Doping of n-type Bi2Se3 single crystal with Fe, Ru, Os, and Mo

Doping is one of the most suitable methods for tuning the electronic properties of topological insulators and a promising approach for band gap opening in surface states. In this study, we developed a reliable method for preparing high-quality single crystal substrates comprising Bi2Se3 doped with VIIIB and VIB column elements. We combined experimental photoelectron spectroscopy (X-ray photoelectron spectroscopy, angle resolved photoelectron emission spectroscopy, and ultraviolet photoelectron spectroscopy) and theoretical (ab initio) methods to analyze the electronic properties and chemical states of atoms in the substitutional position and native defects in the topological insulator, which can be achieved using the free melt crystallization method for sample growth. The relationship between the position of the Dirac cone and valence band maximum was explored and discussed.