EFFECT OF SUBSTRATE-TEMPERATURE AND HEAT-TREATMENT ON THE MICROSTRUCTURE OF DIAMOND-LIKE CARBON-FILMS

Nonhydrogenated diamondlike carbon films prepared at a substrate tempe rature (ST) of 100, 300, and 500 degrees C by the laser ablation of gr aphite on a single-crystal silicon substrate have been characterized b y scanning tunneling microscopy for the surface structure and Raman sp ectroscopy for the microstructure. Distorted pentagonal and hexagonal rings are observed on the surface of the film grown at 100 degrees C w hile only hexagonal rings are observable for the one grown at 500 degr ees C. The rise in ST is found to increase the surface roughness. To a ssign the various coexisting carbonaceous species formed at different growth temperatures and to check their thermal stability, heat treatme nt was performed at up to 1300 degrees C in vacuum and 600 degrees C i n air. The changes occurring on heat treatment in vacuum in these film s around 600 degrees C have been correlated with the release of defect s from the threefold network. Likewise, 950 degrees C temperature has been associated with the conversion of disordered tetrahedral bonding to a distorted trigonal one. The heat treatment in air shows that the microstructure induced due to lower ST is thermally more stable. (C) 1 996 American Institute of Physics.