Abstract
Multilayered Co-doped TiO2 thin films with postannealing treatment were investigated. Based on x-ray photoelectron spectroscopy, Co(II) binding state was found after annealing. Its intensity increases with the annealing temperature. Postannealing in an ultrahigh vacuum system is an efficient way to drive Co atoms to diffuse into TiO2. It is interesting to find that samples with partial cosputtering structure have a much stronger Co(II) peak than those of pure multilayer structure. Transmission electron microscope patterns show that the annealed films have a polycrystal rutile-TiO2 phase. The saturation magnetization of annealed sample at 150 K is 1.325 u(B) per Co atom, which is close to the value expected for low-spin Co(II). (C) 2004 American Institute of Physics.