109 results on '"Shengxi Huang"'
Search Results
2. Topology stabilized fluctuations in a magnetic nodal semimetal
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Nathan C. Drucker, Thanh Nguyen, Fei Han, Phum Siriviboon, Xi Luo, Nina Andrejevic, Ziming Zhu, Grigory Bednik, Quynh T. Nguyen, Zhantao Chen, Linh K. Nguyen, Tongtong Liu, Travis J. Williams, Matthew B. Stone, Alexander I. Kolesnikov, Songxue Chi, Jaime Fernandez-Baca, Christie S. Nelson, Ahmet Alatas, Tom Hogan, Alexander A. Puretzky, Shengxi Huang, Yue Yu, and Mingda Li
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Science - Abstract
Abstract The interplay between magnetism and electronic band topology enriches topological phases and has promising applications. However, the role of topology in magnetic fluctuations has been elusive. Here, we report evidence for topology stabilized magnetism above the magnetic transition temperature in magnetic Weyl semimetal candidate CeAlGe. Electrical transport, thermal transport, resonant elastic X-ray scattering, and dilatometry consistently indicate the presence of locally correlated magnetism within a narrow temperature window well above the thermodynamic magnetic transition temperature. The wavevector of this short-range order is consistent with the nesting condition of topological Weyl nodes, suggesting that it arises from the interaction between magnetic fluctuations and the emergent Weyl fermions. Effective field theory shows that this topology stabilized order is wavevector dependent and can be stabilized when the interband Weyl fermion scattering is dominant. Our work highlights the role of electronic band topology in stabilizing magnetic order even in the classically disordered regime.
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- 2023
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3. Exploring Topological Semi-Metals for Interconnects
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Satwik Kundu, Rupshali Roy, M. Saifur Rahman, Suryansh Upadhyay, Rasit Onur Topaloglu, Suzanne E. Mohney, Shengxi Huang, and Swaroop Ghosh
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local interconnect ,global interconnect ,Weyl semi-metal ,propagation delay ,instructions per cycle ,cache design ,Applications of electric power ,TK4001-4102 - Abstract
The size of transistors has drastically reduced over the years. Interconnects have likewise also been scaled down. Today, conventional copper (Cu)-based interconnects face a significant impediment to further scaling since their electrical conductivity decreases at smaller dimensions, which also worsens the signal delay and energy consumption. As a result, alternative scalable materials such as semi-metals and 2D materials were being investigated as potential Cu replacements. In this paper, we experimentally showed that CoPt can provide better resistivity than Cu at thin dimensions and proposed hybrid poly-Si with a CoPt coating for local routing in standard cells for compactness. We evaluated the performance gain for DRAM/eDRAM, and area vs. performance trade-off for D-Flip-Flop (DFF) using hybrid poly-Si with a thin film of CoPt. We gained up to a 3-fold reduction in delay and a 15.6% reduction in cell area with the proposed hybrid interconnect. We also studied the system-level interconnect design using NbAs, a topological semi-metal with high electron mobility at the nanoscale, and demonstrated its advantages over Cu in terms of resistivity, propagation delay, and slew rate. Our simulations revealed that NbAs could reduce the propagation delay by up to 35.88%. We further evaluated the potential system-level performance gain for NbAs-based interconnects in cache memories and observed an instructions per cycle (IPC) improvement of up to 23.8%.
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- 2023
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4. Quantized thermoelectric Hall effect induces giant power factor in a topological semimetal
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Fei Han, Nina Andrejevic, Thanh Nguyen, Vladyslav Kozii, Quynh T. Nguyen, Tom Hogan, Zhiwei Ding, Ricardo Pablo-Pedro, Shreya Parjan, Brian Skinner, Ahmet Alatas, Ercan Alp, Songxue Chi, Jaime Fernandez-Baca, Shengxi Huang, Liang Fu, and Mingda Li
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Science - Abstract
Theories predict a large thermopower and a quantized thermoelectric Hall conductivity in topological semimetals. Here, the authors observe an ultrahigh longitudinal thermopower and a giant power factor attributed to the quantized thermoelectric Hall effect in a Weyl semimetal TaP.
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- 2020
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5. Raman Spectroscopy on Brain Disorders: Transition from Fundamental Research to Clinical Applications
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Jeewan C. Ranasinghe, Ziyang Wang, and Shengxi Huang
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Raman spectroscopy ,brain disorders ,clinical treatment ,biomarker identification ,statistical analysis ,Biotechnology ,TP248.13-248.65 - Abstract
Brain disorders such as brain tumors and neurodegenerative diseases (NDs) are accompanied by chemical alterations in the tissues. Early diagnosis of these diseases will provide key benefits for patients and opportunities for preventive treatments. To detect these sophisticated diseases, various imaging modalities have been developed such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). However, they provide inadequate molecule-specific information. In comparison, Raman spectroscopy (RS) is an analytical tool that provides rich information about molecular fingerprints. It is also inexpensive and rapid compared to CT, MRI, and PET. While intrinsic RS suffers from low yield, in recent years, through the adoption of Raman enhancement technologies and advanced data analysis approaches, RS has undergone significant advancements in its ability to probe biological tissues, including the brain. This review discusses recent clinical and biomedical applications of RS and related techniques applicable to brain tumors and NDs.
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- 2022
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6. Chemical and Bio Sensing Using Graphene-Enhanced Raman Spectroscopy
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Alexander Silver, Hikari Kitadai, He Liu, Tomotaroh Granzier-Nakajima, Mauricio Terrones, Xi Ling, and Shengxi Huang
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2D materials ,biochemical sensing ,graphene-mediated surface enhanced Raman spectroscopy ,chemical mechanism ,nanocomposite ,Chemistry ,QD1-999 - Abstract
Graphene is a two-dimensional (2D) material consisting of a single sheet of sp2 hybridized carbon atoms laced in a hexagonal lattice, with potentially wide usage as a Raman enhancement substrate, also termed graphene-enhanced Raman scattering (GERS), making it ideal for sensing applications. GERS improves upon traditional surface-enhanced Raman scattering (SERS), combining its single-molecule sensitivity and spectral fingerprinting of molecules, and graphene’s simple processing and superior uniformity. This enables fast and highly sensitive detection of a wide variety of analytes. Accordingly, GERS has been investigated for a wide variety of sensing applications, including chemical- and bio-sensing. As a derivative of GERS, the use of two-dimensional materials other than graphene for Raman enhancement has emerged, which possess remarkably interesting properties and potential wider applications in combination with GERS. In this review, we first introduce various types of 2D materials, including graphene, MoS2, doped graphene, their properties, and synthesis. Then, we describe the principles of GERS and comprehensively explain how the GERS enhancement factors are influenced by molecular and 2D material properties. In the last section, we discuss the application of GERS in chemical- and bio-sensing, and the prospects of such a novel sensing method.
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- 2019
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7. Strain-Level Identification and Analysis of Avian Coronavirus Using Raman Spectroscopy and Interpretable Machine Learning.
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Peng Jin, Yin-Ting Yeh, Jiarong Ye, Ziyang Wang, Yuan Xue 0002, Na Zhang, Shengxi Huang, Elodie Ghedin, Huaguang Lu, Anthony Schmitt, Sharon X. Huang, and Mauricio Terrones
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- 2023
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8. Accurate Virus Identification with Interpretable Raman Signatures by Machine Learning.
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Jiarong Ye, Yin-Ting Yeh, Yuan Xue 0002, Ziyang Wang, Na Zhang, He Liu, Kunyan Zhang, RyeAnne Ricker, Zhuohang Yu, Allison Roder, Nestor Perea Lopez, Lindsey Organtini, Wallace Greene, Susan Hafenstein, Huaguang Lu, Elodie Ghedin, Mauricio Terrones, Shengxi Huang, and Sharon Xiaolei Huang
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- 2022
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9. EllipsoNet: Deep-learning-enabled optical ellipsometry for complex thin films.
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Ziyang Wang, Yuxuan Cosmi Lin, Kunyan Zhang, Wenjing Wu, and Shengxi Huang
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- 2022
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10. Ab Initio Computational Screening and Performance Assessment of van der Waals and Semimetallic Contacts to Monolayer WSe2 P-Type Field-Effect Transistors
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Ning Yang, Yuxuan Cosmi Lin, Chih-Piao Chuu, M. Saifur Rahman, Tong Wu, Ang-Sheng Chou, Hung-Yu Chen, Wei-Yen Woon, Szuya Sandy Liao, Shengxi Huang, Xiaofeng Qian, Jing Guo, Iuliana Radu, H.-S. Philip Wong, and Han Wang
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Electrical and Electronic Engineering ,Electronic, Optical and Magnetic Materials - Published
- 2023
11. Single-Photon Emission from Two-Dimensional Materials, to a Brighter Future
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Sunny Gupta, Wenjing Wu, Shengxi Huang, and Boris I. Yakobson
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General Materials Science ,Physical and Theoretical Chemistry - Published
- 2023
12. Understanding the Excitation Wavelength Dependence and Thermal Stability of the SARS-CoV-2 Receptor-Binding Domain Using Surface-Enhanced Raman Scattering and Machine Learning
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Kunyan Zhang, Ziyang Wang, He Liu, Néstor Perea-López, Jeewan C. Ranasinghe, George Bepete, Allen M. Minns, Randall M. Rossi, Scott E. Lindner, Sharon X. Huang, Mauricio Terrones, and Shengxi Huang
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Electrical and Electronic Engineering ,Atomic and Molecular Physics, and Optics ,Biotechnology ,Electronic, Optical and Magnetic Materials - Published
- 2022
13. Recent Advances in 2D Material Theory, Synthesis, Properties, and Applications
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Yu-Chuan Lin, Riccardo Torsi, Rehan Younas, Christopher L. Hinkle, Albert F. Rigosi, Heather M. Hill, Kunyan Zhang, Shengxi Huang, Christopher E. Shuck, Chen Chen, Yu-Hsiu Lin, Daniel Maldonado-Lopez, Jose L. Mendoza-Cortes, John Ferrier, Swastik Kar, Nadire Nayir, Siavash Rajabpour, Adri C. T. van Duin, Xiwen Liu, Deep Jariwala, Jie Jiang, Jian Shi, Wouter Mortelmans, Rafael Jaramillo, Joao Marcelo J. Lopes, Roman Engel-Herbert, Anthony Trofe, Tetyana Ignatova, Seng Huat Lee, Zhiqiang Mao, Leticia Damian, Yuanxi Wang, Megan A. Steves, Kenneth L. Knappenberger, Zhengtianye Wang, Stephanie Law, George Bepete, Da Zhou, Jiang-Xiazi Lin, Mathias S. Scheurer, Jia Li, Pengjie Wang, Guo Yu, Sanfeng Wu, Deji Akinwande, Joan M. Redwing, Mauricio Terrones, and Joshua A. Robinson
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General Engineering ,General Physics and Astronomy ,General Materials Science ,Article - Abstract
Two-dimensional (2D) material research is rapidly evolving to broaden the spectrum of emergent 2D systems. Here, we review recent advances in the theory, synthesis, characterization, device, and quantum physics of 2D materials and their heterostructures. First, we shed insight into modeling of defects and intercalants, focusing on their formation pathways and strategic functionalities. We also review machine learning for synthesis and sensing applications of 2D materials. In addition, we highlight important development in the synthesis, processing, and characterization of various 2D materials (e.g., MXnenes, magnetic compounds, epitaxial layers, low-symmetry crystals, etc.) and discuss oxidation and strain gradient engineering in 2D materials. Next, we discuss the optical and phonon properties of 2D materials controlled by material inhomogeneity and give examples of multidimensional imaging and biosensing equipped with machine learning analysis based on 2D platforms. We then provide updates on mix-dimensional heterostructures using 2D building blocks for next-generation logic/memory devices and the quantum anomalous Hall devices of high-quality magnetic topological insulators, followed by advances in small twist-angle homojunctions and their exciting quantum transport. Finally, we provide the perspectives and future work on several topics mentioned in this review.
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- 2023
14. New optical features of substitutional defects in 2D materials
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Shengxi Huang
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- 2023
15. Rapid Biomarker Screening of Alzheimer’s Disease by Interpretable Machine Learning and Graphene-Assisted Raman Spectroscopy
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Ziyang Wang, Jiarong Ye, Kunyan Zhang, Li Ding, Tomotaroh Granzier-Nakajima, Jeewan Ranasinghe, Yuan Xue, Shubhang Sharma, Isabelle Biase, Mauricio Terrones, Se Hoon Choi, Chongzhao Ran, Rudolph E. Tanzi, Sharon X. Huang, Can Zhang, and Shengxi Huang
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Computer science ,General Physics and Astronomy ,Disease ,Machine learning ,computer.software_genre ,Spectrum Analysis, Raman ,Machine Learning ,symbols.namesake ,Mice ,Alzheimer Disease ,medicine ,Effective treatment ,Dementia ,Animals ,General Materials Science ,business.industry ,General Engineering ,medicine.disease ,Monolayer graphene ,Magnetic Resonance Imaging ,symbols ,Biomarker (medicine) ,Graphite ,Artificial intelligence ,business ,Raman spectroscopy ,computer ,Biomarkers - Abstract
As the most common cause of dementia, the study of Alzheimer’s disease (AD) faces challenges in terms of understanding the cause, monitoring the pathogenesis, and developing early diagnosis and effective treatment. Rapid and accurate identification of AD biomarkers in the brain is critical to provide key insights into AD and facilitate the development of early diagnosis methods. In this work, we developed a platform that enables a rapid screening of AD biomarkers by employing graphene-assisted Raman spectroscopy and machine learning interpretation in AD transgenic animal brains. Specifically, we collected Raman spectra on slices of mouse brains with and without AD and used machine learning to classify AD and non-AD spectra. By contacting monolayer graphene with the brain slices, the accuracy was significantly increased from 77% to 98% in machine learning classification. Further, using linear supporting vector machine (SVM), we identified a spectral feature importance map that reveals the importance of each Raman wavenumber in classifying AD and non-AD spectra. Based on this spectral feature importance map, we identified AD biomarkers including Aβ and tau proteins, and other potential biomarkers, such as triolein, phosphatidylcholine, and actin, which have been confirmed by other biochemical studies. Our Raman-machine learning integrated method with interpretability is promising to greatly accelerate the study of AD and can be extended to other tissues, biofluids, and for various other diseases.
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- 2022
16. Probing charge transfer in 2D MoS2/tellurene type-II p–n heterojunctions
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Kunyan Zhang, Basant Chitara, Fei Yan, Tej B. Limbu, Shengxi Huang, Bikram Adhikari, and Martha Y. Garcia Cervantes
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Kelvin probe force microscope ,Range (particle radiation) ,Materials science ,Photoluminescence ,business.industry ,Heterojunction ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,7. Clean energy ,0104 chemical sciences ,symbols.namesake ,Monolayer ,Microscopy ,symbols ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Raman spectroscopy ,Spectroscopy - Abstract
2D heterostructures offer new opportunities for harnessing a wider range of the solar spectrum in high-performance photovoltaic devices. Here, we explore a type-II p–n heterojunction, by exploiting air-stable tellurene (Te) in combination with MoS2, to study its charge transfer for photovoltaic applications. The charge transfer of MoS2/Te heterojunction is confirmed by photoluminescence spectroscopy, Raman spectroscopy and Kelvin probe force microscopy. The exciton binding energy for MoS2/Te heterojunction is estimated to be around 10 meV, which is much lower than that for monolayer MoS2. This strategy can be exploited to develop next-generation intrinsically ultrathin light-harvesting devices.
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- 2021
17. Computational Screening and Multiscale Simulation of Barrier-Free Contacts for 2D Semiconductor pFETs
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Ning Yang, Yuxuan Cosmi Lin, Chih-Piao Chuu, Saifur Rahman, Tong Wu, Ang-Sheng Chou, San-Lin Liew, Kohei Fujiwara, Hung-Yu Chen, Junya Ikeda, Atsushi Tsukazaki, Duen-Huei Hou, Wei-Yen Woon, Szuya Liao, Shengxi Huang, Xiaofeng Qian, Jing Guo, Iuliana Radu, H.-S. Philip Wong, and Han Wang
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- 2022
18. Step engineering for nucleation and domain orientation control in WSe2 epitaxy on c-plane sapphire
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Haoyue Zhu, Nadire nayir, Tanushree Choudhury, Anushka Bansal, Benjamin Huet, Kunyan Zhang, Alexander Puretzky, Saiphaneendra Bachu, Krystal York, Thomas Mc Knight, Nicholas Trainor, Ke Wang, Robert Makin, Steven Durbin, Shengxi Huang, Nasim Alem, Vincent Crespi, Adri Van Duin, and Joan Redwing
- Abstract
Epitaxial growth of 2D transition metal dichalcogenides (TMDs) on sapphire has emerged as a promising route to wafer-scale single crystal films. Steps on the sapphire act as sites for TMD nucleation and can impart a preferred domain orientation resulting in a significant reduction in mirror twins. Here we demonstrate control of both the nucleation site and unidirectional growth direction of WSe2 on c-plane sapphire by metalorganic chemical vapor deposition (MOCVD). The unidirectional orientation is found to be intimately tied to growth conditions via changes in the sapphire surface chemistry which control the step edge location of WSe2 nucleation imparting either a 0° or 60° orientation relative to the underlying sapphire lattice. The results provide insight into the role of surface chemistry on TMD nucleation and domain alignment and demonstrate the ability to engineer domain orientation over wafer-scale substrates.
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- 2022
19. A case study of on-chip sensor network in multiprocessor system-on-chip.
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Yu Wang 0002, Jiang Xu 0001, Shengxi Huang, Weichen Liu, and Huazhong Yang
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- 2009
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20. Photoluminescence Induced by Substitutional Nitrogen in Single-Layer Tungsten Disulfide
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Qingkai Qian, Wenjing Wu, Lintao Peng, Yuanxi Wang, Anne Marie Z. Tan, Liangbo Liang, Saban M. Hus, Ke Wang, Tanushree H. Choudhury, Joan M. Redwing, Alexander A. Puretzky, David B. Geohegan, Richard G. Hennig, Xuedan Ma, and Shengxi Huang
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General Engineering ,General Physics and Astronomy ,General Materials Science - Abstract
The electronic and optical properties of two-dimensional materials can be strongly influenced by defects, some of which can find significant implementations, such as controllable doping, prolonged valley lifetime, and single-photon emissions. In this work, we demonstrate that defects created by remote N
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- 2022
21. Measuring complex refractive index through deep-learning-enabled optical reflectometry
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Ziyang Wang, Yuxuan Cosmi Lin, Kunyan Zhang, Wenjing Wu, and Shengxi Huang
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,General Chemistry ,Condensed Matter Physics - Abstract
Optical spectroscopy is indispensable for research and development in nanoscience and nanotechnology, microelectronics, energy, and advanced manufacturing. Advanced optical spectroscopy tools often require both specifically designed high-end instrumentation and intricate data analysis techniques. Beyond the common analytical tools, deep learning methods are well suited for interpreting high-dimensional and complicated spectroscopy data. They offer great opportunities to extract subtle and deep information about optical properties of materials with simpler optical setups, which would otherwise require sophisticated instrumentation. In this work, we propose a computational approach based on a conventional tabletop optical microscope and a deep learning model called ReflectoNet. Without any prior knowledge about the multilayer substrates, ReflectoNet can predict the complex refractive indices of thin films and 2D materials on top of these nontrivial substrates from experimentally measured optical reflectance spectra with high accuracies. This task was not feasible previously with traditional reflectometry or ellipsometry methods. Fundamental physical principles, such as the Kramers–Kronig relations, are spontaneously learned by the model without any further training. This approach enables in-operando optical characterization of functional materials and 2D materials within complex photonic structures or optoelectronic devices.
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- 2023
22. Engineered 2D materials for optical bioimaging and path toward therapy and tissue engineering
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Jeewan C. Ranasinghe, Arpit Jain, Wenjing Wu, Kunyan Zhang, Ziyang Wang, and Shengxi Huang
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Abstract
Two-dimensional (2D) layered materials as a new class of nanomaterial are characterized by a list of exotic properties. These layered materials are investigated widely in several biomedical applications. A comprehensive understanding of the state-of-the-art developments of 2D materials designed for multiple nanoplatforms will aid researchers in various fields to broaden the scope of biomedical applications. Here, we review the advances in 2D material-based biomedical applications. First, we introduce the classification and properties of 2D materials. Next, we summarize surface and structural engineering methods of 2D materials where we discuss surface functionalization, defect, and strain engineering, and creating heterostructures based on layered materials for biomedical applications. After that, we discuss different biomedical applications. Then, we briefly introduced the emerging role of machine learning (ML) as a technological advancement to boost biomedical platforms. Finally, the current challenges, opportunities, and prospects on 2D materials in biomedical applications are discussed.
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- 2022
23. Unravelling the Thickness Dependence and Mechanism of Surface-Enhanced Raman Scattering on Ti3C2TX MXene Nanosheets
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Yu Zhou, Tej B. Limbu, Basant Chitara, Fei Yan, Shengxi Huang, Yongan Tang, and Martha Y. Garcia Cervantes
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Materials science ,Intercalation (chemistry) ,02 engineering and technology ,Substrate (electronics) ,010402 general chemistry ,01 natural sciences ,symbols.namesake ,chemistry.chemical_compound ,Molecule ,Physical and Theoretical Chemistry ,Titanium carbide ,business.industry ,Resonance ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,General Energy ,chemistry ,symbols ,Optoelectronics ,0210 nano-technology ,Raman spectroscopy ,business ,MXenes ,Raman scattering - Abstract
MXenes have attracted great attention as promising substrates for surface-enhanced Raman scattering (SERS) applications. However, the underlying SERS mechanism has not been a focus of any investigation. Herein, we report the first systematic experimental study on the SERS activity of titanium carbide (Ti3C2TX) nanosheets with thicknesses ranging from 5 to 120 nm, using methylene blue (MB) as a probe molecule. The experimental and mathematical modeling results show that the Raman enhancement factor (EF) increases monotonically with the increasing thickness of Ti3C2TX nanosheets; however, it falls drastically around a sheet thickness of 0.8 and 1.0 μm under 532 and 633 nm laser excitations, respectively. The Raman EF reaches a maximum value around a thickness of 2.0 μm, suggesting that a maximum EF can be achieved with a 2.0 μm-thick Ti3C2TX film substrate. The thickness dependence of the Raman enhancement can be accounted for by the adsorption and intercalation of MB molecules into the interlayer spacing of Ti3C2TX. Furthermore, by combining experimental observations and numerical calculation, we confirm that the charge-transfer mechanism is dominantly responsible for Raman enhancement on Ti3C2TX. Additionally, we report an observation of resonance coupling of charge transfer and molecular transition as a contributing factor to the higher EF obtained with a 633 nm laser excitation. Taken together, these findings have significant implications for cost and performance optimization in designing MXene-based SERS substrates for next-generation chemical and biological sensing platforms.
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- 2020
24. Coherent Lattice Wobbling and Out-of-Phase Intensity Oscillations of Friedel Pairs Observed by Ultrafast Electron Diffraction
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Xiaozhe Shen, Alexander H. Reid, Yu Zhou, Shengxi Huang, Ming-Fu Lin, Duan Luo, Suji Park, Qingkai Qian, Michael Kozina, Jie Yang, Kunyan Zhang, Lanxin Jia, Stephen Weathersby, Renkai Li, and Xijie Wang
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Physics ,Condensed matter physics ,Scattering ,Phonon ,Ultrafast electron diffraction ,General Engineering ,General Physics and Astronomy ,Bragg peak ,Laser ,law.invention ,Condensed Matter::Materials Science ,law ,Lattice (order) ,General Materials Science ,Excitation ,Monoclinic crystal system - Abstract
The inspection of Friedel's law in ultrafast electron diffraction (UED) is important to gain a comprehensive understanding of material atomic structure and its dynamic response. Here, monoclinic gallium telluride (GaTe), as a low-symmetry, layered crystal in contrast to many other 2D materials, is investigated by mega-electronvolt UED. Strong out-of-phase oscillations of Bragg peak intensities are observed for Friedel pairs, which does not obey Friedel's law. As evidenced by the preserved mirror symmetry and supported by both kinematic and dynamic scattering simulations, the intensity oscillations are provoked by the lowest-order longitudinal acoustic breathing phonon. Our results provide a generalized understanding of Friedel's law in UED and demonstrate that by designed misalignment of surface normal and primitive lattice vectors, coherent lattice wobbling and effective shear strain can be generated in crystal films by laser pulse excitation, which is otherwise hard to achieve and can be further utilized to dynamically tune and switch material properties.
- Published
- 2020
25. Defect creation in WSe2 with a microsecond photoluminescence lifetime by focused ion beam irradiation
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Xuedan Ma, Lintao Peng, Qingkai Qian, Mauricio Terrones, Xiaotian Zhang, Shengxi Huang, Kunyan Zhang, Tanushree H. Choudhury, Nestor Perea-Lopez, Joan M. Redwing, and Kazunori Fujisawa
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Materials science ,Photoluminescence ,Orders of magnitude (temperature) ,business.industry ,Exciton ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Focused ion beam ,Microsecond ,symbols.namesake ,0103 physical sciences ,Valleytronics ,symbols ,Optoelectronics ,General Materials Science ,Irradiation ,010306 general physics ,0210 nano-technology ,Raman spectroscopy ,business - Abstract
Defect engineering is important for tailoring the electronic and optical properties of two-dimensional materials, and the capability of generating defects of certain types at specific locations is meaningful for potential applications such as optoelectronics and quantum photonics. In this work, atomic defects are created in single-layer WSe2 using focused ion beam (FIB) irradiation, with defect densities spanning many orders of magnitude. The influences of defects are systematically characterized. Raman spectroscopy can only discern defects in WSe2 for a FIB dose higher than 1 × 1013 cm-2, which causes blue shifts of both A'1 and E' modes. Photoluminescence (PL) of WSe2 is more sensitive to defects. At cryogenic temperature, the low-energy PL induced by defects can be revealed, which shows redshifts and broadenings with increased FIB doses. Similar Raman shifts and PL spectrum changes are observed for the WSe2 film grown by chemical vapor deposition (CVD). A four microsecond-long lifetime is observed in the PL dynamics and is three orders of magnitude longer than the often observed delocalized exciton lifetime and becomes more dominant for WSe2 with increasing FIB doses. The ultra-long lifetime of PL in single-layer WSe2 is consistent with first-principles calculation results considering the creation of both chalcogen and metal vacancies by FIB, and can be valuable for photo-catalytic reactions, valleytronics and quantum light emissions owing to the longer carrier separation/manipulation time.
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- 2020
26. Spectroscopic Signatures of Interlayer Coupling in Janus MoSSe/MoS
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Kunyan, Zhang, Yunfan, Guo, Daniel T, Larson, Ziyan, Zhu, Shiang, Fang, Efthimios, Kaxiras, Jing, Kong, and Shengxi, Huang
- Abstract
The interlayer coupling in van der Waals heterostructures governs a variety of optical and electronic properties. The intrinsic dipole moment of Janus transition metal dichalcogenides (TMDs) offers a simple and versatile approach to tune the interlayer interactions. In this work, we demonstrate how the van der Waals interlayer coupling and charge transfer of Janus MoSSe/MoS
- Published
- 2021
27. Designing artificial two-dimensional landscapes via atomic-layer substitution
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Enzheng Shi, Qingqing Ji, Zhengyang Cai, Haowei Xu, Jihoon Park, Jiangtao Wang, Letian Dou, Cong Su, Changan HuangFu, Juan Carlos Idrobo, Jiadi Zhu, Xiaochuan Dai, Shengxi Huang, Biao Yuan, Pin Chun Shen, Jing Kong, Kaichen Xie, Liying Jiao, Ang-Yu Lu, Yuxuan Lin, Ju Li, Yunfan Guo, Xuezeng Tian, Yi Yu, Tomas Palacios, Kunyan Zhang, and Ting Cao
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Exothermic reaction ,Polarization density ,Multidisciplinary ,Materials science ,Physical Sciences ,Monolayer ,Energy landscape ,Heterojunction ,Nanotechnology ,Material Design ,Janus ,Lithography - Abstract
Technology advancements in history have often been propelled by material innovations. In recent years, two-dimensional (2D) materials have attracted substantial interest as an ideal platform to construct atomic-level material architectures. In this work, we design a reaction pathway steered in a very different energy landscape, in contrast to typical thermal chemical vapor deposition method in high temperature, to enable room-temperature atomic-layer substitution (RT-ALS). First-principle calculations elucidate how the RT-ALS process is overall exothermic in energy and only has a small reaction barrier, facilitating the reaction to occur at room temperature. As a result, a variety of Janus monolayer transition metal dichalcogenides with vertical dipole could be universally realized. In particular, the RT-ALS strategy can be combined with lithography and flip-transfer to enable programmable in-plane multiheterostructures with different out-of-plane crystal symmetry and electric polarization. Various characterizations have confirmed the fidelity of the precise single atomic layer conversion. Our approach for designing an artificial 2D landscape at selective locations of a single layer of atoms can lead to unique electronic, photonic, and mechanical properties previously not found in nature. This opens a new paradigm for future material design, enabling structures and properties for unexplored territories.
- Published
- 2021
28. (Invited) Novel Van Der Waals Compounds and Their Potential for Optical Biosensing
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Shengxi Huang
- Abstract
Emerging 2D van der Waals compounds have gained increasing attention due to their unique electronic and optical properties, and have shown promise in sensing applications. The realization of sensing devices using these materials still faces several challenges. For example, it is critical to gain clear understandings of (1) the fundamental light-matter interactions and their relations to the atomic structures, which govern many key material properties and device performances; and (2) the coupling with other nanostructures and molecules, which is a required structure for sensing devices and systems. This talk introduces new discoveries and pioneering works on these critical challenges, and novel applications of these materials in biochemical sensing. The first part of this talk presents light-matter interactions and techniques to augment material performance, such as 2D Janus transition metal dichalcogenides. The second part of this talk focuses on the interaction of 2D materials with organic molecules and related sensing applications. In particular, a novel enhancement effect of molecular Raman signals on 2D surface was discovered, which offers a new paradigm of biochemical sensing with high specificity, high multiplexity, and low noise. The selection rule for the 2D material substrates has been revealed, which is critical for device design. Two sensing applications for Alzheimer’s disease and respiratory viruses will also be discussed. Overall, the works presented in this talk are significant in fundamental quantum science, and offer important guidelines for practical applications in sensing and quantum technologies. The methodologies used here also provide a framework for the future study of many emerging materials and sensing scenarios.
- Published
- 2022
29. Signature of Many-Body Localization of Phonons in Strongly Disordered Superlattices
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Thanh D. Nguyen, Yoichiro Tsurimaki, Hong Lu, Bogdan M. Leu, Esen E. Alp, Joseph A. Garlow, Yong Q. Cai, Yimei Zhu, Alessandro Cunsolo, Alexander A. Puretzky, Mingda Li, Arthur C. Gossard, Nathan Drucker, David B. Geohegan, Lijun Wu, Qichen Song, Hoi Chun Po, Nina Andrejevic, Shengxi Huang, and Ahmet Alatas
- Subjects
Phonon ,Superlattice ,Population ,FOS: Physical sciences ,Bioengineering ,02 engineering and technology ,Quantum entanglement ,Bose–Hubbard model ,01 natural sciences ,Condensed Matter::Materials Science ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,General Materials Science ,Wave vector ,010306 general physics ,education ,Quantum ,Physics ,Condensed Matter - Materials Science ,education.field_of_study ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Mechanical Engineering ,Materials Science (cond-mat.mtrl-sci) ,General Chemistry ,Models, Theoretical ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Thermalisation ,Phonons ,0210 nano-technology - Abstract
Many-body localization (MBL) has attracted significant attention because of its immunity to thermalization, role in logarithmic entanglement entropy growth, and opportunities to reach exotic quantum orders. However, experimental realization of MBL in solid-state systems has remained challenging. Here, we report evidence of a possible phonon MBL phase in disordered GaAs/AlAs superlattices. Through grazing-incidence inelastic X-ray scattering, we observe a strong deviation of the phonon population from equilibrium in samples doped with ErAs nanodots at low temperature, signaling a departure from thermalization. This behavior occurs within finite phonon energy and wavevector windows, suggesting a localization-thermalization crossover. We support our observation by proposing a theoretical model for the effective phonon Hamiltonian in disordered superlattices, and showing that it can be mapped exactly to a disordered 1D Bose-Hubbard model with a known MBL phase. Our work provides momentum-resolved experimental evidence of phonon localization, extending the scope of MBL to disordered solid-state systems.
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- 2021
30. Accurate Virus Identification with Interpretable Raman Signatures by Machine Learning
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Ning Zhang, Huaguang Lu, Zhang K, Hong Liu, Greene W, Jiarong Ye, Shengxi Huang, Elodie Ghedin, Mauricio Terrones, Zhuohang Yu, Shue Huang, Susan Hafenstein, Lindsey J. Organtini, Allison Roder, Zhong Wang, Yin Ting Yeh, Yuan Xue, and Lopez Np
- Subjects
Artificial neural network ,business.industry ,Computer science ,viruses ,Machine learning ,computer.software_genre ,Convolutional neural network ,Virus ,symbols.namesake ,Identification (information) ,Virus identification ,Classifier (linguistics) ,symbols ,Artificial intelligence ,Avian coronavirus ,business ,Raman spectroscopy ,computer - Abstract
Rapid identification of newly emerging or circulating viruses is an important first step toward managing the public health response to potential outbreaks. A portable virus capture device coupled with label-free Raman Spectroscopy holds the promise of fast detection by rapidly obtaining the Raman signature of a virus followed by a machine learning approach applied to recognize the virus based on its Raman spectrum. In this paper, we present a machine learning analysis on Raman spectra of human and avian viruses. A Convolutional Neural Network (CNN) classifier specifically designed for spectral data achieves very high accuracy for a variety of virus type or subtype identification tasks. In particular, it achieves 99% accuracy for classifying influenza virus type A vs. type B, 96% accuracy for classifying four subtypes of influenza A, 95% accuracy for differentiating enveloped and non-enveloped viruses, and 99% for differentiating avian coronavirus (infectious bronchitis virus, IBV) from other avian viruses. Furthermore, interpretation of neural net responses in the trained CNN model using a full-gradient algorithm highlights Raman spectral ranges that are most important to virus identification. By correlating ML-selected salient Raman ranges with the signature ranges of known biomolecules and chemical functional groups (e.g. amide, amino acid, carboxylic acid) we verify that our ML model effectively recognizes the Raman signatures of proteins, lipids and other vital functional groups present in different viruses and uses a weighted combination of these signatures to identify viruses. The accurate and interpretable machine learning model developed for Raman virus identification presents promising potential in a real-time virus detection system.Significance StatementA portable micro-fluidic platform for virus capture promises rapid enrichment and label-free optical identification of viruses by Raman spectroscopy. A large Raman dataset collected on a variety of viruses enables the training of machine learning (ML) models capable of highly accurate and sensitive virus identification. The trained ML models can then be integrated with the portable device to provide real-time virus detection and identification capability. We validate this conceptual framework by presenting highly accurate virus type and subtype identification results using a convolutional neural network to classify Raman spectra of viruses.
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- 2021
31. Enhanced Raman Scattering on Nine 2D van der Waals Materials
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Shengxi Huang, Hikari Kitadai, Xi Ling, Nannan Mao, and Xingzhi Wang
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Materials science ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Positive correlation ,01 natural sciences ,0104 chemical sciences ,symbols.namesake ,Adsorption ,Chemical physics ,Copper phthalocyanine ,symbols ,Molecule ,General Materials Science ,Physical and Theoretical Chemistry ,van der Waals force ,0210 nano-technology ,Spectroscopy ,Raman spectroscopy ,Raman scattering - Abstract
Since the discovery of graphene-enhanced Raman scattering in 2010, other 2D materials have been reported to show a Raman enhancement effect on molecules adsorbed on their surfaces. The mechanism for this phenomenon, however, still remains elusive. Here we performed a comparative investigation of the Raman enhancement effect on nine 2D materials with an identical number of copper phthalocyanine (CuPc) as probe molecules. Furthermore, the degree of charge transfer for different CuPc/2D material combinations was calculated, and a positive correlation with enhancement factors was observed, providing evidence to support the charge-transfer-dominated chemical mechanism for this amplification. This study also suggests that Raman enhancement spectroscopy can be used as a nondestructive and rapid probe for the interface interaction between molecules and 2D materials, crucial for organic molecule/2D material-based electronic and optoelectronic devices.
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- 2019
32. Defect Engineering in Single-Layer MoS2 Using Heavy Ion Irradiation
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Xinwei Wang, Ran Zhao, Huijun Chen, Xiaofei Chen, Shengxi Huang, Shuang Cheng, Yunmin Zhu, Huimin Su, Zuyun He, Yan Chen, Junfeng Dai, Jianming Xue, and Meilin Liu
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Photoluminescence ,Materials science ,Ion beam ,business.industry ,Defect engineering ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Ion ,symbols.namesake ,Transition metal ,symbols ,Optoelectronics ,General Materials Science ,Irradiation ,0210 nano-technology ,business ,Raman spectroscopy ,Single layer - Abstract
Transition metal dichalcogenides (TMDs) have attracted much attention due to their promising optical, electronic, magnetic, and catalytic properties. Engineering the defects in TMDs represents an effective way to achieve novel functionalities and superior performance of TMDs devices. However, it remains a significant challenge to create defects in TMDs in a controllable manner or to correlate the nature of defects with their functionalities. In this work, taking single-layer MoS2 as a model system, defects with controlled densities are generated by 500 keV Au irradiation with different ion fluences, and the generated defects are mostly S vacancies. We further show that the defects introduced by ion irradiation can significantly affect the properties of the single-layer MoS2, leading to considerable changes in its photoluminescence characteristics and electrocatalytic behavior. As the defect density increases, the characteristic photoluminescence peak of MoS2 first blueshifts and then redshifts, which is l...
- Published
- 2018
33. Probing interlayer interaction via chiral phonons in layered honeycomb materials
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Takashi Taniguchi, Shengxi Huang, Xiaolong Chen, Chen Chen, Bingchen Deng, Fengnian Xia, and Kenji Watanabe
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Materials science ,Condensed matter physics ,Phonon ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,symbols.namesake ,Quantum capacitance ,Condensed Matter::Superconductivity ,0103 physical sciences ,Honeycomb ,symbols ,Density functional theory ,Tensor ,van der Waals force ,010306 general physics ,0210 nano-technology ,Chirality (chemistry) ,Raman spectroscopy - Abstract
van der Waals (vdW) interaction plays a significant role in controlling the physical properties of layered materials. Typically, the vdW interlayer interaction can be calculated by density functional theory or experimentally characterized by quantum capacitance measurement. Here, we report the probing of the interlayer interaction in layered honeycomb materials via chiral phonons. Through helicity resolved Raman measurements, we observed a reduced chirality of the Raman $G$ mode with increasing layer numbers. We introduced interlayer coupling terms into the traditional Raman $G$ mode tensor to simulate the reduced phonon chirality in Raman spectra. Our Raman tensor calculation results agree with the experiments well, suggesting that the interlayer interaction can significantly influence the lattice vibration. Our demonstration provides a perspective for characterizing the interlayer interactions in vdW layered materials with honeycomb lattice structure.
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- 2021
34. Spectroscopic Signatures of Interlayer Coupling in Janus MoSSe/MoS2 Heterostructures
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Shiang Fang, Jing Kong, Kunyan Zhang, Ziyan Zhu, Daniel T. Larson, Yunfan Guo, Efthimios Kaxiras, and Shengxi Huang
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Materials science ,Exciton ,General Physics and Astronomy ,FOS: Physical sciences ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,symbols.namesake ,Condensed Matter::Materials Science ,Electric field ,General Materials Science ,Janus ,Condensed Matter - Materials Science ,Condensed matter physics ,General Engineering ,Charge density ,Materials Science (cond-mat.mtrl-sci) ,Heterojunction ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,0104 chemical sciences ,Dipole ,symbols ,van der Waals force ,0210 nano-technology ,Raman spectroscopy - Abstract
The interlayer coupling in van der Waals heterostructures governs a variety of optical and electronic properties. The intrinsic dipole moment of Janus transition metal dichalcogenides (TMDs) offers a simple and versatile approach to tune the interlayer interactions. In this work, we demonstrate how the van der Waals interlayer coupling and charge transfer of Janus MoSSe/MoS2 heterobilayers can be tuned by the twist angle and interface composition. Specifically, the Janus heterostructures with a sulfur/sulfur (S/S) interface display stronger interlayer coupling than the heterostructures with a selenium/sulfur (Se/S) interface as shown by the low-frequency Raman modes. The differences in interlayer interactions are explained by the interlayer distance computed by density-functional theory (DFT). More intriguingly, the built-in electric field contributed by the charge density redistribution and interlayer coupling also play important roles in the interfacial charge transfer. Namely, the S/S and Se/S interfaces exhibit different levels of photoluminescence (PL) quenching of MoS2 A exciton, suggesting enhanced and reduced charge transfer at the S/S and Se/S interface, respectively. Our work demonstrates how the asymmetry of Janus TMDs can be used to tailor the interfacial interactions in van der Waals heterostructures.
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- 2021
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35. Anisotropic Fano resonance in the Weyl semimetal candidate LaAlSi
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Xiaoqi Pang, Riichiro Saito, Kunyan Zhang, Tong Wang, Shengxi Huang, Mingda Li, Fei Han, Zi Kui Liu, Shun Li Shang, and Nguyen T. Hung
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Physics ,Condensed matter physics ,Phonon ,Weyl semimetal ,Fano resonance ,02 engineering and technology ,Fermion ,021001 nanoscience & nanotechnology ,01 natural sciences ,Semimetal ,symbols.namesake ,0103 physical sciences ,symbols ,010306 general physics ,0210 nano-technology ,Electronic band structure ,Raman spectroscopy ,Kohn anomaly - Abstract
Topological Weyl semimetal (WSM) is a solid-state realization of chiral Weyl fermions, whose phonon behaviors provide in-depth knowledge of their electronic properties. In this work, anisotropic Fano resonance is observed in a type-II WSM candidate LaAlSi by polarized Raman spectroscopy. The asymmetric line shape occurs for the ${B}_{1}^{2}$ phonon mode of LaAlSi only for 488- and 532-nm laser excitations but not for 364-, 633-, and 785-nm excitations, suggesting the excitation selectivity. The asymmetry, frequency, and linewidth of the ${B}_{1}^{2}$ phonon mode, along with the spectral background, all show fourfold rotational symmetry as a function of the polarization angle in the polarized Raman spectra. While the shift of Raman frequency in a metal or semimetal is typically attributed to Kohn anomaly, here we show that the anisotropic frequency shift in LaAlSi cannot be explained by the effect of Kohn anomaly, but potentially by the anisotropic scattering background of Fano resonance. Origins of the excitation-energy dependence and anisotropic behavior of the Fano resonance are discussed by the first-principles calculated electronic band structure and phonon dispersion.
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- 2020
36. Enhancement of van der Waals Interlayer Coupling through Polar Janus MoSSe
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Shengxi Huang, Xiaofeng Qian, Yunfan Guo, Alexander A. Puretzky, Hua Wang, Efthimios Kaxiras, David B. Geohegan, Kunyan Zhang, Jing Kong, Shiang Fang, Cong Su, Ang-Yu Lu, and Qingqing Ji
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Condensed matter physics ,Chemistry ,Heterojunction ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,symbols.namesake ,Dipole ,Colloid and Surface Chemistry ,Monolayer ,symbols ,Density functional theory ,Janus ,Symmetry breaking ,van der Waals force ,Raman spectroscopy - Abstract
Interlayer coupling plays essential roles in the quantum transport, polaritonic, and electrochemical properties of stacked van der Waals (vdW) materials. In this work, we report the unconventional interlayer coupling in vdW heterostructures (HSs) by utilizing an emerging 2D material, Janus transition metal dichalcogenides (TMDs). In contrast to conventional TMDs, monolayer Janus TMDs have two different chalcogen layers sandwiching the transition metal and thus exhibit broken mirror symmetry and an intrinsic vertical dipole moment. Such a broken symmetry is found to strongly enhance the vdW interlayer coupling by as much as 13.2% when forming MoSSe/MoS2 HS as compared to the pristine MoS2 counterparts. Our noncontact ultralow-frequency Raman probe, linear chain model, and density functional theory calculations confirm the enhancement and reveal the origins as charge redistribution in Janus MoSSe and reduced interlayer distance. Our results uncover the potential of tuning interlayer coupling strength through Janus heterostacking.
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- 2020
37. Chirality-Dependent Second Harmonic Generation of MoS
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Qingkai, Qian, Rui, Zu, Qingqing, Ji, Gang Seob, Jung, Kunyan, Zhang, Ye, Zhang, Markus J, Buehler, Jing, Kong, Venkatraman, Gopalan, and Shengxi, Huang
- Abstract
Materials with high second harmonic generation (SHG) efficiency and reduced dimensions are favorable for integrated photonics and nonlinear optical applications. Here, we fabricate MoS
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- 2020
38. Board 62: Work In Progress for Developing Project-Based Experiential Learning of Engineering Electromagnetics
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Adriyel Nieves, Julio Urbina, Tim Kane, Shengxi Huang, and Diego Penaloza
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- 2020
39. Chirality-Dependent Second Harmonic Generation of MoS 2 Nanoscroll with Enhanced Efficiency
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Venkatraman Gopalan, Qingkai Qian, Gang Seob Jung, Ye Zhang, Kunyan Zhang, Markus J. Buehler, Shengxi Huang, Jing Kong, Rui Zu, and Qingqing Ji
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Nanotube ,Materials science ,business.industry ,General Engineering ,General Physics and Astronomy ,Second-harmonic generation ,Physics::Optics ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Nonlinear optical ,Condensed Matter::Materials Science ,Optoelectronics ,General Materials Science ,Photonics ,0210 nano-technology ,business ,Chirality (chemistry) ,Computer Science::Databases - Abstract
© 2020 American Chemical Society. Materials with high second harmonic generation (SHG) efficiency and reduced dimensions are favorable for integrated photonics and nonlinear optical applications. Here, we fabricate MoS2 nanoscrolls with different chiralities and study their SHG performances. As a 1D material, MoS2 nanoscroll shows reduced symmetry and strong chirality dependency in the polarization-resolved SHG characterizations. This SHG performance can be well explained by the superposition theory of second harmonic field of the nanoscroll walls. MoS2 nanoscrolls with certain chiralities and diameters in our experiment can have SHG intensity up to 95 times stronger than that of monolayer MoS2, and the full potential can still be further exploited. The same chirality-dependent SHG can be expected for nanoscrolls or nanotubes composed of other noncentrosymmetric 2D materials, such as WS2, WSe2, and hBN. The characterization and analysis results presented here can also be exploited as a nondestructive technique to determine the chiralities of these nanoscrolls and nanotubes.
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- 2020
40. Topological Singularity Induced Chiral Kohn Anomaly in a Weyl Semimetal
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Anuj Apte, E. Ercan Alp, Zhijun Xu, Thanh D. Nguyen, Yoichiro Tsurimaki, Fei Han, Kunyan Zhang, Yang Zhao, Zhiwei Ding, Jeffrey W. Lynn, Songxue Chi, Nina Andrejevic, Ricardo Pablo-Pedro, Jaime A. Fernandez-Baca, Mingda Li, Masaaki Matsuda, Shengxi Huang, Ahmet Alatas, and David Tennant
- Subjects
Physics ,Superconductivity ,Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Phonon ,General Physics and Astronomy ,Weyl semimetal ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Fermi surface ,Neutron scattering ,16. Peace & justice ,Polaron ,Topology ,01 natural sciences ,Article ,Condensed Matter::Materials Science ,0103 physical sciences ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Wave vector ,Condensed Matter::Strongly Correlated Electrons ,010306 general physics ,Kohn anomaly - Abstract
The electron-phonon interaction (EPI) is instrumental in a wide variety of phenomena in solid-state physics, such as electrical resistivity in metals, carrier mobility, optical transition and polaron effects in semiconductors, lifetime of hot carriers, transition temperature in BCS superconductors, and even spin relaxation in diamond nitrogen-vacancy centers for quantum information processing. However, due to the weak EPI strength, most phenomena have focused on electronic properties rather than on phonon properties. One prominent exception is the Kohn anomaly, where phonon softening can emerge when the phonon wavevector nests the Fermi surface of metals. Here we report a new class of Kohn anomaly in a topological Weyl semimetal (WSM), predicted by field-theoretical calculations, and experimentally observed through inelastic x-ray and neutron scattering on WSM tantalum phosphide (TaP). Compared to the conventional Kohn anomaly, the Fermi surface in a WSM exhibits multiple topological singularities of Weyl nodes, leading to a distinct nesting condition with chiral selection, a power-law divergence, and non-negligible dynamical effects. Our work brings the concept of Kohn anomaly into WSMs and sheds light on elucidating the EPI mechanism in emergent topological materials., Comment: 30 pages, 4 main figures, 11 supplementary figures and 1 theoretical derivation. Feedback most welcome
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- 2020
41. Anomalous Phonon-mode Dependence in Polarized Raman Spectroscopy of Topological Weyl Semimetal TaP
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Tong Wang, Shun Li Shang, Riichiro Saito, Shengxi Huang, Ahmad R. T. Nugraha, Nguyen T. Hung, Xiaoqi Pang, Kunyan Zhang, Mingda Li, Fei Han, and Zi Kui Liu
- Subjects
Physics ,Condensed Matter - Materials Science ,Phonon ,Weyl semimetal ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,02 engineering and technology ,Fermion ,021001 nanoscience & nanotechnology ,Topology ,01 natural sciences ,Symmetry (physics) ,Semimetal ,symbols.namesake ,0103 physical sciences ,symbols ,010306 general physics ,0210 nano-technology ,Raman spectroscopy ,Excitation ,Energy (signal processing) - Abstract
Topological Weyl semimetals (WSMs) have attracted widespread interest due to the chiral Weyl fermions and surface Fermi arcs that enable unique optical and transport phenomena. In this work, we present angle-resolved Raman spectroscopy of TaP, a prototypical noncentrosymmetric WSM, for five excitation wavelengths ranging from 364 to 785 nm. The Raman-active modes, ${A}_{1}$, ${B}_{1}^{1}$, and ${B}_{1}^{2}$ modes, exhibit two main unique features beyond the conventional Raman theory. First, the relative intensities of Raman-active modes change as a function of the excitation wavelength. Second, angle-resolved polarized Raman spectra show systematic deviation from the Raman tensor theory. In particular, the ${B}_{1}^{1}$ mode is absent for 633-nm excitation, whereas the ${B}_{1}^{2}$ mode shows an unusual twofold symmetry instead of a fourfold symmetry for 488-, 532-, and 633-nm excitations. These unconventional phenomena are attributed to the interference effect in the Raman process owing to the existence of multiple carrier pockets with almost the same energy but different symmetries.
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- 2020
42. Defect creation in WSe
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Qingkai, Qian, Lintao, Peng, Nestor, Perea-Lopez, Kazunori, Fujisawa, Kunyan, Zhang, Xiaotian, Zhang, Tanushree H, Choudhury, Joan M, Redwing, Mauricio, Terrones, Xuedan, Ma, and Shengxi, Huang
- Abstract
Defect engineering is important for tailoring the electronic and optical properties of two-dimensional materials, and the capability of generating defects of certain types at specific locations is meaningful for potential applications such as optoelectronics and quantum photonics. In this work, atomic defects are created in single-layer WSe2 using focused ion beam (FIB) irradiation, with defect densities spanning many orders of magnitude. The influences of defects are systematically characterized. Raman spectroscopy can only discern defects in WSe2 for a FIB dose higher than 1 × 1013 cm-2, which causes blue shifts of both A'1 and E' modes. Photoluminescence (PL) of WSe2 is more sensitive to defects. At cryogenic temperature, the low-energy PL induced by defects can be revealed, which shows redshifts and broadenings with increased FIB doses. Similar Raman shifts and PL spectrum changes are observed for the WSe2 film grown by chemical vapor deposition (CVD). A four microsecond-long lifetime is observed in the PL dynamics and is three orders of magnitude longer than the often observed delocalized exciton lifetime and becomes more dominant for WSe2 with increasing FIB doses. The ultra-long lifetime of PL in single-layer WSe2 is consistent with first-principles calculation results considering the creation of both chalcogen and metal vacancies by FIB, and can be valuable for photo-catalytic reactions, valleytronics and quantum light emissions owing to the longer carrier separation/manipulation time.
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- 2020
43. Understanding Interlayer Coupling in TMD-hBN Heterostructure by Raman Spectroscopy
- Author
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Tanushree H. Choudhury, Mikhail Chubarov, Riichiro Saito, Rui Yang, Mingda Li, Mauricio Terrones, Jonathan A. Fan, Fu Zhang, Shengxi Huang, Joan M. Redwing, Teng Yang, Muhammad Shoufie Ukhtary, Ao Zhang, and Li Ding
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Materials science ,Heterojunction ,02 engineering and technology ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Electronic, Optical and Magnetic Materials ,Blueshift ,law.invention ,Condensed Matter::Materials Science ,symbols.namesake ,law ,Optical cavity ,Molecular vibration ,0103 physical sciences ,Monolayer ,symbols ,Electrical and Electronic Engineering ,van der Waals force ,010306 general physics ,0210 nano-technology ,Raman spectroscopy - Abstract
© 2018 IEEE. In 2-D van der Waals heterostructures, interactions between atomic layers dramatically change the vibrational properties of the hybrid system and demonstrate several interesting phenomena that are absent in individual materials. In this paper, we have investigated the vibrational properties of the heterostructure between transition metal dichalcogenide (TMD) and hexagonal boron nitride (hBN) on gold film at low- and high-frequency ranges by Raman spectroscopy. Nineteen Raman modes have been observed from the sample, including a new interlayer coupling mode at 28.8 cm-1. Compared to reported experimental results of tungsten disulfide (WS2) on SiO2/Si substrates, the Raman spectrum for WS2 on hBN/Au emerges a blue shift of about 8 cm-1. Furthermore, a remarkable enhancement of Raman intensity can be obtained when tuning hBN thickness in the heterostructure. Through systematic first-principles calculations, numerical simulations, and analytical calculations, we find that the 28.8 cm-1 mode originates from the shearing motion between monolayer TMD and hBN layers. In addition, the gold substrate and hBN layers form an optical cavity and the cavity interference effects enhance the obtained Raman intensity. This paper demonstrates the novel vibrational modes of 2-D van der Waals heterostructure as an effective tool to characterize a variety of such heterostructures and reveals a new method to enhance the Raman response of 2-D materials.
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- 2018
44. Direct Observation of Symmetry-Dependent Electron-Phonon Coupling in Black Phosphorus
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Shengxi Huang, Qingqing Ji, Liangbo Liang, Bobby G. Sumpter, William A. Tisdale, Nannan Mao, Xingzhi Wang, Yuxuan Lin, Mildred S. Dresselhaus, Vincent Meunier, Xi Ling, Tomas Palacios, and Jing Kong
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Condensed matter physics ,Chemistry ,Direct observation ,Electron phonon coupling ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,Black phosphorus ,Symmetry (physics) ,0104 chemical sciences ,Nanomaterials ,Coupling (electronics) ,Condensed Matter::Materials Science ,Colloid and Surface Chemistry - Abstract
Electron-phonon coupling in two-dimensional nanomaterials plays a fundamental role in determining their physical properties. Such interplay is particularly intriguing in semiconducting black phosphorus (BP) due to the highly anisotropic nature of its electronic structure and phonon dispersions. Here we report the direct observation of symmetry-dependent electron-phonon coupling in BP by performing the polarization-selective resonance Raman measurement in the visible and ultraviolet regimes, focusing on the out-of-plane A
- Published
- 2019
45. Raman Enhancement of Blood Constituent Proteins Using Graphene
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Shengxi Huang, Ishan Barman, Jing Kong, Mildred S. Dresselhaus, and Rishikesh Pandey
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Analyte ,Materials science ,Graphene ,Nanotechnology ,02 engineering and technology ,Substrate (electronics) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Signal ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,law.invention ,symbols.namesake ,law ,symbols ,Molecule ,Electrical and Electronic Engineering ,0210 nano-technology ,Raman spectroscopy ,Biosensor ,Excitation ,Biotechnology - Abstract
Raman spectroscopy has drawn considerable attention in biomedical sensing due to the promise of label-free, multiplexed, and objective analysis along with the ability to gain molecular insights into complex biological samples. However, its true potential is yet to be realized due to the intrinsically weak Raman signal. Here, we report a simple, inexpensive and reproducible signal enhancement strategy featuring graphene as a substrate. Taking key blood constituent proteins as representative examples, we show that Raman spectra acquired from biomacromolecules can be reproducibly enhanced when these molecules are placed in contact with graphene. In particular, we demonstrate that hemoglobin and albumin display significant, but different, enhancement with the enhancement factor depending on the Raman modes, excitation wavelengths, and analyte concentrations. This technique offers a new strategy for label-free biosensing owing to the molecular fingerprinting capability, signal reliability, and simplicity of th...
- Published
- 2018
46. Tuning Electronic Structure of Single Layer MoS2 through Defect and Interface Engineering
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Jing Kong, Kiran Kumar Adepalli, Kedi Yin, Jianmin Xue, Bilge Yildiz, Xiang Ji, Xinwei Wang, Yan Chen, Mildred S. Dresselhaus, Xi Ling, and Shengxi Huang
- Subjects
Materials science ,Graphene ,business.industry ,General Engineering ,General Physics and Astronomy ,Nanotechnology ,02 engineering and technology ,Electronic structure ,Substrate (electronics) ,Chemical vapor deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,chemistry ,law ,General Materials Science ,Scanning tunneling microscope ,Photonics ,0210 nano-technology ,business ,Molybdenum disulfide - Abstract
Transition-metal dichalcogenides (TMDs) have emerged in recent years as a special group of two-dimensional materials and have attracted tremendous attention. Among these TMD materials, molybdenum disulfide (MoS2) has shown promising applications in electronics, photonics, energy, and electrochemistry. In particular, the defects in MoS2 play an essential role in altering the electronic, magnetic, optical, and catalytic properties of MoS2, presenting a useful way to engineer the performance of MoS2. The mechanisms by which lattice defects affect the MoS2 properties are unsettled. In this work, we reveal systematically how lattice defects and substrate interface affect MoS2 electronic structure. We fabricated single-layer MoS2 by chemical vapor deposition and then transferred onto Au, single-layer graphene, hexagonal boron nitride, and CeO2 as substrates and created defects in MoS2 by ion irradiation. We assessed how these defects and substrates affect the electronic structure of MoS2 by performing X-ray pho...
- Published
- 2018
47. Sensitive Phonon-Based Probe for Structure Identification of 1T′ MoTe2
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Jing Kong, Ya-Qing Bie, Lijun Wu, Huaihong Guo, Yuki Tatsumi, Yimei Zhu, Mildred S. Dresselhaus, Keiji Ueno, Lin Zhou, Shengxi Huang, Riichiro Saito, and Teng Yang
- Subjects
Phonon ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,law.invention ,symbols.namesake ,Colloid and Surface Chemistry ,Optics ,law ,Coherent anti-Stokes Raman spectroscopy ,Anisotropy ,business.industry ,Chemistry ,General Chemistry ,021001 nanoscience & nanotechnology ,Laser ,Polarization (waves) ,0104 chemical sciences ,Wavelength ,symbols ,Optoelectronics ,0210 nano-technology ,Raman spectroscopy ,business ,Excitation - Abstract
In this work, by combining transmission electron microscopy and polarized Raman spectroscopy for the 1T′ MoTe2 flakes with different thicknesses, we found that the polarization dependence of Raman intensity is given as a function of excitation laser wavelength, phonon symmetry, and phonon frequency, but has weak dependence on the flake thickness from few-layer to multilayer. In addition, the frequency of Raman peaks and the relative Raman intensity are sensitive to flake thickness, which manifests Raman spectroscopy as an effective probe for thickness of 1T′ MoTe2. Our work demonstrates that polarized Raman spectroscopy is a powerful and nondestructive method to quickly identify the crystal structure and thickness of 1T′ MoTe2 simultaneously, which opens up opportunities for the in situ probe of anisotropic properties and broad applications of this novel material.
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- 2017
48. Chemical and Bio Sensing Using Graphene-Enhanced Raman Spectroscopy
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Xi Ling, Tomotaroh Granzier-Nakajima, Mauricio Terrones, He Liu, Alexander Silver, Hikari Kitadai, and Shengxi Huang
- Subjects
biochemical sensing ,Nanocomposite ,Materials science ,nanocomposite ,Graphene ,Sensing applications ,graphene-mediated surface enhanced Raman spectroscopy ,General Chemical Engineering ,Nanotechnology ,Substrate (electronics) ,Review ,2D materials ,law.invention ,lcsh:Chemistry ,symbols.namesake ,lcsh:QD1-999 ,law ,chemical mechanism ,symbols ,Molecule ,General Materials Science ,Doped graphene ,Raman spectroscopy ,Raman scattering - Abstract
Graphene is a two-dimensional (2D) material consisting of a single sheet of sp2 hybridized carbon atoms laced in a hexagonal lattice, with potentially wide usage as a Raman enhancement substrate, also termed graphene-enhanced Raman scattering (GERS), making it ideal for sensing applications. GERS improves upon traditional surface-enhanced Raman scattering (SERS), combining its single-molecule sensitivity and spectral fingerprinting of molecules, and graphene’s simple processing and superior uniformity. This enables fast and highly sensitive detection of a wide variety of analytes. Accordingly, GERS has been investigated for a wide variety of sensing applications, including chemical- and bio-sensing. As a derivative of GERS, the use of two-dimensional materials other than graphene for Raman enhancement has emerged, which possess remarkably interesting properties and potential wider applications in combination with GERS. In this review, we first introduce various types of 2D materials, including graphene, MoS2, doped graphene, their properties, and synthesis. Then, we describe the principles of GERS and comprehensively explain how the GERS enhancement factors are influenced by molecular and 2D material properties. In the last section, we discuss the application of GERS in chemical- and bio-sensing, and the prospects of such a novel sensing method.
- Published
- 2019
49. Quantized Thermoelectric Hall Effect Induces Giant Power Factor in a Topological Semimetal
- Author
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Quynh T. Nguyen, Brian Skinner, Shengxi Huang, Ahmet Alatas, Songxue Chi, E. Ercan Alp, Tom Hogan, Fei Han, Shreya Parjan, Mingda Li, Zhiwei Ding, Jaime A. Fernandez-Baca, Ricardo Pablo-Pedro, Nina Andrejevic, Liang Fu, Thanh D. Nguyen, and Vladyslav Kozii
- Subjects
Science ,General Physics and Astronomy ,Weyl semimetal ,FOS: Physical sciences ,02 engineering and technology ,Topology ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,Condensed Matter::Materials Science ,Affordable and Clean Energy ,Hall effect ,Seebeck coefficient ,Condensed Matter::Superconductivity ,0103 physical sciences ,Thermoelectric effect ,cond-mat.mes-hall ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Topological insulators ,010306 general physics ,Electronic entropy ,Thermoelectrics ,Physics ,Condensed Matter - Materials Science ,Multidisciplinary ,Condensed Matter - Mesoscale and Nanoscale Physics ,Quantum limit ,Materials Science (cond-mat.mtrl-sci) ,General Chemistry ,021001 nanoscience & nanotechnology ,Thermoelectric materials ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Semimetal ,cond-mat.mtrl-sci ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology - Abstract
Thermoelectrics are promising by directly generating electricity from waste heat. However, (sub-)room-temperature thermoelectrics have been a long-standing challenge due to vanishing electronic entropy at low temperatures. Topological materials offer a new avenue for energy harvesting applications. Recent theories predicted that topological semimetals at the quantum limit can lead to a large, non-saturating thermopower and a quantized thermoelectric Hall conductivity approaching a universal value. Here, we experimentally demonstrate the non-saturating thermopower and quantized thermoelectric Hall effect in the topological Weyl semimetal (WSM) tantalum phosphide (TaP). An ultrahigh longitudinal thermopower \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$S_{xx} \sim 1.1 \times 10^3 \, \mu \, {\mathrm{V}} \, {\mathrm{K}}^{ - 1}$$\end{document}Sxx~1.1×103μVK−1 and giant power factor \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sim 525 \, \mu \, {\mathrm{W}} \, {\mathrm{cm}}^{ - 1} \, {\mathrm{K}}^{ - 2}$$\end{document}~525μWcm−1K−2 are observed at ~40 K, which is largely attributed to the quantized thermoelectric Hall effect. Our work highlights the unique quantized thermoelectric Hall effect realized in a WSM toward low-temperature energy harvesting applications., Theories predict a large thermopower and a quantized thermoelectric Hall conductivity in topological semimetals. Here, the authors observe an ultrahigh longitudinal thermopower and a giant power factor attributed to the quantized thermoelectric Hall effect in a Weyl semimetal TaP.
- Published
- 2019
- Full Text
- View/download PDF
50. Double Resonance Raman Spectroscopy of Two-Dimensional Materials
- Author
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Huaihong Guo, Yuki Tatsumi, Riichiro Saito, Lin Zhou, Shengxi Huang, Mildred S. Dresselhaus, and Teng Yang
- Subjects
Brillouin zone ,symbols.namesake ,Materials science ,Phonon ,Resonance Raman spectroscopy ,symbols ,Resonance ,Wave vector ,Physics::Atomic Physics ,Electronic structure ,Raman spectroscopy ,Molecular physics ,Characterization (materials science) - Abstract
In this chapter, we overview double resonance Raman spectra of two dimensional materials. Many weak Raman spectral peaks are observed in the two dimensional materials which can be attributed to second order, double resonance Raman spectra. It is useful for material characterization to understand not only first order Raman spectra but also second order Raman spectra since the second order Raman spectra has more information on electronic structure of the materials than the first order Raman spectra. Combined with the conventional first order resonance Raman theory, we will explain why the double resonance condition can be strong in the two dimensional materials. Since the double resonance Raman spectra give the information of phonon with non-zero wavevectors in the Brillouin zone, both the resonant wavevector and corresponding Raman spectra can shift with changing the incident laser energy. Here we will discuss the physics of double resonance Raman spectra of graphene, transition metal dichalcogenides by theoretical analysis using the first principles calculation.
- Published
- 2018
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