN coatings deposited at a substrate temperature of 300 °C and a nitrogen flow rate of 2.5 sccm.
RMS roughness values (in nm) of as-deposited and heat-treated (in air) CrN and CrAIN coatings Table 3
Potentiodynamic polarization data of CrN and CrAIN coatings deposited on mild steel substrates in 3.5% NaCl solution under free-air conditions at room temperature the chemical attack Al forms an Al,O3 layer on the surface of the coating, which passivates the surface and prevents the coating from further attack [42]. The presence of the passive layer leads to an additional resistance to the corrosive medium passing through the pores. It is clearly evident from the corrosion data that the CrAIN coatings exhibit superior corrosion behavior as compared to the CrN coatings.
Fig. 9. Three-dimensional AFM images of as-deposited CrN coating and CrN coatings heat-treated at 400, 500, 600, 650 and 700 °C The corrosion behavior of CrN and CrAIN coatings deposited on mild steel substrates was investigated using potentiodynamic polarization in 3.5% NaCl solution under free- air conditions at room temperature. The Tafel plots obtained for the mild steel substrate, CrN and CrAIN coatings are shown in Fig. 11. The corrosion potential, the corrosion current density, the polarization resistance and the Tafel constants (b, and b,) obtained from the measurements are given in Table 4. The corrosion potential of the mild steel substrate was found to be —0.62 V. The E.o. values of the CrN and CrAIN samples showed a shift towards the positive side, when compared to the The surface morphologies of the heat-treated CrN and CrAIN coatings were studied using AFM. The 3-dimensional AFM images of the as-deposited and heat-treated (400, 500, 600, 650 and 700 °C) CrN and CrAIN coatings are shown in Figs. 9 and 10, respectively. The root mean square roughness values of the as-deposited and the heat-treated CrN and CrAIN coatings are given in Table 3. The as-deposited CrN coating (Fig. 9) showed a root mean square roughness (RMS) value of 7.3 nm, whereas in the case of CrAIN coatings (Fig. 10), the surface roughness was very low (1.13 nm). The roughness value of heat-treated CrN coating almost doubled at a temperature of 500 °C (14 nm). On the other hand, the CrAIN coating retained a smooth surface up to a temperature of 500 °C (1.59 nm). At 600 °C, the surface roughness of the CrAIN coating was 7 nm, which was much less than that of the CrN coating (15 nm). With further increase in temperature to 650 and 700 °C, the RMS roughness of CrN coating increased to 23 and 43 nm,
A comparison of onset of oxidation and ex situ high temperature hardness of CrN and CrAIN coatings * Hardness of as-deposited films.
Fig. 5. Schematic representations of load vs. displacement curves for (a) CrAIN coating, (b) CrN coating and (c) silicon substrate at 5 mN load. For hardness measurements, indentations were made on the sample using a Berkovich diamond indenter. After pressing the indenter on to the sample, the load was increased at a predetermined rate (10 mN/min) to the desired maximum load and then decreased at the same rate (10 mN/min) to zero. For all the samples, the maximum applied load was 5 mN. For each loading and unloading cycle, the load was plotted against the displacement of the indenter. Fig. 5 shows typical load vs. displacement curves for CrN, CrAIN and silicon substrate at 5 mN load. The maximum indentation depth for CrAIN coating was approximately 100 nm, which is less than 1/10th of the coating thickness. CrN coating and the uncoated silicon substrate showed maximum indentation depths of 114 and 130 nm, respectively. CrN and CrAIN coatings prepared under identical conditions displayed hardness values of 18 and 33 GPa, respectively. The high hardness can be attributed to several factors such as: small inter-atomic distance, covalent nature, solution hardening and small crystallite size of CrAIN coatings. As mentioned previously a decrease in the lattice parameter of CrAIN (approximately 1.4%) due to the substitution of some of the Cr atoms by Al atoms in the CrN lattice was observed. Similar decrease in lattice parameter has been reported in the literature for TIAIN coatings [32,33]. As the inter-atomic distance (d) is related to the covalent band gap (Ej) according to the expression Rake [32], a decrease in the inter-atomic distance therefore causes an increase in the covalent energy. Furthermore, addition of Al in CrN increases the covalent bonding as CrN is a metallic hard material and AIN is a covalent bonded material [34]. Therefore, an increasing covalent contribution is expected for CrAIN as compared to CrN. Alloying of solvent with an element having smaller atomic size also contributes to enhanced hardness, which is commonly known as solution hardening [35]. Furthermore, small grain size
Fig. 11. Potentiodynamic polarization curves of CrN and CrAIN coating: deposited on mild steel substrate. Also shown is the polarization curve of milk steel substrate. less corrosion resistant. On the other hand, CrAIN coating exhibited dense microstructure, thus preventing diffusion of the corrosive medium into the substrate. The corrosion behavior of CrAIN may also have been affected because of the presence of Al. It has been reported that the addition of Al to the transition metal nitrides improves the corrosion resistance [41]. During
Fig. 8. Variations of hardness values of CrN and CrAIN coatings with annealing temperature.
Fig. 4. SEM images of as-deposited CrN (a—c) and CrAIN (d-f) coatings. The surface morphologies of the as-deposited CrN and CrAIN coatings examined using SEM at three different locations are shown in Fig. 4. The SEM image of CrN coating (Fig. 4(a), (b) and (c)) showed the presence of surface defects under higher magnifications. The coating also displayed significant amount of micro-porosity. On the other hand, only minute surface defects were visible for CrAIN coating (Fig. 4 (d), (e) and (f)). Results of the SEM surface analysis showed a more compact and dense microstructure for CrAIN coatings. Fig. 2 shows high-resolution XPS core-level spectra of CrN coatings. The peak associated with Cr metal (Fig. 2(a)) consists of two peaks centered at 575.3 and 585.4 eV. These peaks originate from Cr 2p3/. and Cr 2pj,/2, respectively. Deconvolu- tion of Cr 2p3/2 peak indicated that it consisted of two peaks centered at 575.3 and 577.4 eV. The peak centered at 577.4 eV could be due to the formation of CrO3 [29]. Peaks pertaining to free chromium (574.3 eV) and Cr.N (574.5 eV) were not
Fig. 3. XPS core-level spectra of: (a) Cr 2p, (b) N Is and (c) Al 2p of CrAIN coatings.
Fig. 2. XPS core-level spectra of: (a) Cr 2p and (b) N 1s of CrN coatings. The stoichiometric phase of CrN with Bl NaCl structure exists only in a limited range of nitrogen concentration [26]. Therefore, the process parameters were first optimized by varying the nitrogen partial pressure, target power, operating pressure and substrate bias. The XRD pattern of a typical CrN coating deposited under the experimental conditions used in the present study is shown in Fig. 1. The high intensity peak centered at 20=37.38° is assigned to cubic CrN (111) and the peak with a lower intensity at 20=43.51° is assigned to cubic CrN (200). Other higher angle reflections such as (220) and (311) were very weak, indicating that the films were oriented along (111).
Fig. 6. Composite Raman spectra of as-deposited CrN and CrN coatings heat- treated up to 800 °C in air.
Fig. 10. Three-dimensional AFM images of as-deposited CrAIN coating and CrAIN coatings heat-treated at 400, 500, 600, 650 and 700 °C.
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Interface microstructure engineering by high power impulse magnetron sputtering for the enhancement of adhesion
by Arutiun Ehiasarian

2007, Journal of Applied Physics

An excellent adhesion of hard coatings to steel substrates is paramount in practically all application areas. Conventional methods utilize Ar glow etching or cathodic arc discharge pretreatments that have the disadvantage of producing... more
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ZnO/Ag/ZnO multilayer films for the application of a very low resistance transparent electrode
by DIPTIRANJAN SAHU

2006, Applied Surface Science

Transparent conductive ZnO/Ag/ZnO multilayer electrodes having much lower electrical resistance than the widely used transparent electrodes were prepared by simultaneous RF magnetron sputtering of ZnO and DC magnetron sputtering of Ag. An... more
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Highly transparent and conductive rare earth-doped ZnO thin films prepared by magnetron sputtering
by Jadav Nayak

2000, Thin Solid Films

Highly transparent and conductive thin films of ZnO doped with a rare-earth element, Sc or Y, have been prepared by d.c. magnetron sputtering using a powder target. The resistivity of the ZnO:Sc thin films was always lower than that of... more
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Preparation and characterization of AlCrTaTiZr multi-element nitride coatings
by Jien-wei Yeh

2006, Surface and Coatings Technology

Multi-element nitride films of AlCrTaTiZr high-entropy alloy have been prepared in this study by reactive radio-frequency magnetron sputtering. The influences of nitrogen flow ratio on the chemical composition, microstructure and... more
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Microstructure modification of amorphous titanium oxide thin films during annealing treatment
by Nicolas Martin

1997, Thin Solid Films

Thin films of titanium oxide have been deposited on (100) silicon wafers and on quartz substrates by reactive r.f. magnetron sputtering from a 99.6% pure Titanium target. Amorphous and overoxidised coatings (TiO2. 2) have been obtained... more
Fig. 6. The evolution of absorption coefficient with wavelength of titanium oxide films as deposited and for various annealing temperatures until 700 °C.
Fig. 2. Conditions for the occurrence of amorphous, anatase or rutile TiO, films structure. Energy of the particles impinging on the substrate and substrate temperature are the relevant parameters (Lobl et ai. [7]).
Fig. 8. Optical absorption spectrum of titanium oxide films plotted as a'!/? ys. photon energy (E) graphs. The influence of the annealing temperature on the optical bandgap can be determined.
Fig. 5. The variation of refractive index as a function of wavelength of titanium oxide films before heat treatment and for annealing temperatures contained between 300 °C and 700 °C. Fig. 4 shows, the transmission spectrum of annealed coatings (6000 A thick) in air for 1 h and for different temperatures. It can be seen that the transmittance of the films decreases weakly when the materials are calcined up to 700 °C. Since XRD analyses did not show a change of structure until 700 °C but only the presence of anatase phase, it can be assumed that coatings become denser and denser with the annealing temperature. Then, refractive index has been determined in order to show the densifica- tion (since the optical transmission of coatings annealed at 900 °C and 1100 °C is too weak in the visible region,
Fig. 9. Surface morphology by AFM of titanium oxide films deposited by reactive r.f. sputtering magnetron. Coatings have been annealed in air at differen temperatures for 1 h. (a) as-deposited, (b) 300 °C, (c) 700 °C, (d) 900 °C, (e) 1100 °C, @) 1100 °C.
Fig. 3. Influence of the annealing temperature on the tetragonal structure of titanium oxide films deposited by reactive r.f. sputtering magnetron. Evolution of cell parameters of rutile and anatase phases.
Fig. 4. Optical transmittance as a function of wavelength of titanium oxide thin films deposited on quartz substrates at 150 °C and annealed in air for 1 h for different temperatures up to 1100 °C.
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Comparison with anatase and rutile powders clearly shows phase transformation. The increase of the annealing temperature causes crystallization of the films. Anatase crystalline structure can be observed from 300 °C until 700 °C. Then, first crystals of rutile appear and the material is completely transformed to rutile when the temperature reaches 1100 °C.
Fig. 7. Effect of annealing in air for different temperatures on the extinction coefficient of titanium oxide thin films deposited on quartz substrates. The absorption coefficient and extinction coefficient have been also calculated from refractive index values with the method described in Ref. [11]. Figs. 6 and 7 show the variations of these optical properties with the wave- length and with the annealing temperature. It is seen that
Fig. 10. The influence of annealing temperature on RMS roughness (R,) of TiO, layers. RMS as calculated (with flatting corrections) on the z scale from the AFM images.
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Sensing characteristics of NiO thin films as NO2 gas sensor
by Simonetta Capone

2002, Thin Solid Films

In this paper we present the results concerning the characterisation of nickel oxide thin films deposited by d.c. reactive magnetron sputtering. Different NiO thin films have been prepared by changing some deposition parameters, as the... more
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Mg doping of thermochromic VO[sub 2] films enhances the optical transmittance and decreases the metal-insulator transition temperature
by Gunnar Niklasson

2009, Applied Physics Letters

Thermochromic films of Mg x V 1−x O 2 were made by reactive dc magnetron sputtering onto heated glass. The metal-insulator transition temperature decreased by ϳ3 K/ at. %Mg, while the optical transmittance increased concomitantly.... more
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Thermochromic multilayer films of VO2 and TiO2 with enhanced transmittance
by Gunnar Niklasson

2009, Solar Energy Materials and Solar Cells

Thermochromic films of VO 2 , as well as multilayer films of VO 2 and TiO 2 , were made by reactive DC magnetron sputtering. Spectrophotometrically measured transmittance and reflectance were used to determine optical constants pertinent... more
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Influence of annealing temperature on RF magnetron sputtered calcium phosphate coatings
by Joop Wolke

1996, Biomaterials

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XPS analysis of new lithium cobalt oxide thin-films before and after lithium deintercalation
by Jean-charles Dupin

2001, Thin Solid Films

Lithium cobalt oxides thin-films, prepared by radio frequency magnetron sputtering and which could be used as positive electrode materials in microbatteries, were studied by X-ray photoelectron spectroscopy. The results have shown two... more
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The grain size effects on the photoluminescence of ZnO/alpha-Al2O3 grown by radio-frequency magnetron sputtering
by Kyoung Hoon Song

2000, Journal of Applied Physics

ZnO thin films were epitaxially grown on α-Al2O3 (0001) substrate by radio-frequency (rf) magnetron sputtering. Among the ZnO films deposited at 550 °C, the film deposited at 80 W has the narrowest full width half maximum (FWHM) of x-ray... more
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Optical and electrochromic properties of oxygen sputtered tungsten oxide (WO 3) thin films
by Aryasomayajula Subrahmanyam

2007, Solar Energy Materials and Solar Cells

Thin films of tungsten oxide (WO 3 ) were deposited onto glass, ITO coated glass and silicon substrates by pulsed DC magnetron sputtering (in active arc suppression mode) of tungsten metal with pure oxygen as sputter gas. The films were... more
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Experimental comparison of N(1s) X-ray photoelectron spectroscopy binding energies of hard and elastic amorphous carbon nitride films with reference organic compounds
by Brian Holloway

2003, Carbon

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In-situ TEM tensile testing of DC magnetron sputtered and pulsed laser deposited Ni thin films
by Rahul Mitra

2003, Acta Materialia

Two nanocrystalline Ni thin films, one prepared via DC Magnetron Sputtering and the other prepared via Pulsed Laser Deposition, were strained in-situ in the Transmission Electron Microscope. Although the grain sizes were similar, the two... more
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Light enhanced gas sensing properties of indium oxide and tin dioxide sensors
by G. Sberveglieri

2000, Sensors and Actuators, B: Chemical

The effects of UV light illumination on the performance of SnO and In O semiconductor gas sensors toward CO and NO are 2 2 3 2 Ž . reported. The sample were prepared with DC sputtering in Ar atmospheres by the Rheotaxial Growth and... more
Fig. 2. Kinetic response to 1 ppm of NO, at room temperature for the SnO, sensor with UV irradiation.
Fig. 1. Kinetic response to 3 ppm of NO, at room temperature in dark conditions for the SnO, sensor. At room temperature, when the sample is irradiated with UV light, the conductance rises. The increase in the
Indium oxide gas sensor results Table 2
Tin oxide gas sensor results Table 1 When the radiation does not change the the lattice, the semiconductor remembers i some time and then gradually ‘‘forgets’’ th The ‘‘impurities’’ introduced into the samp of illumination gradually disappear. chemical com- position of the semiconductor, but produces structural (radiation) defects, i.e., introduces additional disorder into lumination for e event. Radia- tion-induced disorder gradually relaxes itself after the illu- mination has been turned off, the higher the temperature the greater the relaxation rate. Therefore, heating proves to be a factor helping to ‘‘erase’’ the memory of illumination. e by the effect surface and, at last, the sensor is mounted on a microelec tronic socket and introduced in the test chamber.
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General mobility and carrier concentration relationship in transparent amorphous indium zinc oxide films
by David Ginley

2008, Physical Review B

We report the dependence of the electronic properties on the metal composition and oxygen content of transparent conducting amorphous indium zinc oxide ͑a-IZO͒ films deposited by dc magnetron sputtering. a-IZO shows a clear Burstein-Moss... more
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Polycrystalline TiN films deposited by reactive bias magnetron sputtering: Effects of ion bombardment on resputtering rates, film composition, and microstructure
by Lars Hultman

1992, Journal of Vacuum Science &amp; Technology A: Vacuum, Surfaces, and Films

Transmission electron microscopy, x-ray diffraction, and Rutherford backscattering have been used to investigate the effects of ion irradiation during growth on the deposition rate, composition, and microstructure of single-phase... more
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Mn+1AXn phases in the Ti-Si-C system studied by thin-film synthesis and ab initio calculations
by Jens Emmerlich

2004, Physical Review B

Thin films of M n+1 AX n layered compounds in the Ti-Si-C system were deposited on MgO͑111͒ and Al 2 O 3 ͑0001͒ substrates held at 900°C using dc magnetron sputtering from elemental targets of Ti, Si, and C. We report on single-crystal... more
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Advantages of using self-lubricating, hard, wear-resistant MoS2-based coatings
by Nathalie M Renevier

2001, Surface and Coatings Technology

The paper reports a summary of MoS development through years. The properties of MoS coatings can be improved by the 2 2 co-deposition of small amounts of titanium. These MoS rTi composite coatings known as MoST produced by closed-field 2... more
Fig. 6. Influence of hard coatings rubbing on SS AISI 316L counterpart. Two extreme forms of the coatings have been re- ported (low- and high-Ti and MoST), both tested in previous studies [28,29], and wear rates and friction coefficients for MoST coatings are shown in Fig. 4. With increasing load, the friction coefficient decreases and the wear rate increases. The specific wear rate for
Fig. 3. Results from 100-N reciprocating wear test on progressive MoS, and MoST coatings.
Fig. 7. Influence of hard coatings rubbing on Al 311G counterparts.
Fig. 5. MoST tested: (a) dry, 41% R.H.; and (b) under water.
Fig. 9. MoS, matrix and hypothetical titanium addition.
Fig. 1. (a) Initial MoS, RF sputtering; and (b) early MoS, DC sputtered in CFUBMSIP system.
Fig. 2. Deposition of: (a) MoS, and MoS,/titanium composite coatings; and (b) MoS,/material composite coatings. (c) UDP 650/4 (Standa: Research) in a closed-field arrangement. Type II coatings are denser than type I and the basal plane orientation develops in and below the wear track, due to stress-induced crystallisation [19]. These mi- crostructures can be deposited by adjusting the deposi- tion conditions (pressure, deposition rate) or by the incorporation of co-sputtered or multilayer dopants [20]. *.. DC closed-field unbalanced magnetron-sputter ion plating (CFUBMS) as a means of depositing MoS, overcomes some of these problems, and has the advan- tages of close compositional and microstructural con- trol, good adherence and good uniformity. If the mag- netic field of the magnetron is unbalanced [25], the intensity of the bombardment is increased and further
Fig. 4. Results from pin-on-disc testing at 10-, 40- and 80-N loads showing friction coefficient and wear rates for low- and high-Ti MoST coatings. For the MoS,/Ti composite coating (referred as MoST in the paper), three MoS, and one titanium argets were used. A thin adhesion layer of titanium was deposited first and then the substrates were ro- ated to pass in front of each of the targets in turn, so hat a coating consisting of a mixture of MoS, and itanium was deposited. The power on the titanium and MoS, targets was chosen to give a coating with a itanium content of approximately 5-15% (low to high Ti content). The amount of metal in the coating is critical in defining the properties. The coating thickness was typically 1 wm. The titanium target was switched off at the end of the process to ensure a uniform, blue/grey coloration. Temperature during the deposi- tion process was less than 100°C. The wear was tested in a reciprocating wear tester. The results for MoS, and MoST coatings are shown in Fig. 3, illustrating the improvement as the coatings were developed. It should be noted that the first gener- ation of MoS, coatings developed in this study lasted for approximately 100 cycles in this test, and this coat- ing was considered to be a significant improvemen compared to coatings produced by other techniques at hat time. From Fig. 3, it is evident that MoS, and MoST show a very low friction coefficient at 100-N oad, and that the development of the coating has led 0 a coating with a much higher wear life. Incorpora- ion of Ti into MoS, to produce the MoST coating resulted in an increase in life from approximately 3000
Fig. 8. X-Ray diffraction pattern showing: (a) pure MoS,; (b) MoST; (c) MoS, /titanium multi-layer; and (d) pure titanium. TEM cross-section showing MoST coating (from interface to surface: Ti, Ti-MoS, multilayers, MoST, MoS,). Dynamic hardness measurements were performed (conditions reported in [28]). The test gave a spread of results, depending on the Ti concentration in the dif- ferent coatings, but all of the tests give a hardness value for MoST (high Ti) coating of above 15 GPa, with values ranging up to 21 GPa. A Young’s modulus of 138 GPa has been recorded, much higher than typical values for pure MoS, coatings (approx. 70 GPa). MoST has a lower hardness value compared to traditional hard coatings (22 < plastic hardness < 30 GPa) and a lower Young’s modulus than hard coatings (229 < E/(1 — 0”) < 287). Extensive TEM analysis of the MoST coating has been carried out [29]. No multilayers were detected within the bulk of the MoST coatings (low and high titanium content, 5—20 at.%). Selected area diffraction
Fig. 10. (a) Standard production system; and (b) range of applications for MoST (bearings, punches, dies, hobs, cutters). Various tools have been coated with MoST coating for testing by industrial users (Fig. 10). Previous indus- trial test results have been reported for the coating elsewhere [29,30]. The following testing was carried out under conditions determined by the coating users.
Fig. 11. Average resultant force during end milling of AISI 304 stainless steel using TiCN (with coolant) and TiCN + MoST (dry and with coolant) coated inserts.
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Dependence of oxygen flow on optical and electrical properties of DC-magnetron sputtered ITO films
by B. Ocker

1998, Thin Solid Films

Indium-tin-oxide (ITO) thin films have been prepared by DC-magnetron reactive sputtering in an vertical Inline sputtering system. The oxygen content of the ITO films was changed by variation of the sputtering gas composition. All other... more
Fig. 2. Transmission (a) and reflection (b) spectra of the ITO films. For comparison the spectra of the uncoated quartz substrate are also plotted. tion band to the dielectric function derived from the trans- mission measurements and the reflection measurements. The relationship between the complex index of refraction near the energy gap is The Burstein-Moss-Shift as an absorption edge effect because of conduction band filling with free carriers has usually been used for interpreting the experimental variation of the band gap of ITO [13]. Assuming parabolic band edges the energy gap is
Sputtering atmosphere, measured properties, calculated sheet resistivities and figures of merit of the investigated ITO samples
Specific resistivities of ITO films calculated from optical properties
Fig. 4. Plasma frequency w, vs. E gay. The dashed line shows a linear fit to the calculated values of Ea). The agreement between linear fit and calculated values confirms the assumption of parabolic band edges of ITO.
Fig. 3. Complex index of refraction of the ITO samples. In (a) the index of refraction n is plotted, in (b) the extinction coefficient « is shown.
Fig. 1. Specific resistivities and sheet resistances of the ITO films treated in this work vs. oxygen content in sputtering atmosphere. A minimum resistivity o 216.2 »Qcm is achieved at 0.56% oxygen content.
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Influence of dc magnetron sputtering parameters on surface morphology of indium tin oxide thin films
by Duk Young Jeon

2004, Applied Surface Science

Amorphous or crystalline indium zinc oxide (IZO) thin films, which are highly transparent and conducting, were deposited by DC magnetron sputtering. X-Ray diffraction technique was used for analyzing microstructures of the films, and also... more
Fig. 4. Changes of (a) In3d, (b) Zn2p and (c) O1s XPS spectra of IZO thin films as a function of oxygen flow rate. Fig. 4a-c show the XPS peaks of In3d, Zn2p and Ols, respectively. The samples were deposited with different oxygen flow rates at room temperature. The detailed deposition conditions (sample numbers: 1, 3, 4 and 5) are specified in Table 1. Fig. 4a,b indicates no
Fig. 3. (a) Surface roughness change depending upon deposition tem- perature and three-dimensional images of IZO films deposited at (b) RT and (c) 350 °C.
Fig. 7. Transmittance curves depending upon (a) oxygen flow rate, (b) deposition temperature, (c) sputtering gas and (d) heat treatment atmosphere.
Process conditions for depositing IZO thin films (Unspecified units are sccm) Table 1
Fig. 6. Variations of indices of refraction and extinction coefficients depending upon (a), (b) oxygen flow rate, (c), (d) deposition temperature and (e), (f) sputtering gas, respectively.
Fig. 1. XRD spectra taken from IZO thin films deposited on glass substrates depending upon (a) deposition temperature and (b) heat treatment temperature.
Fig. 2. DTA curves of a bare Si wafer and an IZO thin film deposited on Si wafer.
Fig. 5. Variations of the resistivity, the carrier concentration and the mobility of IZO films depending upon (a) oxygen flow rate, (b) sputtering power, (c) substrate temperature and (d) heat treatment atmosphere.
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Tetrahedral amorphous carbon films prepared by magnetron sputtering and dc ion plating
by S. Ravi P. Silva

1996, Journal of applied …

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Electrochemical characterization of TiO2 blocking layers prepared by reactive DC magnetron sputtering
by Sebastian Waita and 
3 more
Gerrit Boschloo
Bernard O Aduda
Gunnar Niklasson

2009, Journal of Electroanalytical Chemistry

This is an author produced version of a paper published in Journal of Electroanalytical Chemistry. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. Citation for the... more
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Preparation of nickel oxide thin films for gas sensors applications
by J. Huran

1999, Sensors and Actuators B: Chemical

In this paper, we present the results concerning the Pt surface modification of nickel oxide thin films deposited by dc reactive magnetron sputtering. Pt very thin overlayers with a thickness of about 3 and 5 nm have been sputtered on the... more
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Physical and structural properties of ZnO sputtered films
by Sheng-Yuan Chu

2002, Materials Letters

In this paper, poly-crystal zinc oxide (ZnO) films with c-axis (002) orientation have been successfully grown on the silicon substrate by r.f. magnetron sputtering technique. The deposited films were characterized as a function of... more
Fig. 5. Roughness of films as a function of substrate temperature. The data of Yamazaki et al.’s [18] report have shown that the the lowered su smooth surface could be obtained at bstrate temperature. As shown in our data, the optimum substrate temperature to obtain the smoothest surface is 300 °C, however, we found that this was not the strongest c-axis (002) orientation. Growing ZnO films at low substrate temperature had stronger c-axis (002) orientation than at high substrate
Fig. 8. Stress of films as a function of annealing temperature. Relieving the stress, postdeposition annealing is a popular method. During annealing process, the atoms of ZnO have energy to rearrange and will reduce t intrinsic stress. On the other hand, the thermal expan- sion coefficient of ZnO is bigger than that of Si, t tensile stress of silicon and compressive stress intrinsic stress will cancel out each other. Since t ZnO films were grown during low sputtering pressure (3x 10~ > Torr), the stress of films was bigger than the other groups [14,19,23]. In Fig. 8, we find that t ne he of he ne annealing temperature about 600°C 1 h in air will make the stress free.
Fig. 4. AFM of ZnO films were deposited by (a) 100 °C and (b) 300 °C substrate temperature.
Fig. 6. Roughness of films as a function of oxygen ratio.
actual deposition begins to delete any contamination on the target surface to make the system stable and reach optimum condition. The ratio of argon to oxy- gen was controlled by the electronic mass flow con- troller. The substrate temperature was monitored utilizing a thermo-coupler attached near the substrate. The substrate heating was initiated to attain the desired deposition temperature. Fig. 2. The surface SEM picture of ZnO Films. (a) Substrate temperature is 100 °C. (b) Substrate temperature is 300 °C. utilizing a thermo-coupler attached near the substrate.
Fig. 3. Cross-sectional view of the ZnO film. (a) Substrate temperature is 100 °C. (b) Substrate temperature is 300 °C. SEM observation by the secondary-electron mode revealed the layer morphology and thickness. Fig. 2 showed the surface microstructures of ZnO films grown in 100 and 300 °C substrate temperature, separately. The other sputtering conditions were the same as shown in Table 1. The film deposited in 100 °C substrate was cloudy with a rough surface. The temperature of substrate controlled the mobility of the
Table 2 C33 (single) is elastic constant C33 of single crystal ZnO. type’s value 1s mainly due to the compressive strain produced within the film. The angular peak position of the deposited film is less than that of the bulk- type’s value. This is because of the uniform state of stress with compressive components parallel to sub- strate. The stress in sputtered ZnO films investigated by various workers has been found associated with interstitial oxygen [14,17,19—21]. The compressive stress would change the elastic constant C33 value. The elastic constant C33 plays an important role in SAW devices; it will change the acoustic wave veloc- ity and the corresponding electromechanical coupling constant k°. The estimated values of lattice constant, stress and C33 were listed in Table 2.
Fig. 1. X-ray pattern of ZnO film with c-axis (002) orientation deposited on silicon substrate. ZnO films were deposited by r.f. magnetron sput- tering system using a Zn target (99.99%) with diam- eter of 3 in. and thickness of 6 mm. Substrate is p-type silicon with (100) orientation. The substrates were thoroughly cleaned with organic solvents and dried before loading in the sputtering system. was down to 6x 10~° Torr using di before introducing the premixed Ar and The chamber ffusion pump O, sputtering gases into the chamber through a precision leak valve and controlled by the main valve of diffusion pump. Throughout all experiments, the target was presput- tered for 15 min under 150-W RF power before the Throughout all experiments, the target was presput-
Fig. 7. Stress of films as a function of substrate temperature.
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Structure, hardness and thermal stability of TiAlN and nanolayered TiAlN/CrN multilayer films
by Harish C Barshilia, Ph D

2005, Vacuum

TiAlN films were deposited on silicon (1 1 1) substrates from a TiAl target using a reactive DC magnetron sputtering process in Ar+N2 plasma. Films were prepared at various nitrogen flow rates and TiAl target compositions. Similarly, CrN... more
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Comparative study of zinc oxide and aluminum doped zinc oxide transparent thin films grown by direct current magnetron sputtering
by Mirela Suchea and 
1 more
Savvas Christoulakis

2007, Thin Solid Films

Pure and aluminum (Al) doped zinc oxide (ZnO and ZAO) thin films have been grown using direct current (dc) magnetron sputtering from pure metallic Zn and ceramic ZnO targets, as well as from Al-doped metallic ZnAl2at.% and ceramic... more
Fig. 3. RMS surface variation as a function of O, concentration in plasma for ZnO and ZAO films.
Fig. 4. UV—VIS transmittance spectra variation with O, concentration in plasma for films grown: a) from Zn metallic target; b) from ZnO ceramic target; c) fror ZnAl2% metallic target; d) from ZAO ceramic target. corresponding full width at half maximum (FWHM deg) o (002) diffraction ranges from 0.862° to 0.304°. In the case of ZAO films the diffraction angle of 26/o ranges from 33.980° for films grown from ZnA12% metallic target, to 34.085° for films grown from ceramic target. The corresponding FWHM deg of (002) diffraction ranges from 0.317° to 0.402°. The diffraction peak position of 20/~@ approaches, but never reaches that of the bulk ZnO which has the value of 34.42°. It is obviously observed hat the films show (002) textures and the (002) peak shifts to ower angle for metallic targets, as well as a decrease of film crystallinity reflected on lower peak intensity and crude peak broadening. Cebulla et al. [10] attributed the lower diffraction angles shift to a significant increase of compressive stress with AFM imaging of the surfaces of ZnO thin films deposited at room temperature from metallic and ceramic targets, under varying O,/Ar flow ratios, are shown in Fig. 3. AFM characterization for the films deposited from a metallic target (Fig. 2a, b ZnO, c, d ZAO) revealed a granular, polycrystalline morphology with grain size decreasing and roughness increas- ing as the oxygen partial pressure in the plasma decreases. In the case of films grown from a ZnO ceramic target (Fig. 2e, f ZnO) the surface had a complete different morphology, which was mainly dominated by grains agglomerations and very tall features while films grown from ZAO ceramic target show a very smooth and homogeneous surface as shown in Fig. 2g, h. The grain size, derived with SPIP from AFM measurements, varied from 50 to 20 nm for ZnO deposited from a metallic
Fig. 2. AFM images of | x 1 um scan size on films grown: a) from Zn metallic target in 80% O, concentration in plasma; b) in 100% O35; c) from ZnAl2% metallic target in 80% O concentration in plasma; d) in 100% O32; e from ZnO ceramic target in 0% O, in plasma; f) in 20% O,; g) from ZAO ceramic target in 0% Oz in plasma; h) in 15% Op.
Fig. 1. a) XRD patterns of ZnO and ZAO films deposited on Corning glass; b) zoom on XRD pattern near (002) reflexion plane of ZnO and ZAO films (grown at RT in a 100%O) or Ar for ceramic targets). It is well known that sputtered ZnO films are highly textured with the c axis perpendicular to the substrate surface. The
Fig. 5. a) UV—VIS transmittance spectra as a function of target material; b) E, variation as a function of O, concentration in plasma for ZnO and ZAO films.
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Thin film TiO2 photocatalyst deposited by reactive magnetron sputtering
by salah din

2003, Thin Solid Films

TiO films were deposited by r.f. reactive magnetron sputtering on non-alkali glass at 200 8C under total gas pressure of 0.3, 2 1.0 and 3.0 Pa with oxygen flow ratio wO y(O qAr)x of 30%. All films showed polycrystalline anatase structure,... more
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Hydrogen sensing characteristics of WO 3 thin film conductometric sensors activated by Pt and Au catalysts
by Kourosh Kalantar-Zadeh

2005, Sensors and Actuators B-chemical

The hydrogen gas sensing performance of platinum (Pt) and gold (Au) catalyst activated WO3 thin films were investigated. The WO3 thin films were deposited onto alumina transducers with platinum inter-digital electrodes using a R.F.... more
Fig. 5. Direct comparison of response magnitude for Pt-W0O3, Au-WO3 and bare WO3 sensors at 70, 262 and 180°C, respectively. mum sensitivity. It is worthy to note that the baseline cur. rent (lair) for the Pt-WO3, Au-WO3 and bare WO3 sen- sors was approximately 0.1nA, 1.9 A and 200nA, respec- tively. Hence, the Au-WO3 sensor would be the easiest of
Fig. 4. Response of (top) Pt-WO3, (middle) Au-WO3 and (bottom) bare WOs sensor towards the Hz pulse sequence (0.125, 0.25, 0.50, 1.0. 0.25 and 0.125%) in air at operating temperature of 70, 262 and 180°C, respectively.
Changes in the conductivity of the WO3 selective layer can be correlated to the exposed gas concentration. Since it is unlikely that the conductivity will be uniform throughout the modified W 03 selective layer, it would be meaningless to compute the absolute parameter of conductivity. Therefore, all results are presented in terms of change in conductivity of the selective layer. An increase or decrease in the conductivity depends on the type o f gas being exposed, either oxidizing or reducing. The sensor response, denoted by S, is the ratio of current at the baseline (Iai) to the current change caused by the target gas (Igas defined as: . For an oxidizing gas, this could be TheAuand Ptactivator layers were deposited on top of the WOs3 thin film, via DC sputtering at room temperature. The thickness of the Pt and Au layers was estimated to be approx- imately 4 and 6 nm, respectively. Due to the relatively small thickness, the layers were assumed to be non-continuous. After deposition, greenish and light blackish colors were ob- served for the Au and Pt films, respectively. Fig. 2 shows a SEM micrograph of the bare alumina substrate. Fig. 3 shows a SEM micrograph of the Au-W0O3 on the alumina substrate. The WO3 grains are visible on top of the unpolished alumina substrate and appear as a thin coating on the alumina grains. Unfortunately, the thin film of Au that was deposited on top of the WO3 is not distinguishable in the SEM image. This could be due to the small thickness deposited. It is assumed that the small white fragments in the micrograph are contam- ination, possibly excess Pt from the inter-digital transducer IDT) fabrication process. The fragments did not appear to be on any of the other devices and are under the WO3 layer.
Fig. 3. Micrograph of Au-W03 (~0.16 »m) on alumina substrate. Fig. 1. Cross-section of conductometric sensor structure. Each sensor was tested separately, however, care was taken to ensure that the sensors were tested under the same condi- tions using the same testing protocol. The sensors were placed in a computerised multi-channel gas calibration system. The system was used to mix and deliver six pulses of Hz gas in synthetic air at a constant flow rate of 0.2 l/min. The H2 gas concentration of each of the six pulses in the sequence was 0.125, 0.25, 0.50, 1.0, 0.25 and 0.125%. This sequence was exposed to the sensor at each tested operating temperature. Synthetic air was used as both the reference (baseline) gas
Acknowledgment Fig. 6. Response magnitude vs. operating temperature: (top) Pt- WOs3, (mid- dle) Au-W0O3, (bottom) bare WO3. Platinum and gold catalyst activated WO3 conductomet- ric sensors were tested towards H2 concentration below 1% in air. The sensors were based on alumina conductometric substrates with platinum inter-digital electrodes. Maximum sensitivity for the Pt-WO3, Au-WO3 and bare WO3 sen- sors were obtained at operating temperatures of 70, 262 and 180°C, respectively. The response of the sensors with Pt and Au activator layers showed that they are approximately 161 and 40 times more sensitive than the bare WO3 film, respec- tively. The response of the Au-W0O3 sensor was found to be more stable than that of the Pt-WO3, although it required a significantly higher operating temperature. the three sensors to develop signal conditioning and inter face circuitry. 4. Conclusions
Fig. 2. Micrograph of alumina substrate.
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Bacterial cellulose membrane as flexible substrate for organic light emitting devices
by Cristiano Legnani

2008, Thin Solid Films

Bacterial cellulose (BC) membranes produced by gram-negative, acetic acid bacteria (Gluconacetobacter xylinus), were used as flexible substrates for the fabrication of Organic Light Emitting Diodes (OLED). In order to achieve the... more
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Photoluminescence and Raman spectroscopy in hydrogenated carbon films
by S. Ravi P. Silva

1997, Magnetics, IEEE …

films prepared by DC-magnetron sputtering in an :Ar mixture exhibit strong p~o t~l~r n i~e s c e~c~ (P peaks superimposed upon the Raman § c a t t e~~~g spectrum. PL becomes observable at a ent of ca. 34%, and increases expmentially en by... more
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Carrier transport in polycrystalline ITO and ZnO:Al II: The influence of grain barriers and boundaries
by Klaus Ellmer

2008, Thin Solid Films

ITO and ZnO:Al films have been deposited by magnetron sputtering from ceramic and metallic targets at different substrate temperatures and with different plasma excitation modes: DC and RF (13.56 and 27.12 MHz). Temperature-dependent... more
Fig. 3. (a) Carrier concentration and (b) mobility of ZnO:AlI films prepared at different oxygen partial pressures and plasma excitation frequencies as a function of the temperature from 300 to 50 K. The films have the following carrier concentrations in [em >}: () 2.2-10'°, (O) 1.1- 107°, (>) 1.9- 107°, (A) 2.4-10°°, (@) 2.6: 107°, (Ml) 7: 107°.
In order to shed light into the effective transport processes, carrier concentrations and Hall mobilities were also measured Fig. 2. (a) Carrier concentration and (b) mobility of ITO films prepared at different oxygen partial pressures and plasma excitation frequencies as a function of the temperature from 300 to 50 K. For some samples fit curves have been drawn (see text). The films have the following carrier concentrations in [om 3}: (@) 6.2: 10'7, (A) 3.3-10'8, (@) 2.3: 10!, (C1) 6.8- 101°, () 8.3-10!°, (#) 1.5- 107°, (OC) 3.1- 107°, (>) 4.6: 107°.
Fig. 1. (a) Hall mobility data (own measurements and literature data) as a function of the carrier concentration for ITO films. The films have been deposited by DC, RF (13.56 and 27.12 MHz) at room temperature (RT) and at 300 °C. For comparison some data from literature have been added: Szczyrbowski et al. (+, diode sputtering at 400 °C) [40], Hamberg and Granqvist (®, electron beam evaporation) [41] and Frank and K6stlin (#, spray pyrolysis at 500 °C) [42]. The dotted lines are the fits with the model of combined grain barrier and ionized impurity scattering for room temperature (Xl) and 300 °C (L) depositions. (b) Hall mobility data (own measurements and literature data) as a function of the carrier concentration for undoped ZnO and doped ZnO:Me films deposited onto float glass (MM) as well as sapphire substrates (A, >, <))[27]. For comparison, data from literature have been added, which were reported for films deposited by magnetron sputtering and by pulsed laser deposition (PLD): Minami et al. (1, #, @ — PLD) [6], Brehme et al. (V, V) [2], Kon et al. (J) [43], Suzuki (O — PLD) [44] and Lorenz et al. (®, ® — PLD) [45]. The thin lines are the fits with the model of combined grain barrier and ionized impurity scattering for the data sets of different authors: — Lorenz etal. [45], Minami et al. [6], Ellmer and Vollweiler, [27], -+ Kon et al. [43],--- Brehme et al. [2]. The thick lines, marked by c-In,O; and c-ZnO, are semiempirical fit curves for the reported mobility data of single crystalline In.03 and ZnO (@), respectively, (see [8]).
Fig. 4. Seebeck coefficients of ITO and ZnO:AI films deposited at different oxygen partial pressures and plasma excitation frequencies as a function of the carrier concentration. The films have the following deposition parameters: (A) ITO, 13.56 MHz, 300 °C, (W) ITO, 27.12 MHz, 300 °C, (P) ITO, DC, 300 °C, (A) ITO, 27.12 MHz, 25 °C, (0) ZnO, DC, 25 °C. Theoretical curves (Eq. (9)) are shown for ITO and ZnO:Al which fit to the experimental data for N>10'° cm * only if different scattering exponents y in Eq. (9) were used for ITO and ZnO, respectively: ITO (- - -), y=—0.5 (left)...0 (right) ZnO:Al (~), y= 1.5 (left)...2 (right).
Scattering processes in metals (according to [16,17])
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