HYDROGEN-INDUCED MICROSTRUCTURAL VARIATION IN DIAMOND AND DIAMOND-LIKE CARBON THIN-FILMS

Hydrogen plays a crucial role in the growth of micro-crystalline diamo nd (MCD) and diamond like carbon (DLC) thin films grown by plasma assi sted chemical vapour deposition (PACVD) processes. It selectively etch es graphite phase and helps in stabilizing the diamond phase. The pres ence of various hydrocarbon species in the plasma and their reaction w ith atomic, excited or molecular hydrogen on the substrate surface dec ide the mechanism of diamond nucleation and growth. Several mechanisms have been proposed but the process is still not well understood. Cont rol of hydrogen and other deposition parameters in the PACVD process l eads to; deposition of yet another class of materials called diamond l ike carbon. By varying the concentration of hydrogen it is possible to produce purely amorphous carbon films on the one hand and amorphous h ydrogenated carbon films (with as high as 60% hydrogen) on the other. Very hard, optically transparent and electrically insulating films cha racterize the diamond like behaviour. The proportion of hydrogen and i ts bonding with carbon or hydrogen in the film can be varied to obtain very hard to very soft films which could be optically transparent or opaque, The microstructure of these films have been investigated by a large number of techniques. The results show interesting situations. T his paper reviews the work on the role of hydrogen on the growth,struc ture and properties of MCD and DLC thin films.