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Effect of Carboxylic Acid on Sintering of Inkjet-Printed Copper Nanoparticulate Films
Woo, Kyoohee,Kim, Youngwoo,Lee, Byungyoon,Kim, Jonghee,Moon, Jooho American Chemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.7
<P>The reduction effect of various carboxylic acids on inkjet-printed copper film was investigated. Carboxylic acids were exposed to the film by nitrogen gas that was bubbled through the liquid acids during the annealing process. It was observed that in the case of saturated monocarboxylic acid (formic, acetic, propionic, butyric), the acids with shorter hydrocarbon chains perform better in reducing the surface copper oxides in the printed copper conductive film. The printed films exposed to formic acid vapor exhibited the lowest resistivity (3.10 and 2.30 μΩ cm when annealed at 200 and 250 °C, respectively). In addition, the oxalic acid more effectively reduces copper oxide than formic acid and its usage can shorten the annealing time for highly conductive printed copper film. This reductive annealing process allows fabrication of copper patterns with low resistivity, (3.82 μΩ cm annealed at 250 °C) comparable to the resistivity of bulk copper.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2011/aamick.2011.3.issue-7/am2002907/production/images/medium/am-2011-002907_0004.gif'></P>
Relationship between printability and rheological behavior of ink-jet conductive inks
Woo, Kyoohee,Jang, Daehwan,Kim, Youngwoo,Moon, Jooho Elsevier 2013 Ceramics international Vol.39 No.6
<P><B>Abstract</B></P> <P>The application of ink-jet printing technologies suitable for the direct writing of complex patterns requires ink-jet printable inks with appropriate properties. Good ink-jet printability and particle-dispersion stability of inks are necessary for ink-jet printing in a particle-included dispersion system. This study investigates the effects of the rheological properties of silver nanoparticle conductive inks with different dispersion states on printability and ink stability. In addition, the electrical properties (i.e., resistivity) of films that were annealed at temperatures ranging from 300°C to 500°C and fabricated by three inks with different dispersion states were measured, revealing that film conductivity was strongly related to the dispersion state of the ink.</P>
Early Admissions with Multi-type Students
( Woo-jin Kim ),( Youngwoo Koh ) 한양대학교 경제연구소 2021 JOURNAL OF ECONOMIC RESEARCH Vol.26 No.3
We study a college admissions problem in which colleges admit students in the early and regular admissions, and students’ types are revealed sequentially through the admission process. We show that a less popular college has an incentive to preempt students based on partial information about their types in the early stage, especially when the quality gap between colleges is small or colleges’ capacity is large. The preemptive movement of the less popular college makes a more popular college admit students in the early stage who otherwise would admit students in the regular stage after observing full information about students’ types. This makes the admission more competitive and the matching between colleges and students less assortative.
A non-toxic, solution-processed, earth abundant absorbing layer for thin-film solar cells
Woo, Kyoohee,Kim, Youngwoo,Moon, Jooho The Royal Society of Chemistry 2012 Energy & environmental science Vol.5 No.1
<p>Copper zinc tin sulfide (Cu<SUB>2</SUB>ZnSnS<SUB>4</SUB>, CZTS) has attracted significant attention in the past few years as a next generation absorber material for the production of thin film solar cells on large scales due to the high natural abundance of all constituents, tunable direct band gap energy ranging from 1.0 to 1.5 eV, and large absorption coefficient. In addition, to address the issue of expensive vacuum-based processes, non-vacuum solution-based approaches are being developed for CZTS absorber layer deposition. Here, we demonstrate the fabrication of a high quality CZTS absorber layer with a thickness of 2.8–3.0 μm and micrometre-scaled grains (1–2.5 μm) using air-stable non-toxic solvent-based inks. Our approach for the fabrication of CZTS absorber, reported here, will be the first step in achieving low-cost and large area solar cells with high efficiency.</p> <P>Graphic Abstract</P><P>High quality CZTS absorber was successfully fabricated by readily achievable precursor ink, without complex particle synthesis, toxic solvents, or organic additives. <img src='http://pubs.rsc.org/ej/EE/2012/c1ee02314d/c1ee02314d-ga.gif'> </P>
Graphene p–n–p junctions controlled by local gates made of naturally oxidized thin aluminium films
Nam, Youngwoo,Lindvall, Niclas,Sun, Jie,Park, Yung Woo,Yurgens, August Elsevier 2012 Carbon Vol.50 No.5
<P><B>Abstract</B></P><P>Graphene structures with both top- and bottom-electrostatic gates are studied. The top gate is made of thin aluminium (Al) film deposited directly onto graphene, with no prior dielectric layer in between. Natural oxidation of Al at the interface with graphene results in an insulating barrier proving useful in making top gates to graphene. For electrically disconnected top gate, graphene resistance as a function of the slowly-varying back-gate voltage shows hysteresis which reveals dielectric properties of the barrier. The estimated barrier thickness is only 2nm allowing for very sharp profiles of the electric field in graphene devices. By applying voltages to both back- and top gates, effective p–n–p junctions with sharp interfaces can be created.</P>
Jae-Woo SONG,Jae-Min JUNG,Youngwoo NAM,Sunghoon JUNG,Wang-Hee LEE 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
Recent outbreak of gypsy moths (Lymantria dispar) has caused damages on forests and landscapes in South Korea under the effects of climate change. For this reason, there is a demand on evaluating the potential distribution of gypsy moth to establish data for prevention of future damage. In this study, we evaluated the potential distribution of the gypsy moth according to climate change by using CLIMEX (version 4.0, Hearne software, Australia). Parameter values were determined based on previous studies, distribution records, and species biology; then, the model was simulated to define climatically suitable areas for establishing gypsy moth population under domestic meteorological data. The suitable areas were then projected on the map of South Korea by using ArcMap (version10. 4. 1; ESRI, Redlands, USA) so that areas at risk of gypsy moth distribution were visually identified. As a result, high climatic suitability was observed throughout the country under the current climate, whereas suitable areas were predicted to gradually decrease with climate change due to excessive summer temperature.