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Kim, Sunbo,Jung, Junhee,Kim, YoungKuk,Le, Anh Huy Tuan,Ahn, Shihyun,Park, Jinjoo,Kim, Yongjun,Dao, Vinh Ai,Lee, Jaehyeong,Lee, Youn-Jung American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.5
<P>This study investigates the effect of hydrogen gas ratio [H-2/H-2+Ar] had on the structural, optical and electrical properties of ITO films for use in amorphous/crystalline silicon hetero-junction solar cells. The pulsed DC magnetron sputtered ITO films showed a higher optical transmittance for a hydrogen gas ratio of 3.2%. The lowest sheet resistance (43.12 Omega/square) and resistivity (3.25x10(-4) Omega.cm) were observed for ITO films where the hydrogen gas ratio was in the range from 1.31 to 3.22%. The Hall mobility of the ITO films decreased from 55.3 to 42.5 cm(2)/V.s with an increase in the hydrogen gas ratio from 1.31 to 3.2%. The surface morphology and crystallinity of films improved for the low hydrogen gas ratio while the characteristics of the ITO films deteriorated when the hydrogen ratio was higher than 3.2%. Then, we fabricated amorphous/crystalline silicon hetero-junction solar cells using ITO films for the front anti-reflection layer, and a hydrogen gas ratio of 3.22% resulted in a short circuit current density (J(sc)) of 38.17 mA/cm(2) and an efficiency of 19.02%.</P>
Near-field exciton imaging of chemically treated MoS<sub>2</sub> monolayers
Kim, Youngbum,Lee, Yongjun,Kim, Hyun,Roy, Shrawan,Kim, Jeongyong The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.18
<P>The exciton-dominated light emission of two-dimensional (2D) semiconductors is determined largely by the doping state and the formation of defects. Extensive studies have shown that chemical treatment critically modifies the doping state and defect state of chemical vapor deposition (CVD)-grown or exfoliated monolayer MoS2 (1L-MoS2), suggesting a promising possibility for engineering the optoelectronic properties of 2D semiconductors. However, chemical treatment inevitably modifies both the doping state and defect states, and their independent roles in the exciton emission of 1L-MoS2 have been difficult to study, significantly limiting the practical and reliable uses of chemical treatment to improve the optical properties of 1L-TMDs. Herein, we used near-field imaging and spectroscopy to investigate the effects of chemical treatment on the exciton emission of 1L-MoS2. CVD-grown 1L-MoS2 was treated with bis(trifluoromethane)-sulfonimide (TFSI) or 7,7,8,8-tetracyanoquinodimethane (TCNQ), and nanoscale maps of neutral exciton and trion emission before and after chemical treatment were obtained with 80 nm spatial resolution. A comparison of the local spatial and spectral compositions of neutral excitons and trions suggested that the p-doping effect of TFSI was especially strong around local defects, whereas electron depletion by TCNQ was spatially uniform. The specific reaction of TFSI to defect locations observed in our study provides the clue for the reason that TFSI is notably effective at improving the light emission of 1L-MoS2.</P>
Kim, Jin Won,Im, Seock-Ah,Kim, Miso,Cha, Yongjun,Lee, Kyung-Hun,Keam, Bhumsuk,Kim, Min A,Han, Sae-Won,Oh, Do-Youn,Kim, Tae-You,Kim, Woo Ho,Bang, Yung-Jue Potamitis Press 2012 Anticancer research Vol.32 No.4
<P>We aimed to clarify the prognostic significance of HER2 positivity in advanced gastric cancer.</P>
Asset Redeployability and the q-theory of Investment
( Yongjun Kim ) 서강대학교 지암남덕우경제연구원(구 서강대학교 시장경제연구소) 2020 시장경제연구 Vol.49 No.1
A key prediction of the q-theory of investment is the negative relation between corporate investment and expected return. This relation should be strong for firms that face high adjustment costs. In this study, I use the asset redeployability index of Kim and Kung (2017) as a proxy of capital adjustment costs to examine the notion about the q-theory of investment. Asset redeployability effectively captures the liquidity dimension of adjustment costs, because redeployable assets are traded more actively in secondary markets. Using publicly listed firms on the U.S. stock market, I find a strong relation between investment and return for the firms that use less redeployable assets. This empirically supports the q-theory of investment.