Investigate the Nb doping position and its relationship with bulk topological superconductivity in NbxBi2Se3 by X-ray photoelectron spectra

The relationship between the doping position of Nb in Bi 2 Se 3 and its superconductivity is investigated by XPS, magnetic measurement and transport measurement. It is found that for Nb x Bi 2 Se 3 , the main impurity phase comes from BiNbSe 3 . Superconducting volume fraction of Nb doped Bi 2 Se 3 increases with the ratio of Nb inserted in the van der Waals layers. The van der Waals-layer-position doped Nb may lead to superconductivity in Bi 2 Se 3 . This work may stimulate further investigation on topological superconductivity mechanism of Nb x Bi 2 Se 3 .