ECR plasma pretreatment for ZnO epitaxy on sapphire and silicon substrates

The effects of precleaning the substrate on the epitaxial growth of ZnO were investigated. Dry cleaning techniques employing argon, oxygen, and hydrogen ECR plasmas were employed, respectively, to remove organic contaminants and native oxides on sapphire and silicon substrates prior to the growth of the ZnO film by atomic layer epitaxy. The incubation period for ZnO nucleation was measured by using scanning electron microscopy (SEM) and Auger electron emission spectroscopic analysis (AES) to investigate the incubation period for ZnO nucleation. ECR plasma pretreatment reduced the cleaning efficiency. Oxygen ECR plasma pretreatment was more effective than any other plasma pretreatment because oxygen ECR plasma treatment increased the hydroxyl packing density at the substrate surface, and its effects on sapphire substrates were especially prominent.