RADIO-FREQUENCY ION PLATING-INDUCED PHASE-TRANSITION FROM H-BN TO NANOCRYSTALLINE C-BN

Boron nitride thin films were deposited by unbalanced r.f. magnetron s puttering from a hexagonal boron nitride (h-BN) target and by r.f. ion plating at low gas pressures. The content of cubic boron nitride (c-B N) is determined by IR spectroscopy to be higher than 90%. The grain s ize derived from X-ray diffraction (XRD) is in the region of 5 nm. Fur thermore, the films are characterized by Auger electron spectroscopy ( AES) and stress measurements. The deposition of the cubic phase is onl y possible in a small range of boron to nitrogen ratio (0.9 < B/N < 1. 1). The film-forming particles (flux Phi(n)) are mainly neutral boron and nitrogen atoms with typical sputtering energies of a few electronv olts, and the plating particles (flux Phi(i)) are argon and krypton io ns with a well defined energy up to 140 eV. The current density is mor e than 2 mA cm(-2), as determined from energy and mass analysis. The a rrival ratio Phi(i)/Phi(n) is approximately 20. The high ion current d ensity causes a substrate temperature of about 510 K, and external sub strate heating allows us to raise the temperature to 800 K. The c-BN f ormation depends mostly on the r.f. substrate bias and slightly on the substrate temperature and the rare gas masses. The results are compar ed with TRIM calculations. The film properties are discussed on the ba sis of the subplantation model.