Thermal resistance and electrical insulation of thin low-temperature-deposited diamond films

Diamond layers only a few microns thick were deposited by microwave plasma-assisted chemical vapour deposition (CVD) on silicon at different substrate temperatures (500, 550 and 800 degrees C) using different methods for nucleation enhancement (ex situ mechanical pretreatment or in situ substrate biasing). The thermal resistance was measured for conduction normal to these thin layers, which span a wide range of structural properties from random small-grained over columnar to highly oriented grain structures. It was shown that the thermal resistance normal to thin CVD diamond layers depends strongly, for a given layer thickness, on the grain size and the degree of grain orientation in the direction of growth. The smallest thermal resistances were observed for bias-nucleated, highly oriented films deposited al 800 degrees C with pronounced fibre textures. An upper limit for the effective thermal resistance of the diamond-silicon boundary of 1.8 x 10(-9) m(2)K/W was determined for mechanically pretreated: columnar-grained films deposited at low temperatures, which suggests a small interfacial disorder for these films. Furthermore, the electrical insulation of the low-temperature deposited films was shown to be comparable with that of high-temperature-deposited diamond. (C) 1997 Elsevier Science S.A.