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arXiv 2023年

作者： Sassi, Lucas M. Iyengar, Sathvik Ajay Puthirath, Anand B. Huang, Yuefei Li, Xingfu Terlier, Tanguy Mojibpour, Ali Teixeira, Ana Paula C. Bharadwaj, Palash Tiwary, Chandra Sekhar Vajtai, Robert Talapatra, Saikat Yakobson, Boris Ajayan, Pulickel M. Department of Materials Science & NanoEngineering Rice University 6100 Main Street HoustonTX77005 United States SIMS laboratory Shared Equipment Authority Rice University 6100 Main Street HoustonTX77005 United States Department of Electrical and Computer Engineering Rice University 6100 Main Street HoustonTX77005 United States Department of Chemistry Universidade Federal de Minas Gerais UFMG MG Belo Horizonte31270-901 Brazil Metallurgical and Materials Engineering Indian Institute of Technology Kharagpur Kharagpur382355 India School of Physics and Applied Physics Southern Illinois University CarbondaleIL62901 United States

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) remain a topic of immense interest. Specifically, given their low operational switching costs, they find many niche applications in new computing architectures with the promise of continued miniaturization. However, challenges lie in Back End of Line (BEOL) integration temperature and time compliance regarding current requirements for crystal growth. Additionally, deleterious and time-consuming transfer processes and multiple steps involved in channel/contact engineering can cripple device performance. This work demonstrates kinetics-governed in-situ growth regimes (surface or edge growth from gold) of WSe2 and provides a mechanistic understanding of these regimes via energetics across various material interfaces. As a proof-of-concept, field effect transistors (FET) with an in-situ grown WSe2 channel across Au contacts are fabricated, demonstrating a 2D semiconductor transistor via a "transfer-free" method within the 450-600 C 2h-time window requirement BEOL integration. We leverage directional edge growth to fabricate contacts with robust thickness-dependent Schottky-to-Ohmic behavior. By transitioning between Au and SiO2 growth substrates in situ, this work achieves strain-induced subthreshold swing of ~140 mV/decade, relatively high mobility of 107 ± 19 cm2V-1s-1, and robust ON/OFF ratios ~106 in the fabricated FETs. Copyright © 2023, The Authors. All rights reserved.

关键词： Ohmic contacts

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Ultrathin quantum light source enabled by a nonlinear van der Waals crystal with vanishing interlayer-electronic-coupling

arXiv

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arXiv 2022年

作者： Guo, Qiangbing Qi, Xiao-Zhuo Gao, Meng Hu, Sanlue Zhang, Lishu Zhou, Wenju Zang, Wenjie Zhao, Xiaoxu Wang, Junyong Yan, Bingmin Xu, Mingquan Wu, Yun-Kun Eda, Goki Xiao, Zewen Gou, Huiyang Feng, Yuan Ping Guo, Guang-Can Zhou, Wu Ren, Xi-Feng Qiu, Cheng-Wei Pennycook, Stephen J. Wee, Andrew T.S. Department of Materials Science and Engineering National University of Singapore Singapore117575 Singapore Centre for Advanced 2D Materials Graphene Research Centre National University of Singapore Singapore117546 Singapore Key Laboratory of Quantum Information CAS University of Science and Technology of China Anhui Hefei230026 China Synergetic Innovation Center of Quantum Information & Quantum Physics University of Science and Technology of China Anhui Hefei230026 China School of Physical Sciences CAS Key Laboratory of Vacuum Physics University of Chinese Academy of Sciences Beijing100049 China Wuhan National Laboratory for Optoelectronics Huazhong University of Science and Technology Wuhan430074 China Department of Physics National University of Singapore Singapore117542 Singapore Center for High Pressure Science and Technology Advanced Research Beijing100094 China School of Materials Science and Engineering Nanyang Technological University Singapore639798 Singapore Department of Electrical and Computer Engineering National University of Singapore Singapore117583 Singapore

Interlayer electronic coupling in two-dimensional (2D) materials enables tunable and emergent properties by stacking engineering. However, it also brings significant evolution of electronic structures and attenuation of excitonic effects in 2D semiconductors as exemplified by quickly degrading excitonic photoluminescence and optical nonlinearities in transition metal dichalcogenides when monolayers are stacked into van der Waals structures. Here we report a novel van der Waals crystal, niobium oxide dichloride, featuring a vanishing interlayer electronic coupling and scalable second harmonic generation intensity of up to three orders higher than that of exciton-resonant monolayer WS2. Importantly, the strong second-order nonlinearity enables correlated parametric photon pair generation, via a spontaneous parametric down-conversion (SPDC) process, in flakes as thin as ~46 nm. To our knowledge, this is the first SPDC source unambiguously demonstrated in 2D layered materials, and the thinnest SPDC source ever reported. Our work opens an avenue towards developing van der Waals material-based ultracompact on-chip SPDC sources, and high-performance photon modulators in both classical and quantum optical technologies. © 2022, CC BY-NC-ND.

关键词： Monolayers

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Learning across multi-stimulus enhances target recognition methods in SSVEP-based BCIs

Learning across multi-stimulus enhances target recognition m...

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作者： Wong, Chi Man Wan, Feng Wang, Boyu Wang, Ze Nan, Wenya Lao, Ka Fai Mak, Peng Un Vai, Mang I. Rosa, Agostinho Department of Electrical and Computer Engineering Faculty of Science and Technology University of Macau China Centre for Cognitive and Brain Sciences Institute of Collaborative Innovation University of Macau China Department of Computer Science University of Western Ontario LondonON Canada Department of Psychology Shanghai Normal University Shanghai China State Key Laboratory of Analog and Mixed-Signal VLSI University of Macau China LaSEEB-ISR-LARSyS Universidade de Lisboa Lisbon Portugal

Objective. Latest target recognition methods that are equipped with learning from the subject's calibration data, represented by the extended canonical correlation analysis (eCCA) and the ensemble task-related component analysis (eTRCA), can achieve extra high performance in the steady-state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs), however their performance deteriorate drastically if the calibration trials are insufficient. This paper develops a new scheme to learn from limited calibration data. Approach. A learning across multiple stimuli scheme is proposed for the target recognition methods, which applies to learning the data corresponding to not only the target stimulus but also the other stimuli. The resulting optimization problems can be simplified and solved utilizing the prior knowledge and properties of SSVEPs across different stimuli. With the new learning scheme, the eCCA and the eTRCA can be extended to the multi-stimulus eCCA (ms-eCCA) and the multi-stimulus eTRCA (ms-eTRCA), respectively, as well as a combination of them (i.e. ms-eCCA+ms-eTRCA) that incorporates their merits. Main results. Evaluation and comparison using an SSVEP-BCI benchmark dataset with 35 subjects show that the ms-eCCA (or ms-eTRCA) performs significantly better than the eCCA (or eTRCA) method while the ms-eCCA+ms-eTRCA performs the best. With the learning across stimuli scheme, the existing target recognition methods can be further improved in terms of the target recognition performance and the ability against insufficient calibration. Significance. A new learning scheme is proposed towards the efficient use of the calibration data, providing enhanced performance and saving calibration time in the SSVEP-based BCIs. © 2020 IOP Publishing Ltd.

关键词： Brain computer interface

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Spatially and spectrally resolved orbital angular momentum interactions in plasmonic vortex generators

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Light(science & Applications) 2019年第1期8卷 907-915页

作者： Jordan A.Hachtel Sang-Yeon Cho Roderick B.Davidson II Matthew A.Feldman Matthew F.Chisholm Richard F.Haglund Juan Carlos Idrobo Sokrates T.Pantelides Benjamin J.Lawrie Center for Nanophase Materials Science Oak Ridge National LaboratoryOak RidgeTN 37831USA Klipsch School of Electrical and Computer Engineering New Mexico State UniversityLas CrucesNM 88003USA Department of Physics and Astronomy Vanderbilt UniversityNashvilleTN 37235USA Quantum Information Science Group Oak Ridge National LaboratoryOak RidgeTN 37831USA Materials Science and Technology Division Oak Ridge National LaboratoryOak RidgeTN 37831USA Department of Electrical Engineering and Computer Science Vanderbilt University NashvilleNashvilleTN 37235USA Chemistry Division U.S.Naval Research LaboratoryWashingtonD.C.20375USA

Understanding the near-field electromagnetic interactions that produce optical orbital angular momentum(OAM)is crucial for integrating twisted light into ***,we examine the cathodoluminescence(CL)of plasmonic vortices carrying OAM generated in spiral *** nanospiral geometry defines a photonic local density of states that is sampled by the electron probe in a scanning transmission electron microscope(STEM),thus accessing the optical response of the plasmonic vortex with high spatial and spectral *** map the full spectral dispersion of the plasmonic vortex in spiral structures designed to yield increasing topological ***,we fabricate nested nanospirals and demonstrate that OAM from one nanospiral can be coupled to the nested nanospiral,resulting in enhanced luminescence in concentric spirals of like handedness with respect to concentric spirals of opposite *** results illustrate the potential for generating and coupling plasmonic vortices in chiral nanostructures for sensitive detection and manipulation of optical OAM.

关键词： momentum spectral angular

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In-Situ Nanoscale Focusing of Extreme Ultraviolet Solid-State High Harmonics

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Physical Review X 2022年第4期12卷 041036-041036页

作者： Aleksey Korobenko Sabaa Rashid Christian Heide Andrei Yu Naumov David A. Reis Pierre Berini Paul B. Corkum Giulio Vampa Joint Attosecond Science Laboratory National Research Council of Canada and University of Ottawa Ottawa K1N 5A2 Canada Center for Research in Photonics University of Ottawa Ottawa K1N 6N5 Canada Stanford PULSE Institute SLAC National Accelerator Laboratory Menlo Park California 94025 USA School of Electrical Engineering and Computer Science University of Ottawa Ottawa K1N 6N5 Canada Department of Physics University of Ottawa Ottawa K1N 6N5 Canada

Extreme ultraviolet light delivering radiation with a wavelength shorter than approximately 100 nm is now available from solid-state sources. However, despite exceptional progress, efficient focusing of extreme ultraviolet photons to their ultimate diffraction limit remains a formidable challenge because of the precision of the focusing by curved, optical surfaces. Here we integrate coherent short-wavelength high-order harmonics from a MgO crystal, with a high-numerical-aperture, nanostructured, focusing element etched onto the surface of the crystal itself. We focus extreme ultraviolet light, seventh harmonic of an 800-nm laser, with a zone plate of numerical aperture 0.35, down to a waist radius of 150 nm, with 18% focusing efficiency. The estimated intensity approaches 107 W/cm2. Future developments may demonstrate nanoscale laser ablation and miniaturization of extreme ultraviolet coherent sources on a chip.

关键词： High-order harmonic generation Ultrafast optics

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Atomic scale understanding of the electronic structure of 5d-3d perovskite oxide heterostructures using STEM-EELS.

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Microscopy and Microanalysis 2021年第S1期27卷 356-358页

作者： Sandhya Susarla Xiaoxi Huang Shehrin Sayed Lucas Caretta Hongrui Zhang Sayeef Salahuddin Peter Ercius Ramamoorthy Ramesh National Center for Electron Microscopy Lawrence Berkeley National Laboratory Berkeley CA94720 USA Berkeley California United States Department of Materials Science and Engineering University of California Berkeley CA94720 USA United States Department of Electrical Engineering and Computer Science University of California Berkeley CA94720 USA United States Lawrence Berkeley National Laboratory United States University of California Berkeley Berkeley California United States

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Giant optomechanical coupling in the charge density wave state of tantalum disulfide

arXiv

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arXiv 2021年

作者： Haldar, Anubhab Cortes, Cristian L. Gray, Stephen K. Sharifzadeh, Sahar Darancet, Pierre Department of Electrical and Computer Engineering Boston University BostonMA02215 United States Center for Nanoscale Materials Argonne National Laboratory ArgonneIL60439 United States Division of Materials Science and Engineering Boston University BostonMA02215 United States Northwestern Argonne Institute of Science and Engineering EvanstonIL60208 United States

We study the coupling between light and the structural order parameter in the charge density wave (CDW) state of the layered transition-metal dichalcogenide, tantalum disulfide (1T - TaS2). Using time-dependent density functional theory calculations of the dielectric properties along the distortions coordinates, we show that 1T - TaS2displays a very large change in its dielectric function along the amplitude (Higgs) mode. This behavior originates from the coupling of the periodic lattice distortion with an in-plane metal-insulator transition, leading to optomechanical coupling coefficients two orders of magnitude larger than the ones of diamond and ErFeO3. In addition, we derive an effective model of the light-induced dynamics, which is in quantitative agreement with experimental observations in 1T - TaS2. We show that light-induced dynamics along the structural order parameter in 1T - TaS2can be deterministically controlled to engineer large third-order non-linear optical susceptibilities. Our findings suggest that CDW materials are promising active materials for non-linear optics. Copyright © 2021, The Authors. All rights reserved.

关键词： Sulfur compounds

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Optimal Measurement Configuration In Computational Diffractive Imaging

arXiv

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arXiv 2020年

作者： Widloski, Evan Kamaci, Ulas Kamalabadi, Farzad Department of Electrical and Computer Engineering and Coordinated Science Laboratory University of Illinois at Urbana-Champaign UrbanaIL61801 United States

Diffractive lenses have recently been applied to the domain of multispectral imaging in the X-ray and UV regimes where they can achieve very high resolution as compared to reflective and refractive optics. Conventionally, spectral components are reconstructed by taking measurements at the focal planes. However, the reconstruction quality can be improved by optimizing the measurement configuration. In this work, we adapt a sequential backward selection algorithm to search for a configuration which minimizes expected reconstruction error. By approximating the forward system as a circular convolution and making assumptions on the source and noise, we greatly reduce the complexity of the algorithm. Numerical results show that the configuration found by the algorithm significantly improves the reconstruction performance compared to a standard configuration. Copyright © 2020, The Authors. All rights reserved.

关键词： Computational Imaging

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Social bubbles and superspreaders: Source identification for contagion processes on hypertrees

arXiv

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arXiv 2020年

作者： Spencer, Sam Varshney, Lav R. Coordinated Science Laboratory Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States

Previous work has shown that for contagion processes on extended star networks (trees with exactly one node of degree > 2), there is a simple, closed-form expression for a highly accurate approximation to the maximum likelihood infection source. Here, we generalize that result to a class of hypertrees which, although somewhat structurally analogous, provides a much richer representation space. In particular, this approach can be used to estimate patient zero sources, even when the infection has been propagated via large group gatherings rather than person-to-person spread, and when it is spreading through interrelated social bubbles with varying degrees of overlap. In contact tracing contexts, this estimator may be used to identify the source of a local outbreak, which can then be used for forward tracing or for further backward tracing (by similar or other means) to an upstream source. Copyright © 2020, The Authors. All rights reserved.

关键词： Maximum likelihood

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Efficient Image Super-Resolution with Feature Interaction Weighted Hybrid Network

arXiv

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arXiv 2022年

作者： Li, Wenjie Li, Juncheng Gao, Guangwei Deng, Weihong Yang, Jian Qi, Guo-Jun Lin, Chia-Wen Pattern Recognition and Intelligent System Laboratory School of Artificial Intelligence Beijing University of Posts and Telecommunications Beijing100080 China Intelligent Visual Information Perception Laboratory Institute of Advanced Technology Nanjing University of Posts and Telecommunications Nanjing210046 China Key Laboratory of Artificial Intelligence Ministry of Education Shanghai200240 China Provincial Key Laboratory for Computer Information Processing Technology Soochow University Suzhou215006 China School of Communication and Information Engineering Shanghai University Shanghai200444 China School of Computer Science and Technology Nanjing University of Science and Technology Nanjing210094 China Research Center for Industries of the Future the School of Engineering Westlake University Hangzhou310024 China OPPO Research SeattleWA98101 United States Department of Electrical Engineering National Tsing Hua University Hsinchu30013 Taiwan

Lightweight image super-resolution aims to reconstruct high-resolution images from low-resolution images using low computational costs. However, existing methods result in the loss of middle-layer features due to activation functions. To minimize the impact of intermediate feature loss on reconstruction quality, we propose a Feature Interaction Weighted Hybrid Network (FIWHN), which comprises a series of Wide-residual Distillation Interaction Block (WDIB) as the backbone. Every third WDIB forms a Feature Shuffle Weighted Group (FSWG) by applying mutual information shuffle and fusion. Moreover, to mitigate the negative effects of intermediate feature loss, we introduce Wide Residual Weighting units within WDIB. These units effectively fuse features of varying levels of detail through a Wide-residual Distillation Connection (WRDC) and a Self-Calibrating Fusion (SCF). To compensate for global feature deficiencies, we incorporate a Transformer and explore a novel architecture to combine CNN and Transformer. We show that our FIWHN achieves a favorable balance between performance and efficiency through extensive experiments on low-level and high-level tasks. Codes will be available at https://***/IVIPLab/FIWHN. Copyright © 2022, The Authors. All rights reserved.

关键词： Image reconstruction

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