Mass transport in chalcogenide electrolyte films – materials and applications

Certain metals can be added to thin films of chalcogenide glasses by photodissolution to create materials with unique morphology and properties. When Ag is combined in this fashion with Ge–Se or Ge–S glasses, the resulting ternary contains a dispersed nanocrystalline Ag₂S(e) phase that has large quantities of mobile metal ions. The presence of these ions allows the ternaries to act as solid electrolytes. If an anode which has an oxidizable form of the ionic metal and an inert cathode are applied in contact with such a phase-separated electrolyte, an ion current can flow under an applied bias in excess of a few hundred millivolt. Electrons from the cathode reduce the excess metal due to the ion flux and an electrodeposit forms on or in the electrolyte. Utilizing this effect, we developed programmable metallization cell (PMC) technology which offers new functionality for such materials. Based on mass transport driven by electrochemical processes, PMC technology may be applied in solid state electronics, integrated optics, microelectromechanical systems (MEMS), and microfluidics. This paper is a review of the unique materials aspects of thin film solid electrolytes formed by photodissolution of metal into a chalcogenide base glass and the demonstrated applications of this technology.