Biomedical subjects

George Kirczenow

Publications and source records attributed to George Kirczenow.

4 recordsLinked to original sources

PubMed2006

Controlling the charge of a specific surface atom by the addition of a non-site-specific single impurity in a Si nanocrystal.

We show, by use of self-consistent calculations, that the charge on a radical surface site (RSS) on a hydrogen-terminated silicon nanocrystal can be controlled by the addition of a non-site-specific dopant atom. An RSS is a surface defect where the H-termination is missing. This new effect has important implications for future hybrid semiconductor/molecular nanoelectronics. We also calculate the energy and wave function of the RSS state and its nanoscale interactions with the dopant atom.

Journal Article↗

PubMed2006

A new approach to the realization and control of negative differential resistance in single-molecule nanoelectronic devices: designer transition metal-thiol interface States.

On the basis of ab initio and semiempirical calculations, we predict single alkane dithiolate molecules bridging transition metal nanoelectrodes (including Pd/Rh, Pt/Rh, and Pt/Pt) to exhibit negative differential resistance (NDR). The mechanism is resonant conduction via interface states arising from hybridization between molecular thiol groups and transition metal d orbitals. We show how the NDR realized in this new way can be controlled by tailoring interface state properties through appropriate choice of nanoelectrode transition metals and surface structures.

Computer Simulation↗

PubMed2003

The smallest molecular switch.

Ab initio total energy calculations reveal benzene-dithiolate molecules on a gold surface, contacted by a monatomic gold STM tip to have two classes of low-energy conformations with differing symmetries. Lateral motion of the tip or excitation of the molecule cause it to change from one conformation class to the other and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity, these Au/BDT/Au nanowires are shown to be electrically bistable switches, the smallest two-terminal molecular switches to date.

Journal Article↗

PubMed2002

Charging effects, forces, and conduction in molecular wire systems.

Recently, experiments have shown that effects arising from charging and conformational changes in a molecular wire due to an applied voltage bias can have a significant influence on the transport characteristics of the system. We introduce a tractable theoretical approach based on Landauer theory and total energy methods that treats transport nonlinearities, conformational changes, and charging effects in molecular wires in a unified way. We apply this approach to molecular wires consisting of short chain molecules with different electronic and structural properties bonded to metal contacts. We find that the nonlinear conductance characteristics of these systems are remarkably similar and can be understood in terms of a single physical mechanism. We predict that negative differential resistance should occur at high bias in such molecular wires due to the combined effects of charging and conformational changes on their electronic structure.

Electric Conductivity↗