Misorientation angle dependence of surface morphology in homoepitaxial diamond film growth at a low CH 4/H 2 ratio

Abstract

We studied the misorientation angle dependence of the surface morphology in homoepitaxial diamond film grown by the microwave plasma chemical vapor deposition (CVD) method using an extremely low CH 4 concentration gas system (less than 0.15% CH 4/H 2 ratio). We found that, for a misorientation angle ( θ off) of less than 1°, the surfaces of diamond films are atomically flat surface. Their mean roughness (Ra) determined by atomic force microscopy (AFM) is less than 0.04 nm. Ra subsequently increases as θ off increases above θ off>1.5°. This tendency is opposite to that of the conventional homoepitaxial growth using a high CH 4/H 2 ratio. We also found that the θ off dependence of Ra of surfaces formed by hydrogen (H 2) plasma etching has the same tendency as that of the CVD growth at the low CH 4/H 2 ratio mentioned above. Specifically, Ra is less than 0.17 nm for θ off<1° and increases as θ off increases. These experimental results suggest that the surface morphology of the homoepitaxial CVD diamond films grown at low CH 4/H 2 ratios is mainly determined by the H 2 plasma etching process that strongly depends on the θ off of the diamond substrate.