Structural and optical properties of electrodeposited ZnO thin films

Zinc oxide thin films were electrodeposited on different substrates. Electrodeposition was performed with hydrogen peroxide, as hydroxide ions source, at - 1.5 V versus mercurial sulfate electrode during one hour, and a temperature maintained at 70 degrees C. The resulting thin films have a good crystallinity and a high c-axis orientation, and the unit cell parameters determined by X-ray diffraction experiment are a=0.326 nm and c=0.523 nm, respectively. Microstructure studies using scanning electron microscopy and atomic force microscopy show a good homogeneity of the film and a roughness around 22 nm. Optical properties were studied with Raman spectroscopy and photoluminescence spectroscopy. Optical properties of the films revealed a low defect emission in photoluminescence spectra. The E-2 vibration mode for ZnO was observed near 439 cm(-1), indicating that the as-deposited films were under compressive stress. Oscillations were observed in the photoluminescence spectra, from which the refractive index of ZnO thin films was extracted, that is similar to 1.90. (C) 2008 Elsevier B.V. All rights reserved.