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Investigation of the cap layer for improved GeSn multiple quantum well laser performance

Optics Letters 2023年第7期48卷 1626-1629页

作者： Abernathy, Grey Ojo, Solomon Stanchu, Hryhorii Zhou, Yiyin Olorunsola, Oluwatobi Grant, Joshua Du, Wei Jheng, Yue-Tong Chang, Guo-En Li, Baohua Yu, Shui-Qing Department of Electrical Engineering University of Arkansas FayettevilleAR72701 United States Materials Science & Engineering Program University of Arkansas FayettevilleAR72701 United States Institute for Nanoscience and Engineering University of Arkansas FayettevilleAR72701 United States Department of Mechanical Engineering National Chung Cheng University Chiayi County62102 Taiwan Arktonics LLC 1339 South Pinnacle Drive FayettevilleAR72701 United States

The study of all-group-IV SiGeSn lasers has opened a new avenue to Si-based light sources. SiGeSn heterostructure and quantum well lasers have been successfully demonstrated in the past few years. It has been reported that, for multiple quantum well lasers, the optical confinement factor plays an important role in the net modal gain. In previous studies, adding a cap layer was proposed to increase the optical mode overlap with the active region and thereby improve the optical confinement factor of Fabry–Perot cavity lasers. In this work, SiGeSn/GeSn multiple quantum well (4-well) devices with various cap layer thicknesses, i.e., 0 (no cap), 190, 250, and 290 nm, are grown using a chemical vapor deposition reactor and characterized via optical pumping. While no-cap and thinner-cap devices only show spontaneous emission, the two thicker-cap devices exhibit lasing up to 77 K, with an emission peak at 2440 nm and a threshold of 214 kW/cm2 (250 nm cap device). The clear trend in device performance disclosed in this work provides guidance in device design for electrically injected SiGeSn quantum well lasers. © 2023 Optica Publishing Group.

关键词： Semiconductor quantum wells

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Second law of thermodynamics: Spontaneous cold-to-hot heat transfer in a nonchaotic medium

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Physical Review E 2024年第5期110卷 054113-054113页

作者： Yu Qiao Zhaoru Shang Program of Materials Science and Engineering University of California San Diego La Jolla California 92093 USA Department of Structural Engineering University of California San Diego La Jolla California 92093-0085 USA

It has long been known that, fundamentally different from a large body of rarefied gas, when a Knudsen gas is immersed in a thermal bath, it may never reach thermal equilibrium. The root cause is nonchaoticity: as the particle-particle collisions are sparse, the particle trajectories tend to be independent of each other. Usually, this counterintuitive phenomenon is studied through kinetic theory and is not considered a thermodynamic problem. In current research, we show that if incorporated in a compound setup, such an intrinsically nonequilibrium behavior has nontrivial consequences and cannot circumvent thermodynamics: cold-to-hot heat transfer may happen spontaneously, either continuously (with an energy barrier), or cyclically (with time-dependent entropy barriers). It allows for production of useful work by absorbing heat from a single thermal reservoir without any other effect. As the system obeys the first law of thermodynamics, it breaks the boundaries of the second law of thermodynamics.

关键词： Classical statistical mechanics Nonequilibrium & irreversible thermodynamics Thermodynamics Monte Carlo methods

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Magnetoelastic coupling driven magnon gap in a honeycomb antiferromagnet

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Physical Review B 2024年第10期110卷 104419页

作者： Jeongheon Choe Andrey Baydin Gaihua Ye Bowen Ma Cynthia Nnokwe Martin Rodriguez-Vega David Lujan Swati Chaudhary Fuyang Tay Jiaming He Hiroyuki Nojiri Jianshi Zhou Gregory A. Fiete Junichiro Kono Rui He Xiaoqin Li Department of Physics Center of Complex Quantum Systems Center for Dynamics and Control of Materials Department of Electrical and Computer Engineering Smalley–Curl Institute Department of Physics Applied Physics Graduate Program Smalley–Curl Institute Department of Mechanical Engineering Institute for Materials Research Department of Physics and Astronomy Department of Materials Science and NanoEngineering

Cobalt titanate, CoTiO3, is a honeycomb antiferromagnet recently confirmed experimentally to host Dirac magnons, topological spin-orbit excitons, and chiral phonons. Here, we investigate a magnon gap at the zone center which calls for a refined spin Hamiltonian. We propose a microscopic model for the magnon gap and attribute it to a lattice-distortion (phonon)-induced higher-order spin interaction. Strong magnetoelastic coupling in CoTiO3 is also evident in Raman spectra, in which the magnetic order exerts a stronger influence on phonons corresponding to in-plane ionic motions than those with out-of-plane motions. We further examine the evolution of the zone-center magnons in a high magnetic field up to 18.5 T via THz absorption spectroscopy measurements. Based on this field dependence, we propose a spin Hamiltonian that not only agrees with magnon dispersion measured by inelastic neutron scattering but also includes fewer exchange constants and a realistic anisotropy term. Our work highlights the broad implications of magnetoelastic coupling in the study of topologically protected bosonic excitations.

关键词： Magnetism Magnons Topological materials Raman spectroscopy Terahertz spectroscopy

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Frequency-dependent phonon-mediated unidirectional magnetoresistance in a metal on an insulator with highly nonequilibrium magnons

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Physical Review B 2023年第14期107卷 L140412-L140412页

作者： Sean E. Sullivan Hwijong Lee Annie Weathers Li Shi Materials Science and Engineering Program The University of Texas at Austin Austin Texas 78712 USA Department of Mechanical Engineering The University of Texas at Austin Austin Texas 78712 USA

Heavy-metal (HM)/magnet bilayers host many magnetoresistance (MR) and spin caloritronic effects. Here, we show that the spin Peltier effect and electron-phonon scattering produce much larger unidirectional MR of an HM on a magnetic insulator than existing theories that neglect the interplay between MR and spin caloritronic effects. By accounting for local nonequilibrium in both the magnon chemical potential and temperature, our analytical model attributes the observed frequency dependence of the spin Peltier MR and the spin Seebeck effect to the reduction of the thermal penetration depth, which approaches the 1−μm-scale magnon spin-diffusion length at high frequencies.

关键词： Magnetic anisotropy Magnetotransport Spin dynamics Spintronics Temperature Thermal conductivity Thermoelectric effects Thermomagnetic effects

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When graphite meets Li metal

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National science Review 2020年第10期7卷 1521-1522页

作者： Yu Ding Guihua Yu Materials Science and Engineering Program and Department of Mechanical Engineering The University of Texas at Austin

Wetting, indicating the ability of a liquid to spread out over solid surfaces,is of vital importance in addressing the scientific issues related to energy and environment technologies. The study of wetting encompasses the academic disciplines of surface chemistry, nanotechnology, materials science and energy *** past several decades have witnessed significant progress in achieving desirable wetting performance with water,

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Topological band gaps and edge modes materialized by symmetric silicon-on-insulator photonic crystal slabs in the mid-IR range

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Physical Review A 2023年第4期107卷 043507-043507页

作者： Afshan Begum Yuanzhao Yao Takashi Kuroda Yoshihiko Takeda Naoki Ikeda Yoshimasa Sugimoto Takaaki Mano Kazuaki Sakoda Center for Green Research on Energy and Environmental Materials National Institute for Materials Science Tsukuba 305-0003 Japan Doctoral Program in Materials Science and Engineering University of Tsukuba Tsukuba 305-8577 Japan Research Center for Functional Materials National Institute for Materials Science Tsukuba 305-0044 Japan Research Network and Facility Service Division National Institute for Materials Science Tsukuba 305-0047 Japan

We successfully fabricated silicon-on-insulator (SOI) photonic crystal (PhC) slabs in which electromagnetic topological band gaps and edge modes were materialized for symmetric transverse-electric-like modes. Because the structure of our specimens can be regarded as symmetric about the horizontal middle plane of the PhC slab, their symmetric and antisymmetric eigenmodes were rigorously separated, so we could achieve genuine photonic band gaps for the former. We fabricated those specimens by electron beam lithography of the top Si layer of SOI wafers and successive plasma-enhanced chemical vapor deposition of a SiO2 capping layer. We confirmed the complete common band gap of topologically trivial and nontrivial PhCs and the topological edge modes on the boundary between them by angle-resolved reflection spectroscopy in the mid-infrared range. This is an observation of the common band gap and edge modes that materialized in symmetric PhC slabs without a membrane structure, that is, without the etching of a sacrificial layer under the PhC to increase the refractive-index contrast and the width of the common band gap.

关键词： Nanophotonics Photonic crystals Photonics Topological effects in photonic systems

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Development of exosome membrane materialsfused microbubbles for enhanced stability and efficient drug delivery of ultrasound contrast agent

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Acta Pharmaceutica Sinica B 2023年第12期13卷 4983-4998页

作者： Yongho Jang Jeehun Park Pilsu Kim Eun-Joo Park Hyungjin Sun Yujin Baek Jaehun Jung Tai-kyong Song Junsang Doh Hyuncheol Kim Department of Chemical and Biomolecular Engineering Sogang UniversitySeoul 04107Republic of Korea Research Institute of Advanced Materials(RIAM) Institute of Engineering ResearchSeoul National UniversitySeoul 08826Republic of Korea Department of Electronic Engineering Sogang UniversitySeoul 04107Republic of Korea Biomedical Research Institute&Department of Radiology Seoul National University HospitalSeoul 03080Republic of Korea Interdisciplinary Program in Bioengineering Seoul National UniversitySeoul 08826Republic of Korea Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Republic of Korea Institute of Engineering Research Bio-MAX InstituteSeoul National UniversitySeoul 08826Republic of Korea Department of Biomedical Engineering Sogang UniversitySeoul 04107Republic of Korea

Lipid-coated microbubbles are widely used as an ultrasound contrast agent,as well as drug delivery ***,the two main limitations in ultrasound diagnosis and drug delivery using microbubbles are the short half-life in the blood system,and the difficulty of surface modification of microbubbles for active *** exosome,a type of extracellular vesicle,has a preferentially targeting ability for its original *** this study,exosome-fused microbubbles(Exo-MBs)were developed by embedding the exosome membrane proteins into *** a result,the stability of Exo-MBs is improved over the conventional *** the same principle that under the exposure of ultrasound,microbubbles are cavitated and self-assembled into nano-sized particles,and Exo-MBs are self-assembled into exosome membrane proteins-embedded nanoparticles(Exo-NPs).The Exo-NPs showed favorable targeting properties to their original cells.A photosensitizer,chlorin e6,was loaded into Exo-MBs to evaluate therapeutic efficacy as a drug *** higher therapeutic efficacy of photodynamic therapy was confirmed,followed by cancer immunotherapy from immunogenic cell *** have therefore developed a novel ultrasound image-guided drug delivery platform that overcomes the shortcomings of the conventional ultrasound contrast agent and is capable of simultaneous photodynamic therapy and cancer immunotherapy.

关键词： Exosomes Microbubbles Photodynamic therapy Ultrasound Sonoporation Cancer immunotherapy Drug delivery

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Correlating the Ambient Conditions and Performance Indicators of the LoRaWAN via Surrogate Gaussian Process-Based Bidirectional LSTM Stacked Autoencoder

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IEEE Transactions on Network and Service Management 2023年第3期20卷 3413-3427页

作者： Bhat, Showkat Ahmad Huang, Nen-Fu Hussain, Imtiyaz Sajjad, Uzair National Tsing Hua University College of Electrical and Computer Science Hsinchu1300044 Taiwan National Tsing Hua University Department of Computer Science Hsinchu1300044 Taiwan National Taipei University of Technology Graduate Program in Energy and Opto-Electronic Materials Taipei10608 Taiwan National Taipei University of Technology Department of Energy and Refrigerating Airconditioning Engineering Taipei10608 Taiwan

LoRa's biggest advantage is its flexibility, which is the ability to increase or decrease data rate and range while decreasing or increasing sensitivity. Whenever propagation conditions change frequently, this function allows the spreading factor to be modified accordingly. Despite their efficiency and scalability, adaptive data rate algorithms ignore and fail to factor in the complex correlation between ambient weather parameters influencing the communication channel design. In this research, a Bayesian surrogate Gaussian process-based bidirectional LSTM stacked autoencoder model (BSGP-BLSTM-SAE) is proposed to estimate the channel performance indicators such as received signal strength indicator (RSSI) and signal-to-noise ratio (SNR) and to determine the correlation between the ambient weather conditions and performance indicators for the LoRaWAN network. Bayesian optimization algorithm has been used to optimize the hyper-parameters of the developed model. A LoRaWAN experimental multivariate time series dataset has been used for the evaluation of the developed model, which upon testing and validation produces high accuracy in predicting the channel performance indicators and ambient conditions of the experimental LoRaWAN network. The mean absolute error of the developed model was around 0.45. Thus, the proposed model can predict the link performance indicators and thereby assist in real-time optimization of the transmission parameters to enhance the network performance in LoRaWAN-based systems at different ambient conditions. © 2004-2012 IEEE.

关键词： Internet of things

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Impact of Electrical Current Stressing on ?'-Cu6Sn5 in Electronics Packaging 19

Impact of Electrical Current Stressing on ?'-Cu6Sn5 in Elect...

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19th International Microsystems, Packaging, Assembly and Circuits Technology Conference, IMPACT 2024

作者： Mukherjee, Shubhayan Lin, Shih-Kang National Cheng Kung University Department of Materials Science and Engineering Tainan70101 Taiwan Research Center Tainan70101 Taiwan Academy of Innovative Semiconductor and Sustainable Manufacturing National Cheng Kung University Program on Smart and Sustainable Manufacturing Tainan70101 Taiwan

ISBN: (纸本)9798331532246

In advanced electronic packaging, the stability of intermetallic compounds (IMCs) under high electric current density is crucial for the reliability of solder joints. Cu6Sn5, a predominant IMC formed between Sn-based solders and Cu substrates, exists in two allotropes: the high-temperature hexagonal phase and the low-temperature monoclinic ?' phase, with a transition temperature of 186°C. This study investigates the effects of electric current on ?'-Cu6Sn5 phase, focusing on structural characterization and mechanical properties. Various electric current densities were applied to thermally aged ?'-Cu6Sn5. Synchrotron radiation-based X-ray diffraction (SR-XRD) was used to examine crystallographic changes, while nanoindentation tests assessed mechanical property alterations. These observations contribute to understanding the impact of electric current density on the structural and mechanical behavior of the monoclinic ?'-Cu6Sn5 phase. © 2024 IEEE.

关键词： Synchrotron radiation

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Coupling of mechanical deformation and electromagnetic fields in biological cells

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Reviews of Modern Physics 2022年第2期94卷 025003-025003页

作者： Mehdi Torbati Kosar Mozaffari Liping Liu Pradeep Sharma Departments of Mechanical Engineering Physics and the Materials Science and Engineering Program University of Houston Houston Texas 77204 USA

The cell, as the most fundamental unit of life, is a microcosm of biology in which the confluence of nearly all aspects of classical physics (mechanics, statistical physics, condensed matter, and electromagnetism) plays out. This leads to a rich and complex emergent behavior that determines the entire gamut of biological functions. Specifically, at the cellular scale, mechanical forces and deformations are inextricably linked to electrical fields (and, to a lesser degree, magnetic fields). This in turn is responsible for phenomenology such as cell-cell communication, morphological evolution, cell fusion, self-assembly, cell fission, magnetoreception, endocytosis, and adhesion, among others. From the viewpoint of biomedicine, cellular response to the combined influence of electrical, magnetic, and mechanical fields has applications in cancer treatment, targeted transfer of medicine, gene therapy, and wound amelioration. As an example of the profound influence of the combined electrical-mechanical coupling, one needs to take cognizance only of the operation of ion channels that form the basis for our sensing system (such as hearing, sight, and tactile sense). The coupled mechanical and electromagnetic behavior of a cell is a highly interdisciplinary endeavor and this review provides a distillation of both the theoretical underpinnings of the subject and the pertinent biological interpretation. The key developments pertaining to this topic are reviewed, a unified mathematical framework that couples nonlinear deformation and electromagnetic behavior as germane for soft biological entities is summarized, gaps in current knowledge are pointed out, and the central issues that are pertinent to future research are commented upon.

关键词： Electromagnetism Mechanical deformation

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