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 1000 Pa. 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 1000 Pa 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 1.3 eV.