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- 저자 : Seungjin LEE (검색결과 450 건)
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Formation of ZnO nanostructures grown on Si and SiO2 substrates.
Lee, Seungjin,Park, Eunkyung,Lee, Jongtack,Park, Taehee,Lee, Sang-Hwa,Kim, Jae-Yong,Yi, Whikun American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.9
<P>ZnO nanorods are grown on Si-based substrate by chemical bath deposition method in aqueous solution using zinc nitrate hexahydrate. Various substrates having different surface morphology are used to evaluate their effect on growing ZnO nanorods, such as flat Si(100) wafer, small and large textured-Si wafer, porous silicon, flat SiO2 wafer, small and large textured-SiO2 wafer. The length, diameter, geometry, and coverage density of ZnO nanorods are investigated by field-emission scanning electron microscopy and summarized. SiO2 is a preferred substrate for the growth of ZnO nanorods to Si if the surface morphology of substrate is same, and the textured surface has much higher coverage density (> 95%) than the flat surface. Each nanorod is vertically grown along the c-axis on the top of each pyramid face for textured substrate, and forms the 3D sea sponge-like ZnO structure. The characteristics of ZnO nanorods grown on various substrates are analyzed by grazing-angle X-ray diffraction (XRD) and photoluminescence (PL) measurements.</P>
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Lee, Seungjin,Kim, Youngwoong,Wu, Ziang,Lee, Changyeon,Oh, Seung Jin,Luan, Nguyen Thanh,Lee, Junbok,Jeong, Dahyun,Zhang, Kai,Huang, Fei,Kim, Taek-Soo,Woo, Han Young,Kim, Bumjoon J. American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.48
<P>Aqueous-processed all-polymer solar cells (aq-APSCs) are reported for the first time by developing a series of water/ethanol-soluble naphthalenediimide (NDI)-based polymer acceptors [P(NDIDEG-T), P(NDITEG-T), and P(NDITEG-T2)]. Polymer acceptors are designed by using the backbones of NDI-bithiophene and NDI-thiophene in combination with nonionic hydrophilic oligoethylene glycol (OEG) side chains that facilitate processability in water/ethanol mixtures. All three polymers exhibit sufficient solubility (20-50 mg mL<SUP>-1</SUP>) in the aqueous medium. The P(NDIDEG-T) polymer with shorter OEG side chains is the most crystalline with the highest electron mobility, enabling the fabrication of efficient aq-APSCs with the maximum power conversion efficiency (PCE) of 2.15%. Furthermore, these aq-APSCs are fabricated under ambient atmosphere by taking advantage of the eco-friendly aqueous process and, importantly, the devices exhibit outstanding air-stability without any encapsulation, as evident by maintaining more than 90% of the initial PCE in the air after 4 days. According to a double cantilever beam test, the interfacial adhesion properties between the active layer and electron/hole transporting layers were remarkably improved by incorporating the hydrophilic OEG-attached photoactive layer, which hinders the delamination of the constituent layers and prevents the increase of series resistance, ultimately leading to enhanced durability under ambient conditions. The combination of increased device stability and minimal environmental impact of these aq-APSCs demonstrates them to be worthy candidates for continued development of scalable polymer solar cells.</P> [FIG OMISSION]</BR>
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Choi, Hyeongsu,Lee, Jeongsu,Shin, Seokyoon,Lee, Juhyun,Lee, Seungjin,Park, Hyunwoo,Kwon, Sejin,Lee, Namgue,Bang, Minwook,Lee, Seung-Beck,Jeon, Hyeongtag IOP Pub 2018 Nanotechnology Vol.29 No.21
<P>Representative tin sulfide compounds, tin monosulfide (SnS) and tin disulfide (SnS<SUB>2</SUB>) are strong candidates for future nanoelectronic devices, based on non-toxicity, low cost, unique structures and optoelectronic properties. However, it is insufficient for synthesizing of tin sulfide thin films using vapor phase deposition method which is capable of fabricating reproducible device and securing high quality films, and their device characteristics. In this study, we obtained highly crystalline SnS thin films by atomic layer deposition and obtained highly crystalline SnS<SUB>2</SUB> thin films by phase transition of the SnS thin films. The SnS thin film was transformed into SnS<SUB>2</SUB> thin film by annealing at 450 °C for 1 h in H<SUB>2</SUB>S atmosphere. This phase transition was confirmed by x-ray diffractometer and x-ray photoelectron spectroscopy, and we studied the cause of the phase transition. We then compared the film characteristics of these two tin sulfide thin films and their switching device characteristics. SnS and SnS<SUB>2</SUB> thin films had optical bandgaps of 1.35 and 2.70 eV, and absorption coefficients of about 10<SUP>5</SUP> and 10<SUP>4</SUP> cm<SUP>−1</SUP> in the visible region, respectively. In addition, SnS and SnS<SUB>2</SUB> thin films exhibited p-type and n-type semiconductor characteristics. In the images of high resolution-transmission electron microscopy, SnS and SnS<SUB>2</SUB> directly showed a highly crystalline orthorhombic and hexagonal layered structure. The field effect transistors of SnS and SnS<SUB>2</SUB> thin films exhibited on–off drain current ratios of 8.8 and 2.1 × 10<SUP>3</SUP> and mobilities of 0.21 and 0.014 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>, respectively. This difference in switching device characteristics mainly depends on the carrier concentration because it contributes to off-state conductance and mobility. The major carrier concentrations of the SnS and SnS<SUB>2</SUB> thin films were 6.0?×?10<SUP>16</SUP> and 8.7?×?10<SUP>13</SUP> cm<SUP>−3</SUP>, respectively, in this experiment.</P>
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Lee Seungjin,Reo Seung Hyeon,Kim Seokjoon,Kim Seokhwan,이은성,Cha Byung Seok,Shin Jiye,한진주,Ahn So Min,신한승,Park Ki Soo 한국바이오칩학회 2024 BioChip Journal Vol.18 No.1
In this study, Staphylococcus aureus (S. aureus ) was detected using a system that combined direct loop-mediated isothermal amplification (LAMP) and lateral flow assays (LFA). This technology relies on sequence-specific hybridization in LFA; furthermore, it has high specificity and addresses the limitations associated with nonspecific amplification in general colori- metric LAMP. In addition, a direct boiling method was adopted to streamline DNA extraction and enable simple detection. The established technology was used to successfully detect S. aureus at a concentration as low as 10 2 colony-forming unit/ mL, without cross-reactivity with other strains. The practical applicability of this technology was demonstrated by analyzing real samples such as beef jerky, cabbage, and eggshell, which were artificially spiked with S. aureus . This developed system may be beneficial with regard to operational simplicity, short analysis time, and high detection performance, which would enable its application in point-of-care settings and as a novel platform for detecting various pathogens.
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Applying Chaos and Complexity Theory to Language Learning
Seungjin Lee 현대문법학회 1999 현대문법연구 Vol.15 No.-
This paper attempts to suggest ways in which complexity theory can become a more explicit tool for understanding students’ learning and design of learning processes. These are remarkably consistent with whole language approach in schools. Although complexity theory is based on mathematics and physics, many of these principles are equally relevant to a second language learning situation. Now that complexity theory is in its third decade in the West, and has been evolving, it seems that the time is right for a fuller look at the language teaching principle offered by chaos-complexity theory in the field of a second language learning. This paper reviews complex adaptive systems theory through neuroscience and brain research to learning theory and practice. The complexity theory originated not in linguistics but in the mathematical field, and it is interesting to observe that both complexity theory and whole language theory having taken different routes, came to many of the same conclusions about teaching students. Both complexity theory and whole language theory show a very high agreement on issues such as method, approach, affect, effect, role of the teacher, psychological needs of the language learner, and the philosophy of engaging the learner beyond the cognitive domain. By looking at the chaos and complexity theory for learning process, I discuss that learning occurs at the edge of chaos through equilibrium, whole-brain involvement, and “risk-taking”. Finally, it seems that complexity and whole language theory affirm the recent shift toward a richer, more open, and more comfortable environment as the most effective way in which educators can optimize the natural human capacity for the learning process.
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