FERMI LEVEL TUNING IN TOPOLOGICAL INSULATORS: MOLECULAR DOPING OF Bi\(_{2}\)Te\(_{2}\)Se (BTS) SURFACES

Abstract

Fermi level tuning in Bi\(_{2}\)Te\(_{2}\)Se crystals is investigated with the use of X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Spectra of clean BTS samples are compared with spectra after solution deposition of tetrachloro-o-benzoquinone and phenanthrenequinone at 0.5 mM, 1 mM, and 5 mM concentrations. XPS spectra of reacted samples display prominent oxidation features, consistent with chemisorbed quinone species. Tetrachloroobenzoquinone reacts to a greater extent with BTS surfaces than phenanthrenequinone. UPS spectra suggest Fermi level shifts on the order of 0.5 eV for 5 mM concentrations and indicate a possible trend of larger shifts corresponding to both increasing concentration and oxidative ability of the quinone.