Suppressing carrier density in (Bi x Sb1− x )2Te3 films using Cr2O3 interfacial layers

Abstract

Band structure engineering and interfacial buffer layers have been demonstrated as effective means to tune the Fermi level in topological insulators (TIs). In particular, the charge compensated compound (Bi x Sb1−x )2Te3 (BST) plays a critical role in the molecular beam epitaxy growth of magnetic TIs. Here we introduce a strategy of exploiting epitaxial Cr2O3 as a buffer layer and amorphous Cr2O3 as a capping layer in the growth of BST films. These films exhibit carrier density lower than 1012 cm−2 over a wide range of Bi contents and higher mobility than BST films directly grown on Al2O3 substrate, shedding light on the importance of interfacial layers for TI films and paving a new avenue to the application of magnetic BST films.