Solution growth of ZnO films and nanostructures

Abstract

Zinc Oxide, a wide bandgap semiconductor, is gaining interest, as it is a promising material for optoelectronic applications. The effect of solution based method, low temperature hydrothermal synthesis, on the growth of Zinc Oxide (ZnO) films was examined. Gallium Nitrate was used to achieve n-type ZnO films to improve the electrical conductivity of ZnO. Introduction of citrate ions induces the formation of plate-like zinc oxide. Mircowave heating at 90°C is adopted as the rapid temperature heating acts as a driving force, leading to a large magnitude decrease in solubility of ZnO. Hence, this method gives higher growth rate and higher level of nucleation compared to conventional heating. Transmittance of ZnO films grown using this method was tested, and experimental results have shown that the transmittance ranged between 70-90%. Heat treatment was used to improve the electrical conductivity. However, there is a trade off between electrical conductivity and transparency as a thicker film will increase the charge concentration, but it decreases the transparency of the film. Scanning Electron Microscopy is used to characterize the samples and to determine the film thickness, which will be used to compute the bulk resistivity of the samples. These results could be integrated into applications that require the use of ZnO films to replace the expensive Indium Tin Oxide (ITO).