Wet-chemistry Synthesis And Oriented Growth Research Of Al Doped ZnO Thin Films

Transparent conducting oxide thin films have good conductivity and high transparency in the visible region. They have been extensively applied to a variety of photoelectric devices, such as thin film solar cells and flat panel display. Currently, indium-tin-oxide thin films are widely used in the flat panel display field. Indium resources are limited, so exploiting other substitute materials is a vital task.Zinc oxide is an inexpensive n-type semiconductor having band gap of3.3eV and hexagonal Wurtzite structure. It can possess desirable optical and electrical properties by effective doping. Therefore, Zinc oxide will become a promising candidate for transparent conductive oxide thin films.ZnO:Al thin films prepared by some physical techniques can attain excellent optoelectronic properties. Still, most of these methods couldn’t be widely used in practical production due to the high cost and preparing temperature. The sol-gel method is a simple and effective way for technological production. However, the basic research about ZnO thin films prepared by sol-gel method is still not systematical, and the properties of ZnO thin films need to be improved. Simultaneously, the preparing temperature should be lower for the application of the flexible substrates.This dissertation is focused on the basic research, improvement of optoelectronic properties and low temperature growing. The main conclusions are obtained as follows:a. The optimum chemical system had been ascertained. The precursor solution should include zinc acetate dihydrate as the precursor,2-Methoxyethanol as the solvent, aluminum nitrate nonahydrate as the dopant source, and ethanolamine as the stabilizer. As-deposited films attained good crystallinity and c-axis oriented ZnO.b. The effect of Al doping concentration, precursor solution concentration and heat treatment process were studied. As-deposited films were prepared by spin-coating method, and the precursor solution concentration was0.6mol/L. After350℃pre-heat treatment,400℃post-heat treatment in air and further annealing at450℃in Ar2, the Al doped zinc oxide thin films attained the electrical resistivity of1.57Ω·cm.c. Hydrothermal method and solvothermal method with different precursor solution systems, precursor solution concentrations and reaction times, were employed to fabricate the ZnO:Al thin films. The crystal growth process was investigated. It indicated that the ZnO nanostructure was hexagonal microdisk structure which transformed into hexagonal micro-cups structure as the solution concentration changed and reaction time extended.