Surface state conductivity in epitaxially grown Bi1-xSbx(111) films

Abstract

Topologically non-trivial surface stateswere reported first on Bi1-xSbx bulk crystals. In this studywe present transportmeasurements performed on thin Bi1-x1-xSbx-films (up to 24 nmthickness) grown epitaxially on Si(111) with various Sb-concentrations (up to x=0.22). The analysis of the temperature dependency allowed us to distinguish between different transport channels originating from surface and bulk bands as well as impurity states. At temperatures below 30 Kthe transport is mediated by surface states while at higher temperatures activated transport via bulk channels sets in. The surface state conductivity and bulk band gaps can be tuned by the Sb-concentration and film thickness, respectively. For films as thin as 4 nmthe surface state transport is strongly suppressed in contrast to Bi(111) films grown under identical conditions. The impurity channel is of intrinsic origin due to the growth and alloy formation process and turns out to be located at the buried interface.