Highly oriented diamond (111) films synthesized by pulse bias-enhanced nucleation and epitaxial grain selection on a 3C-SiC/Si (111) substrate

We report the synthesis of highly oriented diamond (HOD) (111) films on 3C-SiC/Si (111) substrates. Bias-enhanced nucleation (BEN) is a key process for the heteroepitaxial growth of HOD films. Conventional long nucleation periods have been found to lead to a polycrystalline diamond film on the 3C-SiC (111) surface. Here, we propose a method that combines brief BEN (<30 s), called pulse BEN, and epitaxial grain selection by oxidative etching. Smaller diamond nuclei with a higher spatial density on the substrate were formed by pulse BEN with a pulse duration of <30 s. We found that precisely controlling the pulse duration is important for obtaining a nucleation density that is sufficiently high to obtain the HOD films. By adding oxygen gas to the subsequent growth process, non-epitaxial nuclei were removed and epitaxial diamond grains selectively remained. There was no notable difference in the relative growth rate of [111] to [100] with and without oxygen, and the orientation improvement was observed on both the (100) and (111) substrates. This suggests that the mechanism of oxidative removal was not evolutionary selective growth, but etching of the non-epitaxial interfaces between the nuclei and the (111) substrate. Finally, the HOD (111) films covering the entire 3C-SiC surface were synthesized, and they exhibited distinct diffraction spots, indicating the formation of the oriented diamond.