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arXiv 2020年

作者： Kandel, Mikhail E. He, Yuchen R. Lee, Young Jae Chen, Taylor Hsuan-Yu Sullivan, Kathryn Michele Aydin, Onur Saif, Taher M.A. Kong, Hyunjoon Sobh, Nahil Popescu, Gabriel Beckman Institute University of Illinois at Urbana-Champaign UrbanaIL United States Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign UrbanaIL United States Neuroscience Program University of Illinois at Urbana-Champaign UrbanaIL United States Department of Bioengineering University of Illinois at Urbana-Champaign UrbanaIL United States Department of Mechanical Science and Engineering University of Illinois at Urbana-Champaign UrbanaIL United States Chemical and Biomolecular Engineering University of Illinois at Urbana-Champaign UrbanaIL United States Carl Woese Institute for Genomic Biology University of Illinois at Urbana-Champaign UrbanaIL United States

Due to its specificity, fluorescence microscopy (FM) has become a quintessential imaging tool in cell biology. However, photobleaching, phototoxicity, and related artifacts continue to limit FM’s utility. Recently, it has been shown that artificial intelligence (AI) can transform one form of contrast into another. We present PICS, a combination of quantitative phase imaging and AI, which provides information about unlabeled live cells with high specificity. Our imaging system allows for automatic training, while inference is built into the acquisition software and runs in real-time. Applying the computed fluorescence maps back to the QPI data, we measured the growth of both nuclei and cytoplasm independently, over many days, without loss of viability. Using a QPI method that suppresses multiple scattering, we measured the dry mass content of individual cell nuclei within spheroids. In its current implementation, PICS offers a versatile quantitative technique for continuous simultaneous monitoring of individual cellular components in biological applications where long-term label-free imaging is desirable. Copyright © 2020, The Authors. All rights reserved.

关键词： Fluorescence microscopy

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Low resistivity and high breakdown current density of 10-nm diameter van der waals tase3nanowires by chemical vapor deposition

arXiv

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arXiv 2019年

作者： Empante, Thomas A. Martinez, Aimee Wurch, Michelle Zhu, Yanbing Geremew, Adane K. Yamaguchi, Koichi Isarraraz, Miguel Rumyantsev, Sergey Reed, Evan J. Balandin, Alexander A. Bartels, Ludwig Department of Chemistry and Material Science & Engineering Program University of California - Riverside RiversideCA92521 United States Department of Materials Science and Engineering Stanford University StanfordCA94304 United States Nano-Device Laboratory Department of Electrical and Computer Engineering University of California RiversideCA92521 United States Center for Terahertz Research and Applications Institute of High Pressure Physics Polish Academy of Sciences Warsaw01-142 Poland

Micron-scale single-crystal nanowires of metallic TaSe3, a material that forms -Ta-Se3-TaSe3- stacks separated from one another by a tubular van der Waals (vdW) gap, have been synthesized using chemical vapor deposition (CVD) on a SiO2/Si substrate, in a process compatible with semiconductor industry requirements. Their electrical resistivity was found unaffected by downscaling from the bulk to as little as 7 nm in width and height, in striking contrast to the resistivity of copper for the same dimensions. While the bulk resistivity of TaSe3is substantially higher than that of bulk copper, at the nanometer scale the TaSe3wires become competitive to similar-sized copper ones. Moreover, we find that the vdW TaSe3nanowires sustain current densities in excess of 108A/cm2and feature an electromigration energy barrier twice that of copper. The results highlight the promise of quasi-onedimensional transition metal trichalcogenides for electronic interconnect applications and the potential of van der Waals materials for downscaled electronics. Copyright © 2019, The Authors. All rights reserved.

关键词： Van der Waals forces

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Low Temperature Electron Microscopy of “Charge-Ordered” Phases

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Microscopy and Microanalysis 2019年第S2期25卷 934-935页

作者： Ismail El Baggari David J. Baek Benjamin H. Savitzky Michael J. Zachman Robert Hovden Lena F. Kourkoutis Department of Physics Cornell University Ithaca NY USA. School of Electrical and Computer Engineering Cornell University Ithaca NY USA. School of Applied and Engineering Physics Cornell University Ithaca NY USA. Department of Materials Science & Engineering University of Michigan Ann Arbor MI USA. Kavli Institute at Cornell for Nanoscale Science Cornell University Ithaca NY USA.

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Interplay of Purcell effect, stimulated emission, and leaky modes in photoluminescence spectra of microsphere cavities

arXiv

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arXiv 2019年

作者： Chien, Ching-Hang Wu, Shang-Hsuan Ngo, Trong Huynh-Buu Chang, Yia-Chung Research Center for Applied Sciences Academia Sinica Taipei115 Taiwan Nano Science and Technology Program TIGP Academia Sinica Taipei115 Taiwan Department of Engineering and System Science National Tsing Hua University Hsinchu300 Taiwan Department of Electrical and Computer Engineering University of Texas at Austin United States Department of Electrical and Computer Engineering University of Alberta EdmontonABT6G 2V4 Canada

A theoretical model for describing the emission spectra of microsphere cavities is presented, and its predictions of detailed lineshapes of emission spectra associated with whispering gallery modes (WGMs) of various orders in ZnO microspheres (MSs) are verified experimentally by photoluminescence (PL) spectroscopy. The interplay of Purcell effect, quality factor, and leaky modes in spontaneous and stimulated emission spectra related to WGMs of all orders is revealed. The key success of the theory is based on the expansion of the full Green function of the MS in terms of all possible resonance modes in complex frequency space, which allows incorporation of contributions from leaky modes, stimulated emission processes, and Purcell effect. We show that the spontaneous emission spectrum calculated according to Mie theory (without Purcell effect) is dominated by the contribution of leaky modes, while the spontaneous and stimulated emission enhanced by Purcell effect are responsible for the main WGM resonance peaks observed experimentally. It is found that the stimulated emission peaks are doubly enhanced by their respective mode quality factor Q: one factor from the Purcell effect and the other factor from the photon number derived from the rate equation. After combining all these effects the theory can provide a quantitative description of fine features of both TE and TM modes (including higher-order modes) observed in the PL spectra of ZnO MSs. Surprisingly, it is found that for ZnO MS with diameter larger than 5 µm, the PL emission spectrum is dominated by higher-order modes. The quantitative understanding of the interplay of these emission mechanisms should prove useful for optimizing the performance of light-emitting devices based on micro resonators. Copyright © 2019, The Authors. All rights reserved.

关键词： Microspheres

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Author Correction: 3D-printed liquid metal polymer composites as NIR-responsive 4D printing soft robot

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Nature communications 2024年第1期15卷 943页

作者： Liwen Zhang Xumin Huang Tim Cole Hongda Lu Jiangyu Hang Weihua Li Shi-Yang Tang Cyrille Boyer Thomas P Davis Ruirui Qiao Australian Institute of Bioengineering & Nanotechnology The University of Queensland Brisbane QLD 4072 Australia. Department of Electronic Electrical and Systems Engineering University of Birmingham Birmingham UK. School of Mechanical Materials Mechatronic and Biomedical Engineering University of Wollongong Wollongong NSW 2522 Australia. School of Electronics and Computer Science University of Southampton Southampton SO17 1BJ UK. shiyang.tang@soton.ac.uk. Cluster for Advanced Macromolecular Design School of Chemical Engineering The University of New South Wales Sydney NSW 2052 Australia. Australian Institute of Bioengineering & Nanotechnology The University of Queensland Brisbane QLD 4072 Australia. t.davis@uq.edu.au. Australian Institute of Bioengineering & Nanotechnology The University of Queensland Brisbane QLD 4072 Australia. r.qiao@uq.edu.au.

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Tunneling spectroscopy of c-axis epitaxial cuprate junctions

arXiv

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arXiv 2020年

作者： Zhou, Panpan Chen, Liyang Sochnikov, Ilya Wu, Tsz Chun Foster, Matthew S. Bollinger, Anthony T. He, Xi Božović, Ivan Natelson, Douglas Department of Physics and Astronomy Rice University HoustonTX77005 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Physics University of Connecticut StorrsCT06269 United States Brookhaven National Laboratory UptonNY11973-5000 United States Department of Chemistry Yale University New HavenCT06520 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

Atomically precise epitaxial structures are unique systems for tunneling spectroscopy that minimize extrinsic effects of disorder. We present a systematic tunneling spectroscopy study, over a broad doping, temperature, and bias range, in epitaxial c-axis La2−xSrxCuO4/La2CuO4/La2−xSrxCuO4 heterostructures. The behavior of these superconductor/insulator/superconductor (SIS) devices is unusual. Down to 20 mK there is complete suppression of c-axis Josephson critical current with a barrier of only 2 nm of La2CuO4, and the zero-bias conductance remains at 20-30% of the normal-state conductance, implying a substantial population of in-gap states. Tunneling spectra show greatly suppressed coherence peaks. As the temperature is raised, the superconducting gap fills in rather than closing at Tc. For all doping levels, the spectra show an inelastic tunneling feature at ∼ 80 meV, suppressed as T exceeds Tc. These nominally simple epitaxial cuprate junctions deviate markedly from expectations based on the standard Bardeen-Cooper-Schrieffer (BCS) theory. Copyright © 2020, The Authors. All rights reserved.

关键词： Copper compounds

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A Multifunctional Molecular Modifier Enabling Efficient Large-Area Perovskite Light-Emitting Diodes

SSRN

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SSRN 2020年

作者： Wang, Haoran Gong, Xiwen Zhao, Dewei Zhao, Yong-Biao Wang, Sheng Zhang, Jianfeng Kong, Lingmei Wei, Bin Quintero-Bermudez, Rafael Voznyy, Oleksandr Shang, Yuequn Ning, Zhijun Yan, Yanfa Sargent, Edward H. Yang, Xuyong Shanghai University 149 Yanchang Road Shanghai 200072 China The Edward S. Rogers Sr. Department of Electrical and Computer Engineering University of Toronto 35 St. George Street TorontoONM5S 1A4 Canada Institute of Solar Energy Materials and Devices College of Materials Science and Engineering Sichuan University 24 South Section 1 Yihuan Road Chengdu610065 China Department of Physics and Astronomy Wright Center for Photovoltaics Innovation and Commercialization The University of Toledo OH Toledo43606 United States School of Physical Science and Technology ShanghaiTech University 393 Middle Huaxia Road Shanghai Pudong201210 China

With rapid progress in perovskite light-emitting diodes (PeLEDs), the electroluminescence performance of large-area perovskite devices is increasingly important. We investigate why large-area performance lags behind that achieved in laboratory-scale devices, and found that defects in perovskite films – emerging from thermal convection during solvent evaporation and electronic traps formed during perovskite crystallization – are chief causes. Here we report a molecular modification strategy that simultaneously eliminates pinholes in perovskite layers by controlling the dynamics of film formation, and passivates the defects in perovskites by incorporating Br species, thereby preventing shorts and non-radiative recombination. The molecular modifier 1,3,5-tris (bromomethyl) benzene (TBB) also modulates the electronic structure of injection/transport materials to achieve improved charge injection and balanced charge transport. As a result, we demonstrate a 20 mm × 20 mm green perovskite nanocrystal LED that achieves an external quantum efficiency (EQE) of over 16%, the record efficiency for large-area PeLEDs. Our work opens a route to scaling perovskite LEDs. © 2020, The Authors. All rights reserved.

关键词： Perovskite

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Terahertz strong-field physics without a strong external terahertz field

arXiv

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arXiv 2019年

作者： Bamba, Motoaki Li, Xinwei Kono, Junichiro Department of Materials Engineering Science Osaka University Toyonaka560-8531 Japan PRESTO Japan Science and Technology Agency Kawaguchi332-0012 Japan Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

Traditionally, strong-field physics explores phenomena in matter (atoms, molecules, and solids) driven by an extremely strong laser field nonperturbatively. However, even in the complete absence of an external electromagnetic field, strong-field phenomena can arise when matter strongly couples with the zero-point field of the quantum vacuum state, i.e., fluctuating electromagnetic waves whose expectation value is zero. Some of the most striking examples of this occur in a cavity setting, in which an ensemble of two-level atoms resonantly interacts with a single photonic mode of vacuum fields, producing vacuum Rabi splitting. In particular, the nature of the matter-vacuum-field coupled system fundamentally changes when the coupling rate (equal to one half of the vacuum Rabi splitting) becomes comparable to, or larger than, the resonance frequency. In this so-called ultrastrong coupling regime, a non-negligible number of photons exist in the ground state of the coupled system. Furthermore, the coupling rate can be cooperatively enhanced (via so-called Dicke cooperativity) when the matter is comprised of a large number of identical two-level particles, and a quantum phase transition is predicted to occur as the coupling rate reaches a critical value. Low-energy electronic or magnetic transitions in many-body condensed matter systems with large dipole moments are ideally suited for searching for these predicted phenomena. Here, we discuss two condensed matter systems that have shown cooperative ultrastrong interactions in the terahertz frequency range: a Landau-quantized two-dimensional electron gas interacting with high-quality-factor cavity photons, and an Er3+ spin ensemble interacting with Fe3+ magnons in ErFeO3. Copyright © 2019, The Authors. All rights reserved.

关键词： Atoms

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Thermoelectric properties of semimetals

arXiv

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arXiv 2019年

作者： Markov, Maxime Rezaei, Emad Sadeghi, Safoura Nayeb Esfarjani, Keivan Zebarjadi, Mona Department of Electrical and Computer Engineering University of Virginia CharlottesvilleVA22904 United States Department of Mechanical and Aerospace Engineering University of Virginia CharlottesvilleVA22904 United States Department of Physics University of Virginia CharlottesvilleVA22904 United States Department of Materials Science and Engineering University of Virginia CharlottesvilleVA22904 United States

Heavily doped semiconductors are by far the most studied class of materials for thermoelectric applications in the past several decades. They have Seebeck coefficient values which are 2-3 orders of magnitude higher than metals, making them attractive for thermoelectric applications. Semimetals generally demonstrate smaller Seebeck coefficient values due to lack of an energy bandgap. However, when there is a large asymmetry in their electron and hole effective masses, semimetals could have large Seebeck coefficient values. In this work, we study the band structure of a class of 18 semimetals using first principles calculations and calculate their Seebeck coefficient using the linearized Boltzmann equation within the constant relaxation time approximation. We conclude, despite the absence of the band gap, that some semimetals are good thermoelectrics with Seebeck coefficient values reaching up to 200 µV/K. We analyze the metrics often used to describe thermoelectric properties of materials, and show that the effective mass ratio is a key parameter resulting in high Seebeck coefficient values in semimetals. Copyright © 2019, The Authors. All rights reserved.

关键词： Seebeck coefficient

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Opposite current-induced spin polarizations in bulk-metallic Bi2Se3 and bulk-insulating Bi2Te2Se topological insulator thin flakes

arXiv

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arXiv 2020年

作者： Tian, Jifa Şahin, Cüneyt Miotkowski, Ireneusz Flatté, Michael E. Chen, Yong P. Department of Physics and Astronomy Purdue University West LafayetteIN47907 United States Birck Nanotechnology Center Purdue University West LafayetteIN47907 United States Department of Physics and Astronomy University of Wyoming LaramieWY82071 United States Optical Science and Technology Center Department of Physics and Astronomy University of Iowa Iowa CityIA52242 United States Purdue Quantum Science and Engineering Institute Purdue University West LafayetteIN47907 United States School of Electrical and Computer Engineering Purdue University West LafayetteIN47907 United States Institute of Physics and Astronomy and Villum Centers for Dirac Materials and for Hybrid Quantum Materials Aarhus University Aarhus-C8000 Denmark

One of the most fundamental and exotic properties of 3D topological insulators (TIs) is spin-momentum-locking (SML) of their topological surface states (TSSs), promising for potential applications in future spintronics. However, other possible conduction channels, such as a trivial two-dimensional electron gas (2DEG) with strong Rashba type spin-orbit interaction (SOI) and bulk conducting states that may possess a spin Hall effect (SHE), can coexist in 3D TIs, making determining the origin of the current induced spin polarization (CISP) difficult. In this work, we directly compared the CISP between bulk-insulating Bi2Te2Se (BTS221) and bulk-metallic Bi2Se3 thin flakes using spin potentiometry. In the bulk insulating BTS221, the observed CISP has a sign consistent with the expected helicity of the SML of the TSS, but an opposite sign to its calculated bulk spin Hall conductivity (SHC). However, compared to BTS221, an opposite CISP is observed in the bulk metallic Bi2Se3, consistent instead with both the expectations of its Rashba-Edelstein effect of the band-bending induced 2DEG and bulk spin Hall Effect (SHE). Our results provide an electrical way to distinguish the TSS from other possible conducting channels in spin transport measurements on 3D TIs, and open ways for the potential applications in charge-spin conversion devices. Copyright © 2020, The Authors. All rights reserved.

关键词： Selenium compounds

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