GROWTH OF CUBIC BORON-NITRIDE ON DIAMOND PARTICLES BY MICROWAVE PLASMA ENHANCED CHEMICAL VAPOR-DEPOSITION

The nucleation and growth of cubic boron nitride (c-BN) onto diamond powder using solid NaBH4 in low pressure gas mixtures of NH3 and H-2 by microwave plasma enhanced chemical vapor deposition has been studied. Boron nitride was deposited on submicron diamond seed crystals scattered on (100) silicon single crystal wafers and evidence was found for the formation of the cubic phase. Diamond powder surfaces appear to preferentially nucleate c-BN. In addition it was found that the ratio of c-BN to turbostratic structure boron nitride (t-BN) deposited increases with decreasing NH3 concentration in H-2. It is suggested that this may be due to an increased etching rate for t-BN by atomic hydrogen whose partial pressure may vary with NH3 concentration.