Electrophysical properties of PCM-materials in crystalline and amorphous states

The temperature dependences of the resistivity, thermopower, and Nernst coefficient were experimentally investigated on the samples of phase change materials with a composition of Ge_0.15Sb_0.85 in both the amorphous and crystalline states. It was observed that the crystalline state is characterized by a metallic type of the thermopower temperature dependences, while the resistivity increases slightly with decreasing temperature and the Nernst coefficient has a positive value and demonstrates the complicated temperature dependence. The conductivity in the amorphous state has an activated character with two different activation energies in low and high temperature ranges; the temperature of the transition between these ranges corresponds to the point of a change of thermopower sign. The results obtained point to a need to take into account a contribution of two types of carriers in the conduction process in both phase states