The Synthesis and Optical Properties of Zinc-Nitrogen Co-Doped TiO2 Thin Films Using Sol–Gel Derived Spin-Coating Method

Abstract

All of the TiO2 films including intrinsic TiO2 film, Zn single doped film with 2.0 at% content and N doped films with 4.0 at%, 6.0 at%, 8.0 at% and 10.0 at% content, were obtained by butyl titanate (Ti(OC4H9)4) as a titanium source, zinc nitrate (Zn(NO3)2·6H2O) as zinc source and urea (H2 NCONH2) as nitrogen source, which was calcined at 600 °C on the glass substrate and Si substrate using sol–gel spin coating method. The structures, morphology and optical properties of various films were analyzed and studied by X ray diffract meter (XRD), ultraviolet-visible spectrophotometer (UV-Vis) and scanning electron microscope (SEM). The results indicated that the main crystal plane of TiO2 film was (101) and any impurity crystal plane didn't appear. All samples had obvious red shifts in the absorbing edge overall and reduced significantly the width of forbidden band, especially, the N doping content with 8.0 at% was surprised to investigate the strongest (101) peak intensity, the sharpest peak type, the best meritocratic orientation, the greatest red shift of the absorption spectrum, the lowest optical band gap value of 3.356 eV, and the highest utilization rate of visible light of the sample. However, the surface morphology of the others films except the N doping content with 8.0 at% is not further improved by co-doping, that is, their surfaces were still rough, had obvious voids and uneven distribution between the grains. Meanwhile, the intensity of the (101) crystalline diffraction peaks of these samples were reduced and the crystalline spacing generally increased after co-doping.