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RISS 인기검색어
- 검색키워드
- 저자 : Hyowon Tak (검색결과 6 건)
- 무료
- 기관 내 무료
- 유료
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Surface energy-tunable iso decyl acrylate based molds for low pressure-nanoimprint lithography
Tak, Hyowon,Tahk, Dongha,Jeong, Chanho,Lee, Sori,Kim, Tae-il IOP 2017 Nanotechnology Vol.28 No.40
<P>We presented surface energy-tunable nanoscale molds for unconventional lithography. The mold is highly robust, transparent, has a minimized haze, does not contain additives, and is a non-fluorinated isodecyl acrylate and trimethylolpropane triacrylate based polymer. By changing the mixing ratio of the polymer components, the cross-linking density, mechanical modulus, and surface energy (crucial factors in low pressure ((1–2) × 10<SUP>5</SUP> N m<SUP>−2</SUP>) low pressure-nanoimprint lithography (LP-NIL)), can be controlled. To verify these properties of the molds, we also characterized the surface energy by measuring the contact angles and calculating the work of adhesion among the wafer, polymer film, and mold for successful demolding in nanoscale structures. Moreover, the molds showed high optical clarity and precisely tunable mechanical and surface properties, capable of replicating sub-100 nm patterns by thermal LP-NIL and UV-NIL.</P>
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Permeability- and Surface-Energy-Tunable Polyurethane Acrylate Molds for Capillary Force Lithography
Suh, Dongchul,Tak, Hyowon,Choi, Se-jin,Kim, Tae-il American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.43
<P>A permeability- and surface-energy-controllable polyurethane acrylate (PUA) mold, a “capillary-force material (CFM)” mold, is introduced for capillary-force lithography (CFL). In CFL, the surface energy and gas permeability of the mold are crucial. However, the modulation of these two main factors at a time is difficult. Here, we introduce new CFM molds in which the surface energy and permeability can be modified by controlling the degree of cross-linking of the CFM. As the degree of cross-linking of the CFM mold increases, the surface energy and air permeability decrease. The high average functionality of the mold material makes it possible to produce patterns relatively finely and rapidly due to the high rate of capillary rise and stiffness, and the low functionality allows for patterns to form on a curved surface with conformal contact. CFMs with different functionality and controllable-interfacial properties will extend the capabilities of capillary force lithography to overcome the geometric limitations of patterning on a scale below 100 nm and micro- and nanopatterning on the curved region.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-43/acsami.5b06975/production/images/medium/am-2015-06975p_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b06975'>ACS Electronic Supporting Info</A></P>
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Hyejin Jang,Dongjae Kim,Hyowon Tak,남재욱,김태일 한국물리학회 2016 Current Applied Physics Vol.16 No.1
Mechanically ultra-robust, transparent and flexible electrodes assembled from silver nanowires (Ag NWs) are presented. Highly aligned NWs embedded in ultrathin (100 nm thick) adhesive are demonstrated for ultra-mechanical stability, negligible hysteresis against harsh bending on 0.15 mm radius of curvature. Instead of random arrangement, we utilize a grid array structure of NWs fabricated from multiple transfer printing. The grid structure allows to have low areal fraction, which leads to high transmittance, yet low sheet resistance, i.e. improved opto-electrical performance comparing with the random arrangement. In addition, a simplified lithography method of NW array is demonstrated. We strongly believe that such flexible and transparent electrodes can be used in many applications including optoelectronic devices and flexible/wearable electronics.
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High Aspect Ratio Conductive Lines Fabricated by Electrohydrodynamic (EHD) Jet Printing
Ayodya Pradhipta Tenggara,Yonghee Jang,Hyowon Tak,Hadi Teguh Yudistira,Vu Dat Nguyen,Doyoung Byun 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
Fabricating high-density integrated circuits require three dimensional electrode lines with high aspect-ratio. Nowadays, many electrode lines for electronic circuits are fabricated by printing technologies to give simple and environmental friendly fabrication technique. However, most applications of printing technologies are in two dimensional structures. In this study, we propose printing technology to fabricate three dimensional electrode lines. Electrohydrodynamic (EHD) jet printing with printing speed up to 800 mm/s was used to make three dimensional electrode lines with aspect ratio greater than 5 by using multiple printing methods. Two kinds of NPK silver inks with viscosity 5000 and 8000 cP were used. Parametric studies were done to observe the effect of printing parameters, i.e. printing numbers and printing speed into the aspect ratio of the lines. The results showed that increasing printing numbers and printing speed could increase the aspect ratio of lines. The high aspect ratio lines conducted by this study have great potential to improve efficiency of solar cells.
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Shin, Dong-Youn,Seo, Jun-Young,Tak, Hyowon,Byun, Doyoung Elsevier 2015 Solar energy materials and solar cells Vol.136 No.-
<P><B>Abstract</B></P> <P>Conventional silver paste for crystalline silicon solar cells exhibits low cell efficiency when deposited by non-contact electrohydrodynamic jet printing because of either high volumetric shrinkage or low packing density when there is no printing pressure applied to the silver paste. Therefore, we develop bimodally dispersed silver paste for electrohydrodynamic jet printing to resolve both volumetric shrinkage and packing density of the conventional silver paste, and its electrical and rheological traits are investigated. The bimodally dispersed silver paste exhibits lower unit-line resistance, which is inversely proportional to the weight ratio of small-to-large silver particles due to the increased packing density, and higher contact resistivity above a certain weight ratio for small-to-large silver particles. This behaviour results from the obstructed melt flow of glass frit by the early coarsened and densified small silver particles at an elevated temperature. The increased weight ratio of the small particles also raises the viscosity of the bimodally dispersed silver paste above the point where electrohydrodynamic jet printing is possible. By employing a binary solvent mixture and metallorganic silver as a viscosity reducing agent, the bimodally dispersed silver paste is tuned for electrohydrodynamic jet printing, and the front-side metallization of a polycrystalline silicon solar cell with the emitter sheet resistance of 60Ω/sq is constructed. With the abnormally high aspect ratio of silver electrodes at 0.86, a cell efficiency of 16.72% is achieved, which is higher than that of screen-printed cells with the similar emitter sheet resistance by +0.22–0.52%p.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A bimodally dispersed silver paste was developed for EHD jet printing. </LI> <LI> The inclusion of small silver particles contributed to low electrical resistance. </LI> <LI> The excessive addition of small silver particles increased contact resistivity. </LI> <LI> Using EHD jet printing, the height-to-width aspect ratio was as high as 0.86. </LI> <LI> A 16.72% cell efficiency was achieved, higher than screen-printed efficiency. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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