[ODCAD] Cu(TCNQ) as active Layer in Memory Device

Cu(TCNQ) is organometallic material. Organic compound TCNQ has CN group that is good electron acceptor, and form charge transfer complex (CT) with Cu.  There is a set of this type material. They are Cu(TCNE), Cu(TCNAP), Cu(DM-TCNQI).   The conductivity of the material can be manipulated by applying voltage. A structure Cu/Cu(TCNQ)(5~10um)/Cr can be switched from off to On with conductivity change over 100 times when V>Vt~3V. This switch is independent of voltage polarity.  The "On" state stays even after removing  the field.  This memory effect has data retention up to days.  The "on" state can be switched "off" after applying opposite voltage on the device. There are two models to descibe the switching mechanism. Model 1 is Field Induced Electrochemical Reaction.     Cu(TCNQ)  <=> Cu + TCNQ Off state has more Cu(TCNQ) that is thermodynamically more favored.  With the help of field, Cu gains electron back and the mixture Cu+TCNQ is more conductive. This state is less stable and can change back to Cu(TCNQ) either after certain time or with opposite field. A  recent work [1] suggests that the switch is due to Phase change.  CU(TCNQ has two phases. Phase 1 has Cu bonded with two sets of TCNQ in two perpendicular planes.   Phase II has Cu bonded with all TCNQ in almost on teh same plane. Therefore, this allows more dilocalized space for conductive electrone.  Concequently, Phase II has higher conductivity.  This work reports that the phase II has conductivity upto 1000 S/cm, and Phase 1 has conductivity 1.0E-5 S/cm.  The phase I is more stable and can be switched to phase II by external field, and this state can be changed back by opposite field.   1. R. A. Heintz, H. Zhao, X. Ouyang, G. Grandinetti, J. Cowen, and K. R. Dunbar; Inorg. Chem.; 38, 144 (1999) 2. R. S. Potember, T. O. Poehler; Semiconducting Organic Thin Films; 17, 233 (1982) 3. R. S. Potember, T. O. Poehler; Appl. Phys. Lett.; 34, 405 (1979)

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