XPS study of Sb-/In-doping and surface pinning effects on the Fermi level in SnO2 (101) thin films

To investigate the doping and surface electron accumulation layer properties of tin dioxide (SnO2), the Fermi level and surface band bending of unintentionally-, antimony (Sb)-, and indium (In)-doped SnO2 (101) films were investigated by aluminum and hard x-ray photoelectron spectroscopy, which probe surface and bulk regions, respectively. The Fermi level was above the conduction band minimum (CBM) for unintentionally-doped films and for highly Sb-doped films, which showed the conduction band feature, and deep in the band gap for In-doped films. The band bending and surface Fermi level indicated a surface Fermi level pinning in the CBM.