Influences of the iron ion (Fe 3+)-doping on structural and optical properties of nanocrystalline TiO 2 thin films prepared by sol–gel spin coating

Abstract

Titanium dioxide (TiO 2) thin films doping of various iron ion (Fe 3+) concentrations were deposited on silicon (Si) (100) and quartz substrates by sol–gel Spin Coating technique followed by a thermal treatment at 600 °C. The structure, surface morphology and optical properties, as a function of the doping, have been studied by X-ray diffractometer (XRD), Raman, ultraviolet-visible (UV–vis) and Spectroscopic Ellipsometry (SE). XRD and Raman analyzes of our thin films show that the crystalline phase of TiO 2 thin films comprised only the anatase TiO 2, but the crystallinity decreased when the Fe 3+ content increased from 0% to 20%. During the Fe 3+ addition to 20%, the phase of TiO 2 thin film still maintained the amorphous state. The grain size calculated from XRD patterns varies from 29.3 to 22.6 nm. The complex index and the optical band gap ( E g) of the films were determined by the spectroscopic ellipsometry analysis. We have found that the optical band gap decreased with an increasing Fe 3+ content.