Senior Researcher, Electro-nanocharacterization Group, Nanomaterial Laboratory, National Institute for Materials Science (NIMS)
Exploration of electron transport phenomena in atomic-scale wires fabricated through surface reconstruction
Various kinds of surface reconstructions can be grown on the surface of clean semiconductor substrates by depositing a monolayer atoms followed by the appropriate processing. Generally, surface reconstructions are fundamentally distinct from their bulk counterparts due to strong interactions with the substrate and low-dimensionality of the systems.
Among the different surface structures, we are focused on one-dimensional (1D) reconstructions, i.e. atomic-scale surface nanowires. Our objectives are to elucidate experimentally their electron transport properties and to develop them for use in nanoelectronics in the future.
One example of 1D surface reconstructions is indium atomic wire arrays on silicon, which are two-atom wide chain assemblies. We have, for the first time, determined their electron transport properties, and remarkably, over a large area, the reconstruction has high conductivity that corresponds to a sheet resistance of about 30 kΩ. Furthermore, current through the atomic wires is strongly suppressed by defects near surface steps and/or a minute amount of point defects introduced into the wires themselves.
The conductivity of the atomic wires decreases drastically at around 130 K, accompanying a metal-insulator transition. The phenomenon, which is interesting from the viewpoint of fundamental physics, is ascribed to the so-called Peierls instability intrinsic to a 1D electron system.
In order to measure the electron conduction through individual atomic-scale wires, we are now developing a technique to connect the wires to microelectrodes without contaminating the sample surface. So far, we have attached microelectrodes to a single erbium disilicide nanowire grown on silicon. In the future, we will incorporate organic molecules into the constructs and utilize the magnetic properties of the wires.
