THERMAL-CONDUCTIVITY OF ISOTOPICALLY MODIFIED SINGLE-CRYSTAL DIAMOND

We present new experimental results on the thermal conductivity of iso topically enriched C-12 diamond crystals at low temperatures. To our k nowledge, the measured value for a 99.9% C-12 crystal at 104 K, 410 W/ cm K, is the highest measured thermal conductivity for a solid above l iquid nitrogen temperature. Our measured temperature dependent conduct ivities for the isotopically enriched diamond and natural abundance di amond specimens are well described by Callaway's theoretical model. We predict that the thermal conductivity of a 99.999% C-12 diamond cryst al should exceed 2000 W/cm K at approximately 80 K.