Chalcogenide-based van der Waals epitaxy: Interface conductivity of tellurium on Si(111)

Abstract

We present a combined experimental and theoretical analysis of a Te rich interface layer which represents a template for chalcogenide-based van der Waals epitaxy on Si(111). On a clean Si(111)-$(1\ifmmode\times\else\texttimes\fi{}1)$ surface, we find Te to form a Te/Si(111)-$(1\ifmmode\times\else\texttimes\fi{}1)$ reconstruction to saturate the substrate bonds. A problem arising is that such an interface layer can potentially be highly conductive, undermining the applicability of the on-top grown films in electric devices. We perform here a detailed structural analysis of the pristine Te termination and present direct measurements of its electrical conductivity by in situ distance-dependent four-probe measurements. The experimental results are analyzed with respect to density functional theory calculations and the implications of the interface termination with respect to the electrical conductivity of chalcogenide-based topological insulator thin films are discussed. In detail, we find a Te/Si(111)-$(1\ifmmode\times\else\texttimes\fi{}1)$ interface conductivity of ${\ensuremath{\sigma}}_{2\mathrm{D}}^{\mathrm{Te}}=2.6(5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}\phantom{\rule{0.28em}{0ex}}\mathrm{S}/\ensuremath{\square}$, which is small compared to the typical conductivity of topological surface states.