Effects of the Cr doping on structure and optical properties of ZnO thin films

Cr-doped ZnO thin films are prepared on glass substrates by the magnetron sputtering technique. An X-ray diffraction (XRD) is used to analyze the structural properties of the thin films. It indicates that all the thin films have a preferential c-axis orientation. The peak position of the (002) plane shifts to the higher 2θ value, and the peak intensity decreases with the increase of Cr doping. The results of the scanning electron microscopy (SEM) show that the surface morphology becomes loose with the increase of Cr doping. Besides, it is found from the photoluminescence (PL) measurement at room temperature that the ultraviolet emission peak and green emission band are located at 375 nm and 520 nm, respectively, and both intensities of them decrease with the increase of the Cr doping concentration, while the band gap of the ultraviolet emission shifts to the lower wavelength. The experimental results confirm that the optimal Cr doping concentration is 2 at. %. © 2010 Tianjin University of Technology and Springer-Verlag Berlin Heidelberg.