Electrical switching and memory phenomena in Cu-TCNQ thin films

Stable and reproducible current-controlled bistable electrical switching has been observed in polycrystalline organic semiconducting films. The effect has been observed in a lamellar structure with a film of microcrystalline Cu-TCNQ between Cu and Al electrodes where the Cu-TCNQ is grown on a Cu substrate via a spontaneous electrolysis technique. The switching effect is insensitive to moisture and is observed over a large temperature range. The current-voltage characteristics reveal an abrupt decrease in impedance from 2 MΩ to less than 200 Ω at a field strength of 4×103 V/cm. The transition from a high- to low-impedance state occurs with delay and switching times of approximately 15 and 10 nsec, respectively. Switching with high-power dissipation yields a low-impedance memory state which can be erased by application of a short current pulse. An interpretation of this behavior is based on the bulk properties of the mixed valence semiconductor Cu-TCNQ.