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Author: search.filters.author.Tunhoo, BenchapolSubject: search.filters.subject.Nanoparticles

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    Flexible and fully transparent WORM memory devices based on Ag nanoparticles blended with poly(ethylene-co-vinyl acetate)
    (2019-12-01)
    Onlaor, Korakot
    ;
    Thiwawong, Thutiyaporn
    ;
    Tunhoo, Benchapol
    Silver nanoparticles (Ag NPs) blended with poly(ethylene-co-vinyl acetate) (EVA) were used as an active layer to fabricate flexible and fully transparent memory devices by using the spin-coating method followed by the thermal roll lamination technique with the structure of ITO/EVA:Ag NPs/ITO. The devices exhibited a non-volatile write-once-read-many-times (WORM) memory type and possessed current bi-stability with ON/OFF current ratio within the range of 10<sup>4</sup>-10<sup>5</sup> at a reading voltage of +1 V. The data continuous read operations reached more than 10 h, which revealed the stability of the memory devices over a long period of time. The conduction mechanisms of the memory device could be explained by theoretical models and proposed by electron trapping at the trapping center of Ag NPs inside the EVA matrix. In addition, the memory device showed a fast response of 231 ns and was fully transparent with maximum transmittance of the device at 83.2%. Further, the devices could be operated under the bending condition of more than 0.83% strain.
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    Multilevel conductance switching and carrier transport mechanisms of memory devices based on an ITO/PVK:Ag nanoparticles/Al structure
    (2018-01-25)
    Onlaor, Korakot
    ;
    Thiwawong, Thutiyaporn
    ;
    Tunhoo, Benchapol
    Multilevel conductance switching was achieved using silver nanoparticles (Ag NPs) embedded in poly(9-vinylcarbazole) (PVK) with a structure of ITO/PVK:Ag NPs/Al. The current-voltage (I-V) curves of the memory devices at low reading voltages showed three distinguished states of current. The memory devices exhibited non-volatile rewritable memory characteristics. The carrier transport mechanisms of the devices in each state were analyzed by theoretical models based on the experimental I-V data. In addition, retention time measurements showed clearly three current states with good data retention properties. From the retention times test, the average values of ON/OFF, ON/intermediate (INTERM) and INTERM/OFF current ratios of the memory devices were 1.7 × 10<sup>6</sup>, 3.5 × 10<sup>2</sup> and 5.0 × 10<sup>3</sup>, respectively.
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    Electrical mechanisms of bi-stable memory devices based on an Al/PVK:ZnO NPs/ITO structure with different ZnO NPs annealing temperatures
    (2016-10-01)
    Onlaor, Korakot
    ;
    Chaithanatkun, Natpasit
    ;
    Tunhoo, Benchapol
    We reported on the influence of the structural properties of zinc oxide nanoparticles (ZnO NPs) on electrical bi-stable device based on an aluminum/poly(9-vinylcarbazole):ZnO NPs/indium-tin oxide structure. ZnO NPs were synthesized by simple precipitation method with different annealing temperatures. When annealing temperature was increased, the ZnO NPs crystallite increased and the ZnO NPs gradually changed shape from nanostar-like to nanospherical. The structural parameters, such as the crystallite size of ZnO NPs and dislocation density, can be calculated from the XRD spectra. The effect of ZnO NPs annealing temperature on memory properties can be measured by current-voltage characteristics and retention time measurements. The maximum ON/OFF current ratio for the memory devices was about 10<sup>3</sup> and the devices exhibited the Write-Once, Read-Many (WORM) memory type. The operating mechanisms of the memory device were analyzed using theoretical models, in which electrons trapping in the ZnO NPs and electrons tunneling among a PVK matrix by direct tunneling process were discussed.
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    Bi-stable switching behaviors of ITO/EVA:ZnO NPs/ITO transparent memory devices fabricated using a thermal roll lamination technique
    (2016-04-01)
    Onlaor, Korakot
    ;
    Thiwawong, Thutiyaporn
    ;
    Tunhoo, Benchapol
    This research reported the transparent non-volatile write-once-read-many-times (WORM) memory behaviors of memory devices based on zinc oxide nanoparticles (ZnO NPs) embedded in an insulating poly(ethylene-co-vinyl acetate) (EVA), sandwiched between two ITO-coated flexible polyethylene naphthalate (PEN) substrates. The memory devices were fabricated employing a thermal roll lamination technique with the laminated-structure of PEN/ITO/EVA:ZnO NPs/ITO/PEN. The average transmittance of the laminated memory device was over 70% for an optical visible range of 400-800 nm. The maximum ON/OFF current ratio for the memory device was about 10<sup>3</sup>. In addition, a reliability study for continuous read operations in a long time memory device is presented. The conductance switching mechanisms of the laminated memory device were analyzed using theoretical models on the basis of the experimental data.