SPECIFIC-HEAT OF SINGLE-CRYSTALLINE, POLYCRYSTALLINE AND NANOCRYSTALLINE DIAMOND

Measurements of the specific heat C-p were performed on several CVD-di amond samples, type IIb single-crystal diamond and on an amorphous car bon film in a differential scanning calorimeter between room temperatu re and 300 degrees C. The C-p measurement results of the CVD diamond s amples were only weakly affected by the grain size ranging from 20 nm to 100 mu m, by the film thickness ranging from 300 nm to 300 mu m and by the hydrogen concentration ranging from <1 to 10 at.%. The specifi c heat of single-crystal diamond of 0.54 J g K-1 at 50 degrees C is si milar to the coarse-grained diamond film, but differs slightly from th e specific heat of the nanocrystalline diamond film of 0.68 J g K-1. C ompared to the diamond samples the specific heat of an amorphous carbo n him with a hydrogen concentration of 30 at.% was found to be increas ed by 0.5 J g K-1. These results justify the assumption that the speci fic heat of polycrystalline CVD diamond samples is similar to their si ngle-crystalline counterparts. In the case of pure amorphous carbon fi lms this assumption is no longer valid. (C) 1998 Elsevier Science S.A.