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- Michael Nolan, Sean O'Callaghan, Giorgos Fagas, James C Greer, Thomas Frauenheim
- Nano letters
- 2007

Band gap modification for small-diameter (approximately 1 nm) silicon nanowires resulting from the use of different species for surface termination is investigated by density functional theory calculations. Because of quantum confinement, small-diameter wires exhibit a direct band gap that increases as the wire diameter narrows, irrespective of surface… (More)

- Shane McDermott, Christopher B. George, Giorgos Fagas, James C. Greer, Mark A. Ratner
- 2009

Two different first-principles methods, one based on density functional theory combined with Green's functions and the other on a configuration interaction method, are used to calculate the electronic transport properties of alkane and silane chains terminated by amine end groups in metal-molecule-metal junctions. The low-voltage conductance is found to… (More)

- Giorgos Fagas, James C Greer
- Nano letters
- 2009

The influence of local oxidation in silicon nanowires on hole transport, and hence the effect of varying the oxidation state of silicon atoms at the wire surface, is studied using density functional theory in conjunction with a Green's function scattering method. For silicon nanowires with growth direction along [110] and diameters of a few nanometers, it… (More)

A formulation for transport in an inhomogeneous, interacting electron gas is described. Electronic current is induced by a constraint condition imposed as a vector Lagrange multiplier. Constrained minimization of the total energy functional on the manifold of an arbitrary constant current leads to a many-electron Schrödinger equation with a complex,… (More)

- Giorgos Fagas, James C Greer
- Nanotechnology
- 2007

For investigation of electron transport on the nanoscale, a system possessing a simple-to-interpret electronic structure is composed of alkane chains bridging two electrodes via end groups; to date, the majority of experiments and theoretical investigations on such structures have considered thiols bonding to gold electrodes. Recently experiments show that… (More)

- F Murphy-Armando, G Fagas, J C Greer
- Nano letters
- 2010

The role of reduced dimensionality and of the surface on electron-phonon (e-ph) coupling in silicon nanowires is determined from first principles. Surface termination and chemistry is found to have a relatively small influence, whereas reduced dimensionality fundamentally alters the behavior of deformation potentials. As a consequence, electron coupling to… (More)

- Thomas P Kelly, Ajith Perera, Rodney J Bartlett, James C Greer
- The Journal of chemical physics
- 2014

Dissociation energies for the diatomic molecules C2, N2, O2, CO, and NO are estimated using the Monte Carlo configuration interaction (MCCI) and augmented by a second order perturbation theory correction. The calculations are performed using the correlation consistent polarized valence "triple zeta" atomic orbital basis and resulting dissociation energies… (More)

- Lida Ansari, Giorgos Fagas, James C. Greer
- ESSDERC
- 2012

- L. Ansari, B. Feldman, G. Fagas, J. C. Greer
- 2012

In this work, we present atomic scale simulation of junctionless semiconducting single–walled carbon nanotubes field effect transistors (CNT–FETs) and compare their performance to silicon nanowire (SiNW) transistors with similar dimensions. The energy dispersions relations for p–type SiNW and CNT are compared. The response of the transistors to source–drain… (More)

- Thomas M Henderson, Giorgos Fagas, Eoin Hyde, James C Greer
- The Journal of chemical physics
- 2006

The electronic conductance of a molecule making contact to electrodes is determined by the coupling of discrete molecular states to the continuum electrode density of states. Interactions between bound states and continua can be modeled exactly by using the (energy-dependent) self-energy or approximately by using a complex potential. We discuss the relation… (More)