Thermoelectric power of amorphous alloys near the metal-insulator transition

The thermoolectric powerS and the electrical conductivity σ of amorphous Au_xSb_100-x and Cu_xSb_100-x films have been measured in the temperature range between about 2 K and 350 K for concentrations close to the eetal-insulator transition. In both systems the transition occurs at a critical concentrationx _c≈8 at.% noble metal content. A characteristic feature of the transition is in both cases a strong increase of the low temperature slope of the thermopower, i.e.S/T| _t»0 , when approachingx _c from the metallic side. The results are compared with different theoretical predictions for the metal-insulator transition. Furthermore we report on the changes ofS and σ during annelaing. It will be shown that especiallyS(T) of the samples withx close tox _c depends strongly on the annealing state of the films.