Thermal conductivity of diamond films

The thermal diffusivity of diamond films grown on the Si substrate by the hot-filament chemical vapor deposition technique in gas mixtures of 1% to 5% methane in hydrogen were studied. Thermal conductivity of the film prepared at 1% CH4 concentration reached about 1200W/mK, which is almost equal to that for type I natural diamond, and decreased rapidly to less than 200W/mK with increasing CH4 concentration. Hydrogen contents in the films increased with a decrease in thermal conductivity. This indicates that the thermal conductivity for diamond films is correlated to the amount of incorporated hydrogen impurity.