Dirac delta nucleation in the framework of Avrami's model: The case of diamond growth on deformed Si(100)

The nucleation and growth kinetics of diamond deposited by hot-filament chemical vapour deposition (HFCVD) on Si(100) substrates, previously deformed by uniaxial compression dong the [100] direction, have been investigated Although the nucleation density at saturation (0.04-0.06 mu m(-2)) was similar to those measured on virgin, as-received Si(100) wafers, the kinetics of stable nucleus formation resembled the fast kinetics observed for substrates which were mechanically abraded prior to CVD in order to enhance diamond nucleation. The results definitely indicate that diamond nucleation occurs randomly with a rate that is a Dirac delta function. The time dependence of the substrate fraction which is covered by islands was measured, and a good agreement with Avrami's kinetics for 2D phase transitions was found. The total island perimeter has also been measured as a function of the covered surface, and is well described by the analytical model recently developed [M. Tomellini and M. Fanfoni, Surf Sci. 349 (1996) L191]. The observed fast nucleation has been attributed to stress-induced defects pre-existing at the surface and which provides suitable sites for diamond growth. (C) 1997 Elsevier Science B.V.