Formation of Co nanoclusters in epitaxial Ti_{0.96} Co_{0.04} O_2 thin films and their ferromagnetism

摘要: Anatase Ti0.96Co0.04O2 films were grown epitaxially on SrTiO3 (001) substrates by using plused laser deposition with in-situ reflection high-energy electron diffraction. The oxygen partial pressure, PO2, during the growth was systematically varied. As PO2 decreased, behavior changed from a 2-dimensional layer-by-layer-like to 3-dimensional island-like one, which resulted in an increase saturation magnetization. These structural and magnetic changes explained terms of formation cobalt clusters whose existence proved transmission-electron-microscopie studies. Our work clearly indicates that clustering will cause room-temperature ferromagnetism Co-doped TiO2 films.