ULTRASONIC PRETREATMENT FOR ENHANCED DIAMOND NUCLEATION

The nucleation of diamond has been investigated as a function of surfa ce pre-treatment by ultrasonic agitation of diamond powder in differen t liquids. The diamond nucleation density on silicon has been measured as a function of ultrasonic treatment time and liquid properties. A s tandard ultrasonic bath for cleaning has been used and diamond powder was tested in 11 liquids with densities between 0.63 and 2.89 g cm(-3) . Diamond was deposited in a microwave plasma CVD system. The influenc e of pre-treatment on nucleation density has been related to ultrasoni c theory, and correlations have been found between the surface tension and the density of the Liquid. The results indicate that by themselve s, jet streams from collapsing cavities cannot form surface defects ac ting as nucleation sites, whereas particles accelerated by the jet str eams can. The density of cavities close to the surface is important an d the velocity of the diamond particles scales linearly with the diamo nd nucleation density.