Biomedical subjects

Norton D Lang

Publications and source records attributed to Norton D Lang.

3 recordsLinked to original sources

PubMed2006

The role of chemical contacts in molecular conductance.

Density-functional calculations show that biaryl dithiolates compared with analogues having dicarbene and diisocyanide alligator clips have a lower conductance arising from a lower density of electronic states at the metal electrode Fermi energy. The differences in state density originate from shifts in the energies of molecular orbitals that extend across the molecule to the electrodes. Nonlocal effects consistent with the compounds' electronegativities account for the shifts in orbital energies, beyond the electrostatic potential variations from charge transfer at the metal-molecule interface.

Journal Article↗

PubMed2005

Charge control in a model biphenyl molecular transistor.

We study charge control in a gated 4,4'-biphenyl diradical molecular transistor using ab initio density functional theory calculations. I-V curves and intrinsic gate capacitances were derived. We find charge control in this transistor to be strongly affected by polarization of the sigma-states of the molecule, leading to strong electrostatic coupling of the internal potentials to the source and drain electrodes, and relatively weak coupling to the gate. We suggest that this spatially dependent and anisotropic polarization is an essential element in the operation of molecular transistors.

Biphenyl Compounds↗

PubMed2002

First-principles simulations of molecular electronics.

This paper gives an overview of recent work by the authors in first-principles, parameter-free calculations of electronic transport in molecules in the context of experimental measurements of current-voltage (I-V) characteristics of several molecules by Reed et al. The results show that the shape of I-V characteristics is determined by the electronic structure of the molecule in the presence of the external voltage, whereas the absolute magnitude of the current is determined by the chemistry of individual atoms at the contacts. A three-terminal device has been simulated, showing gain. Finally, recent data that show large negative differential resistance and a peak that shifts substantially as a function of temperature have been accounted for in terms of rotations of ligands attached to the main molecule, a phenomenon that is not present in semiconductor nanostructures.

Benzene↗