Measuring transport anisotropy in Cu/Si multilayers using weak localization

Abstract

We have determined the anisotropy of electron transport in a series of Cu/Si multilayers, by measuring their low-temperature transverse magnetoresistance due to weak localization (WL). For each sample, the measurements were carried out for two different orientations of the applied magnetic field: parallel and perpendicular to the plane of the sample film. Using an analysis based on an anisotropic 3D theory of WL we find that the ratio of the in-plane and out-of-plane components of the electron diffusivity, , varies from essentially 1 to more than 2 as the ratio of the Cu to Si nominal layer thicknesses is increased. X-ray diffraction studies indicate the formation of a copper silicide at the interfaces of the multilayers, and a simple stratified conductor model based on this provides an estimate of the anisotropy that is consistent with that measured through the magnetoresistance. In some samples the magnetoresistance shows departures from the expected WL behaviour that are consistent with the presence of superconducting fluctuations.