Negative resistance in cadmium sulphide films

( I, V ) characteristics of aluminium-cadmium-sulphide-aluminium (or indium) thin film structures have been studied. After an irreversible breakdown, the ( I , V ) curve shows an interesting dual negative resistance phenomenon. When the upper electrode is positive the curve first follows a low-conductivity path from which it switches over to a high-conductivity state through a current-controlled negative resistance. On decreasing the voltage, the high-conductivity path is maintained until a critical voltage in the opposite direction is reached when the structure switches back to the low-conductivity state through a voltage-controlled negative resistance region.