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

The temperature dependence of the thermal conductivity $\kappa(T)$ of single-crystal silicon highly enriched in $^{29}$Si (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 $^{29}$Si crystal is higher than that of the $^{28}$Si (99.983%) crystal. At high temperatures where the thermal conductivity is determined by anharmonic processes of phonon scattering, the thermal conductivity of $^{29}$Si is lower than that of $^{28}$Si. The conclusions of the theory of phonon thermal conductivity on the mass dependence of $\kappa(T)$ agree with the experimental results.