Browsing by Author "Lang, N. D."

Now showing 1 - 3 of 3
  • Thumbnail Image
    Comment on "First-principles treatments of electron transport properties for nanoscale junctions"
    Lang, N. D.; Di Ventra, M. (American Physical Society, 2003-10)
    The use of a jellium model for the electrodes gives a good account of the conductance of a gold nanowire linking two metallic electrodes. The statement to the contrary in the recent paper of Fujimoto and Hirose [Phys. Rev. B 67, 195315 (2003)] is based on an incorrect positioning of the edge of the jellium relative to the outermost lattice plane of the electrode it represents.
  • Thumbnail Image
    Effects of geometry and doping on the operation of molecular transistors
    Yang, Z. Q.; Lang, N. D.; Di Ventra, M. (AIP Publishing, 2003-03)
    We report first-principles calculations of current versus gate voltage characteristics of a molecular transistor with a phenyldithiolate molecule as active element. We show that (i) when the molecule is placed in proximity to the gate electrode, current modulation and resonant tunneling can occur at very small gate voltages. This is due to the first-order perturbation of the electronic states induced by the electrostatic potential of the gate in the molecular region. Such perturbation is present even if the molecule does not have an intrinsic dipole moment. (ii) The molecular transistor can be converted from n-type to p-type by the simple co-adsorption of a single oxygen atom placed near the molecule. While the latter finding suggests that the character of molecular transistors can be easily changed by doping the electrode surfaces, it also puts severe constraints on the experimental control of such structures for molecular electronics applications. (C) 2003 American Institute of Physics.
  • Thumbnail Image
    Transport in nanoscale conductors from first principles
    Di Ventra, M.; Lang, N. D. (American Physical Society, 2002-01)
    We describe a first-principles atomistic approach to calculate the electronic and atomic dynamics of nanoscale conductors under steady-state current flow. The approach is based on a self-consistent solution of the Lippmann-Schwinger equation within the density-functional formalism for a sample connected to two bare metallic electrodes with a finite bias. Three-terminal device geometries can also be described easily using the present approach. The formalism provides the most fundamental quantities to describe the dynamics of the whole system: the self-consistent electronic wave functions. With these, the forces on the atoms are determined according to a Helmann-Feynman-like theorem that takes into account the contribution of the continuum of states as well as of the discrete part of the spectrum. Examples of applications will be given in the case of molecular devices with different anchoring groups at the interface between the molecule and the electrodes. In particular, we find that conductances close to the quantum unit (2e(2)/h) can be achieved with a given molecular structure simply by increasing the atomic number of the anchoring group..