Effect of doping on the structural and optical properties of pure and Ag-Doped TiO2 thin films deposited by electro-hydrodynamic spray pyrolysis

Abstract

We investigated the influence of Ag doping on TiO2 thin films. The Undoped TiO2 and 1.5 M Ag-doped TiO2 Films were synthesized by Electrohydrodynamic Spray Pyrolysis Technique, deposited at 270⁰C. The films were characterized by Surface Profilometry, Ultraviolet – Visible light Spectroscopy (UV-Vis Spectroscopy), Optical Microscope and X-ray diffraction (XRD). The results from surface profilometry showed that all the samples were thin films in the range of 300 to 600 nm. XRD results reviewed crystalline structure of TiO2 . Crystal phase observed for both TiO2 and silver-doped TiO2 are anatase. The crystal phase observed was tetragonal anatase phase of TiO2 for films deposited.The Undoped TiO2 exhibited low absorbance within the visible spectrum but increases when doped with 1.5 M Ag ion concentration. Within the visible region, the result showed transmittance around 36-87 while the result of refractive index showed that the films have sharp increase in the wavelength of 390 nm to 400 nm and then the curve decreased slowly with further increase in the wavelength. Absorption coefficient increased as TiO2 was doped with Ag Also, Extinction coefficient increased within the visible region as we doped.The study of the microstructural properties using Optical Microscopy showed increase in reduction of grains and also hardness of film as we doped with Ag, with average particle sizes between 6 µm and 10 µm. The direct band-gap for films ranged from 4.70eV- 3.60eV while the indirect band-gap for films ranged between 4.60eV and 2.80eV. Doped film showed narrowed band-gap.