Microscopic and spectroscopic analysis of tungsten trioxide and titanium-doped tungsten trioxide thin films

Tungsten oxide (WO3) has been a subject of high interest for its unique properties, and recently for its importance in different types of industrial applications which ranges from non-emissive displays, optical, microelectronic, catalytic/photocatalytic, humidity, temperature, gas, and biosensor devices. In this study, WO3 and Ti doped thin films were prepared using radio frequency magnetron reactive sputtering at different substrate temperatures ranging from room temperature to 500 °C in increments of 100 °C. After forming a hypothesis based on knowledge of established WO3 properties, we attempt in this work to investigate how the doping influences the roughness and the mean grain size of the nanoparticles on the surface layer of the thin films, its structure, and crystallinity. Therefore we pursued analysis by Atomic Force Microscopy (AFM), X-ray diffraction (XRD), and Raman spectroscopy, using a comparative approach. The outcomes of these analyses demonstrate that higher temperatures are necessary for growing crystalline material if doping is used. Also, smaller nanoparticles are obtained when a small amount of dopant, e.g. 5% Ti, is incorporated. Both XRD and Raman measurement indicate morphological changes of the doped material. Finally, annealing of the amorphous doped samples at temperatures of 600 °C and 900 °C did not contribute significantly to material properties improvement