Galvanic deposition of hexagonal ZnO thin films on TCO glass substrate

We report an electrochemical deposition of ZnO thin films on SnO2:F coated Transparent Conducting Oxide (TCO) glass substrates from a solution of Zn(NO3)(2). A Zn rod acted as a sacrificial anode, while the TCO glass was the cathode. No external bias was applied. The deposition of ZnO thin films was pH sensitive and a pH between 5 and 6 was found to be optimum for film deposition. The deposition was carried out at 60 and 80 degrees C, with stirring of the solution. X-ray diffraction studies revealed that the ZnO films were of hexagonal phase. Scanning electron microscope (SEM) images showed prominent hexagonal micro-grains with vertical columnar growth. Optical absorption spectra yielded an energy band gap around 3.3 to 3.4 eV. A.C. current-voltage (I-V) and capacitance-voltage (C-V) measurements were carried out using colloidal silver paste as one of the contact. It was found that the ZnO film formed a Schottky junction and the TCO/ZnO/Ag system could be used as an electrical switching device. (c) 2005 Elsevier B.V. All rights reserved.