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Electrical Memory Characteristics of Nitrogen-Linked Poly(2,7-carbazole)s
Hahm, Suk Gyu,Lee, Taek Joon,Kim, Dong Min,Kwon, Wonsang,Ko, Yong-Gi,Michinobu, Tsuyoshi,Ree, Moonhor American Chemical Society 2011 The Journal of Physical Chemistry Part C Vol. No.
<P>We studied the electrical memory characteristics of the following nitrogen-linked poly(2,7-carbazole)s: poly(9-hexadecyl-2,7-carbazole-<I>alt</I>-<I>N</I>,<I>N</I>-(4-hexadecyloxy)aniline), poly(9-hexadecyl-<I>N</I>,<I>N′</I>-diphenylcarbazole-2,7-diamine-<I>alt</I>-1,3-benzene), and poly(9-hexadecyl-<I>N</I>,<I>N′</I>-diphenylcarbazole-2,7-diamine-<I>alt</I>-4,4<I>′</I>-biphenyl). These polymers are amorphous; however, in thin films, they are slightly oriented in the film plane. All polymers in devices with aluminum top and bottom electrodes were found to exhibit similar dynamic random access memory (DRAM) behaviors without polarity. They are operable with a low voltage (less than ±3 V) and a high ON/OFF current ratio (10<SUP>5</SUP>–10<SUP>9</SUP>, depending on the polymer) over the thickness range 8–60 nm. The memory behaviors were found to be governed by space-charge limited conduction and local filament formation. These memory characteristics might originate from the electron-donating carbazole and triphenylamino units in the polymer backbones, which act as charge-trapping sites but have weak electric polarization because of the absence of counterparts. Overall, these polymers are suitable active materials for the mass production at low cost of high-performance, programmable volatile memory devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-44/jp207211e/production/images/medium/jp-2011-07211e_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp207211e'>ACS Electronic Supporting Info</A></P>
Hahm, Suk-Gyu,Jin, Kyeong-Sik,Park, Sam-Dae,Ree, Moon-Hor,Kim, Hyung-Sun,Kwon, Soon-Ki,Kim, Yun-Hi The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.12
With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4'-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4'-trimethylsilylphenyl)pyromellitic dianhydride(BTPD), and 2,2'-bis(4"-tert-butylphenyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyirnides, BBPD-ODA, BBPD-MDA, BBPD-FDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4'-oxydianiline (ODA), 4,4'-methylenediamine (MDA), and 4,4'-(hexafluoroisopropylidene)dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from $0.45{\times}10^{-4}\;-\;1.37{\times}10^{-4}\;J/m^2$ and from $0.86{\times}10^{-5}\;-\;4.26{\times}10^{-5}\;J/m^2$, respectively, depending on the polyimides. The pretilt angles of the LCs were in the range $0.10-0.62^{\circ}$. In summary, the soluble aromatic polyimides reported here are promising LC alignment layer candidates for the production of advanced LC display devices.
Hahm, Suk Gyu,Kang, Nam‐,Goo,Kwon, Wonsang,Kim, Kyungtae,Ko, Yong‐,Gi,Ahn, Seonyoung,Kang, Beom‐,Goo,Chang, Taihyun,Lee, Jae‐,Suk,Ree, Moonhor WILEY‐VCH Verlag 2012 Advanced materials Vol.24 No.8
<P><B>A novel polymer, poly(2‐(<I>N</I> ‐carbazolyl)ethyl methacrylate) end‐capped with fullerene (PCzMA‐C<SUB>60</SUB>)</B>, has been synthesized via living anionic polymerization. Electrically programmable flash memory devices were easily fabricated with this polymer by using solution coating and metal deposition. This polymer was found in these devices to exhibit bipolar and unipolar switching behaviors with a high ON/OFF current ratio, a long retention time, high reliability, and low power consumption. The excellent properties and easy processability of this polymer open up the possibility of the mass production of high performance nonvolatile memory devices at low cost.</P>
Hahm, Suk Gyu,Choi, Seungchel,Hong, Sang-Hyun,Lee, Taek Joon,Park, Samdae,Kim, Dong Min,Kim, Jin Chul,Kwon, Wonsang,Kim, Kyungtae,Kim, Mee-Jung,Kim, Ohyun,Ree, Moonhor Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.15
<P>In this study, novel nonvolatile memory devices, based on a high performance polyimide, poly(3,3′-bis(diphenylcarbamyloxy)-4,4′-biphenylene hexafluoroisopropylidenediphthalimide) (6F-HAB-DPC PI), were fabricated with a simple conventional solution coating process. The devices were found to exhibit programmable, rewritable nonvolatile memory characteristics with a high ON/OFF current ratio of up to 10<SUP>9</SUP>, a long retention time in both ON and OFF states, and low power consumption. Moreover, the active 6F-HAB-DPC PI layer is thermally and dimensionally stable and thus hybridization with a complementary metal-oxide-semiconductor platform is feasible. The advantageous properties and ease of fabrication of the 6F-HAB-DPC PI based devices open up the possibility of the mass production of high performance digital nonvolatile polymer memory devices at low cost.</P> <P>Graphic Abstract</P><P>Electrical devices were fabricated with a thermally stable new polyimide. They reveal excellent memory characteristics, opening up the possibility of mass production of high performance nonvolatile memory devices at low cost. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b814470m'> </P>
High‐Performance n‐Channel Thin‐Film Field‐Effect Transistors Based on a Nanowire‐Forming Polymer
Hahm, Suk Gyu,Rho, Yecheol,Jung, Jungwoon,Kim, Se Hyun,Sajoto, Tissa,Kim, Felix S.,Barlow, Stephen,Park, Chan Eon,Jenekhe, Samson A.,Marder, Seth R.,Ree, Moonhor WILEY‐VCH Verlag 2013 Advanced functional materials Vol.23 No.16
<P><B>Abstract</B></P><P>A new electrontransport polymer, poly{[<I>N,N′</I>‐dioctylperylene‐3,4,9,10‐bis(dicarboximide)‐1,7(6)‐diyl]‐<I>alt</I>‐[(2,5‐bis(2‐ethyl‐hexyl)‐1,4‐phenylene)bis(ethyn‐2,1‐diyl]} (PDIC8‐EB), is synthesized. In chloroform, the polymer undergoes self‐assembly, forming a nanowire suspension. The nanowire's optical and electrochemical properties, morphological structure, and field‐effect transistor (FET) characteristics are investigated. Thin films fabricated from a PDIC8‐EB nanowire suspension are composed of ordered nanowires and ordered and amorphous non‐nanowire phases, whereas films prepared from a homogeneous PDIC8‐EB solution consist of only the ordered and amorphous non‐nanowire phases. X‐ray scattering experiments suggest that in both nanowires and ordered phases, the PDIC8 units are laterally stacked in an edge‐on manner with respect to the film plane, with full interdigitation of the octyl chains, and with the polymer backbones preferentially oriented within the film plane. The ordering and orientations are significantly enhanced through thermal annealing at 200 °C under inert conditions. The polymer film with high degree of structural ordering and strong orientation yields a high electron mobility (0.10 ± 0.05 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>), with a high on/off ratio (3.7 × 10<SUP>6</SUP>), a low threshold voltage (8 V), and negligible hysteresis (0.5 V). This study demonstrates that the polymer in the nanowire suspension provides a suitable material for fabricating the active layers of high‐performance n‐channel FET devices via a solution coating process.</P>
Nam, Sungho,Hahm, Suk Gyu,Khim, Dongyoon,Kim, Hwajeong,Sajoto, Tissa,Ree, Moonhor,Marder, Seth R.,Anthopoulos, Thomas D.,Bradley, Donal D. C.,Kim, Youngkyoo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.15
<P>Three triple bond-conjugated naphthalene diimide (NDI) copolymers, poly{[<I>N</I>,<I>N</I>′-bis(2-R<SUB>1</SUB>)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-<I>alt</I>-[(2,5-bis(2-R<SUB>2</SUB>)-1,4-phenylene)bis(ethyn-2,1-diyl)]} (PNDIR<SUB>1</SUB>-R<SUB>2</SUB>), were synthesized via Sonogashira coupling polymerization with varying alkyl side chains at the nitrogen atoms of the imide ring and 2,5-positions of the 1,4-diethynylbenzene moiety. Considering their identical polymer backbone structures, the side chains were found to have a strong influence on the surface morphology/nanostructure, thus playing a critical role in charge-transporting properties of the three NDI-based copolymers. Among the polymers, the one with an octyldodecyl (OD) chain at the nitrogen atoms of imide ring and a hexadecyloxy (HO) chain at the 2,5-positions of 1,4-diethynylbenzene, P(NDIOD-HO), exhibited the highest electron mobility of 0.016 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>, as compared to NDI-based copolymers with an ethylhexyl chain at the 2,5-positions of 1,4-diethynylbenzene. The enhanced charge mobility in the P(NDIOD-HO) layers is attributed to the well-aligned nano-fiber-like surface morphology and highly ordered packing structure with a dominant edge-on orientation, thus enabling efficient in-plane charge transport. Our results on the molecular structure-charge transport property relationship in these materials may provide an insight into novel design of n-type conjugated polymers for applications in the organic electronics of the future.</P> [FIG OMISSION]</BR>
이승로,전석철,박상규,박영근,함창곡 한양대학교 의과대학 1983 한양의대 학술지 Vol.3 No.2
The authors experienced 2 cases of Sturge-Weber syndrome which showed typical appearance of the disease, clinically and radiologically. Especially, these showed extensive calcification and diffuse cortical atrophy of frontal and parietal lobe, which was known as rarely demonstrated findings. Thus the authors report these cases with emphasis in plain skull and brain C.T. findings with a brief review of the literatures.