Influence of Al concentration on structural and optical properties of Al-doped ZnO thin films

Abstract

Undoped ZnO and Al-doped zinc oxide (ZnO:Al) thin films with different Al concentrations were prepared onto Si (100) substrate by pulsed filtered cathodic vacuum arc deposition system at room temperature. The influence of doping on the structural and optical properties of thin films was investigated. The preferential (002) orientation was weakened by high aluminum doping in films. Raman measurement was performed for the doping effects in the ZnO. Atomic force microscopy images revealed that the surface of undoped ZnO film grown at RT was smoother than that of the Al-doped ZnO (ZnO:Al) films. The reflectance of all films was studied as a function of wavelength using UV-Vis-NIR spectrophotometer. Average total reflectance values of about 35 % in the wavelength range of 400-800 nm were obtained. Optical band gap of the films was determined using the reflectance spectra by means of Kubelka-Munk formula. From optical properties, the band gap energy was estimated for all films.