Temperature dependence of the thermal conductivity of different forms of diamond

We present a systematic theoretical investigation of the thermal conductivity of naturally abundant, isotopically enriched, fast neutron irradiated single crystals of diamond, and chemical vapor deposited diamond films of different types over a large temperature range. Existing experimental data have been analyzed using Callaway's theoretical model [Phys. Rev. 113, 1046 (1959)] for thermal conductivity based on an isotropic continuum phonon dispersion relation and using normal and umklapp phonon-phonon relaxation times derived from the application of time-dependent perturbation theory within an anharmonic continuum model. In contrast to existing theoretical studies of the thermal conductivity of diamond, our approach considers Gruneisen's constant as the only (semi)adjustable parameter for anharmonic phonon interactions. This work quantifies the enhancement of the thermal conductivity of diamond with isotopic purity. This work also accounts for the dip in the thermal conductivity curve for hot filament chemical vapor deposition of diamond films and neutron irradiated diamond at low temperatures and provides an estimate of the amount, type, and size of defects present in such samples. We find that the N-drift term in Callaway's theory provides a significant contribution to the thermal conductivity of all the forms of diamond studied here. (c) 2007 American Institute of Physics.