Analysis of Pure and Ag-Doped TiO2 Thin Films Deposited by Field Assisted Spray Pyrolysis

Abstract

This paper reports the structural and optical properties of Undoped TiO2 and 5% Ag-doped TiO2 nanoparticles under visible- light irradiation. These films were synthesised using Electrohydrodynamic Spray Pyrolysis Technique, deposited at 250°C and later annealed at 400°C few minutes. The films were characterised by Surface Profilnometry, Ultraviolet – Visible light Spectroscopy (UV-Vis Spectroscopy), Optical Microscope and X-ray diffraction (XRD). The result from surface profilometry showed that the thickness of all the samples is thin films. XRD results showed that all the films have crystalline nature of TiO2 and annealed films result in an increase of crystallinity. The crystal phase observed was trigonal for both TiO2 and 5% Ag doped TiO2. The unannealed Undoped TiO2 exhibited low absorbance within the visible spectrum but increases as we dope with 5% Ag-doped TiO2 and effect of annealing increases the absorbance. Extinction coefficient increases within the visible region as we doped and thermal annealing also increases its effect within the visible region. The study of the microstructural properties using Optical Microscopy showed an increase in the hardness of the film for annealed films and they have micro-grains that are closely packed compared to unannealed samples. The direct band-gap for unannealed films range from 4.70 eV- 3.10 eV while annealed films was between 3.20 eV and 2.80 eV. Doped Annealed films showed reduced band-gap.