Fermi-Level Tuning of Epitaxial Sb2Te3 Thin Films on Graphene by Regulating Intrinsic Defects and Substrate Transfer Doping

High-quality Sb2Te3 films are obtained by molecular beam epitaxy on a graphene substrate and

investigated by in situ scanning tunneling microscopy and spectroscopy. Intrinsic defects responsible for

the natural p-type conductivity of Sb2Te3 are identified to be the Sb vacancies and SbTe antisites in

agreement with first-principles calculations. By minimizing defect densities, coupled with a transfer

doping by the graphene substrate, the Fermi level of Sb2Te3 thin films can be tuned over the entire range

of the bulk band gap. This establishes the necessary condition to explore topological insulator behaviors

near the Dirac point.