Chung Kun Song

Dong-A University, Tsau-liang-hai, Busan, South Korea

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Publications (27)34.49 Total impact

  • Organic Electronics 07/2014; · 3.84 Impact Factor
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    ABSTRACT: The effect of solvent additives on the performance of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) field effect transistors (FETs) was investigated. Hole mobilities increased from 0.10 cm2 V−1 s−1 for pristine devices to 0.73 or 0.71 cm2 V−1 s−1, when TIPS-pentacene FETs were processed with diphenyl ether (DPE) or chloronaphthalene (CN), respectively. In order to examine the impact of additives on the surface morphology, molecular ordering and crystallinity of TIPS-pentacene, scanning electron microscopy (SEM), X-ray diffraction (XRD) and optical microscopy measurements were carried out. Appropriate amounts of additives were found to induce the formation of well-ordered crystalline domains in TIPS-pentacene films, resulting in enhanced hole transport as well as consistent device performance. Additionally, reduced contact resistances were observed in devices processed with additives compared to neat TIPS-pentacene FET devices. Our findings indicate that the use of solvent additives constitutes a new and effective methodology for the fabrication of OFETs with improved performance.
    J. Mater. Chem. C. 06/2013; 1(27):4216-4221.
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    ABSTRACT: An AMOLED panel driven by an OTFT-backplane is an attractive display because OTFTs and OLEDs use organic materials with unique characteristics such as low temperature and solution processing ability, and thus are able to implement the key features of future displays. In this study we applied some printing technologies to fabricate an OTFT-backplane for AMOLEDs. Screen printing combined with photolithography with Ag ink was used for the gate electrodes and scan bus lines and contact pads. Ag metal lines with a width of 20 μm and thickness of 60 nm and resistivity of 3.0 × 10−5 Ω cm were achieved. Inkjet printing was applied to deposit TIPS-pentacene as an organic semiconductor. The OTFT-backplane using the Ag gate electrodes and TIPS-pentacene exhibited uniform performance over 17,500 pixels on a 7 in. panel. The mobility was 0.31 ± 0.05 cm2/V s with a deviation of 17%. The AMOLED panel successfully demonstrated its ability to display patterns.
    Organic Electronics 04/2013; 14(4):1218–1224. · 3.84 Impact Factor
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    Jae Seon Kim, Chung Kun Song
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    ABSTRACT: In this paper we analyzed the effects of polystyrene(PS) blended in TIPS-pentacene on the performance of OTFTs. With the various molecular weight and the content of PS the performance of TIPS-pentacene OTFTs was examined and the proper molecular weight and the content were extracted for the best results. With the molecular weight of 9,580 and 0.3 wt% of PS OTFTs produced the mobility of , the subthreshold slope V/dec, the threshold voltage V, the current on/of ratio . Additionally the suitable substrate temperature for ink jet printing of the blended TIPS-pentacene OTFTs was also extracted and it was .
    Journal of the Institute of Electronics and Information Engineers. 01/2013; 50(7).
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    ABSTRACT: We report on methods to control the morphology of droplets of 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-PEN), which are then used in the fabrication of organic thin film transistors (OTFTs). The grain size and distribution of the TIPS-PEN were found to depend on the temperature of the droplets during drying. The performance of the OTFTs could be improved by heating the substrate and also by changing the relative positions of the inkjet-printed droplets. In our experiments, the optimum substrate temperature was 46 °C in air. Transistors with the TIPS-PEN grain boundaries parallel to the current flow between the source and drain electrodes exhibited charge carrier mobilities of 0.44 ± 0.08 cm2/V s.
    Microelectronic Engineering 07/2012; 95:1–4. · 1.22 Impact Factor
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    ABSTRACT: In this study we developed a simple ink-jet process for 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene), which is known as a high-mobility soluble organic semiconductor, to achieve relatively high-mobility and high-uniformity performance for large-area applications. We analyzed the behavior of fluorescent particles in droplets and applied the results to determining a method of controlling the behavior of TIPS-pentacene molecules. The grain morphology of TIPS-pentacene varied depending on the temperature applied to the droplets during drying. We were able to obtain large and uniform grains at 46 °C without any ``coffee stain''. The process was applied to a large-size organic thin-film transistor (OTFT) backplane for an electrophoretic display panel containing 192× 150 pixels on a 6-in.-sized substrate. The average of mobilities of 36 OTFTs, which were taken from different locations of the backplane, was 0.44± 0.08 cm2\cdotV-1\cdots-1, with a small deviation of 20%, over a 6-in.-size area comprising 28,800 OTFTs. This process providing high mobility and high uniformity can be achieved by simply maintaining the whole area of the substrate at a specific temperature (46 °C in this case) during drying of the droplets.
    Japanese Journal of Applied Physics 05/2012; 51(5):1601-. · 1.07 Impact Factor
  • Gi-Seong Ryu, Myung Won Lee, Chung Kun Song
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    ABSTRACT: Printing technologies were applied to fabricate a flexible organic thin-film transistor (OTFT) backplane for electrophoretic displays (EPDs). Various printing processes were adopted to maximize the figures of each layer of OTFT: screen printing combined with reverse offset printing for the gate electrodes and scan bus lines with Ag ink, inkjet for the source/drain electrodes with glycerol-doped Poly (3,4-ethylenedioxythiophene): Poly (styrenesulfonate) (PEDOT:PSS), inkjet for the semiconductor layer with Triisopropylsilylethynyl (TIPS)-pentacene, and screen printing for the pixel electrodes with Ag paste. A mobility of 0.44 cm/V s was obtained, with an average standard deviation of 20%, from the 36 OTFTs taken from different backplane locations, which indicates high uniformity. An EPD laminated on an OTFT backplane with 190×152 pixels on an 8-in panel was successfully operated by displaying some patterns.
    Journal of Information Display. 12/2011; 12(4).
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    ABSTRACT: Organic semiconductor based on anthracene with phenylethynyl end capping units, which has rigid rod-like structure with high aspect ratio, was synthesized by Sonogashira coupling reaction. The structure of obtained material was confirmed by fourier transform infrared spectroscopy, mass and elemental analysis and its physical properties were characterized by ultraviolet–visible spectroscopy and cyclovoltammetry. 2,6-Bis-phenylethynyl-anthracene (BPEA) has deeper highest occupied molecular orbital level with higher stability as well as high intermolecular π–π stacking. The crystalline and morphological properties of BPEA thin film were studied using X-ray diffraction and atomic force microscopy. BPEA forms high long range ordered structure in the film and it exhibited high field effect mobility of 0.42cm2V−1s−1 (on/off ratio of 107) with device reproducibility and high oxidation stability.
    Thin Solid Films 09/2011; 519(22):7998-8002. · 1.87 Impact Factor
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    ABSTRACT: In this article, we describe a supramolecular complex made of cyclodextrin and a chromophoric dye, in which anistropy occurred by the formation of the hexagonal packing of cylindrical cyclodextrin channels. The obtained complex exhibited effective fluorescence quenching in the presence of lead ions based on supramolecular wire assembly and dissociation. Selective and effective fluorescence quenching of the complex is attributed to the break-ups of the supramolecular wire and the unthreading of included dye molecules by lead ions. Though we are not yet sure about the origin of such a high selectivity, a topic that will be elaborated in subsequent investigations, these CD-templated supramolecular properties will be useful in analytical applications as a novel platform for metal ion sensing.
    Dyes and Pigments 01/2011; · 3.53 Impact Factor
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    ABSTRACT: We applied Ar gas injection while drying droplets of TIPS-pentacene in a quartz tube and controlled the growth direction of the grain boundary and the morphology. The organic thin film transistors (OTFTs) showed a high mobility of 0.53±0.02cm2/Vs with a small deviation of 3.7% when the gas direction was parallel to the source–drain current, resulting in the direction of the grain boundary being parallel to the current. In contrast, OTFTs having grain boundaries perpendicular to the current flow displayed mobility of 0.06±0.02cm2/Vs.
    Organic Electronics - ORG ELECTRON. 01/2011; 12(7):1170-1176.
  • Kang Dae Kim, Chung Kun Song
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    ABSTRACT: This study presents low-voltage organic thin-film transistors (OTFT) using a hybrid gate dielectric consisting of aluminum oxide and poly(vinyl phenol). Aluminum oxide with a thickness of 5 nm is directly formed on an aluminum gate electrode by an oxygen plasma process. The poly(vinyl phenol) film with a thickness of 10 nm is deposited on the aluminum oxide by a spin coating process. The proposed OTFTs are able to operate at low voltages lower than 5 V because of the thin gate dielectric. The surface of the hybrid gate dielectric is finished with a hydrophobic poly(vinyl phenol) so that a pentacene semiconductor, which is deposited on the gate dielectric, produces a high quality channel, resulting in a high mobility with 0.63 cm2 V-1 s-1. Additionally, the poly(vinyl phenol) layer reduces the leakage current through the gate dielectric, generating a low off-state current of 0.02 pA/mum and thus a high on/off current ratio of 4.4× 105. Finally, the pin-hole free poly(vinyl phenol) layer protects the thin aluminum oxide gate dielectric from being penetrated by source and drain electrodes; thus, an OTFT with a bottom contact structure is achieved with short channel length.
    Japanese Journal of Applied Physics 11/2010; 49. · 1.07 Impact Factor
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    ABSTRACT: In this paper, The OTFT backplane with bottom contact structure on plastic substrate using combined process will be discussed. The active size of backplane was 6″; in diagonal direction and consisted of 192×150 pixels, containing 1 OTFT and 1 capacitance in each pixel. Each layer of OTFT was used combining process to overcome the problem of printing technique. The gate electrodes were fabricated by screen printing with wet etching. The source drain electrodes were made by ink jet printing combining plasma treatment. Finally, The EPD panel successfully displayed test patterns.
    SID Symposium Digest of Technical Papers. 05/2010; 41(1).
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    Seung Hyeon Jeong, Chung Kun Song, Mihye Yi
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    ABSTRACT: We report a peculiar enhancement in the accumulation capacitance Cacc in the capacitance-voltage (C-V) characteristics of metal-insulator-semiconductor capacitors consisting of poly(4-vinylphenol) (PVP) and pentacene. Cacc at low frequency C-V was five times larger than the PVP dielectric capacitance CPVP. Cacc decreased as the frequency was increased and returned to the level of CPVP at 1 MHz. The origin of the capacitance enhancement appears to be associated with water molecules adsorbed into the PVP dielectric film when considering the correlation with the concentration of PVP polymer in which OH phenol is known to absorb water molecules.
    Applied Physics Letters 01/2009; 94. · 3.52 Impact Factor
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    ABSTRACT: A series of bis-dimethyl-n-octylsilyl end-capped oligothiophenes consisting of two to six thiophene units has been synthesized and characterized to develop novel organic semiconductor materials. The UV–vis spectral data indicate that these silyl end-capped oligothiophenes have longer conjugation lengths as evidenced by the higher λmax values than the corresponding unsubstituted thiophene oligomers. The thermal analyses indicate that the bis-silylated oligothiophenes show lower melting point (DSi-4T=80°C; DSi-5T=115°C; DSi-6T=182°C) than the corresponding dialkylated thiophene oligomers by 100°C and hexamer DSi-6T exhibits a liquid crystalline mesophase at 143°C. The α,ω-bis(dimethyl-n-octylsilyl)oligothiophenes (DSi-6T) have a remarkably high solubility in chloroform which are comparable to the corresponding α,ω-dihexyloligothiophenes. The remarkably increased solubility by these silyl end groups leads bis-silylated oligothiophenes to be applicable to solution processable devices for thin film transisitor (TFT) by utilizing a spin-coating technique. α,ω-Bis(dimethyl-n-octylsilyl)sexithiophene can be deposited as active semiconducting layer in thin film transistors, either by vacuum evaporation or by spin-coating. A high charge-carrier mobility has been obtained for both deposition techniques, μ=4.6×10−2 and 1.4×10−2cm2V−1s−1, respectively.
    Synthetic Metals - SYNTHET METAL. 01/2009; 159(15):1589-1596.
  • Myung Won Lee, Chung Kun Song
    Journal- Korean Physical Society 01/2009; 54. · 0.51 Impact Factor
  • Myung Won Lee, Mi Young Lee, Chung Kun Song
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    ABSTRACT: This is a report on the fabrication of a flexible OTFT backplane for electrophoretic display (EPD) using a printing technology. A practical printing technology for a polycarbonate substrate was developed by combining the conventional screen and inkjet printing technologies with the wet etching and oxygen plasma processes. For the gate electrode, the screen printing technology with Ag ink was developed to define the minimum line width of ∼5 μm and the thickness of ∼70 nm with the resistivity of ∼10 ?•cm, which are suitable for displays with SVGA resolution. For the source and drain (S/D) electrodes, PEDOT:PSS, whose conductivity was drastically enhanced to 450 S/cm by adding 10 wt% glycerol, was adopted. In addition, the modified PEDOT:PSS could be neatly confined in the specific S/D electrode area that had been pretreated with oxygen. The OTFTs that made use of the developed printing technology produced a mobility of 0.13 cm/ and an on/off current ratio of 10, which are comparable to those using thermally evaporated Au for the S/D electrode.
  • Tae Ho Kim, Chang Gi Han, Chung Kun Song
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    ABSTRACT: The instability of threshold voltage and mobility of pentacene thin film transistors using a poly(4-vinylphenol) gate dielectric have been investigated under constant bias stress. The mobility was very stable in vacuum by exhibiting 2% variation after 6 h stress even under the high gate bias stress of VGS=−20 V. Meanwhile, we observe a negative shift of threshold voltage under stress in vacuum. This shift is attributed to charges trapped in deep electronic states in pentacene near the gate interface. We propose a model for the negative shift of the threshold voltage and extract the hole concentration, 4.5×1011 cm−2, needed to avoid the onset of stress effects, resulting in a design rule of the channel width to length ratio larger than 40.
    Thin Solid Films 01/2008; 516(6):1232-1236. · 1.87 Impact Factor
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    ABSTRACT: Two types of nanometer thick gate dielectrics were employed in order to implement a low voltage operation for organic thin film transistors (OTFT). The first device used an organic monolayer that was formed through a self-assembly process of (benzyloxy)-alkyltrichlorosilane (BTS) on a SiO2 substrate. The BTS-OTFTs produced a threshold voltage of -0.50± 0.11 V, a mobility of 0.12± 0.05 cm2 V-1 s-1, and a on/off current ratio of (1.87±1.22)× 102. The second type of gate dielectric used self-grown Al2O3, which was directly grown on a pre-existing Al gate electrode by oxygen plasma process. The self-grown Al2O3-OTFTs exhibited a mobility of 0.12± 0.015 cm2 V-1 s1, a threshold voltage of -1.18± 0.027 V, and an on/off current ratio of (8.76± 5.3)× 103. In particular, as the Al2O3 layer is directly grown on a pre-existing Al gate electrode, an additional patterning process for the gate dielectric is not necessary; thus, the fabrication process is simplified. Furthermore, the process is a low temperature, dry process, thereby allowing for low cost fabrications and flexible applications.
    Japanese Journal of Applied Physics 01/2008; 47. · 1.07 Impact Factor
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    ABSTRACT: We investigate the stability of pentacene thin-film transistors using a poly(4-vinylphenol) (PVP) gate dielectric under constant bias stress. The threshold voltage is shifted to the positive gate voltage when stressed in air, as caused by water vapors in the PVP gate dielectric. Meanwhile, we observe a negative shift under stress in vacuum. This shift is attributed to charges trapped in deep electronic states in pentacene near the gate interface. We propose a model for the negative shift of the threshold voltage and extract the hole concentration 4.5 x 10<sup>11</sup> cm<sup>-2</sup> that is needed to avoid the critical degradation, resulting in a W/L larger than 40.
    IEEE Electron Device Letters 11/2007; · 2.79 Impact Factor
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    Kang Dae Kim, Chung Kun Song
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    ABSTRACT: We propose a method to implement low voltage operation of pentacene thin film transistors (TFTs). Ultrathin Al <sub>2</sub> O <sub>3</sub> was used as a gate dielectric and was directly grown on a preexisting Al gate by an oxygen plasma process. Thus, an extra patterning process for the gate dielectric is not necessary, and the overall fabrication process is thereby simplified. The organic TFTs operated at low voltage, producing 1.5 μ A at V<sub> GS </sub>=-2 V and V<sub> DS </sub>=-1.5 V , with a threshold voltage of -1.18±0.027 V , a mobility of 0.12±0.015 cm <sup>2</sup>/ V s , and an on/off current ratio of 8.76±5.3×10<sup>3</sup> .
    Applied Physics Letters 07/2006; · 3.52 Impact Factor