Low-energy excitations and thermal conductivity of CuxSn100-x films at lowtemperatures

We report on the thermal conductivity lambda(T) and the resistivity rho(T) of amorphous and polycrystalline CuxSn100-x (0 < x < 100). The measurements were performed with an improved steady-state technique by preparing the sa mples on a microchip. Both, lambda(T) and rho(T) were measured after prepar ation at T = 5K in the amorphous and, after annealing, in the crystalline s tate in the temperature range from 1.2 to 360 K. We separate the electronic par; from the total thermal conductivity with the Wiedemann-Franz law. The thermal conductivity is discussed in relation to the atomic structure. The phonon-thermal conductivity of the amorphous state has a plateau region du e to low-energy excitations at temperatures between T = 2K and 30 K. The pl ateau shifts with increasing x to lower temperatures. It can be observed al so after crystallization for alloys with x greater than or equal to 60 at.% Cu due to a low degree of crystallinity but vanishes after further anneali ng. The plateau relates to structural data at scattering vectors K = K-pe a pproximate to 2k(F). (C) 1999 Elsevier Science B.V. All rights reserved.