Effect of calcination on the structural and optical properties of M/TiO2 thin films by RF magnetron co-sputtering

M/TiO2 (M = metal; Ag, Cu) thin films on quartz glass were prepared by RF magnetron co-sputtering process and the calcination effects on their optical and structural properties were investigated. The as-deposited M/TiO2 films are amorphous, and they are the anatase phase at 300-700 degreesC. The Ag-doped films have the anatase phase at 900 degreesC, whereas the Cu-doped films contain the futile phase at 900 degreesC, implying that metal doping affects the temperature of phase transformation from anatase to futile. The crystallite size of the anatase phase and the agglomerates of primary particles of the metal-doped TiO2 thin films increase with increasing calcination temperature. The X-ray photoelectron spectroscopy (XPS) results show that doped-silver is present in the metal state, while doped-copper exists in the mixed metal/oxide state. The as-deposited thin films have high transparency in the visible range. The transmittance of Cu/TiO2 thin films calcined at 900 degreesC is considerably reduced due to the crystal phase transformation, the variation of film composition and the optical scattering effect resulting from increased crystallite size. The absorption edge of transmittance is red-shifted at 900 degreesC due to the change of the optical band gap energy. (C) 2003 Elsevier B.V. All rights reserved.