Electrical switching and memory phenomena in Cu-TCNQ thin films

Abstract

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.

Electronic transport of molecular systems

“…This observation could possibly be caused by excess charge trapped in the junction. Memory effects are also observed in devices with the molecules having only the nitro moiety (2), although in this case the storage was of a low conductivity state 4 after an initial positive sweep from 0 to 1.75 V in 1 min, opposite to that of molecule (1). Fig.…”

“…Electronic memories that operate at the charge limit (e.g., by single electron effects) have been demonstrated [34,35], but have not yet addressed the dimensional limit; i.e., a single molecule. Although memory phenomena has been studied in bulk organic materials (such as organometallic charge-transfer complex salts [1]), we will demonstrate nanoscale electronically programmable and erasable memory devices utilizing molecular SAM; and a memory cell applicable to a random access memory (RAM). Fig.…”

“…Only one molecule is drawn for simplicity. write, read, and erase sequences for (1). An initially low conductivity state (low r) is changed (written) into a high conductivity state (high r) upon application of a voltage pulse.…”

“…In 1979, Potember et al [1] reported bistable, reproducible, and nanosecond electronic switching and memory phenomena in an organometallic charge-transfer (CT) complex salt CuTCNQ formed by TCNQ (7,7,8,8-tetracyanop-quinodimethane), which acts as an electron acceptor with metallic copper as the electron-rich donor. In these materials the switching and memory phenomena are given rise to by the field assisted structural changes such as phase transitions, crystallization, and metal filament formation assisted by highly localized Joule heating.…”

Dynamic Behavior of Resistive Random Access Memories (RRAMS) Based on Plastic Semiconductor

“…One emerging candidate is the resistance random access memory (RRAM) based on metal oxides [2,3] and organic semiconductors [4][5][6]. These RRAMs have shown electrically induced resistive switching effects and have been proposed as the basis for future non-volatile memories.…”