To realize an ultra‐flat diamond surface with a three‐dimensional (3D) structure, we performed dressed‐photon–phonon (DPP) etching. A DPP is generated on nano‐scale protrusions. Hence, the generation of DPPs results in selective removal of nano‐scale protrusions, thereby achieving an ultra‐flat surface even on the sidewall of a diamond mesa structure. By controlling the polarization of the incident light, a smooth diamond mesa structure sidewall was obtained, and a higher etching rate was obtained with a perpendicular polarization on the corrugations. In addition, by selective deposition of n‐layer diamond on the p‐layer diamond mesa structure, smooth n‐layer diamond was confirmed on the DPP etched sidewall.
Schematic of dressed‐photon–phonon (DPP) etching on the sidewall: (a) before and (b) after etching, in which DPP selectively generates on the corrugations and etching automatically stops when the surface was smooth. Scanning electron microscopy image of the selective deposition of the n‐layer (c) without and (d) with the DPP etched sidewall.