Preparation and characterization of TiO2 thin films by sol-gel method

Abstract

Titanium dioxide (TiO2) thin films have been deposited on silicon and glass substrates by the sol-gel process using titanium iso-propoxide [Ti(O-i-C3H7)4]. The bond configuration of the TiO2 thin films was analyzed by using FTIR in the wavenumber range from 400 to 4000 cm−1. The spectral transmittance of as-deposited TiO2 films deposited on fused silica glass was measured in the wavelength range from 200 to 900 nm. X-ray diffraction measurements were performed to determine the crystallinity of the TiO2 films. As-deposited films were amorphous. As the film was annealed at higher temperature, the structure was transformed from amorphous to the anatase crystalline state. The chemical composition of the deposited film was investigated using X-ray photoelectron spectroscopy (XPS). The films are essentially stoichiometric with carbon as the dominant impurity on the surface. Raman spectra show the characteristic of TiO2 anatase phase. The electrical properties of the TiO2 films were measured using capacitance-voltage (C-V) and current-voltage techniques. From C-V measurements, the dielectric constants were calculated to be approximately 26 for the as-deposited films and 75–82 for films annealed at 700°C in different atmosphere. For the as-deposited samples, the breakdown voltage was 2.7 MV/cm, and for an electric field of 1 MV/cm, the leakage current was 5 × 10−5 A/cm2 and the resistivity was 2.2 × 1010 Ω-cm.