Thermal conductivity of CuxSn100-x films at low temperatures

CuxSn100-x serves as a model substance to study amorphous systems. Here we report on the thermal conductivity of amorphous and polycrystalline samples prepared at T = 5 K on a microchip. The measurements were performed with a n improved steady-stale technique in the range from 1.2 K < T < 360 K. We s eparate the electronic part from the total thermal conductivity with the Wi edemann-Franz law. The amorphous samples show superconductivity. Below T-c a T-2-dependence due to disorder is observed. At temperatures between T = 3 and 30 K a plateau region due to low-energy excitations is found in the ph onon part of the thermal conductivity. The plateau relates to structural an omalies at scattering vectors K = 2k(F) and shifts with increasing x to low er temperatures. For alloys with x greater than or equal to 60 at% Cu the p lateau is also observed after crystallization but shifts to lower temperatu res. The plateau vanishes after further annealing. (C) 1999 Elsevier Scienc e B.V. All rights reserved.