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Author: search.filters.author.Nukeaw, J.Subject: search.filters.subject.Conduction mechanism

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    Electrical bistable properties of copper phthalocyanine at different deposition rates
    (2012-06-01)
    Onlaor, K.
    ;
    Tunhoo, B.
    ;
    Keeratithiwakorn, P.
    ;
    Thiwawong, T.
    ;
    Nukeaw, J.
    Organic bistable memory device is a next-generation of the electrical memory unit. In this paper, we report about the influence of structural properties on electrical bistable behavior of copper phthalocyanine organic memory device. Copper phthalocyanine (CuPc) layer was prepared by thermal evaporation technique at different deposition rates. When the deposition rate is increased, the film crystalline decreases and the surface morphology gradually changes from large flat grain to fine grain structure. Structural parameters such as the crystalline size of CuPc films and dislocation density can be calculated from XRD spectra. Moreover, the effect of deposition rate of CuPC layer on the bistable properties can be performed by current-voltage characteristics, retention measurement, impedance spectroscopy and temperature dependence measurement. The conduction mechanism in both ON and OFF states of the bistable device was analyzed by theoretical model, which can be proposed as a possible trap center of the carrier trapping and de-trapping process by structural defects in CuPc layer. Furthermore, the reliability issue such as cycling endurance and data retention is presented. © 2012 Elsevier Ltd. All rights reserved.
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    Electrical bistability of tris-(8-hydroxyquinoline) aluminum (Alq 3)/ZnSe organic-inorganic bistable device
    (2012-01-01)
    Onlaor, K.
    ;
    Tunhoo, B.
    ;
    Thiwawong, T.
    ;
    Nukeaw, J.
    We present that the electrical bistability in organic-inorganic bistable devices based on tris-(8-hydroxyquinoline) aluminum (Alq<inf>3</inf>) and zinc selenide (ZnSe) with the tri-layer structure of Alq<inf>3</inf>/aluminum (Al)/ZnSe. The current-voltage characteristics of the bistable device exhibit two electrical states as low (OFF state) and high (ON state) conductivity with ON/OFF ratio about four orders of magnitude. The conduction mechanisms in both ON and OFF states were analyzed by theoretical model. In the OFF state, the conduction mechanisms can be explained by thermionic emission model, which the ON state can be described by ohmic conduction model. The retention times of both states are more than 8000 s, and the device can reproduce continuous write-read-erase-read switching cycles. Moreover, for the organic-inorganic bistable device was kept at one year in ambient condition without encapsulation. The device still exhibited the electrical bistable behavior. Consequently, the ZnSe layer may be led to improve the lifetime property of the bistable device which acted as a self-encapsulating layer. © 2011 Elsevier B.V. All rights reserved.