EFFECT OF SUBSTRATE PRETREATMENT ON DIAMOND DEPOSITION IN A MICROWAVE PLASMA

The evolution of substrate surface at an early stage of diamond formation in a microwave plasma was studied with a high-resolution scanning electron microscope. Changes in the shape, size and population of diamond particles at the same points were observed at prescribed time intervals. The substrate used was a mirror-polished Si(100) plate which was ultrasonically pretreated with diamond, c-BN or alpha-Al2O3 powders prior to the deposition. The pretreatment introduced fragments of the abrasives as well as many scratches on the substrate surface. When the diamond and c-BN abrasive were used, diamond was formed on the surface of abrasive residues. With alpha-Al2O3 abrasive powder, on the other hand, residues vanished in the plasma and no deposition was observed. These results suggest that the deposition site of diamond from the vapour phase is dependent on the type of abrasive powder used for substrate pretreatment.