Enhanced Performance of Field-Effect Transistors Based on Black Phosphorus Channels Reduced by Galvanic Corrosion of Al Overlayers

Lee, Sangik,Yoon, Chansoo,Lee, Ji Hye,Kim, Yeon Soo,Lee, Mi Jung,Kim, Wondong,Baik, Jaeyoon,Jia, Quanxi,Park, Bae Ho American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.22

<P>Two-dimensional (2D)-layered semiconducting materials with considerable band gaps are emerging as a new class of materials applicable to next-generation devices. Particularly, black phosphorus (BP) is considered to be very promising for next-generation 2D electrical and optical devices because of its high carrier mobility of 200-1000 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP> and large on/off ratio of 10<SUP>4</SUP> to 10<SUP>5</SUP> in field-effect transistors (FETs). However, its environmental instability in air requires fabrication processes in a glovebox filled with nitrogen or argon gas followed by encapsulation, passivation, and chemical functionalization of BP. Here, we report a new method for reduction of BP-channel devices fabricated without the use of a glovebox by galvanic corrosion of an Al overlayer. The reduction of BP induced by an anodic oxidation of Al overlayer is demonstrated through surface characterization of BP using atomic force microscopy, Raman spectroscopy, and X-ray photoemission spectroscopy along with electrical measurement of a BP-channel FET. After the deposition of an Al overlayer, the FET device shows a significantly enhanced performance, including restoration of ambipolar transport, high carrier mobility of 220 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>, low subthreshold swing of 0.73 V/decade, and low interface trap density of 7.8 × 10<SUP>11</SUP> cm<SUP>-2</SUP> eV<SUP>-1</SUP>. These improvements are attributed to both the reduction of the BP channel and the formation of an Al<SUB>2</SUB>O<SUB>3</SUB> interfacial layer resulting in a high-<I>k</I> screening effect. Moreover, ambipolar behavior of our BP-channel FET device combined with charge-trap behavior can be utilized for implementing reconfigurable memory and neuromorphic computing applications. Our study offers a simple device fabrication process for BP-channel FETs with high performance using galvanic oxidation of Al overlayers.</P> [FIG OMISSION]</BR>

Magnetic Properties of V Thin Films on the fcc Co(001) Surface

Wondong Kim,S.-W. Han,D-H. Lee,M. Bellal,C. Hwang,H.-G. Lee,J. Kim 한국자기학회 2007 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

The Shifting Moral Authority of the Conservative Evangelicals’ Anti-LGBT Movement in South Korea

Wondong Lee 고려대학교 한국사연구소 2021 International Journal of Korean History Vol.26 No.2

본 연구는 최근 한국 보수개신교회 내에서 중요한 아젠다로 등장하고 있는 동성애 운동(LGBT movement)에 대항하여 기독교 각계 각층의 리더들이 단순히 성경(the Scripture)에 대한 직접적인 호소를 뛰어넘어 어떻게 이를 효과적으로 저지하기 위한 담론 프레이밍(discursive framing)을 구사하고 있는지 분석한다. 이를 위해 한국의 기독언론매체인 기독신문(Kidok Sinmun)에 기고된 열린 논평(op-ed)들의 콘텐츠 분석을 통해 반동성애 전문가 집단(professionals)이 자신들의 입장을 정당화 하기 위해 동원하는 도덕적 권위와 윤리적 토대의 변천과정을 통시적(1998-2020)으로 추적하였다. 그 결과 정권의 이념적 성향에 따라 이들이 대중적으로 호소하는 도덕적 권위의 유형에 차이가 있음을 발견할 수 있었다. 진보 정권인 노무현, 문재인 행정부 하에서는 동성애 인권을 대한민국의 자유 민주주의와 헌법적 질서에 대한 “실존적 위협(existential threat)”과 연결 짓는 담론적 전략들이 상대적으로 더 자주 동원되었다. 보수 정권인 이명박, 박근혜 행정부 아래에서는 국가 안보나 군사적 방위태세 등과 같은 키워드들이 반동성애 운동을 떠받치는 규범으로서 상대적으로 더 많이 언급되었다. 반면 과학이나 가족의 가치(family value)와 같은 키워드들은 정권의 성향과 관계없이 그 활용 횟수가 점차적으로 증가하였다. 특히 미국의 연방정부 차원에서 동성결혼이 합법화된 2015년을 기점으로 미국과 영국 등을 위시한 서구의 반동성애 엘리트 전문가들이 한국 보수개신교회 내외부의 담론 지형을 형성하는데 지속적인 영향을 미치고 있음을 시론적으로 확인할 수 있었다. This paper reports on content analysis of the Korean Christian newspaper Kidok Sinmun (1998-2020) with regard to how conservative evangelical elites (CEs) change their discursive resources to construct persuasive appeals against the global LGBT movement. Our findings demonstrate that the CEs focus on different sources of moral authority in response to changing political ideologies of the Korean government or regardless of such ideologies (scientific research, family value). During the progressive Roh Moo-hyun and Moon Jae-in administrations, discursive tactics linked LGBT rights with the existential threat to liberal democracy or constitutional value, while the key words such as national security or military discipline were more frequently employed under the conservative Lee Myung-bak and Park Geun-hye governments. Moreover, experiences shared by the transnational network of Christian activists appear to influence the construction of local perceptions on homosexuality.

공급사슬에서 중개 수송모형의 최적해 도출

이원동 ( Lee Wondong ) 한국유통경영학회(구 한국유통정보학회) 2017 유통경영학회지 Vol.20 No.4

운송전략은 경영목표를 달성을 위해서 어떤 방향으로 운송을 전개해 갈 것인가 라는 큰 틀에서의 운송에 대한 전략으로 차량의 확보, 고객서비스 등의 내용이 포함된다. 운송전략 및 운송계획은 물자를 취급하는 제조업체의 원재료 공급을 위한 운송과 운송업체의 화주에 대한운송서비스 제공에 대한 전략과 계획으로 운송 일정 계획의 수립에 있어서 인프라 요소가 된다. 물류기업은 공급사슬에서의 설계 단계에서 수송경로를 결정해야 하며 수요지의 요구물량을 최소비용으로 어떤 경로로 공급할 것인가를 결정해야 한다. 수송모델은 생산 총괄계획을 수립하는데 이용되지만 수송모델의 근본적인 목적은 여러 공급지로부터 다른 수요지로 동질 (Homogeneous)의 제품 및 서비스를 최소의 총 비용으로 수송하는 수송계획을 강구하는 것이다. 물론 수송모델에는 이익의 최대화가 목적인 경우도 있다. 본 연구는 총 수송비용을 최소로 도출해 내는 것을 목적으로 하며, 공급지의 공급물량과 수요지의 요구량을 만족시키기 위하여 중개수송 모형의 각 공급지에서 각 수요지에 얼마를 수송하여야 하는가를 결정하고자 한다. 본 연구를 통하여 수·배송경로에 관한 지식을 응용하여 수·배송경로의 초기해법 및 최적해법을 도출하며, 수·배송관련 솔루션을 활용하여 복잡한 차량경로의 수·배송 운송원가를 절감 할 수 있을 것으로 기대한다. 연구모형의 초기해는 최선의 수송경로를 선택하지 못하였을 때 추가비용을 고려하고 손실을 최소화하기 위하여 VAM(Vogel`s Approximation Method)으로 초기해를 산출하고 최적검사는 모든 빈셀에 대하여 패쇄경로를 사용하지 않고 쌍대변수를 사용하여 기회비용을 계산하는 MODI(Modified Distribution Method)를 활용하여 연구모형의 최적해를 도출한다. The transportation strategy which is about transportation within a large frame that in which direction transportation will be developed to achieve management goals contains the securing of vehicles and customer service. The transportation strategy and plans to transport for supplying raw materials of manufacturers handling materials and to provide transport service for owners of transportation companies are infra elements for establishing plans of transportation schedules. Logistics companies should determine transportation routes in the design stage of the supply chain and routes for providing the amount needed by the market at the lowest costs. Transport models are used for establishing aggregate production plans but the basic goal of transport models is to devise plans for transporting homogeneous goods and service at the lowest total costs from various sources of supply to other markets. Some transport models, of course, are aimed at maximizing profits. This study aims to deduce the lowest total transport costs. For the purpose, the amount that each supply source of mediate transport models should transport to each market should be determined in order to satisfy supplies of a supply source and demand of a market. Through this study, it is expected that the early solution and the optimal solution of transport and delivery routes will be deduced using knowledge of those routes and transport and delivery costs of complicated routes will be reduced using solutions related to transport and delivery. The early solution of study models is calculated with VAM (Vogel`s Approximation Method) to consider additional costs and reduce losses as much as possible when the best transport route couldn`t be chosen. The optimal solution is deduced using the MODI (Modified Distribution Method) for calculating opportunity costs with dual variables, instead of closed routes, about all empty cells.

각군 사관학교의 기계공학 교육 체계 연구

권영진(Youngjin Kwon),이선호(Sunho Lee),한영배(Youngbae Han),김주희(Juhee Kim),Samhyeon Yoo,Jongwoo Lee,Wondong Lee 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.6

Friction and conductance imaging of sp2- and sp3-hybridized subdomains on single-layer graphene oxide

Lee, Hyunsoo,Son, Narae,Jeong, Hu Young,Kim, Tae Gun,Bang, Gyeong Sook,Kim, Jong Yun,Shim, Gi Woong,Goddeti, Kalyan C.,Kim, Jong Hun,Kim, Namdong,Shin, Hyun-Joon,Kim, Wondong,Kim, Sehun,Choi, Sung-Yoo The Royal Society of Chemistry 2016 Nanoscale Vol.8 No.7

<P>We investigated the subdomain structures of single-layer graphene oxide (GO) by characterizing local friction and conductance using conductive atomic force microscopy. Friction and conductance mapping showed that a single-layer GO flake has subdomains several tens to a few hundreds of nanometers in lateral size. The GO subdomains exhibited low friction (high conductance) in the sp(2)-rich phase and high friction (low conductance) in the sp(3)-rich phase. Current-voltage spectroscopy revealed that the local current flow in single-layer GO depends on the quantity of hydroxyl and carboxyl groups, and epoxy bridges within the 2-dimensional carbon layer. The presence of subdomains with different sp(2)/sp(3) carbon ratios on a GO flake was also confirmed by chemical mapping using scanning transmission X-ray microscopy. These results suggest that spatial mapping of the friction and conductance can be used to rapidly identify the composition of heterogeneous single-layer GO at nanometer scale, which is essential for understanding charge transport in nanoelectronic devices.</P>

Perpendicular magnetic anisotropy induced by spin direction of antiferromagnet layers in a ferromagnetic-antiferromagnetic bi-layer system

Wondong Kim,Gwang-Eun Yang,Kyoung-Woog Moon,Byung Sun Chun,Chanyong Hwang,Han-Ku Lee,Jae-Young Kim 한국자기학회 2014 한국자기학회 학술연구발표회 논문개요집 Vol.2014 No.5

Effect of Spectral Line Broadening and Instrument Function on the Spectrum of a Mid-Infrared Flare in a Realistic Environment

Han, Kiwook,Lee, Wondong,Hahn, Jae W. Gordon and Breach Science Publishers 2016 Combustion science and technology Vol.188 No.7

<P>Assessing the similarity between an actual signal from a mid-infrared (IR) flare and the signal emission of a flame from an aircraft requires exact knowledge of the theoretical modeling of the flare's spectrum. In this study, we model the spectrum of an IR flare by considering line-by-line modeling and measurement conditions. First, we calculate the parameters of the spectral lines of a mid-IR flare using the high-temperature molecular spectroscopic database (HITEMP) and the chemical parameters of the IR flare with the combustion model in the thermodynamic equilibrium condition. To calculate the exact spectral line shape function, we introduce spectral line broadening for each spectral line in the IR flare. We also introduce the instrument function of the spectrometer to calculate the measured spectrum of the IR flare. In consideration of realistic measurement environments, we calculate the atmospheric transmission with varying altitudes, measurement angles, and humidity, and obtain the spectra of the IR flare in those conditions. To verify the spectrum model, we confirm that the calculated spectrum is in good agreement with experimental data for the IR flare.</P>

Order-disorder phase transition in Fe/Pt(110)

Chanyong Hwang,Sang Wook Han,Dohyun Lee,Wondong Kim,Hancheol Kim,Mohammad Bellal Hossain,Chul Ki Kim,Jusang Park,Y.P. Lee,Jeongwha Yang,Jisang Hong 한국자기학회 2006 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Room-temperature ferromagnetism observed in graphene oxide

Oh DaYea,Park Bae Ho,Lee Duk Hyun,Kim Wondong,Choi Jun Woo 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.8

We investigate magnetic properties of graphene oxide fake that have been locally oxidized using atomic force microscope (AFM) lithography. This approach reduces the possibility of magnetic contamination. Our Raman spectroscopy analysis reveals that the graphene oxide contains crystalline defects or disorders and difers from the pristine graphene in terms of its atomic structure. Using magnetic force microscopy measurements, we observe that the graphene oxide has a net magnetization pointing out of the surface plane. Furthermore, our magneto-optical Kerr efect data show small but clear hysteresis loops with non-zero remanent magnetization. We also conduct x-ray magnetic circular dichroism (XMCD) photoemission electron microscope measurements and identify remarkable asymmetry in carbon K edge spectra, which strongly suggests that the observed ferromagnetic order in the graphene oxide layer is intrinsic. A careful analysis of XMCD signals depending on the oxidized condition reveals the efects of chemical states of carbon atoms on the formation of ferromagnetic order in the graphene oxide.