Optical properties of pseudo binary oxides (TiO2)1-x-(Al2O3)x thin films prepared by spray pyrolysis technique

Abstract

Pseudo binary oxide thin films,(TiO2)1-x-(Al2O3)x, were prepared by spray pyrolysis technique on cleaned quartz and silicon substrates. The prepared precursor solutions of Al2O3 and TiO2 were mixed thoroughly in appropriate volume, calculated from the molar fraction. The XRD pattern of Al2O3-TiO2 film shows anatase phase and mixed phase of Al2TiO5 (Aluminum Titanium oxide). The SEM micrograph shows spherical grains with nano porous surface and some clusters, it is also composed of crumb like nano particles and average grain sizes are estimated. In the EDAX spectrum, the signals corresponding to oxygen (O2), titanium (Ti), aluminum (Al) and substrate silicon (Si) are seen, elemental analysis shows that weight percentage are in stoichiometric ratio. Transmittance and Reflectance spectra were recorded in normal incidence by UV-Visible Spectrophotometer in wavelength range 350nm to 1200nm. Using these optical data the thickness, refractive index, extinction coefficient, real and imaginary part of dielectric constants, energy band gap, Urbach energy and Packing density are estimated. It is observed that, with the increase in molar fraction there is a variation of the energy band gap, which may be attributed to the mixed phase formation in the films as well as formation of defects. The obtained pseudo binary oxide thin films have wide band gap and porous surface structure; hence these films are further used for sensing application.