Steve Bailey

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Carbon Nanotube Electron Windmills: A Novel Design for Nanomotors

Physical Review Letters, Jun 24, 2008

We propose a new drive mechanism for carbon nanotube (CNT) motors, based upon the torque generate... more We propose a new drive mechanism for carbon nanotube (CNT) motors, based upon the torque generated by a flux of electrons passing through a chiral nanotube. The structure of interest comprises a double-walled CNT, formed from, for example, an achiral outer tube encompassing a chiral inner tube. Through a detailed analysis of electrons passing through such a "windmill", we find that the current due to a potential difference applied to the outer CNT generates sufficient torque to overcome the static and dynamic frictional forces that exists between the inner and outer walls, thereby causing the inner tube to rotate.

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Electrical Properties of Sculpturenes

arXiv: Mesoscale and Nanoscale Physics, 2015

We investigate the electronic properties of sculpturenes, formed by sculpting selected shapes fro... more We investigate the electronic properties of sculpturenes, formed by sculpting selected shapes from bilayer graphene, boron-nitride or graphene-boron-nitride hetero-bilayers and allowing the shapes to spontaneously reconstruct. The simplest sculpturenes are periodic nanotubes, containing lines of non-hexagonal rings. More complex sculpturenes formed from shapes with non-trivial topologies, connectivities and materials combinations may also be constructed. Results are presented for the reconstructed geometries, electronic densities of states and current-voltage relations of these new structures.

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Phase-coherent tunneling through a mesoscopic superconductor coupled to superconducting and normal-metal electrodes

Physical Review B, 1999

Phase-coherent diffusive transport through mesoscopic hybrid superconductor/normal metal tunnelin... more Phase-coherent diffusive transport through mesoscopic hybrid superconductor/normal metal tunneling structures is investigated. For a Ns -S two-barrier tunneling system with bulk S and N electrodes coupled by a mesoscopic superconducting constriction s, zero-bias conductance and non-linear I-V curves are calculated under the assumption that the dwell times of quasiparticles in the s region is shorter than inelastic relaxation time. It is shown that the low voltage conductance of this system determined by the Andreev reflection processes may exceed the conductance in the normal state and its value is very sensitive to the weak pairing interaction of electrons in the s region. We show that even weak pairing electron interaction may result in the significant qualitative and quantitative change of the conductance temperature dependence with respect to the case of structures with the normal mesoscopic region. We calculate the I-V curves and show that they depend on the applied voltage in a non-monotonic way, therefore differential conductance becomes negative with increasing voltage. Such behavior is due to the voltage dependence of the order parameter in the constriction and the phase difference ϕ between the S and s superconductors. It is shown that if the tunneling processes determine the form of the quasiparticle distribution function in the s superconductor, the phase ϕ is stationary at arbitrary voltages. For quasiparticle tunneling interferometers in which the mesoscopic superconductor, s, couples the superconductor, S, and the normal metal, N , the zero bias conductance, as a function of the phase difference between the S electrodes is investigated. It is shown that the amplitude of the conductance oscillations may exceed the conductance of this structure in the normal state.

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Sensing single molecules with carbon–boron-nitride nanotubes

Journal of Materials Chemistry C, 2015

We investigate the molecular sensing properties of carbon nanotube–boron nitride–carbon nanotube ... more

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Application of Molecular Electronics Devices in Digital Circuit Design

Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2009

The Breit-Wigner resonance formula is used to model a class of molecular electronic devices, in o... more The Breit-Wigner resonance formula is used to model a class of molecular electronic devices, in order to establish an abstract model for exploration of their applicability in future nanoelectronic systems. The model is used to characterize molecular device I-V curves in terms of the coupling between the molecule and the leads, and demonstrate digital circuit functionality. Circuit metrics such as noise margin, speed and power are investigated.

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Designing Reliable Digital Molecular Electronic Circuits

Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2009

Reliability is expected to be a critical challenge in designing future molecular electronic circu... more Reliability is expected to be a critical challenge in designing future molecular electronic circuits. Using a compact model that captures the essential physics of the device, the effect on digital gate functionality of variations in the device parameters, as well as the improvements afforded by a TMR majority gate structure are quantified. It is shown that the improvement is substantial, showing the potential viability of such technologies in future massively integrated systems.

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Molecular electronics device modeling for system design

2007 7th IEEE Conference on Nanotechnology (IEEE NANO), 2007

We have used the Breit-Wigner resonance formula to model a class of molecular electronics devices... more We have used the Breit-Wigner resonance formula to model a class of molecular electronics devices with the aim to establish an abstract model for a molecular electronic device that can be used in a general cross bar architecture of future nanoelectronic systems. We show that the molecular I-V curves can be characterized by a very small number of variables including the couplings between the contact and leads.

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Zener quantum dot spin filter in a carbon nanotube

Journal of Physics: Condensed Matter, 2006

We predict and analyse a novel spin filter in semiconducting carbon nanotubes. By using local ele... more We predict and analyse a novel spin filter in semiconducting carbon nanotubes. By using local electrostatic gates, the conduction and valence bands can be modulated to form a double-barrier structure. The confined region below the valence band defines a Zener quantum dot, which exhibits resonant tunnelling. The resonances split in a magnetic field to make a bipolar spin filter for applications in spintronics and quantum information processing. We model this using k• p envelope function theory and show that this is in excellent agreement with a corresponding tight-binding calculation.

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Towards molecular spintronics

Nature materials, 2005

The ability to manipulate electron spin in organic molecular materials offers a new and extremely... more The ability to manipulate electron spin in organic molecular materials offers a new and extremely tantalizing route towards spin electronics, both from fundamental and technological points of view. This is mainly due to the unquestionable advantage of weak spin-orbit and hyperfine interactions in organic molecules, which leads to the possibility of preserving spin-coherence over times and distances much longer than in conventional metals or semiconductors. Here we demonstrate theoretically that organic spin valves, obtained by sandwiching an organic molecule between magnetic contacts, can show a large bias-dependent magnetoresistance and that this can be engineered by an appropriate choice of molecules and anchoring groups. Our results, obtained through a combination of state-of-the-art non-equilibrium transport methods and density functional theory, show that although the magnitude of the effect varies with the details of the molecule, large magnetoresistance can be found both in t...

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Single channel conductance of H $ _2 $ molecules

TRINITY COLLEGE DUBLIN COLLABORATION, LANCASTER UNIVERSITY COLLABORATION -We report a detailed th... more TRINITY COLLEGE DUBLIN COLLABORATION, LANCASTER UNIVERSITY COLLABORATION -We report a detailed theoretical study of the atomic arrangement and conduction channels of an H 2 molecule joining either Platinum or Palladium electrodes. We find that the bonding state of the molecule does not hybridize with the leads if the molecule forms a bridge, thereby providing a single conductance channel. On the contrary, both channels hybridize heavily, leading to high conductances, if the molecule lies perpendicular to the electrodes,. We propose that the occurrence of additional transitory peaks in conductance histograms of Pd electrodes are due to the dissolution of Hydrogen atoms in the neighborhood of the bridge, which form metastable states.

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Electron transport through single molecular wires

Using a scattering technique combined with density-functional theory, a computational study of el... more Using a scattering technique combined with density-functional theory, a computational study of electron transport through two recently synthesized molecules is presented. The effect of connecting the molecules to gold electrodes is studied by iteratively increasing the number of gold layers, treated self -consistently as part of the molecule.

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