Surface Fermi level tuning in thin epitaxial Bi<i>y</i>Sb2−<i>y</i>Te3−<i>x</i>Se<i>x</i>/Si(111) films

The effects of chemical treatment and aging of BiySb2−yTe3−xSex 3D topological insulator (TI) thin films on the surface electronic structure, morphology, and transport properties have been studied. The surface conditions significantly affect the separation between the Dirac point (DP) and the Fermi level, which is evident in both photoemission and magnetotransport measurements and is explained by the band bending. Depending on the Fermi level's position relative to the DP, the contribution of topological surface states to the nonlinear Hall effect can be solely controlled by the antilocalization effect or enhanced by the effect of gap opening. The wide tuning of the surface Fermi level by the surface/interface modification could be utilized in metal–insulator–semiconductor structures based on a TI thin films.