Effects of cobalt-60 gamma-rays on Ge-Se chalcogenide glasses and Ag/Ge-Se test structures

Solid state electrolytes fabricated with chalcogenide glass (ChG) are considered viable candidates for the next generation of non-volatile memory technologies. These glasses, which are composed of group IV and/or group V elements with those of group VI chalcogens (S, Se, and Te), are excellent metal ion conductors. Because of this property, the resistance across structures composed of ChG films sandwiched between active metal (e.g., Ag) and inert metal (e.g., Ni) electrodes can be switched upon the application of sufficient bias, thereby enabling memristive action. In this paper, the effects of 60°Co gamma-ray irradiations on AgGe₃₀Se₇₀ test structures are investigated. The results show that exposure to high-energy photons can trigger the transport of Ag⁺ ions from an active Ag top layer into an underlying Ge₃₀Se₇₀ ChG film. Post-irradiation annealing experiments also indicate that this "photo-doping" process is reversible once the radiation stress is removed. Numerical simulations which model the mechanisms of radiation-induced photo-doping and recovery are shown to agree well with the data. The results and analysis presented in this paper suggest the ChG-based memristors may be more susceptible to transient radiation effects than cumulative radiation damage.