STUDIES ON STRUCTURAL, SURFACE MORPHOLOGICAL, OPTICAL, LUMINESCENCE AND UV PHOTODETECTION PROPERTIES OF SOL-GEL Mg-DOPED ZnO THIN FILMS

Undoped and magnesium-doped zinc oxide thin films were prepared by the sol-gel method. Results from X-ray diffraction indicated that the films exhibited a hexagonal wurtzite structure and were highly oriented along the c-axis. The intensity of the (002) diffraction peak increased with increasing the Mg doping concentration. Also, Mg doping inhibited the growth of crystallite size which decreased from 46 nm to 38 nm with doping concentration. Morphological studies by atomic force microscopy (AFM) indicated the uniform thin film growth and the decreasing of grain size and surface roughness with Mg doping. Optical analysis showed that the average transmittance of all films was above 90% in the visible range and Mg doping has significantly enhanced the bandgap energy of ZnO. Two Raman modes assigned to E-2L and E-2H for the ZnO wurtzite structure were observed for all films. UV emission peak and three defect emission peaks in the visible region were observed by photoluminescence measurements at room temperature. The intensity ratio of UV emission to the visible emission increased with the Mg concentration. Photocurrent measurements revealed that all films presented the photoresponses with n-type semiconducting behavior and their generated photocurrents were reduced by Mg doping. The prepared thin films of high quality with improved properties by Mg doping could be proposed to workers in the field of optoelectronic devices for using them as a strong candidate.