The structure of some chalcogenide glasses

A study using replica electron microscopy, scanning electron microscopy, electron diffraction, X-ray diffraction, sputter etching and differential thermal analysis of the structural properties of glasses having a range of compositions within the AsTeGeSi quaternary system has shown that phase separation generally occurs in the bulk material. The second phase is dispersed as inclusions in the non-crystalline matrix and is apparently non-crystalline away from the boundary of the glass forming region but is crystalline near to the high Te boundary. The crystalline second phase is probably Te. This quaternary system, AsTeGeSi is often used as source material for the fabrication of devices studied for their monostable electrical switching behaviour and the phase separation observed in these materials needs to be considered in the interpretation of the switching properties and for failure analysis of such devices.