Thermodynamic study on the chemical vapor deposition of boron nitride from the BCl₃-NH₃-H₂ system

The gas-phase reaction thermodynamics in the chemical vapor deposition (CVD) process of preparing boron nitride with the precursors of BCl₃-NH₃-H₂ was investigated with a relatively complete set of 144 species, in which the thermochemistry data were calculated with accurate model chemistry at G3(MP2) and G3//B3LYP levels combined with standard statistical thermodynamics. The data include the heat capacities, entropies, enthalpies of formation, and Gibbs free energies of formation. Three different modifications of condensed phase boron nitride (hexagonal h-BN, cubic c-BN, and wurtzite w-BN) were taken into consideration. Based on these data, the distribution of the equilibrium concentration of the 144 species was obtained with the principle of chemical equilibrium. It was concluded that c-BN is formed at temperatures up to 1,800 K, h-BN is the most stable above this temperature, and w-BN is unstable under considerable conditions.