The development of the physical and electrical characteristics of multi-layer TiO2–W–TiO2 thin films

In this study, two different thin films, TiO 2 thin film and TiO 2 –W–TiO 2 multi-layer thin films (W, tungsten), are prepared by RF magnetron sputtering onto glass substrates. The crystal structure, morphology, and transmittance of TiO 2 and TiO 2 –W–TiO 2 multi-layer thin films are investigated by X-ray diffraction, SEM, and UV-Vis spectrometer, respectively. The amorphous, rutile, and anatase TiO 2 phases are observed in the TiO 2 thin film and in the TiO 2 –W–TiO 2 multi-layer thin films. The deposition of tungsten as the inter-layer will have large effect on the transmittance and phase ratios of rutile and anatase phases in the TiO 2 –W–TiO 2 multi-layer thin films. The crystal intensities of amorous TiO 2 will decrease as the tungsten is used as the middle layer in the multi-layer structure. The band gap energy values of TiO 2 thin film and TiO 2 –W–TiO 2 multi-layer thin films are evaluated from ( α h ν ) 1/2 versus energy plots, and the calculated results show that the energy gap decreases from 3.21 eV (TiO 2 thin film) to 3.08∼3.03 EV (TiO 2 –W–TiO 2 multi-layer thin films).