DIAMOND DEPOSITION ON PLATINUM AND PALLADIUM - RAMAN INVESTIGATIONS

Experimental observations showed that after a diamond deposition on pl atinum or palladium substrates, the diamond crystals had grown either ''into'' or ''out of'' the bulk of the Pt and Pd substrates, respectiv ely, To investigate this phenomenon, the substrate surface was careful ly etched electrochemically. Micro-Raman spectroscopy was used to iden tify particles on the substrate surface and on the etched substrate su rface. Micro-Raman measurements with confocal depth resolution showed that diamond crystals are embedded at least up to 1.5 mu m into a plat inum or palladium substrate. Additionally, on palladium substrates, at the bottom of most embedded diamond crystals also graphite could be d etected. After removing a thin surface layer, carbon aggregates became visible and which were fully covered by platinum prior to etching. Th us, a detailed examination of the embedded carbon aggregates became po ssible by micro-Raman spectroscopy. Most observed carbon aggregates co nsisted of graphite; however, some aggregates showed a peak for diamon d. These results confirm the hypothesis that nucleation and growth of diamond can take place in the bulk of platinum and palladium. (C) 1998 Elsevier Science S.A.