The Variation of Optical Band Gap for ZnO:In Films Prepared by Sol-Gel Technique

Abstract

ZnO:In films with different concentrations (0–5 at.%) are successfully synthesized on quartz substrates using sol-gel technique. The structure, morphology, and optical properties of ZnO:In films are investigated by X-ray diffraction, atomic force microscopy, and UV-visible spectrophotometer. It is found that all the films with columnar structural morphology grow along the preferred [001] orientation and the incorporation of indium can improve the crystallinity of ZnO films. The transmittance of the films is about 80% in the visible range. A change of the optical absorption edge from blue shift to red shift is observed for ZnO:In films as the doping concentration increases, which means that the optical band gap first increases and then decreases. The blue shift is due to the Burstein-Moss effect. The sharp jump of the absorption edge from blue-shift to red shift is ascribe to the band gap narrowing caused by the merging of the donor and conduction bands of ZnO:In at high doping concentration.

The influence of Y contribution on crystallographic, topographic and optical properties of ZnO: A heterojunction diode application

“…Then it starts to decrease to the values of 3.271 eV and 3.258 eV for 5 at.% and 7 at.% Y contents. The E g values for pure and Y incorporated ZnO samples are a good agreement with values varied between 3.151 eV and 3.42 eV for Ga, In, Al and B doped ZnO samples [32,[36][37][38]. Unlike our results, Lin et al [25] found that E g value for pure ZnO dropped off from 3.2827 eV to 3.2656 eV with Y contribution in a sol-gel spin coating study.…”

Effect of Zn Site for Ca Substitution on Optical and Microwave Dielectric Properties of ZnAl2O4Thin Films by Sol Gel Method

“…Figure 2 also shows the peaks in the XRD spectra shift to a higher angle implying the formation of (Ca/Zn)Al 2 O 4 . The diffraction peaks shifted, perhaps because the ionic radius of Ca 2+ (0.99 nm) is larger than Zn 2+ (0.74 nm) [24]. The shift of XRD diffraction peaks indicates that the lattice parameter (a) was changed.…”

The effect of Pb doping on the characteristic properties of spin coated ZnO thin films: Wrinkle structures

“…Besides, the optical band gap shows different characteristic based on the type of the dopant. For example, the optical band gap values belonging to In, Al, Ni, Fe doped ZnO thin films indicate that it firstly increases at the lower doping content and then decreases at the higher doping content [34,35]. In fact, there are various factors such as quantum confinement, lattice distortion, carrier concentration etc.…”