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Cho, Hyunduck,Kim, Seohee,Hong, Yongtaek,Lee, Changhee TaylorFrancis 2009 Molecular Crystals and Liquid Crystals Vol.513 No.1
<P> Inverters were fabricated with pentacene organic thin film transistors (OTFTs) using inkjet printing method. The gate, source and drain electrodes were printed with Ag ink. The mobility and threshold voltage of the bottom-contact OTFT were 0.078 cm2/Vs and 2.8 V, respectively. Printed inverters operated well in 200 Hz at VDD = -20 V.</P>
게이트 바이어스 스트레스 변화를 줄일 수 있는 다층 게이트 절연층 OTFT 제작
조현덕(Hyunduck Cho),곽정훈(Jeonghun Kwak),이창희(C. H. Lee) 대한전자공학회 2007 대한전자공학회 학술대회 Vol.2007 No.11
The change of pentacene OTFT Characteristics under negative gate bias stress is analyzed. For PVA gate dielectric, positive threshold voltage shift was observed. But for PMMA gate dielectric, the polarity of threshold voltage shift was in the opposite direction. The cause of these different gate bias effects are considered as electron trap from gate electrode for PVA and hole trap from source/drain for PMMA. OTFT with multi-layer gate dielectric(PMMA/PVA) is fabricated and shows small gate-bias-stress effect.
Cho, Hyunduck,Kwak, Jeonghun,Lim, Jaehoon,Park, Myeongjin,Lee, Donggu,Bae, Wan Ki,Kim, Youn Sang,Char, Kookheon,Lee, Seonghoon,Lee, Changhee American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.20
<P>To realize the full-color displays using colloidal nanocrystal quantum dot (QD)-based light emitting diodes (QLEDs), the emissive QD layer should be patterned to red (R), green (G), and blue (B) subpixels on a micrometer scale by the solution process. Here, we introduced a soft contact QD-transplanting technique onto the vacuum-deposited small molecules without pressure to pattern the QD layer without any damage to the prior organic layers. We examined the patternability of QDs by studying the surface properties of various organic layers systematically. As a result, we found that the vacuum-deposited 4,4′,4″-tri(<I>N</I>-carbazolyl)triphenylamine (TCTA) layer is suitable for QD-transplanting. A uniform and homogeneous QD patterns down to 2 μm could be formed for all the RGB QDs (CdSe/CdS/ZnS, CdSe@ZnS, and Cd<SUB>1–<I>x</I></SUB>Zn<SUB><I>x</I></SUB>S@ZnS, respectively) with this method. Finally, we demonstrated the R, G, and B QLEDs by transplanting each QD onto the soft TCTA layer, exhibiting higher brightness (2497, 14 102, and 265 cd m<SUP>–2</SUP>, respectively) and efficiency (1.83, 8.07, and 0.19 cd A<SUP>–1</SUP>, respectively) than those of the previous QLEDs fabricated by other patterning methods. Because this pressure-free technique is essential for patterning and stacking the QDs onto the soft organic layer, we believe that both fundamental study and the engineering approach presented here are meaningful for the realization of the colloidal QD-based full-color displays and other optoelectronic devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-20/acsami.5b01738/production/images/medium/am-2015-01738a_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b01738'>ACS Electronic Supporting Info</A></P>
High-Mobility Pyrene-Based Semiconductor for Organic Thin-Film Transistors
Cho, Hyunduck,Lee, Sunyoung,Cho, Nam Sung,Jabbour, Ghassan E.,Kwak, Jeonghun,Hwang, Do-Hoon,Lee, Changhee American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.9
<P>Numerous conjugated oligoacenes and polythiophenes are being heavily studied in the search for high-mobility organic semiconductors. Although many researchers have designed fused aromatic compounds as organic semiconductors for organic thin-film transistors (OTFTs), pyrene-based organic semiconductors with high mobilities and on–off current ratios have not yet been reported. Here, we introduce a new pyrene-based p-type organic semiconductor showing liquid crystal behavior. The thin film characteristics of this material are investigated by varying the substrate temperature during the deposition and the gate dielectric condition using the surface modification with a self-assembled monolayer, and systematically studied in correlation with the performances of transistor devices with this compound. OTFT fabricated under the optimum deposition conditions of this compound, namely, 1,6-bis(5′-octyl-2,2′-bithiophen-5-yl)pyrene (BOBTP) shows a high-performance transistor behavior with a field-effect mobility of 2.1 cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP> and an on–off current ratio of 7.6 × 10<SUP>6</SUP> and enhanced long-term stability compared to the pentacene thin-film transistor.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-9/am4005368/production/images/medium/am-2013-005368_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am4005368'>ACS Electronic Supporting Info</A></P>
Organic complementary inverter and ring oscillator on a flexible substrate
Mingyu Kim,Hyunduck Cho,곽정훈,Chan-mo Kang,Myeong-jin Park,이창희 한국정보디스플레이학회 2011 Journal of information display Vol.12 No.1
A complementary inverter was fabricated using pentacene and N-N-dioctyl-3,4,9,10-perylene tetracarboxylic diimide-C8(PTCDI-C8) for p- and n-type transistors on a poly(ether sulfone) substrate, respectively. The mobilities of the p- and n-type transistors were 0.056 and 0.013 cm2/Vs, respectively. The inverter, which was composed of p- and n-type transistors, showed a gain of 48.6 when VDD = −40V and at the maximum noise margin of VDD/2. A ring oscillator was also fabricated by cascading five inverters. The five-stage ring oscillator showed the maximum output frequency of 10 kHz whenVDD = −170 V.
PCBM을 이용한 n-type OTFT 제작 및 TFT 저항 연구
곽정훈(Jeonghun Kwak),조현덕(Hyunduck Cho),이창희(Changhee Lee) 대한전자공학회 2007 대한전자공학회 학술대회 Vol.2007 No.11
We fabricated n-type OTFTs using PCBM as an active layer by spin-coating and vacuum evaporation. Both devices showed the mobility about 0.003~0.01 ㎠/Vs, and the threshold voltage about 40V. The TFT-on resistance was compared by measuring the TFT characteristics. We also compared the contact resistance between Al and Au for the source and drain electrode. We can apply TFT resistance analysis to electronic circuitry for OTFTs.
Meta - Analysis를 통한 스키 리조트의 서비스품질 연구의 효과 크기분석
최용성 ( Yongsung Choi ),김현덕 ( Hyunduck Kim ) 한국스포츠산업경영학회 2015 한국스포츠산업경영학회지 Vol.20 No.5
본 연구는 메타분석을 활용하여 스키리조트 서비스품질 연구의 하위 요인과 만족, 재방문의 영향력을 실증적으로 규명하는 것이다. 자료의 분석을 위해 스키리조트 서비스 품질 하위요인과 지각된 요인간의 만족, 재방문의 상관관계 수치가 적용된 랜덤효과를 분석 하였으며, 구체적인 자료처리에는 메타분석 소프트웨어 프로그램인 Comprehensive Meta Analysis Version2(CMA)를 사용하였다. 연구결과는 다음과 같다. 첫째, 스키 리조트에서 서비스 품질 연구들에 보고된 서비스 품질 요인들이 만족 효과 크기(95% CI [0.37, 0.48] ES=.0.427) 및 재방문 효과 크기(95% CI [0.37, 0.48] ES=.0.412)는 전반적으로 큰 수준이었으며 만족 및 재방문에 긍정적인 영향을 미치는 것으로 분석 되었다. 둘째, 스키 리조트에서 서비스 품질 하위요인과 만족의 효과 크기는 신뢰성(95% CI [0.27, 0.58] ES=.436)이 가장 큰 수준으로 나타났으며 유형성, 보장성, 공감성, 반응성의 순서로 분석 되었다. 셋째, 스키 리조트에서 서비스 품질 하위요인과 재방문의 효과 크기는 반응성(95% CI [0.14, 0.73] ES=.0.487)이 가장 큰 수준으로 나타났으며 유형성, 보장성, 신뢰성, 공감성 순서로 높게 나타났다. This study empirically investigates the sub-factors of service quality at ski resorts and their effects on satisfaction and revisit intention through meta-analysis methodology utilizing the Comprehensive Meta Analysis Version 2(CMA) software package to process the data. The findings of this study are as follows: first, the service quality factor overall had a high effect level and a positive effect on satisfaction (95% CI [0.37, 0.48] ES=.0.427) and repeat visits 95% CI [0.37, 0.48] ES=.0.412). Second, in terms of the effect size by sub-factors of service quality on satisfaction, the sub-factor of reliability was highest (95% CI [0.27, 0.58] ES=.436), followed by tangibility, assurance, empathy, and responsiveness. Third, in terms of the effect size regarding the sub-factors of service quality on repeat visits, the sub-factor of responsiveness was highest (95% CI [0.14, 0.73] ES=.0.487), followed by tangibility, assurance, reliability, and empathy.
Kim, Seohee,Cho, Hyunduck,Hong, Yongtaek,Lee, Changhee TaylorFrancis 2009 Molecular Crystals and Liquid Crystals Vol.513 No.1
<P> We report the electrode-area dependence of the high-frequency characteristics of polymer diodes fabricated on a flexible poly(ether sulfone) (PES) substrate with inkjet-printed Ag electrode as an anode. Active layer of poly(3-hexylthiophene-2,5-diyl) (P3HT) layer was spin-coated on the Ag anode and then Al cathode was evaporated on the P3HT layer. The rectifying characteristics of P3HT diodes with different area sizes were compared, and their frequency response was analyzed for the sinusoidal input of different frequencies. The diode with smaller area exhibited higher breakdown voltage and operating frequency: The diode with a small area of 0.05 mm2 showed a 3 dB point at 1.8 MHz.</P>