Thermochemical polishing of single-crystal HPHT diamond substrates: surface analysis

This work examines the results of processing single-crystal HPHT diamond substrates using the method of thermochemical polishing (TCP). The primary application of this method is to refine the surface of mechanically polished diamond substrates to a state close to atomically smooth. For the first time, optical profilometry was used to obtain results for the entire surface area (4 $\times$ 4 mm) of high-quality diamond substrates. It is shown that thermochemical polishing can significantly improve the morphological characteristics of diamond substrates, with 80–90% of the surface having height variations of less than 200 nm. Data obtained using atomic force microscopy indicate that surface roughness can be reduced to a level of $Ra$ (0.5–0.7) nm. During polishing, depressions of various sizes and depths are also formed, distributed unevenly; as the surface homogeneity increases, the number of these depressions may increase. The study results demonstrate the significant potential of thermochemical polishing of diamond substrates for their industrial use in high-tech fields of microelectronics and micromechanics, which require flat surfaces with minimal roughness.