FABRICATION AND CHARACTERIZATION OF Al DOPED ZnO THIN FILM BY PVD TECHNIQUE

Abstract

ZnO thin films were deposited onto quartz substrates at room temperature by dc sputtering of a ZnO target. Al was thermally evaporated onto the ZnO thin films in an evaporation chamber, with the thickness of the Al layer being monitored using a thickness monitor. To achieve Al doping, the Al coated ZnO thin films were then rapid thermal annealed at 773K for 1 minute. This helped in incorporating Al within the ZnO lattice. The amount of Al doping in the ZnO thin films was verified by energy dispersive x-ray analysis (EDAX). Scanning electron microscopy (SEM) of the Al doped ZnO (AZO) samples indicated excellent surface coverage with compact smooth film and x-ray diffraction (XRD) confirmed the hexagonal crystal growth with wurtzite structure. The optical transmittance of the thin films showed appreciable transparency of the thin films in the visible range. The optical constant and the thickness of the thin films were determined by a modified Kramers Kronig approach. Dark conductivity measurement indicated decrease in resistivity of the sample with the increase in Al doping, while the conductivity increased.