Investigation of the nucleation layer in c-BN film growth

The nucleation of c-BN during an inductively coupled plasma chemical vapour deposition (CVD) process is investigated. The transition from the textured h-BN nucleation layer to the c-BN layer turned out to be not abrupt but to take place rather gradually in several steps. Increasing the substrate temperature sharpens the transition and increases the maximum c-BN content. It is speculated that this is correlated with a decreasing hydrogen content of the films at higher temperatures. Experiments with different bias voltages during the nucleation step revealed that c-BN nucleation is possible only within the well-known c-BN region of the parameter space. Thus, this region might be determined by the nucleation of c-BN rather than by the growth step. Experiments with boron-rich interlayers finally results in extremely high c-BN contents of the subsequent c-BN layers. (C) 1997 Elsevier Science S.A.