CORRELATING OPTICAL-ABSORPTION AND THERMAL-CONDUCTIVITY IN DIAMOND

The presence of defects in diamond induces one-phonon infrared absorption which is not allowed in the perfect crystal due to symmetry. Concomitantly the thermal conductivity is reduced by additional phonon-defect scattering. For single crystal diamonds irradiated with fast neutrons, we find a correlation between the one-phonon absorption and the room-temperature thermal conductivity valid over three orders of magnitude in defect concentration. This relation holds for both unannealed and annealed crystals for which the detailed configuration of defects is different, as well as for a synthetic diamond film containing a similar type of disorder. Infrared absorption can thus be used to determine the thermal conductivity of diamonds containing vacancy-related defect centers.