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Probing the upper band gap of atomic rhenium disulfide layers

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Light(Science & Applications) 2018年第1期7卷 163-173页

作者： Krishna P.Dhakal hyunmin Kim Seonwoo Lee Youngjae Kim JaeDong Lee jong-hyun ahn School of Electrical and Electronic Engineering Yonsei UniversitySeoul 03722Republic of Korea Companion Diagnostics&Medical Technology Research Group DGISTDaegu 42988Republic of Korea Department of Emerging Materials Science DGISTDaegu 42988Republic of Korea

Here,we investigate the ultrafast carrier dynamics and electronic states of exfoliated ReS2 films using time-resolved second harmonic generation(TSHG)microscopy and density functional theory(DFT)*** second harmonic generation(SHG)of layers with various thicknesses is probed using a 1.19-eV *** to~13 nm,a gradual increment is observed,followed by a decrease caused by bulk interferometric light *** addition of a pump pulse tuned to the exciton band gap(1.57 eV)creates a decay-to-rise TSHG profile as a function of the probe *** power and thickness dependencies indicate that the electron–hole recombination is mediated by defects and *** two photon absorptions of 2.38 eV in the excited state that are induced by pumping from 1.57 to 1.72 eV are restricted because these transitions highly correlate with the forbidden d–d intrasubshell orbital ***,the combined usage of a frequency-doubled pump(2.38 eV)with wavelength-variant SHG probes(2.60–2.82 eV)allows us to vividly monitor the variations in TSHG profiles from decay-to-rise to rise-to-decay,which imply the existence of an additional electron absorption state(s-orbital)at an approximate distance of 5.05 eV from the highest occupied molecular orbital *** observation was critically examined by considering the allowance of each electronic transition and a small upper band gap(~0.5 eV)using modified DFT calculations.

关键词： pump pumping transitions

Crypto primitive of MOCVD MoS_(2) transistors for highly secured physical unclonable functions

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Nano Research 2021年第6期14卷 1784-1788页

作者： Bangjie Shao Tsz Hin Choy Feichi Zhou Jiewei Chen Cong Wang Yong Ju Park jong-hyun ahn Yang Chai Department of Applied Physics The Hong Kong Polytechnic UniversityHong KongChina School of Electrical and Electronic Engineering Yonsei UniversitySeoul03722Republic of Korea

Physically unclonable crypto primitives have potential applications for anti-counterfeiting,identification,and authentication,which are clone proof and resistant to variously physical *** physical unclonable function(PUF)based on Si complementary metal-oxide-semiconductor(CMOS)technologies greatly suffers from entropy loss and bit instability due to noise *** we grow atomically thick MoS2 thin film and fabricate field-effect transistors(FETs).The inherently physical randomness of MoS2 transistors from materials growth and device fabrication process makes it appropriate for the application of PUF *** perform electrical characterizations of MoS2 FETs,collect the data from 448 devices,and generate PUF keys by splitting drain current at specific levels to evaluate the response *** selection of splitting threshold enables to generate binary,ternary,and double binary *** generated PUF keys exhibit good randomness and uniqueness,providing a possibility for harvesting highly secured PUF devices with two-dimensional materials.

关键词： transition metal dichalcogenides two-dimensional materials physical unclonable function metal-organic chemical vapor deposition field-effect transistor

Graphene-based flexible and wearable electronics

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Journal of Semiconductors 2018年第1期39卷 86-104页

作者： Tanmoy Das Bhupendra K.Sharma Ajit K.Katiyar jong-hyun ahn School of Electrical and Electronic Engineering Yonsei University

Graphene with an exceptional combination of electronic, optical and outstanding mechanical features has been proved to lead a completely different kind of 2-D electronics. The most exciting feature of graphene is its ultra-thin thickness, that can be conformally contacted to any kind of rough surface without losing much of its transparency and conductivity. Graphene has been explored demonstrating various prototype flexible electronic applications, however, its potentiality has been proven wherever transparent conductive electrodes（TCEs） are needed in a flexible, stretchable format. Graphene-based TCEs in flexible electronic applications showed greatly superior performance over their conventionally available competitor indium tin oxide（ITO）. Moreover, enormous applications have been emerging, especially in wearable devices that can be potentially used in our daily life as well as in biomedical areas. However, the production of high-quality, defect-free large area graphene is still a challenge and the main hurdle in the commercialization of flexible and wearable products. The objective of the present review paper is to summarize the progress made so far in graphene-based flexible and wearable applications. The current developments including challenges and future perspectives arc also highlighted.

关键词： graphene flexible electronics wearable electronics transparent conductive electrode

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Flexible micro-LED display and its application in Gbps multi-channel visible light communication

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npj Flexible Electronics 2022年第1期6卷 973-979页

作者： Luhing Hu Jaeyong Choi Sumin Hwangbo Do-Hoon Kwon Bongkyun Jang Seunghyeon Ji Jae-hyun Kim Sang-Kook Han jong-hyun ahn School of Electrical and Electronic Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Nanomechanics Nano-Convergence Mechanical Systems Research DivisionKorea Institute of Machinery&Materials(KIMM)156 Gajeongbuk-roYuseong-guDaejeon 34103Republic of Korea

A flexible full-color micro-LED display with high mechanical robustness was fabricated by printing quantum dots(QDs)on a blue micro-LED array using standard *** red and green colors yielded from QDs exhibit a better color gamut than conventional color *** light conversion efficiency was enhanced by adding TiO2 nanoparticles to the QD-photoresist *** full-color micro-LED display was successfully mounted on various unusual substrates such as curved glass,fabrics,and human skin,enabling diverse optoelectronic *** addition,wireless multi-channel visible light communication(VLC)based on the wavelength-division-multiplexing orthogonal-frequency-division-multiplexing(WDM-OFDM)technique was demonstrated using a QD-based color micro-LED panel.A high data transmission rate of 1.9 Gbps was successfully obtained owing to the high electrical-optical modulation bandwidth of the QD-based micro-LED panel.

关键词： communication Gbps visible

Graphene:fabrication and applications

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Graphene:fabrication and applications

Prominent cycling reversibility and kinetics enabled by CaTiO3 protective layer on Zn metal for aqueous Zn-ion batteries

第三届微电子及等离子体技术国际会议

作者： Seoung-Ki Lee Houk Jang jong-hyun ahn School of Advanced Materials Science and Engineering SKKU Advanced Institute of NanotechnologySungkyunkwan University（SKKU）

An important goal for realization of flexible and stretchable electronics is to use print-processable materials that can be directly printed and realize high performance in devices on a flexible and stretchable ***,the thinnest elastic material,has superb electronic and thermal properties that make it a promising host for device *** particular,graphene has an extremely good mechanical property,offering a great opportunity to flexible and stretchable electronics that should maintain a stable operation under a high *** we demonstrate the high-performance and low voltage operating field effect transistor（FET） on the soft substrates such as plastic or rubber using high quality,large area graphene films grown by CVD *** graphene based FET on the soft substrate indicates that high mobility under low operating voltage less than ***,the printed graphene FET on the plastic substrate exhibited remarkably stable performance under strain configuration an important feature flexible and stretchable electronic system.

关键词： Graphene Field effect transistor Flexible electronics Stretchable electronics

来源： cnki会议评论

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Journal of Energy Chemistry 2025年第1期100卷 245-258页

作者： Gaeun Lee Yong Nam ahn Seongjoon So Chanwoo Park jong-Seong Bae Taehyun Park Il Tae Kim Jaehyun Hur School of Chemical Biological and Battery Engineering Gachon University Seongnam Busan Center Korea Basic Science Institute

Aqueous Zn-ion batteries （AZIBs） have received considerable attention owing to their various advantages such as safety,low cost,simple battery assembly conditions,and high ionic ***,they still suffer from serious problems,including uncontrollable dendrite growth,corrosion,hydrogen evolution reaction （HER） from water decomposition,electrode passivation,and unexpected *** creation of a uniform artificial nanocrystal layer on the Zn anode surface is a promising strategy for resolving these ***,we propose the use of a perovskite CaTiO3（CTO） protective layer on Zn（CTO@Zn） as a promising approach for improving the performance of *** CTO artificial layer provides an efficient pathway for Zn ion diffusion towards the Zn metal because of the high dielectric constant （εr=180） and ferroelectric characteristics that enable the alignment of dipole moments and redistribute the Zn2+ions in the CTO *** avoiding the direct contact of the Zn anode with the electrolyte solution,the uneven dendrite growth,corrosion,parasitic side reactions,and HER are mitigated,while CTO retains its mechanical and chemical robustness during ***,CTO@Zn demonstrates an improved lifespan in a symmetric cell configuration compared with bare ***@Zn shows steady overpotential （～68 m V） for 1500 h at 1 mA cm-2/0.5 mA h cm-2,excelling bare ***,when paired with the V2O5-C cathode,the CTO@Zn//V2O5-C full battery delivers 148.4 mA h g-1（based on the mass of the cathode） after 300 *** study provides new insights into Zn metal anodes and the development of high-performance AZIBs.

关键词： Artificial layer Dielectric constant Zn metal anode Zinc aqueous battery

Fibrinogen’s potential role in connecting cerebrovascular abnormalities with glymphatic dysfunction in Alzheimer’s disease

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Neural Regeneration Research 2025年第1期20卷 203-204页

作者： Vishal Singh Arnab Choudhury hyung Jin ahn Department of Pharmacology Physiology and NeurosciencesRutgers-New Jersey Medical SchoolNewarkNJUSA Brain Health Institute Rutgers UniversityPiscatawayNJUSA

Alzheimer’s disease(AD)stands out as the primary manifestation of age-related dementia,portraying a chronic neurodegenerative disorder distinguished by the accumulation of fibrillar amyloid-β(Aβ)plaques and neurofibrillary tangles of hyperphosphorylated ***,from a clinical standpoint,AD presents itself as a complex condition with a spectrum of dysfunctions rather than a singular pathological *** often-overlooked aspect of the disease is the presence of extensive cerebrovascular abnormalities,given that the majority of AD patients experience altered cerebral blood flow,damaged vasculature,increased microinfarcts and *** models of AD further support this observation,showing cerebrovascular dysfunction such as impaired cerebral blood flow and altered cerebrovascular reactivity(Tataryn et al.,2021;Gareau et al.,2023).

关键词： cerebrovascular dysfunction Alzheimer

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Maximizing biomass utilization: An integrated strategy for coproducing multiple chemicals

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Journal of Energy Chemistry 2025年第1期100卷 180-191页

作者： Byeongchan ahn Sua Jo jonggeol Na J.Jay Liu Young-Ju Kim Wangyun Won Department of Chemical and Biological Engineering Korea University Department of Chemical Engineering (Integrated process) Kyung Hee University Department of Chemical Engineering and Materials Science Ewha Womans University Department of Chemical Engineering Pukyong National University Resources Engineering Plant Research Department Korea Institute of Geoscience and Mineral Resources

Lignocellulosic biomass is one of the viable solutions to alleviate the global warming. However, the limited utilization of biomass majorly focused on cellulose and hemicellulose restricts the economic and environmental feasibilities. To cope with this issue, we proposed an integrated process of co-producing 1,6-hexanediol（1,6-HDO） with tetrahydrofuran and adipic acid from biomass, referred to as Strategy A. To compare the impacts of lignin upgrading and feedstock, Strategy B, which co-produces tetrahydrofuran alone, and Strategy C, which is the traditional route to produce 1,6-HDO from fossil fuels, were used. Heat networks are also designed to reduce operating costs and indirect carbon emissions due to energy consumption, saving 87% and 83% of the heat and cooling requirements, respectively, in Strategy A. The market competitiveness of Strategy A was evaluated by determining the minimum selling price through techno-economic analysis, and sustainability was thoroughly investigated by quantifying the environmental impacts through both midpoint and endpoint life-cycle assessments（LCAs）.Strategy A was found to be the most favorable both economically（USRDSCHARDOLLAR3,402/ton） and environmentally（-26.9 kg CO2eq.）. This indicates that lignin valorization is not only economically but also environmentally preferred. Finally, changes in economic and environmental feasibilities depending on economic, process, and environmental parameters were investigated using sensitivity and uncertainty analyses. The results of these analyses provide valuable insight into bio-based chemical production.

关键词： Biorefinery Carbon mitigation Climate change Global warming Lignin utilization Bioeconomy

Formal Approach to Workow Application Fragmentations Over Cloud Deployment Models

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Computers, Materials & Continua 2021年第6期67卷 3071-3088页

作者： hyun ahn Kwanghoon Pio Kim Division of Computer Science and Engineering Gyeonggi16227Korea

Workow management technologies have been dramatically improving their deployment architectures and systems along with the evolution and proliferation of cloud distributed computing ***,such cloud computing environments ought to be providing a suitable distributed computing paradigm to deploy very large-scale workow processes and applications with scalable on-demand *** this paper,we focus on the distribution paradigm and its deployment formalism for such very large-scale workow applications being deployed and enacted across the multiple and heterogeneous cloud computing *** propose a formal approach to vertically as well as horizontally fragment very large-scale workow processes and their applications and to deploy the workow process and application fragments over three types of cloud deployment models and *** concretize the formal approach,we rstly devise a series of operational situations fragmenting into cloud workow process and application components and deploying onto three different types of cloud deployment models and *** concrete approaches are called the deployment-driven fragmentation mechanism to be applied to such very large-scale workow process and applications as an implementing component for cloud workow management ***,we strongly believe that our approach with the fragmentation formalisms becomes a theoretical basis of designing and implementing very large-scale and maximally distributed workow processes and applications to be deployed on cloud deployment models and architectural computing environments as well.

关键词： Cloud workows cloud deployment model workow application fragmentations information control net