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The Post Annealing to Control the Number of Layers of 2D MoS<sub>2</sub> and SnS<sub>2</sub>
Choi, Moonsuk,Lim, Donghwan,Sergeevich, Andrey Sokolov,Son, Seok Ki,Kim, Young Jin,Han, Hoon Hee,Choi, Changhwan American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.11
<P>We have demonstrated that post annealing could control the layer thickness of 2D MoS2 and SnS2 films transferred on a SiO2/Si substrate by varying the annealing temperature and time. Atomic force microscopy and Raman spectroscopy characterizations revealed that higher annealing temperature and longer treatment time led to thinner films, lower residues and fewer impurities on the surface of 2D materials. In addition, a higher possibility to attain few-layers on both 2D films was achieved using post annealing. The multiple layers of pristine films having the thickness over 15 nm were reduced down to bi-layers after annealing. We observed that the moderate annealing temperature of 450 degrees C on led to effective layer-thinning compared to the films annealed at 340 degrees C. The post annealing at 450 degrees C produced very smooth few-layers (<= 4 nm thickness, >1 mu m size) of 2D MoS2 and SnS2. However, the 2D films decomposed or disappeared at temperature greater than 650 degrees C. In addition, process time also affected the number of layers and the sweet spot turned out to be 2 to 3 hours in our experiment.</P>
Characteristics of Nano-Laminated Al-Doped ZnO (AZO) Multilayers
Choi, Moonsuk,Lim, Donghwan,Kim, Jinok,Park, Jin-Hong,Choi, Changhwan American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.11
<P>The structural, morphological, optical, and electrical properties of Al-doped ZnO (AZO) single layer and AZO/metal (Ag and Au: 3 nm)/AZO multilayer thin films prepared via sputtering processes were characterized. Additionally, the effect of post-annealing on the properties of films was investigated. X-ray diffraction revealed that the crystal properties of hexagonal wurtzite crystal structures and the preferred orientation of ZnO (002), with c-axis growth for both AZO single layer and AZO multilayer films. Surface roughness was not degraded by inserting metals into the AZO films. Post air annealing at 300 degrees C improved the crystallinity and surface roughness of the films. AZO multilayer films exhibited lower transmittance values compared with AZO single layer films, but improved after post-annealing. The energy band gap was about 3.5 eV for the AZO multilayer films. Compared to AZO single layer films, AZO multilayer films exhibited lower sheet resistance and resistivity values. Additionally, high carrier concentrations and electron mobilities were attained by inserting metals into AZO. Post-annealing further improved the electrical properties. The post-annealed AZO/Ag/AZO thin films exhibited the best properties (4.26 x 10(-3) Omega(-1)) as Haccke figure of merit (FOM) parameters, due to low sheet resistance (6.75 Omega/sq) and moderate transmittance (70.12%) within the visible light region.</P>
이동환(Donghwan Lee),정우남(Woo-Nam Juhng),이형종(Hyungjong Lee),최보영(Bo-Young Choi),최준석(Choi Junseok) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.9
Waveguide bragg grating(WBG) was fabricated using Loyd mirror system and Ar ion laser. Silica waveguide was fabricated by F.H.D (Flame Hydrolysis Deposition) method and I.C.P(Jnduced Coupled Plasma) etching. Slanted grating was formed 45 degree tilled to beam propagation direction by holographic photo lithography method. We verified that 1300 ㎚ light source was reflected to waveguide side wall.
운행 경유차용 매연 원격측정기(RSD) 국산화 개발 및 현장 적용성 시험에 관한 연구
최동환(Donghwan Choi),김승열(Sunglyul Kim),이승훈(Seunghoon Lee),김계현(Gyehyun Kim),김지훈(Jihoon Kim),최기봉(Kibong Choi),오상기(Sangki Oh) 한국자동차공학회 2021 한국자동차공학회 부문종합 학술대회 Vol.2021 No.6
국내 대기환경에 대한국민 관심도는 점차 증가하고 있으며, 특히 최근에는 미세먼지 이슈가 점차 부각되고 있다. 이에 2016년 6월 정부 관계부처 합동 ‘미세먼지 관리 특별대책’ 발표, 2017년 6월 ‘미세먼지 관리 종합대책 및 로드맵 수립’ 등의 범정부 차원의 노력이 경주되고 있으며, 그에 따라 미세먼지 환경 기준 강화와 각종 저감 정책들이 발효 및 실행되고 있다. 특히 도로이동 오염원(차량)에서 발생하는 매연으로 인한 미세먼지가 국내 미세먼지 발생량의 20%를 차지하며, 수도권에서는 가장 높은 원인으로 조사되는 만큼 경유차량에 대한 미세먼지 대책이 정부대책의 주를 이루고 있다. 본 연구를 통해 디젤 차량에서 발생하는 매연 농도를 원격으로 측정할 수 있는 운행 경유차용 매연 원격 측정기(RSD)를 국산화 개발하였다. 개발된 측정기는 충분한 출력의 광원과 빔 스플리터에 의한 다채널 광로 방식을 채택하여 차종에 관계없이 다용도로 사용할 수 있다. 또한, 고성능 광학 센서와 신호 안정화를 통해 측정 정확도를 확보하였다. 개발된 측정기의 실험실 테스트 결과, 기준분석기 (r<sup>2</sup> = 0.845)와 충분한 상관관계를 보였으며, 벤치마킹 된 해외 분석기의 성능에 필적하는 결과가 도출되었다. 또한 충분한 매연 발생 조건 (> 40km/h) 상황의 일반도로 현장 적용성 시험에서도 높은 상관관계 (평균 r<sup>2</sup> = 0.850)가 관찰되었다. 추가적인 보정요소를 적용한다면 환경부의 운행차량 관리 정책에 널리 활용될 수 있을 것으로 기대된다.
Transcriptome changes in rice (Oryza sativa L.) for high zinc content at the early milky stage
Eun-Beom Heo,Min-Young Yoon,Buung Choi,Donghwan Shim,Beom-Seok Park,Won-Il Kim,Yong-Jin Park 한국육종학회 2015 한국육종학회 심포지엄 Vol.2015 No.07
Zinc (Zn) deficiency is one of the important abiotic factors limiting rice productivity world-wide and also a widespread nutritional disorder affecting human health. Zinc is one of the most important essential micronutrient for human About thirty percentage world’s population doesn’t still get enough zinc through their diets. As a staple food of over half world’s population, rice should take the responsibility to provide much more zinc in the future. We analyzed the transcriptome profiles for rice grain from high zinc content and low zinc content lines at the early milky stage using the Illumina Sequencing method. The analysis results for the sequencing data indicated that many transcripts showed different expressions between high zinc content and low zinc content in early milky stage of rice and RT-qPCR analyses confirmed the expression patterns of selected transcripts. Functional analysis of the differentially expressed transcripts indicated that genes have functional annotation and their functions are mainly involved in oxidation-reduction, metabolic, transport , transcript regulation, defense response and photosynthetic processes. Based on the functional annotation of the differentially expressed genes, the possible process that regulates these differentially expressed transcripts in rice grain responding to Zinc at the early milky stage was further analyzed. The functional classification of those genes indicated their connection with various metabolic pathways, Zinc transport, signal transduction, transcriptional regulation, and other processes related to growth and development in early milky stage of rice. Using Illumina sequencing technology, the differences between the transcriptomes of high zinc content and low zinc content lines the early milky stage was described here for the first time. The candidate transcripts may provide genetic resources that may be useful in the improvement of Zinc concentration of rice. The model proposed here is based on differences in expression and transcription between two rice lines. In addition, the model may support future studies on the molecular mechanisms underlying plant responses to Zinc.