Characteristics and optical properties of iron ion (Fe 3+)-doped titanium oxide thin films prepared by a sol–gel spin coating

Abstract

Titanium dioxide (TiO 2) thin films doping of various iron ion (Fe 3+) concentrations have been prepared on a glass substrate by the sol–gel spin coating process. Characteristics and optical properties of TiO 2 thin films doping of various Fe content were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible spectroscopy (UV–vis) and spectroscopic ellipsometry. 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 25.0 wt%. During the Fe 3+ addition to 25.0 wt%, the phase of TiO 2 thin film still maintained the amorphous state. The absorption edge of TiO 2 thin films shifted towards longer wavelengths (i.e. red shifted) from 355 to 415 nm when the Fe 3+-doped concentration increased from 0 to 25.0 wt%. The values of the refractive index ( n), and extinction coefficient ( k), decreased with an increasing Fe 3+ content. Moreover, the band-gap energy of TiO 2 thin films also decreased from 3.29 to 2.83 eV with an increase in the Fe 3+ content from 0 to 25.0 wt%.