LAUSR

In this work, we have studied the transport properties of two different single crystals, Sb2Te2Se and Sn-doped Sb2Te2Se. By analyzing the Shubnikov–de Haas oscillations for the devices made from both the crystals, we have extracted the Berry phase. The non-trivial value of the Berry phase for both the samples unambiguously indicates the robustness of the topological surface states against the impurity doping. The parent compound is n-type due to excess Te vacancies, and we could show from the sign of the intercept in the Landau level fan diagram and from the Hall effect measurements that doping with Sn makes it p-type. This demonstrates the tuning of the Fermi level in a topological insulator upon Sn doping.