Formation of nanocrystals in BCN thin films deposited by radio-frequency PACVD

Boron-carbon-nitrogen (BCN) coatings were deposited on Si (100) substrates by r.f. plasma-assisted chemical vapour deposition (PACVD). Dimethylamine borane vapour was used as a precursor and an argon-hydrogen mixture as plasma gas. For the first time crystals were observed in BCN-films prepared by PACVD. All the BCN-coatings deposited by PACVD reported in the literature were amorphous and hydrogenated. The films were characterized with High Resolution Transmission Electron Microscopy (HRTEM), Electron Spectroscopic Imaging (ESI), Electron Energy Loss Spectroscopy (EELS), FT-IR spectroscopy, Auger Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS). The results of the different analysis methods indicate with a high probability the formation of cubic crystals containing boron, carbon and nitrogen. Of great interest is the possibility that these crystals form a c-BN/diamond alloy phase. The influence of the substrate temperature (from 200 degrees C to 850 degrees C) and of the gas composition, especially the hydrogen content, on the growth of the crystals are discussed.