Quality assessment of in situ plasma-etched diamond surfaces for chemical vapor deposition overgrowth

In situ plasma etching is a common method to prepare diamond substrates for epitaxial overgrowth to effectuate higher quality. However, there is no feasible direct qualitative method established so far to assess the performance of the etching pretreatment. An optimization of the pretreatment process on grounds of high-resolution X-ray diffraction measurements is proposed to judge the structural quality gain of the diamond substrates and the effectiveness of the polishing-induced subsurface damage removal. The obtained data shows that parameters such as thickness and misorientation angle of the diamond substrates seem to have no clear-cut influence on the gain of structural quality. The process duration, however, is an important key factor when the amount of material removal and the arising roughness are discussed. Furthermore, the impact of the oxygen-to-hydrogen ratio is examined. With rising oxygen percentage, the structural quality gain remains similar; only the overall as well as local mean roughness increases strongly. Within the utilized reactor setup, the best results are obtained after a 20min in situ hydrogen plasma-etching step. The optimal pretreatment process, however, changes for each reactor type and will always embody a trade-off. Due to the introduced method, a better evaluation and comparison of the achievements is accomplishable.