SPACE-FILLING BY NUCLEATION AND GROWTH IN CHEMICAL-VAPOR-DEPOSITION OF DIAMOND

Phase transformations, including chemical vapor deposition (CVD) of di amond, taking place by nucleation and growth are commonly described by Avrami or Johnson-Mehl type models. In order to avoid the restriction s of such models with respect to assumptions concerning nucleation rat es and growth velocities, the variation with time of nucleation and gr owth of diamond particles during the deposition of microwave plasma-as sisted CVD was studied. The size distributions obtained from image ana lysis enabled us to trace back details of the nucleation and growth hi story. Three sources of particle formation were operating during depos ition. A general growth law suitable for all panicles did not exist. T hese observations limited the applicability of Avrami-type models to d escribe space filling. Computer simulation of surface coverage and par ticle growth was successful because one particular mode of particle fo rmation and growth dominated surface coverage. Based on image analysis and the determination of the film growth rate, the evolution of the d iamond volume fraction with time, starting from three-dimensional part icle growth followed by a continuous transition to one-dimensional fil m growth, was described.