Identifying Native Point Defects in the Topological Insulator Bi2Te3

We successfully identified native point defects that occur in Bi2Te3 crystals by combining high-resolution bias-dependent scanning tunneling microscopy and density functional theory based calculations. As-grown Bi2Te3 crystals contain vacancies, antisites, and interstitial defects that may result in bulk conductivity and therefore may change the insulating bulk character. Here, we demonstrate the interplay between the growth conditions and the density of different types of native near-surface defects. In particular, scanning tunneling spectroscopy reveals the dependence on not only the local atomic environment but also on the growth kinetics and the resulting sample doping from n-type toward intrinsic crystals with the Fermi level positioned inside the energy gap. Our results establish a bias-dependent STM signature of the Bi2Te3 native defects and shed light on the link between the native defects and the electronic properties of Bi2Te3, which is relevant for the synthesis of topological insulator materials and the related functional properties.