Thermal conductivity of the single-crystal monoisotopic 29Si in the temperature range 2.4–410 K

The temperature dependence of the thermal conductivity κ(T) of single-crystal silicon highly enriched in 29Si (99.919%) isotope has been measured in the temperature range 2.4–410 K. At low temperatures (T < 6 K) in the boundary phonon scattering regime, the thermal conductivity of the 29Si crystal is higher than that of the 28Si (99.983%) crystal. At high temperatures where the thermal conductivity is determined by anharmonic processes of phonon scattering, the thermal conductivity of 29Si is lower than that of 28Si. The conclusions of the theory of phonon thermal conductivity on the mass dependence of κ(T) agree with the experimental results.