Chemical Characterization of DC-Sputtered In2O3 Films with a Top SnO2 Layer

In2O3 thin films with a top layer of SnO2 were deposited onto glass substrates by DC reactive-magnetron sputtering. After deposition, In2O3/SnO2 samples were annealed in vacuum at 400oC. Structural, optical, and chemical composition was investigated by X-ray diffraction, UV-Vis spectroscopy and XPS, respectively. X-ray data showed that films grow polycrystalline, where indium oxide crystallized in cubic as the main phase, with a preferential growth at the [0002] direction and lattice parameter of 10.11 A. Signals of rhombohedral phase were also detected. XPS depth profiles show that tin coexists in Sn2+ and Sn4+, while indium maintains the In2O3 stoichiometry. Binding energy of Sn4+ bound to oxygen was detected at 468 eV while In2+ bound to oxygen at 444.7 eV. Nor tertiary compounds were detected at the In2O3/SnO2 interface, neither In or Sn in metallic state.