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 °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.