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Kwon, Jinhyeong,Park, Shinyoung,Haque, Md Mominul,Kim, Young-Seok,Lee, Caroline Sunyong American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.4
<P>Sub-50 nm copper nanoparticles coated with sub-5 nm 1-octanethiol layer for oxidation inhibition were examined to confirm the 1-octanethiol removal temperature as the sub-50 nm copper nanoparticles are sintered. As a result, 1-octanethiol Self-Assembled Multi-layers (SAMs) on sub-50 nm copper nanoparticles were successfully removed before sintering of copper nanoparticles so that a high density of copper line could be obtained. Finally, the line resistivity was measured and compared to verify the effect of sintering in different atmospheres. As a result, electrical resistivity of the copper pattern sintered in hydrogen atmosphere was measured at 6.96 x 10(-6) ohm-cm whereas that of the copper pattern sintered in mixed gas atmosphere was measured at 2.62 x 10(-5) ohm-cm. Thus, sintering of copper patterns was successfully done to show low electrical resistivity values. Moreover, removal of 1-octanethiol coating after sintering process was confirmed using X-ray photoelectron spectroscopy (XPS) analysis. By showing no sulfur content, XPS results indicate that 1-octanethiol is completely removed. Therefore, the vapor form of 1-octanethiol coating layers can be safely used as an oxidation inhibition layer for low temperature sintering processes and ink-jet applications.</P>
Kwon, Jinhyeong,Hong, Sukjoon,Suh, Young Duk,Yeo, Junyeob,So, Hye-Mi,Chang, Won Seok,Ko, Seung Hwan The Electrochemical Society 2015 ECS journal of solid state science and technology Vol.4 No.4
<P>Direct printing is an attractive technology for the patterning of nanomaterials that enables low-cost fabrication of micro/nano-sized electrical devices through minimal use of materials with non-vacuum environment. Although direct printing opens new border for the patterning technology, its resolution has been highly restricted mainly due to its solution-based properties. When the solution contains much liquid, it spreads out on the substrate after printing. While less liquid solution causes clogging at the orifice. In this study, electrohydrodynamic (EHD) jet printer is employed to use both low and high content of nanomaterial solutions: low viscosity nanoink and high viscosity nanopaste. Meanwhile, there are several considerable factors including ink property for operating EHD jet printer such as substrates, voltage condition and working speed. Therefore, parametric studies are conducted to gain fine patterning. As a results, EHD jet printed silver conductive line at high resolution is achieved on various plastic substrates for flexible device applications.</P>
Kwon, Jinhyeong,Cho, Hyunmin,Lee, Habeom,Hong, Sukjoon,Suh, Young D.,Moon, Hyunjin,Kim, Dongkwan,Choi, Jun-ho,Lee, Ming-Tsang,Yeo, Junyeob,Ko, Seung Hwan The Electrochemical Society 2015 ECS journal of solid state science and technology Vol.4 No.12
<P>ZnO/Ag hierarchical nanostructure is fabricated by solution-based photoreduction process to demonstrate a photoelectrochimical (PEC) cell charging supercapacitor. The photoreduction process ensures rapid and simple route for employing of Ag nanoparticles onto the surface of ZnO nanorod with well-dispersed and clear crystallization structure. The fabricated ZnO/Ag hierarchical nanostructure showed improved optical and photoelectrochemical properties. Subsequently, the ZnO/Ag hierarchical nanostructure is used as photoanode for PEC cell with enhanced output photocurrent and stability. Furthermore, the PEC cell was connected to lab-made supercapacitors to turn on a light emitting diode. The photoreduction-processed ZnO/Ag hierarchical nanostructures provide a promising and simple production method for energy source in water splitting applications.</P>
Kwon, Jinhyeong,Cho, Hyunmin,Lee, Habeom,Yeo, Junyeob,Hong, Sukjoon,Han, Seungyong,Ko, Seung Hwan The Electrochemical Society 2018 ECS journal of solid state science and technology Vol.7 No.8
<P>Among various solar energy generation methods, a water splitting photoelectrochemical (PEC) cell have been anticipated as a one of the promising source to generate hydrogen by natural sunlight. Owing to unique electrical, electrochemical and optical properties, the nanostructured metal oxides were intensively investigated to adopt as a main material in the water splitting PEC cell. However, most of nanostructured metal oxides have an improper bandgap size/position for splitting water molecule, it needs to be engineered to shift a level of the energy bandgap. In this prospective review, we will briefly discuss solution-processed fabrication methods for water splitting applications. (C) The Author(s) 2018. Published by ECS.</P>
Kwon, Jinhyeong,Hong, Sukjoon,Lee, Habeom,Yeo, Junyeob,Lee, Seung S,Ko, Seung Hwan Springer 2013 Nanoscale research letters Vol.8 No.1
<P>Inkjet printing of functional materials has drawn tremendous interest as an alternative to the conventional photolithography-based microelectronics fabrication process development. We introduce direct selective nanowire array growth by inkjet printing of Zn acetate precursor ink patterning and subsequent hydrothermal ZnO local growth without nozzle clogging problem which frequently happens in nanoparticle inkjet printing. The proposed process can directly grow ZnO nanowires in any arbitrary patterned shape, and it is basically very fast, low cost, environmentally benign, and low temperature. Therefore, Zn acetate precursor inkjet printing-based direct nanowire local growth is expected to give extremely high flexibility in nanomaterial patterning for high-performance electronics fabrication especially at the development stage. As a proof of concept of the proposed method, ZnO nanowire network-based field effect transistors and ultraviolet photo-detectors were demonstrated by direct patterned grown ZnO nanowires as active layer.</P>
Recent progress in silver nanowire based flexible/wearable optoelectronics
Kwon, Jinhyeong,Suh, Young D.,Lee, Jinhwan,Lee, Phillip,Han, Seungyong,Hong, Sukjoon,Yeo, Junyeob,Lee, Habeom,Ko, Seung Hwan The Royal Society of Chemistry 2018 Journal of Materials Chemistry C Vol.6 No.28
<P>Among diverse nanomaterials, silver nanowire (AgNW) has reached a certain level of technological maturity, and numerous commercialized AgNW products are already on the market for research and prototype purposes. One of the potential applications for AgNW and its percolative form is in wearable electronics, owing to the superior electrical, optical and mechanical properties that arise from the material itself or the overall interconnected structure. For successful application towards wearable applications, constituent AgNWs should first have uniform and controllable properties. At the same time, it is preferential to develop relevant scalable fabrication processes, together with the verification of potential applications from a proof-of-concept standpoint. Based on these progresses, we summarize the recent developments in AgNW based flexible/wearable optoelectronic applications and foresee their future development.</P>
Kwon, Jinhyeong,Cho, Hyunmin,Eom, Hyeonjin,Lee, Habeom,Suh, Young Duk,Moon, Hyunjin,Shin, Jaeho,Hong, Sukjoon,Ko, Seung Hwan American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.18
<P>Copper nanomaterials suffer from severe oxidation problem despite the huge cost effectiveness. The effect of two different processes for conventional tube furnace heating and selective laser sintering on copper nanoparticle paste is compared in the aspects of chemical, electrical and surface morphology. The thermal behavior of the copper thin films by furnace and laser is compared by SEM, XRD, FT-IR, and XPS analysis. The selective laser sintering process ensures glow annealing temperature, fast processing speed with remarkable oxidation suppression even in air environment while conventional tube furnace heating experiences moderate oxidation even in Ar environment. Moreover, the laser-sintered copper nanoparticle thin film shows good electrical property and reduced oxidation than conventional thermal heating process. Consequently, the proposed selective laser sintering process can be compatible with plastic substrate for copper based flexible electronics applications.</P>
Digitally patterned resistive micro heater as a platform for zinc oxide nanowire based micro sensor
Kwon, Jinhyeong,Hong, Sukjoon,Kim, Gunho,Suh, Young D.,Lee, Habeom,Choo, Seung-Yeon,Lee, Daeho,Kong, Heejung,Yeo, Junyeob,Ko, Seung Hwan Elsevier BV * North-Holland 2018 Applied Surface Science Vol.447 No.-
<P><B>Abstract</B></P> <P>Among the various techniques for micro patterning of metal oxide nanowire, the resistive micro heater is promising technique due to the merit of localized and selective growth of sensing nanowire. In this study, we introduce a facile maskless fabrication of resistive micro heater using selective laser sintering of silver nanoparticle without using any conventional photolithography or vacuum deposition. By localized hydrothermal synthesis of ZnO nanowire using Joule heating of the resistive micro heater, the digitally patterned resistive micro heater is applied to the ZnO nanowire based micro UV sensor.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The digitally patterned resistive micro heater was fabricated using Ag nanoparticles. </LI> <LI> The ZnO NWs were successfully synthesized on the digitally patterned resistive micro heater. </LI> <LI> The growth rate in resistive micro heater was higher than the conventional synthesis. </LI> <LI> The resistive micro heater was used as a platform for ZnO NW based micro sensor. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kwon, Jinhyeong,Yeo, Junyeob,Hong, Sukjoon,Suh, Young D.,Lee, Habeom,Choi, Jun‐,ho,Lee, Seung S.,Ko, Seung Hwan WILEY‐VCH Verlag 2016 Energy technology Vol.4 No.2
<P><B>Abstract</B></P><P>Hematite is a good candidate for solar water splitting because of its earth‐abundance, moderate band gap, and electrochemical stability. However, the improper energy band position to absorb the visible region of sunlight has limited any increase of the efficiency. In this study, a facile solution‐based photoreduction process is employed to fabricate a hematite/silver hierarchical nanostructure. By irradiating hydrothermally grown hematite nanowire with UV light, Ag nanoparticles are synthesized rapidly on the surface of the hematite nanowire, the size of which is easily controllable by changing the UV irradiation time. The enhanced optical performance of the resultant hierarchical nanostructure is confirmed by various analytical tools that include UV/Vis absorption, photoluminescence, and Raman spectroscopy together with the theoretical estimation through finite‐difference time‐domain simulation. Furthermore, the hierarchical hematite/silver nanostructure is applied as a photoanode in a photo‐electrochemical cell for water splitting with enhanced efficiency.</P>