Effect of Polarity of a Substrate on ZnO Crystal Growth Process by Molecular Dynamics Simulation

Abstract

We examine the effect of polarity of a ZnO substrate on the crystal growth process in physical vapor deposition via molecular dynamics simulation. First, we irradiate ZnO molecules at a velocity of 900 m/s on O-polar, Zn-polar, and nonpolar ZnO substrates and evaluate the crystallinity of the formed ZnO thin film. In the formed thin films on the O-polar and Zn-polar substrates, 8-membered rings are partly observed, while a normal ZnO crystal consists of only 6-membered rings. Thus, the formed thin films on the O-polar and Zn-polar substrates have O and Zn atomic defects. On the other hand, the formed thin film on the nonpolar substrate consists of only 6-membered rings and does not have the atomic defects. We reveal the crystal growth process of ZnO thin films at atomic scale and find that high-quality thin film is formed on the nonpolar substrate.