Suppression of surface cracks on (111) homoepitaxial diamond through impurity limitation by oxygen addition

The use of oxygen in improving diamond quality has been investigated by comparing two (111) homoepitaxial diamond films deposited with H2–CH4 and H2–CH4–O2 mixtures by microwave assisted chemical vapor deposition. The (111) diamond deposited using a H2–CH4 mixture showed surface cracks due to the presence of nondiamond phases as well as a significant amount of hydrogen and silicon impurities. The (111) diamond deposited using a H2–CH4–O2 mixture showed an absence of hydrogen and silicon impurities and nondiamond phases, and exhibited a flat surface. The addition of oxygen is one of the suitable methods to produce high-quality (111) homoepitaxial diamond.