Different Etching Mechanisms of Diamond by Oxygen and Hydrogen Plasma: a Reactive Molecular Dynamics Study

Understanding the plasma etching mechanism of diamond is of great significance to promote diamond applications; however, insights into the atomic-scale etching mechanisms are hidden by the complex chemical reactions during the etching process due to the lack of an in situ characterization technique into the etching process. Herein, we conducted an etching simulation of diamond using the reactive molecular dynamics simulation method to comparatively investigate the different etching mechanisms of diamond by oxygen and hydrogen plasma with different incident energies. In the case of oxygen etching, at all tested incident energies, C-C bonds on the diamond surface are dissociated by the irradiated oxygen, and carbon atoms of diamond are etched away via the generation and desorption of gaseous carbon monoxide and carbon dioxide molecules. In the case of hydrogen etching, at low incident energies, we revealed that the carbon atoms are etched through the desorption of gaseous hydrocarbon molecules similar to the oxygen etching mechanism, while with increasing the incident energies, we interestingly observe an obvious different etching mechanism, that is, the irradiated hydrogen penetrates into the inside of diamond resulting in the formation of the hydrogenated amorphous layer which is then exfoliated from the diamond surface. Meanwhile, we revealed that the loss rate of carbon atoms in the diamond structure by oxygen is higher at low incident energies but lower at high incident energies than that by hydrogen. This study provides more insights into the etching mechanism of oxygen and hydrogen plasma and offers useful theoretical guidance for designing and controlling the etching process.