Morphological characterization of diamond coatings grown by MWPECVD on hexagonal Boron Nitride

A relevant and still unsolved issue in the characterization of diamond coatings deposited on ceramic materials such as hexagonal boron nitride (h-BN) is to enhance the resistance of the substrate to erosion by Kr+ or Xe+ ions generated in the plasma propulsion systems. In this work, diamond films were grown by microwave plasma enhanced chemical vapour deposition on h-BN substrates untreated, for the first time, and pre-treated for short (31-65 min) and long (285-296 min) process times. The morphology of diamond films was analysed by scanning electron microscopy, and atomic force microscopy, and their chemistry and structure by Raman spectroscopy. Microscopy analysis revealed that non-continuous (at short process time) and continuous (at long process time) films were formed, respectively, on both untreated and pre-treated h-BN substrates. In particular, diamond films grown on untreated h-BN substrates exhibited roughness values higher than those of h-BN substrates pre-treated by a conventional ultrasonic method.