Structural and luminescence studies on TiO2-MoO3 thin films

Abstract

Thin films of MoO3 and TiO2-MoO3 were deposited on quartz glass and Silicon (100) substrates by dc magnetron sputtering at two substrate temperatures of 300 K and 600 K and at two sputtering pressure of 5 Pa and 10 Pa and sputtering power of 50 W respectively. The deposited films were characterized by X-ray Photo Electron Spectroscopy (XPS), Raman and photoluminescence spectra. The pure MoO3 films deposited at 300 K exhibited the Raman bands at 242 cm−1 and 974 cm−1 indicating the absorption of water molecules and formation of alpha MoO3-H2O. With increasing Ti content the bands are shifted to 224 cm−1 and 960 cm−1 that correspond to h-MoO3 and absorption of water molecules. For Ti at. % of 2.4 the bands were observed only at low frequencies but at high temperatures, a single peak noticed at 954 cm−1 corresponds to α – MoO3 H2O. The Photo-luminescence spectrum reveals that the MoO3 films deposited at 5 Pa and 300 K exhibits Near Band Edge (NBE) transition at 324 nm. The intensity of NBE increases further and with corresponding shift towards higher wavelength with TiO2 doping. The TiO2 doping also introduces Deep Level (DL) emission in TiO2-MoO3 composite film. With increase of deposition temperature the intensity of emission due to NBE in MoO3 films decrease introducing DL emission. The TiO2 doping enhances the intensity of both NBE and DL emission with a shift in emission wavelength towards higher value. The intensity of these NBE and DL emissions are further increasing with increasing sputtering pressure (10 Pa) and deposition temperature (600 K) of MoO3 and TiO2-MoO3.