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 Greens function scatte
ring method. For silicon nanowires with growth direction along [110] and diameters of a few nanometers, it is found that the introduction of oxygen bridging and back bonds does not significantly degrade hole transport for voltages up to several hundred millivolts relative to the valence band edge. As a result, the mean free paths are comparable to or longer than the wire lengths envisioned for transistor and other nanoelectronics applications. Transport along [100]-oriented nanowires is less favorable, thus providing an advantage in terms of hole mobilities for [110] nanowire orientations, as preferentially produced in some growth methods.
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 investig
ations on such structures have considered thiols bonding to gold electrodes. Recently experiments show that well defined molecular conductances may be resolved if the thiol end groups are replaced by amines. In this theoretical study, we investigate the bonding of amine groups to gold clusters and calculate electron transport across the resulting tunnel junctions. We find very good agreement with recent experiments for alkane diamines and discuss differences with respect to the alkane dithiol system.
