Surface potential dependence of the topological insulator Bi2Se3 studied by scanning photoemission and Kelvin probe microscopy

The atomic composition and electronic structure of topological insulators (TI) Bi2Se3 2 Se 3 grown by the two- temperature Physical Vapor Deposition on n-type Si patterned substrates, have been followed in details during slight variations of the growth temperatures and values of thickness close to that of the topological transition (about 6 nm), by means of submicron lateral probe photoemission with enhanced surface sensitivity (less than 1 nm). Raman and atomic force microscopy together with Kelvin probe microscopy provide a coherent picture where the fine tuning of Se doping and of the growth temperatures constrain the on-set of the gapless state at the exact middle point of the gap.