Nanomechanical shuttle transfer of electrons

Artikel i vetenskaplig tidskrift, 2007

Small metal particles embedded in a material subject to an external electric field can contribute to the conductance by mechanically transporting charge. This was already demonstrated in Millikan's pioneering experiment that proved that charge is quantized. While the effect of charge quantization can be pronounced for submicron conducting particles and lead to Coulomb blockade of W tunnelling, the nanomechanical aspect of single-electron tunnelling becomes prominent only in 5 nanometer-size self-assembled structures. The coupling between mechanical deformations and LU electronic charge transport in composite materials with nanoscale components gives rise to a new class of phenomena-nanoelectromechanical transport-and opens up a new route in nanotechnology. The interplay between the electronic and mechanical degrees of freedom is especially important in nanocomposites consisting of materials with very different elastic properties. A typical system of this kind is a single-electron transistor (SET) with cleformable tunnel barriers, a so called Nano-Electro-Mechanic.al SET (NEM-SET). The new kind of electron transport in this and other types of nanodevices is referred to as "shuttle transport" of electrons, which implies that electrons is transferred between metallic leads via a movable small-sized cluster. The present review is devoted to the fundamental aspects of shuttle transport and to a description of major developments in the theoretical and experimental research in the field. Prospective applications of this exciting phenomenon that remarkably combines traditional mechanics of materials with the most advanced effects of quantum physics, will also be touched upon.