Effects of substrate temperature and precursor amount on optical properties and microstructure of CVD deposited amorphous TiO2 thin films

Abstract

In this research, TiO2 thin films were deposited on glass substrate by chemical vapor deposition using tetra isopropylorthotitanate as a precursor at low temperature. The TiO2thin films were formed without using an oxygen source or annealing. Effects of substrate temperature and amount of the precursor on surface microstructure and optical properties of deposited TiO2 thin films were investigated. X-ray diffraction (XRD), UV-visible spectrophotometry and atomic force microscopy (AFM) were used to analyze the fabricated layers. The XRD analysis revealed that structure of all prepared layers was in amorphous phase. Analysis of AFM images showed that by increasing substrate temperature, the layer surfaces became rougher and simultaneously nanoparticle size was more uniform. Texture analysis revealed that increasing substrate temperature and decreasing precursor amount both increased surface isotropy. Thickness of layers was calculated by applying the Swanepoel method to the transmittance spectra. Variations in optical parameters were studied, including of optical band gap, refractive index, extinction coefficient, complex dielectric function, Urbach energy, single oscillator energy and dispersion energy. The results indicated that optical properties were functions of substrate temperature and precursor amount.