Characterization of RF-sputtered ultra-thin WO3 films grown on TiO2 surface

M. Dobromir, A. Manole, R. Apetrei, D. Luca
Alexandru Ioan Cuza University, RO

Keywords: titanium dioxide, tungsten trioxide, hetero-junctions


We report on TiO2 and WO3/TiO2 bilayers thin films grown on amorphous and crystalline substrates, at room temperature by plasma-assisted sputtering. TiO2/WO3 ceramic targets were used in an RF magnetron discharge running in an Ar + O2 gas mixture. The thickness of the ultra-thin WO3 layer deposited on top of the TiO2 was adjusted by changing the deposition time, while the RF power injected in the discharge remained constant. The XRD patterns of all samples show the presence of a rutile(110) crystalline phase. Film surfaces morphology, as revealed by AFM, is characterized by RMS values decreasing with the increase of the W atomic concentration in the bilayer structure. By analyzing the high-resolution XPS spectra and the valence spectra X-ray photoelectron spectroscopy data, the chemical composition and the band gap values of the sample were inferred. The band gap value of the reference sample (3.07 eV) confirms the presence of the rutile polymorph in the base TiO2 film, while the overall band gap value of 2.53 eV is related to the presence of the top ultra-thin layer of WO3.The current results are significant for the characterization of WO3/TiO2 hetero-junctions, a novel approach to improve the photocatalytic efficiency of titania-based materials.