Interplay between magnetic impurities and photoinduced carriers in surface depletion layer of anatase Ti_1-x Co_x O_2-δ thin film probed by x-ray photoemission spectroscopy

X-ray photoemission spectroscopy measurements with ultraviolet laser illumination have been performed for anatase Ti_1-x Co_x O_2-δ thin films with x=0.05 and 0.10 in order to investigate the interplay between the Co spins and the photoinduced carriers in the surface region. We have found that the surface band bending is removed by the ultraviolet illumination, indicating that photoinduced carriers are injected into the surface depletion layer. After the carrier injection, the position of the chemical potential is governed by the exchange splitting of the Ti ^3d conduction band due to the magnetic interaction between the photoinduced carriers and the Co spins.