Optical pump-probe measurements of sound velocity and thermal conductivity of hydrogenated amorphous carbon films

In this paper, we report the measurements of the thermal conductivity and longitudinal sound velocity of four types of hydrogenated amorphous carbon films. The measurements were made with an ultrafast optical pump-probe apparatus. The films were deposited at various temperatures by plasma enhanced chemical vapor deposition. The films are of a low density (1.0-1.4 g cm(-3)) and are found to have sound velocities that range from as low as 3 km/s to as high as 10 km/s. The thermal conductivities are between 0.6 and 1.4 W/mK which are low compared to amorphous SiO2 but are larger than published measurements of thin films of similar composition and density by a factor of 2-3. (C) 2008 American Institute of Physics.