Thermoelectricity of disordered films near the metal?non-metal transition

The thermopower, S, and the electrical conductivity, sigma, of amorphous CuxSb1-x films were measured in situ at low temperatures (T > 1.5 K). We performed an experimental investigation of the low temperature slope of S(T), i.e. S/T\(T --> 0), in the concentration range close to the metal-non-metal transition (MNT) which appears at a critical concentration, x(c). We observed an increase of S/T\(T --> 0) when approaching the MNT from the metallic side. However, close to the transition S/T\(T) (--> 0) does not diverge as predicted by theoretical calculations for a disorder-driven MNT. These results are contrary to our previous interpretation of S/T\(T --> 0) of amorphous AuxSb1-x near the MNT. Furthermore, our investigations of films with x approximate to x(c) show that annealing changes sigma from metallic to non-metallic whereas S and S/T\(T --> 0) remains unchanged. (C) 1999 Published by Elsevier Science B.V. All rights reserved.