A study on impact of process parameters to metal organic chemical vapor deposition grown (002) zinc oxide thin films, at 320°C

This paper reports preparation of highly oriented (002) ZnO films by atmospheric pressure CVD at 320degreesC, which is far below previous reported values. In this study, a cold wall horizontal system was used to thermally decompose sublimed zinc acetylacetonate (Zn(acaC)(2), Zn(C5H7O2)(2)) vapor, and reacted with water vapor to produce ZnO films at temperatures above 320degreesC. Through experimental data, we discovered that low deposition temperature, using water vapor as co-reactant and substrates with ZnO buffer layer pre-coated by PVD are the key factors to prepare (002) ZnO films. By using Si(100) pre-coated with sputtered ZnO amorphous buffer layer as substrates, the ZnO growth rate is highest. While using copper oxide pre-coated Si substrates gave the lowest growth rate, and deposited ZnO film is amorphous. Considering influence of CVD co-reactant, using Zn(acaC)(2) and water vapor gives higher growth rate and better crystallinity than CVD using Zn(acac)(2) and oxygen. Water vapor may supply hydrogen to react with released acetylacetonyl ligand (C5H7O2), and help the formation of stable acetylaceton (C5H8O2) molecule. DPA shows that film contain 46% O and 54% Zn. XPS of Zn Auger identified the valence of Zn being Zn. It seems that excessive Zn might present as discrete Zn2+ dispersed between ZnO lattices.