Electrical conductivity of melts and their ability to form glasses in the system Ge + As + Te

Abstract

In the system Ge + As + Te, the heavy Te atom facilitates the formation of mesomeric pσ-bonding systems. The glass forming regions are thus small and depend strongly on the quenching conditions. As in the systems Ge + Sb + Se and Ge + As + Se all metallically conducting melts in the system Ge + As + Te solidify to a crystallline structure even when quenched in water. However, not all semiconducting melts belonging to this system become glassy under these conditions. As expected, the transition from melts solidifying to a glass structure to those solidifying to a crystalline structure is more gradual, as is also the transition from metallic to semiconducting melts. All the semiconducting melts become more or less metallically conducting at temperatures between 900 and 1000 °C. The transition can be described by a parabolical or a log log dependence on temperature.

In the chalcogenide systems the melting process often enforces the same bonding mechanism with similar atomic short range order as does the application of high pressures or of strong electric fields. This is especially the case at high temperatures. The enforced mobility of the atoms, their tighter packing and the effect of electrical conductivity often act in the same direction, enhancing structural changes in the same direction.