Surface Chemical Reactions During Atomic Layer Deposition of Zinc Oxynitride (ZnON)

Atomic layer deposition (ALD) is a promising technique for fabricating high-quality thin films. For improving the process conditions and material quality of ALD, understanding the surface chemical mechanisms at the molecular level is important as the entire ALD process is based on the reactions of precursors on the substrate surfaces. Zinc oxynitride (ZnON) is gaining significant research interest as a p-type semiconductor material. Although the ALD of ZnON can be performed by dosing H2O and NH3 as oxygen and nitrogen sources, respectively, the elemental ratio of O and N in the deposited film differs considerably from that in the gaseous sources. In this study, the surface reactions of ZnON ALD are analyzed employing density functional theory calculations. All the ALD surface reactions of ZnO and ZnN are facile and expected to occur rapidly. However, the substitution of a surface *NH2 by H2O to form *OH is preferred, whereas the inverse reaction is implausible. We propose that the differences in the reactivity could originate from the higher bond energy of Zn-O than that of Zn-N.