The in-plane band bending effect around Au islands grown on the Bi2Te3 topological insulator

We have utilized scanning tunneling microscopy and spectroscopy (STM/STS) as well as x-ray linear dichroism (XLD) along with DFT calculations to determine the structural and electronic changes of the gold-covered nonstoichiometric Bi2Te3 single crystal surface. XLD spectra supported by a numerical simulation of several configurations show that at low coverage (< 1.0 ML) gold forms insoluble islands, while for higher coverage (> 1.0 ML) mixing at the Au/Bi2Te3 interface may occur. For local electronic characterization around stand-alone Au islands, small coverages were selected for which the inter-island distance is large enough to avoid overlapping island-wide effects. STS spectra reveal that for small coverages the topological surface states (TSS) are preserved. However, at a distance of about 10 nm from an Au island, by approaching the islands, the electronic structure gradually changes. This is manifested by a gradual shift of the STS spectra to more negative energies with respect to the pristine surface. The results are discussed in view of possible Au-Bi2Te3 mixing, a local charge transfer and the presence of in-plane downward band bending.