Surface potential changes of semiconducting oxides monitored by high-pressure photoelectron spectroscopy: Importance of electron concentration at the surface

The Fermi level position at surfaces of tin-doped indium oxide (ITO) thin films has been recorded during oxygen exposure using high-pressure photoelectron spectroscopy at the BESSY storage ring. The rate of Fermi level shifts varies considerably depending on the surface electron concentration, which is determined by the Fermi level position with respect to the energy of surface states.