Tuning the Phase and Microstructural Properties of TiO 2 Films Through Pulsed Laser Deposition and Exploring Their Role as Buffer Layers for Conductive Films

Titanium oxide (TiO 2 ) is a semiconducting oxide of increasing interest due to its chemical and thermal stability and broad applicability. In this study, thin films of TiO 2 were deposited by pulsed laser deposition on sapphire and silicon substrates under various growth conditions, and characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), optical absorption spectroscopy and Hall-effect measurements. XRD patterns revealed that a sapphire substrate is more suitable for the formation of the rutile phase in TiO 2 , while a silicon substrate yields a pure anatase phase, even at high-temperature growth. AFM images showed that the rutile TiO 2 films grown at 805°C on a sapphire substrate have a smoother surface than anatase films grown at 620°C. Optical absorption spectra confirmed the band gap energy of 3.08 eV for the rutile phase and 3.29 eV for the anatase phase. All the deposited films exhibited the usual high resistivity of TiO 2 ; however, when employed as a buffer layer, anatase TiO 2 deposited on sapphire significantly improves the conductivity of indium gallium zinc oxide thin films. The study illustrates how to control the formation of TiO 2 phases and reveals another interesting application for TiO 2 as a buffer layer for transparent conducting oxides.