CHARACTERISTIC FEATURES OF THE LOW-TEMPERATURE THERMAL-CONDUCTIVITY OF HIGHLY-ENRICHED AND NATURAL GERMANIUM

Experimental data on the thermal conductivity K(T) of natural and high ly enriched (99.99%) Ge-70 crystals with ground and polished surfaces are analyzed in the temperature interval similar to 2-8 K. In all samp les, the boundary scattering mechanism predominates in the interval fr om 2 to 4.0 K. As temperature increases, in highly enriched samples N processes start to contribute to phonon transport and the behavior of K( T) corresponds to viscous Poiseuille flow of a phonon gas. The isot opic scattering mechanism plays a large role in isotopically nonideal samples. (C) 1998 American Institute of Physics. [S1063-7834(98)00709- 6].