Chalcogenide-Based Van Derwaals Epitaxy: Interface Conductivity of Tellurium on Si(111)

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 x 1) surface, we find Te to form a Te/Si(111)-(1 x 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 x 1) interface conductivity of sigma(Te)(2D) = 2.6(5) x 10(-7) S/square, which is small compared to the typical conductivity of topological surface states.