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Baek, Yonghwa,Lim, Sooman,Yoo, Eun Joo,Kim, Lae Ho,Kim, Haekyoung,Lee, Seung Woo,Kim, Se Hyun,Park, Chan Eon American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.17
<P>Organic field-effect transistors (OFETs) that operated with good electrical stability were prepared by synthesizing fluorinated polyimide (PI) gate dielectrics based on 6FDA–PDA–PDA PI and 6FDA–CF3Bz–PDA PI. 6FDA–PDA–PDA PI and 6FDA–CF3Bz–PDA PI contain 6 and 18 fluorine atoms per repeat unit, respectively. These fluorinated polymers provided smooth surface topographies and surface energies that decreased as the number of fluorine atoms in the polymer backbone increased. These properties led to a better crystalline morphology in the semiconductor film grown over their surfaces. The number of fluorine atoms in the PI backbone increased, the field-effect mobility improved, and the threshold voltage shifted toward positive values (from −0.38 to +2.21 V) in the OFETs with pentacene and triethylsilylethynyl anthradithiophene. In addition, the highly fluorinated polyimide dielectric showed negligible hysteresis and a notable gate bias stability under both a N<SUB>2</SUB> environment and ambient air.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-17/am5035076/production/images/medium/am-2014-035076_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5035076'>ACS Electronic Supporting Info</A></P>
Baek, Yonghwa,Li, Xinlin,Kim, Nahae,Park, Chan Eon,An, Tae Kyu,Kim, Juyoung,Kim, Se Hyun The Royal Society of Chemistry 2019 Journal of materials chemistry. C, Materials for o Vol.7 No.37
<P>The sol-gel method is a low-temperature, highly controllable and cost-effective method for producing homogeneous and high-quality ultrafine nanostructured thin films. Despite these advantages, sol-gel derived gate dielectrics have received little attention. Here, we synthesized a sol-gel derived organic-inorganic (O-I) hybrid gate dielectric (AGPTi) and demonstrated the stability and flexibility of organic thin-film transistors (OTFTs) made with it. The AGPTi film was simply fabricated from three conventional precursors, namely (3-glycidyloxypropyl)trimethoxysilane (GPTMS), propyltrimethoxysilane (PTMS), and titanium(iv) isopropoxide (TTiP), and a newly synthesized alkoxysilane-functionalized amphiphilic polymer (AFAP) under mild conditions (120 °C for 60 min). This research revealed several important benefits of including such an amphiphilic polymer in sol-gel derived O-I hybrid gate dielectrics: a considerable enhancement of sol stability; an ability to achieve a high-quality thin film with elaborate structures of small nanoclusters; and a dramatic improvement of adhesion, leakage current density of gate dielectrics, electrical stability and flexibility of devices. We expect this study to open up new applications for O-I hybrid materials in flexible electronics.</P>
Yonghwa Baek(백용화),Xinlin Li,Prerna Chaudhary,Chan Eon Park(박찬언),Sung Soo Han(한승수),Tae Kyu An(안태규),Se Hyun Kim(김세현) 한국고분자학회 2019 폴리머 Vol.43 No.1
폴리이미드는 대부분의 고분자 필름의 단점으로 지적되고 있는 열적, 화학적 취약성을 극복할 수 있는 좋은 재료이다. 이렇게 우수한 특성에도 불구하고, 폴리이미드는 전구체인 폴리아믹산의 낮은 용해도로 인해 가공성이 좋지 않을 뿐만 아니라, 특유의 황토빛을 띠는 성질로 인하여 디스플레이 분야로의 응용이 제한적이다. 본 연구에서는 폴리아믹산의 디아민 단량체에 시아노기(-CN)를 도입하여, 폴리이미드의 우수한 내화학성, 내열성, 전기적특성을 그대로 지니면서도 전자 전이 복합화에 의해 황토색 빛을 띠는 현상을 극복하여 무색 투명한 형태를 띠는 폴리이미드 필름인 poly(2-cyano-p-phenylene pyromellitimide; cy-PPI)를 제조하고 유기전계효과 트랜지스터의 절연층으로 적용시켜보았다. cy-PPI 박막은 우수한 절연특성을 보여주었을 뿐만 아니라, 그 위에서 반도체 결정이 잘 성장하게 해주었다. 그 결과, cy-PPI 절연층이 도입된 펜타센 트랜지스터 소자에서 0.15 ㎠/Vs의 전하이동도와 1.2×10<SUP>5</SUP>의 점멸비의 우수한 전기적 성능을 나타내었다. Polyimides are attractive choices for the formation of films in various industries due to their excellent mechanical, thermal, and chemical stabilities. However, the insolubility of their precursors (poly(amic acid); PAA) and the intrinsically poor optical transmittance of polyimide films have impeded their applications in various fields. In this study, we present newly synthesized cyanated polyimide gate dielectrics, poly(2-cyano-p-phenylene pyromellitimide) (cy-PPI), and applied them to organic field-effect transistors (OFETs). The strongly electron-withdrawing cyano groups of PAA played a critical role in improving the solubility and transparency of the polyimide. The solution-processed cy-PPI films exhibited good dielectric properties, and their smooth surfaces led to a better crystalline morphology in the pentacene film grown over their surfaces. As a result, the good electrical properties (0.15 ㎠/Vs of field-effect mobility and 1.2×10<SUP>5</SUP> of on/off ratio) were achieved for the pentacene-based cy-PPI OFETs.
화물과 여객의 상대적 가치를 기준으로 하는 새로운 공항 처리량단위(WLU) 개발 연구
백소라,박용화,임철현,BAEK, Sora,PARK, Yonghwa,LIM, Cheolhyun 대한교통학회 2017 대한교통학회지 Vol.35 No.5
본 연구는 공항에서 활용되는 새로운 지표를 제시하고자 시작되었다. 일반적으로 공항에서는 여객과 화물을 처리하게 되며, 공항은 이를 통해 수익을 창출하게 되는 것이다. 하지만 공항들 모두가 여객과 화물처리실적이 동일한 분포를 보일 수는 없는 것이다. 여러 공항들을 상호비교 분석할 경우, 통일된 공항처리량 지표가 적용되어야만 공정한 결과를 기대할 수 있는 것이다. 현재 사용되고 있는 여객과 화물을 하나로 통합하여 적용하는 지표로는 '공항처리량단위(Work Load Unit)'가 있으며, 이는 여객 1명의 가치가 화물 100Kg의 화물량과 동등하다는 가정을 한 것이다. 기존의 WLU는 타당한 근거나 분석을 통해 설정되었다기보다는 공항에서 수행된 업무부하 정도에 관한 경험들을 바탕으로 설정된 것이므로 논란의 여지가 많다. 이와 같은 한계를 극복하고 새로운 지표를 제시하는 것이 본 연구의 목적이다. 여러 가지 접근방법을 적용할 수 있겠으나, 본 연구에서는 화물과 여객이 공항수익에 기여하는 상대적 가치가 어떻게 되는지를 비교하는 방법을 적용하였다. 화물가치와 여객가치를 분석하기 위해서 공항수익을 크게 항공기 운항관련 수익, 여객처리 관련 수익, 상업수익 등으로 구분하였다. 상대가치 분석을 위해 아시아 14개 공항, 유럽 18개 공항, 북미 지역 18개 공항 등 총 50개 공항이 선정되었다. 최종분석 결과에 따르면, 여객 1명의 수익기여를 기준으로 할 때 화물 280Kg과 동등하다는 결론을 도출하였다. 이는 기존에 적용되던 여객 1명당 화물의 가치를 100Kg으로 설정한 것보다 높은 수치를 보였다. This study was carried out to suggest new indicators to be used at airports. Generally, passengers and cargo will be handled at the airport, and the airport will achieve revenues through them. However, all airports can not have the same distribution of passenger and cargo throughput. When comparing and analyzing several airports, a uniform result can be expected only if a unit airport throughput indicator is applied. The 'Work Load Unit' is an indicator that integrates passengers and cargo into one, and assumes that the value of one passenger is equivalent to the cargo volume of 100kg. The existing WLU was set up based on the experience at the airport rather than being established through reasonable grounds or analysis, so there was a lot of controversy. The purpose of this study is to overcome these limitations and to suggest new index. In this study, we applied a method to compare the relative value of cargo and passenger to airport revenue. In order to analyze cargo value and passenger value, airport revenues are classified into aircraft operation related revenues, passenger handling related revenues, and commercial revenues. A total of 50 airports were selected, including 14 airports in Asia, 18 airports in Europe and 18 airports in North America. According to the final analysis results, it is concluded that the cargo is equivalent to 280kg of cargo based on the contribution of one passenger averagely. This is higher than the value of 100Kg cargo per passenger.
열교환기용 외경 9.52㎜ 마이크로휜 관의 고성능화 및 경량화에 관한 연구 : 증발 열전달 특성
임용빈(Yongbin IM),하야세 가쿠(Gaku HAYASE),최용화(Yonghwa CHOI),김영민(Youngmin KIM),최형서(Hyoungseo CHOI),길성호(Seongho KIL),윤백(Baek YOUN) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
This paper reports a development of the Samsung electronics' new 9.52 ㎜ micro-fin tube for an air-conditioner and heat pumps. To optimize the micro-fin structure effect on the heat transfer characteristics and unit mass of the tube, empirical correlations are used and verified with experiments for a single-tube and a finned tube type heat exchanger. An experimental investigation of condensation heat transfer is conducted and R-22 is used as test refrigerant. The unit mass of the optimized micro-fin tube against the conventional tube is 12% lighter although wall thickness and strength of the burst pressure are the same degree. The evaporating heat transfer coefficient of the new 9.52 ㎜ micro-fin tube' is increased and the refrigerant pressure drop is decreased compare with the conventional tube. Also, the unit weight per length of the new tube is reduced.
Kim, Lae Ho,Jang, Jin Hyuk,Jeong, Yong Jin,Kim, Kyunghun,Baek, Yonghwa,Kwon, Hyeok-jin,An, Tae Kyu,Nam, Sooji,Kim, Se Hyun,Jang, Jaeyoung,Park, Chan Eon Elsevier 2017 Organic Electronics Vol.50 No.-
<P><B>Abstract</B></P> <P>Polymer substrates are essential components of flexible electronic applications such as OTFTs, OPVs, and OLEDs. However, high water vapor permeability of polymer films can significantly reduce the lifetime of flexible electronic devices. In this study, we examined the water vapor permeation barrier properties of Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> mixed oxide films on polymer substrates. Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> films deposited by plasma-enhanced atomic layer deposition were transparent, chemically stable in water and densely amorphous. At 60 °C and 90% relative humidity (RH) accelerated condition, 50-nm-thick Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> had water vapor transmission rate (WVTR) = 1.44 × 10<SUP>−4</SUP> g m<SUP>−2</SUP> d<SUP>−1</SUP>, whereas single layers of Al<SUB>2</SUB>O<SUB>3</SUB> had WVTR = 3.26 × 10<SUP>−4</SUP> g m<SUP>−2</SUP> d<SUP>−1</SUP> and of HfO<SUB>2</SUB> had WVTR = 6.75 × 10<SUP>−2</SUP> g m<SUP>−2</SUP> d<SUP>−1</SUP>. At 25 °C and 40% RH, 50-nm-thick Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> film had WVTR = 2.63 × 10<SUP>−6</SUP> g m<SUP>−2</SUP> d<SUP>−1</SUP>, which is comparable to WVTR of conventional glass encapsulation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Al<SUB>2</SUB>O<SUB>3</SUB>, HfO<SUB>2</SUB>, and Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> mixed oxide films were deposited by plasma-enhanced atomic layer deposition (PEALD). </LI> <LI> Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> mixed oxide films were prepared by alternating deposition of Al<SUB>2</SUB>O<SUB>3</SUB> and HfO<SUB>2</SUB> (one layer of each per cycle). </LI> <LI> Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> mixed oxide films had densely-packed amorphous structure due to Al<SUB>2</SUB>O<SUB>3</SUB> and high chemical stability due to HfO<SUB>2</SUB>. </LI> <LI> All Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> mixed oxide films were less permeable to moisture than were single Al<SUB>2</SUB>O<SUB>3</SUB> or HfO<SUB>2</SUB> films. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>