Enhancement of ZnO nucleation in ZnO epitaxy by atomic layer epitaxy

Dry cleaning techniques employing argon, oxygen and hydrogen ECR plasma were used, respectively, to remove organic contaminants and native oxides on sapphire and silicon (Si) substrates prior to the growth of the ZnO film by atomic layer epitaxy. The cleaning efficiency was assessed by investigating the nucleation density and the incubation period for ZnO nucleation using scanning electron micrography (SEM) and Auger electron emission spectroscopic analysis (AES). ECR plasma pretreatment increased the ZnO nucleation density and reduced the incubation period for ZnO nucleation. Oxygen ECR plasma pretreatment was found to be more effective in enhancing ZnO nucleation than any other plasma pretreatment, and the effects are more prominent on the sapphire substrate than the silicon substrate. ZnO nucleation on the sapphire substrate is substantially enhanced by treating the substrate surface with oxygen ECR plasma prior to ZnO atomic layer epitaxy (ALE) because the hydroxyl packing density at the substrate surface is increased by oxygen plasma.