Thermal conductivity of isotopically enriched silicon

By means of a steady-state heat-flow technique, we have measured the therma l conductivity in a bulk crystal of highly enriched (99.8588%) Si-28 for te mperatures between 2 and 310 K. Maximum values of about 30 000 W m(-1) K-1 for K are found around 20 K. This is six times larger than in natural silic on and even exceeds the maximum in diamond with natural isotope abundance. At room temperature, we obtain a thermal conductivity enhancement of almost 60% compared to natural Si. Our results agree well with theoretical predic tions. (C) 2000 Elsevier Science Ltd. All rights reserved.