Studies on Growth, Optical And Electrical Properties of Doped and Undoped Zinc Oxide Thin Films

Abstract

In recent years zinc oxide (ZnO) has attracted the researchers because of its excellent optical and electrical properties. The primary aim of this work is to deposit undoped and doped ZnO thin films by sputtering techniques and to study the structural, optical and electrical properties. The thin films were deposited on glass and quartz substrates at room temperature using DC and RF magnetron sputtering. The studies on the effects of annealing on the structural and third-order nonlinear optical properties of ZnO thin films deposited on quartz substrates has been carried out under cw He-Ne laser irradiation at 633 nm wavelength using z-scan technique. The enhanced nonlinear response of the films was observed with the increase in the annealing temperature. X-ray diffraction (XRD) patterns show the appearance of crystalline phases of SiO2 at higher annealing temperatures. The appearance of extraneous phase was confirmed by atomic force microscope (AFM) images and optical transmittance spectra. Multiple diffraction rings due to the refractive index change and thermal lensing were observed when the samples were exposed to laser beam. Also, the films exhibited strong optical limiting properties. Transparent conducting aluminum doped zinc oxide (AZO) films were deposited on glass substrates. Variation of stress values and the lattice parameters confirms the presence of Al3+ ions in the ZnO matrix. Electrical resistivity of the deposited films was found to be as low as 0:5×10−4Ω-cm. XRD patterns of the ZnO/Al/ZnO multilayers show only reflections corresponding to Wurtzite ZnO. The sheet resistance of the multilayers found to decrease with the increase in the Al interlayer thickness. But, the average transmittance in the visible region decreases. The XRD results of manganese doped ZnO (MZO) films deposited using compound targets show the decrease of lattice parameters a and c after doping of Mn into ZnO. The third-order nonlinear optical susceptibility χ(3) is found to be of the order of 10−3 esu for MZO films. Keywords: ZnO; magnetron sputtering; XRD; TCO; AFM; CW laser; NLO