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Organic nonvolatile memory devices with charge trapping multilayer graphene film
Ji, Yongsung,Choe, Minhyeok,Cho, Byungjin,Song, Sunghoon,Yoon, Jongwon,Ko, Heung Cho,Lee, Takhee IOP Pub 2012 Nanotechnology Vol.23 No.10
<P>We fabricated an array-type organic nonvolatile memory device with multilayer graphene (MLG) film embedded in polyimide (PI) layers. The memory devices showed a high ON/OFF ratio (over 10<SUP>6</SUP>) and a long retention time (over 10<SUP>4</SUP> s). The switching of the Al/PI/MLG/PI/Al memory devices was due to the presence of the MLG film inserted into the PI layers. The double-log current–voltage characteristics could be explained by the space-charge-limited current conduction based on a charge-trap model. A conductive atomic force microscopy found that the conduction paths in the low-resistance ON state were distributed in a highly localized area, which was associated with a carbon-rich filamentary switching mechanism. </P>
Flexible Organic Memory Devices with Multilayer Graphene Electrodes
Ji, Yongsung,Lee, Sangchul,Cho, Byungjin,Song, Sunghoon,Lee, Takhee American Chemical Society 2011 ACS NANO Vol.5 No.7
<P>We fabricated 8 × 8 cross-bar array-type flexible organic resistive memory devices with transparent multilayer graphene (MLG) electrodes on a poly(ethylene terephthalate) substrate. The active layer of the memory devices is a composite of polyimide and 6-phenyl-C61 butyric acid methyl ester. The sheet resistance of the MLG film on memory device was found to be ∼270 Ω/◻, and the transmittance of separated MLG film from memory device was ∼92%. The memory devices showed typical write-once-read-many (WORM) characteristics and an ON/OFF ratio of over ∼10<SUP>6</SUP>. The memory devices also exhibited outstanding cell-to-cell uniformity with flexibility. There was no substantial variation observed in the current levels of the WORM memory devices upon bending and bending cycling up to 10 000 times. A retention time of over 10<SUP>4</SUP> s was observed without fluctuation under bending.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-7/nn201770s/production/images/medium/nn-2011-01770s_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn201770s'>ACS Electronic Supporting Info</A></P>
Flexible Nanoporous WO<sub>3–<i>x</i></sub> Nonvolatile Memory Device
Ji, Yongsung,Yang, Yang,Lee, Seoung-Ki,Ruan, Gedeng,Kim, Tae-Wook,Fei, Huilong,Lee, Seung-Hoon,Kim, Dong-Yu,Yoon, Jongwon,Tour, James M. American Chemical Society 2016 ACS NANO Vol.10 No.8
<P>Flexible resistive random access memory (RRAM) devices have attracted great interest for future nonvolatile memories. However, making active layer films at high temperature can be a hindrance to RRAM device fabrication on flexible substrates. Here, we introduced a flexible nanoporous (NP) WO3-x RRAM device using anodic treatment in a room-temperature process. The flexible NP WO3-x RRAM device showed bipolar switching characteristics and a high I-ON/IOFF ratio of similar to 10(5). The device also showed stable retention time over 5 X 10(5) s, outstanding cell-to-cell uniformity, and bending endurance over 10(3) cycles when maximum bending conditions.</P>
Ji, Yongsung,Kim, Juhan,Cha, An-Na,Lee, Sang-A,Lee, Myung Woo,Suh, Jung Sang,Bae, Sukang,Moon, Byung Joon,Lee, Sang Hyun,Lee, Dong Su,Wang, Gunuk,Kim, Tae-Wook IOP 2016 Nanotechnology Vol.27 No.14
<P>A highly efficient solution-processible charge trapping medium is a prerequisite to developing high-performance organic nano-floating gate memory (NFGM) devices. Although several candidates for the charge trapping layer have been proposed for organic memory, a method for significantly increasing the density of stored charges in nanoscale layers remains a considerable challenge. Here, solution-processible graphene quantum dots (GQDs) were prepared by a modified thermal plasma jet method; the GQDs were mostly composed of carbon without any serious oxidation, which was confirmed by x-ray photoelectron spectroscopy. These GQDs have multiple energy levels because of their size distribution, and they can be effectively utilized as charge trapping media for organic NFGM applications. The NFGM device exhibited excellent reversible switching characteristics, with an on/off current ratio greater than 10<SUP>6</SUP>, a stable retention time of 10<SUP>4</SUP> s and reliable cycling endurance over 100 cycles. In particular, we estimated that the GQDs layer trapped ∼7.2?×?10<SUP>12</SUP> cm<SUP>−2</SUP> charges per unit area, which is a much higher density than those of other solution-processible nanomaterials, suggesting that the GQDs layer holds promise as a highly efficient nanoscale charge trapping material.</P>
Stable Switching Characteristics of Organic Nonvolatile Memory on a Bent Flexible Substrate
Ji, Yongsung,Cho, Byungjin,Song, Sunghoon,Kim, Tae-Wook,Choe, Minhyeok,Kahng, Yung Ho,Lee, Takhee WILEY-VCH Verlag 2010 Advanced Materials Vol.22 No.28
<B>Graphic Abstract</B> <P>Organic nonvolatile memory devices fabricated on flexible substrates showed rewritable and nearly consistent switching characteristics, regardless of the bending circumstances. This stable memory performance with bending stress is a promising property for the practical memory devices in future flexible electronics. <img src='wiley_img_2010/09359648-2010-22-28-ADMA200904441-content.gif' alt='wiley_img_2010/09359648-2010-22-28-ADMA200904441-content'> </P>