BN coatings prepared by low pressure chemical vapor deposition using boron trichloride-ammonia-hydrogen-argon mixture gases

Boron nitride (BN) coatings were prepared by low pressure chemical vapor deposition (LPCVD) using boron trichloride (BCl₃)-ammonia (NH₃)-hydrogen (H₂)-argon (Ar) mixture gases. Thermodynamic analysis indicated that BN was the only solid product when the amount of NH₃ was in excess at the temperature of 1000°C and the total pressure of 1000Pa. The deposited BN coating had a turbostratic structure, and the highly ordered graphite substrate may have an effect on the order degree of BN coating near coating/substrate interface. The turbostratic BN was transformed into well-crystallized hexagonal boron nitride (h-BN) after heat treatments at temperatures above 1300°C. The deposition kinetics of LPCVD BN were investigated at the total pressure of 1000Pa and temperatures of 650°C, 800°C and 1000°C, respectively. It was concluded that the deposition process was controlled by the diffusion of BCl₃ with an apparent activation energy of 1.3eV.