Carbon-atom wires: charge-transfer doping, voltage drop, and the effect of distortions

We present first-principles calculations on electrical conduction through carbon atomic wires. The changes in charge distribution induced by a large bias exhibit the primary involvement of the wire's pi states. A significant fraction ( approximately 40%) of the voltage drops across the atomic wire itself. At zero bias, there is a large transfer of charge from the electrodes to the wire, effectively providing doping without introducing scattering centers. This transfer leads, however, to potential barriers at the wire-electrode junctions. Bending the wire reduces its conductance.

First-principles calculation of transport properties of a molecular device

We report first-principles calculations of the current-voltage ( I-V) characteristics of a molecular device and compare with experiment. We find that the shape of the I-V curve is largely determined by the electronic structure of the molecule, while the presence of single atoms at the molecule-electrode interface play a key role in determining the absolute value of the current. The results show that such simulations would be useful for the design of future microelectronic devices for which the Boltzmann-equation approach is no longer applicable.