Tension assisted metal transfer of graphene for Schottky diodes onto wafer scale substrates

Lee, Jooho,Lee, Su Chan,Kim, Yongsung,Heo, Jinseong,Lee, Kiyoung,Lee, Dongwook,Kim, Jaekwan,Lee, Sunghee,Lee, Chang Seung,Nam, Min Sik,Jun, Seong Chan IOP 2016 Nanotechnology Vol.27 No.7

<P>We developed an effective graphene transfer method for graphene/silicon Schottky diodes on a wafer as large as 6 inches. Graphene grown on a large scale substrate was passivated and sealed with a gold layer, protecting graphene from any possible contaminant and keeping good electrical contact. The Au/graphene was transferred by the tension-assisted transfer process without polymer residues. The gold film itself was used directly as the electrodes of a Schottky diode. We demonstrated wafer-scale integration of graphene/silicon Schottky diode using the proposed transfer process. The transmission electron microscopy analysis and relatively low ideality factor of the diodes indicated fewer defects on the interface than those obtained using the conventional poly(methyl methacrylate)-assisted transfer method. We further demonstrated gas sensors as an application of graphene Schottky diodes.</P>

Crack-Release Transfer Method of Wafer-Scale Grown Graphene Onto Large-Area Substrates

Lee, Jooho,Kim, Yongsung,Shin, Hyeon-Jin,Lee, ChangSeung,Lee, Dongwook,Lee, Sunghee,Moon, Chang-Yul,Lee, Su Chan,Kim, Sun Jun,Ji, Jae Hoon,Yoon, Hyong Seo,Jun, Seong Chan American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.15

<P>We developed a crack-release graphene transfer technique for opening up possibilities for the fabrication of graphene-based devices. Graphene film grown on metal catalysts/SiO<SUB>2</SUB>/Si wafer should be scathelessly peeled for sequent transferring to a target substrate. However, when the graphene is grown on the metal catalyst on a silicon substrate, there is a large tensile stress resulting from the difference of the coefficient of thermal expansion in the catalyst and silicon. The conventional methods of detaching graphene from metal catalysts were found to induce considerable mechanical damage on graphene films during separation processes including metal wet etching. Here we report a new technique wherein bubbles generated by electrolysis reaction separate thin metal catalysts from the SiO<SUB>2</SUB>/Si wafer. The dry attachment of graphene to the target wafer was processed utilizing a wafer to wafer bonding technique in a vacuum. We measured the microscopic image, Raman spectra, and electrical properties of the transferred graphene. The optical and electrical properties of the graphene transferred by the bubbles/dry method are better than those of the graphene obtained by mechanical/wet transfer.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-15/am502565z/production/images/medium/am-2014-02565z_0005.gif'></P>

Asymptotic Comparison of Latin Hypercube Sampling and Its Stratified Version

Lee, Jooho The Korean Statistical Society 1999 Journal of the Korean Statistical Society Vol.28 No.2

Latin hypercube sampling(LHS) introduced by McKay et al. (1979) is a widely used method for Monte Carlo integration. Stratified Latin hypercube sampling(SLHS) proposed by Choi and Lee(1993) improves LHS by combining it with stratified sampling. In this article it is shown that SLHS yields an asymptotically more accurate than both stratified sampling and LHS.

Nano-sized metabolic precursors for heterogeneous tumor-targeting strategy using bioorthogonal click chemistry <i>in vivo</i>

Lee, Sangmin,Jung, Seulhee,Koo, Heebeom,Na, Jin Hee,Yoon, Hong Yeol,Shim, Man Kyu,Park, Jooho,Kim, Jong-Ho,Lee, Seulki,Pomper, Martin G.,Kwon, Ick Chan,Ahn, Cheol-Hee,Kim, Kwangmeyung IPC Science and Technology Press 2017 Biomaterials Vol.148 No.-

<P><B>Abstract</B></P> <P>Herein, we developed nano-sized metabolic precursors (Nano-MPs) for new tumor-targeting strategy to overcome the intrinsic limitations of biological ligands such as the limited number of biological receptors and the heterogeneity in tumor tissues. We conjugated the azide group-containing metabolic precursors, triacetylated <I>N</I>-azidoacetyl-<SMALL> <I>D</I> </SMALL>-mannosamine to generation 4 poly(amidoamine) dendrimer backbone. The nano-sized dendrimer of Nano-MPs could generate azide groups on the surface of tumor cells homogeneously regardless of cell types via metabolic glycoengineering. Importantly, these exogenously generated ‘artificial chemical receptors’ containing azide groups could be used for bioorthogonal click chemistry, regardless of phenotypes of different tumor cells. Furthermore, in tumor-bearing mice models, Nano-MPs could be mainly localized at the target tumor tissues by the enhanced permeation and retention (EPR) effect, and they successfully generated azide groups on tumor cells <I>in vivo</I> after an intravenous injection. Finally, we showed that these azide groups on tumor tissues could be used as ‘artificial chemical receptors’ that were conjugated to bioorthogonal chemical group-containing liposomes via <I>in vivo</I> click chemistry in heterogeneous tumor-bearing mice. Therefore, overall results demonstrated that our nano-sized metabolic precursors could be extensively applied to new alternative tumor-targeting technique for molecular imaging and drug delivery system, regardless of the phenotype of heterogeneous tumor cells.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A Review of Empirical Research on Citizen Participation in Government Crowdsourcing Platforms: Lessons for Government Leaders and Managers

Lee, Jooho(이주호) 한국지능정보사회진흥원 2022 정보화정책 Vol.29 No.1

온라인 공동 생산의 한 형태인 정부 크라우드소싱 플랫폼은 정부와 시민의 공동 생산을 활성화하기 위한 수단으로 학계와 실무자들로부터 점점 더 많은 관심을 받고 있다. 이 연구의 목적은 효과적이고 혁신적인 온라인 공동 생산 서비스를 원하는 정부 지도자와 관리자에게 다양한 국가에서 실행된 실제 사례를 경험적으로 연구한 논문들을 소개하고 체계적으로 이 논문들의 발견과 의의를 정리, 논의하여 효과적이고 포용적인 정부 크라우드소싱 플랫폼을 설계, 구현, 관리, 평가하는데 도움을 주고자 합니다. 이 연구는 실제 정부 크라우드소싱 사례를 조사한 일부 실증 연구에 대한 문헌을 검토한다. 특히 이 논문은 크라우드소싱 공동디자인과 크라우드소싱디자인/정부집행 형태의 플랫폼에 관한 경험적 연구에 관한 검토를 통해 주요 발견사항을 논의하고 이를 바탕으로 효과적이고 포용적인 크라우드 소싱 플랫폼을 디자인하고 관리하고자 하는 정부의 리더와 관리자에게 통찰력과 함의를 제공하고자 한다. As a form of online co-production, government crowdsourcing platforms have received growing attention from scholars and practitioners as a means of enhancing government-citizen co-production. This research aims (1) to introduce government leaders and managers to recent empirical research examining real-world cases of government crowdsourcing from different countries, (2) to systematically organize, analyze, and discuss the findings and implications of recent government crowdsourcing empirical studies, and (3) to provide government practitioners with evidence-based insights that could encourage informed decisions about how they design, implement, and evaluate government crowdsourcing platforms effectively and inclusively. Literature review is limited primarily to empirical works that rigorously examined real-world cases of government crowdsourcing. By focusing on a review of empirical research on crowdsourcing co-design and crowdsourcing design/government delivery platforms, this study discusses the key findings systematically and offers some insights and implications for leaders and managers seeking effective and inclusive design and implementation of government crowdsourcing platforms.

Understanding the Critical Role of the Ag Nanophase in Boosting the Initial Reversibility of Transition Metal Oxide Anodes for Lithium-Ion Batteries

Lee, Daehee,Wu, Mihye,Kim, Dong-Hyun,Chae, Changju,Cho, Min Kyung,Kim, Ji-Young,Lee, Sun Sook,Choi, Sungho,Choi, Youngmin,Shin, Tae Joo,Chung, Kyung Yoon,Jeong, Sunho,Moon, Jooho American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.26

<P>The initial reversible capacity, a critical impediment in transition metal oxide-based anodes, is augmented in conversion-reaction-involved CoO anodes for lithium-ion batteries, by incorporating a chemically synthesized Ag nanophase. With an increase in the added amount of Ag nanophase from 5 to 15 wt %, the initial capacity loss decreases linearly up to 31.7%. The Ag nanophase maintains its pristine metallic nature without undergoing phase transformations, even during repeated vigorous electrochemical reactions of the active CoO phase. Complementary ex situ chemical/physical analyses suggest that the Ag nanophase promotes the catalytic generation of reversible gel-like/polymeric films wherein lithium ions are stored capacitively in the low-voltage region below 0.7 V during discharging. These scientific findings would provide a heretofore unrecognized pathway to resolving a major issue associated with the critical irreversibility in conversion-type transition metal oxide anodes.</P>

Epigenetics in non-alcoholic fatty liver disease

Lee, Jooho,Kim, Yuri,Friso, Simonetta,Choi, Sang-Woon Elsevier 2017 Molecular aspects of medicine Vol.54 No.-

<P><B>Abstract</B></P> <P>Non-alcoholic fatty liver disease (NAFLD), a common hepatic disorder ranging from simple steatosis through steatohepatitis to fibrosis and cirrhosis, is an emerging health concern. NAFLD is a pathologic condition characterized by the buildup of extra fat in liver cells that is not caused by alcohol consumption. Excess hepatic fat accumulation results from increased delivery of triglycerides (TG) to the liver or conversion of surplus carbohydrates to TG. Importantly, a subgroup of NAFLD results in hepatocellular injury and inflammation, which is referred to as non-alcoholic steatohepatitis (NASH), and may progress to irreversible cirrhosis and hepatocellular carcinoma (HCC). NAFLD shares, in part, the common pathogenesis of metabolic syndrome including obesity, hyperlipidemia, insulin resistance, mitochondrial damage, oxidative stress response, and the release of inflammatory cytokines. Epigenetics, an inheritable phenomenon that affects gene expression without altering the DNA sequence, provides a new perspective on the pathogenesis of NAFLD. Reversible epigenetic changes take place at the transcriptional level and provide a phenotypic connection between the host and environment. An accumulating body of evidence suggests the importance of epigenetic roles in NAFLD, which in turn can be identified as potential therapeutic targets and non-invasive biomarkers of NAFLD. It is anticipated that the epigenetic modifiers in NAFLD may provide novel molecular indicators that can determine not only the initial risk but also the disease progression and prognosis. In the present review, we update the roles of epigenetics as pathologic mechanisms, therapeutic targets and biomarkers in NAFLD.</P>

Retarding Crystallization during Facile Single Coating of NaCl-Incorporated Precursor Solution for Efficient Large-Area Uniform Perovskite Solar Cells

Lee, Hongseuk,Kim, Areum,Kwon, Hyeok-Chan,Yang, Wooseok,Oh, Yunjung,Lee, Daehee,Moon, Jooho American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.43

<P>We demonstrated crystallization retardation of CH3NH3PbI3 thin film during single coating of precursor solution by simple addition of NaCl. NaCl was codissolved into a precursor mixture solution containing PbI2 and methylammonium iodide (MAI). Dissolved NaCl interacted with the PbI2 in solution and produced a stable intermediate phase, which was converted to a full coverage uniform perovskite absorber layer via reaction with MAI during a single spin-coating. The resulting planar-structure perovskite solar cell made from NaCl-supplemented precursor solution showed a 48% improvement in power conversion efficiency (PCE) (maximum value 15.16%) over the device fabricated without the additive. Our NaCl-supplemented single coating represents an easy approach to effectively obtain highly reproducible uniform performance at an overall position in 5 cm x 5 cm sized cells (divided into 20 subcells with an active area of 0.06 cm(2)) with average PCEs of 12.00 +/- 0.48%.</P>

Wafer Level Package Using Glass Cap and Wafer with Groove-Shaped Via

李周浩(Jooho Lee),朴海錫(Hae-Seok Park),申濟湜(Jeasik Shin),權鍾午(Jongoh Kwon),李相勳(Sanghun Lee),愼廣縡(KwangJae Shin),宋寅相(Insang Song) 대한전기학회 2007 전기학회논문지 Vol.56 No.12

In this paper, we propose a new wafer level package (WLP) for the RF MEMS applications. The Film Bulk Acoustic Resonator (FBAR) are fabricated and hermetically packaged in a new wafer level packaging process. With the use of Au-Sri eutectic bonding method, we bonded glass cap and FBAR device wafer which has groove-shaped via formed in the backside. The device wafer includes a electrical bonding pad and groove-shaped via for connecting to the external bonding pad on the device wafer backside and a peripheral pad placed around the perimeter of the device for bonding the glass wafer and device wafer. The glass cap prevents the device from being exposed and ensures excellent mechanical and environmental protection. The frequency characteristics show that the change of bandwidth and frequency shift before and after bonding is less than 0.5 ㎒. Two packaged devices, Tx and Rx filters, are attached to a printed circuit board, wire bonded, and encapsulated in plastic to form the duplexer. We have designed and built a low-cost, high performance, duplexer based on the FBARs and presented the results of performance and reliability test.

수중함 자유항주모형 개발 및 기본 성능 분석

이주호(Jooho Lee),김선홍(Seonhong Kim),신지환(Jihwan Shin),안진형(Jinhyeong Ahn) 대한조선학회 2023 大韓造船學會 論文集 Vol.60 No.4