Article,
Comparative aspects of c-BN and diamond CVD
Diamond and Related Materials, 4 (5--6): 714--719 (1995)
DOI: doi:10.1016/0925-9635(94)05224-7
Abstract
Various key aspects of the low-pressure synthesis of cubic boron nitride
and diamond are compared and discussed. Based on recent thermodynamic
data for c-BN and h-BN (heats of formation, entropies, specific heats),
c-BN should be the stable phase under standard and low-pressure conditions.
The current problems in c-BN CVD synthesis can be explained by the
empirical rules of Ostwald and Ostwald-Volmer, which show that the
formation of the metastable and less dense phase, h-BN, is favoured.
Thus, for a successful CVD synthesis of c-BN it is necessary to find
a way to circumvent the natural tendencies of the system.
Thermodynamic equilibrium calculations for c-BN and h-BN in different
gas atmospheres suggested a phase-selective reaction y which h-BN
could be preferentially etched. Thus a c-BN CVD process similar to
that of diamond should be possible and impingement with energetic
ions should not be required to grow c-BN.
However, the atomic attachment kinetic during crystal growth caused
by the anisotropy of the c-BN crystals (completely N- or B-terminated
facets), different bonding energies, and differences of bond lengths
of B-N, B-B and N-N bonds must be taken into consideration and could
cause problems.
