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Theoretical Investigation on Electron Mobility in AlInGaN/InGaN Heterostructures
摘要： The dependences of electron mobility in AlInGaN/InGaN heterostructure on the barrier and channel alloy compositions and on temperature are investigated including six scattering processes: acoustic deformation potential (DP) scattering, piezoelectric field (PE) scattering, polar optical phonons (PO) scattering, dislocation impurity (DIS) scattering, interface roughness (IRF) scattering, and alloy disorder (ADO) scattering. The results show that ADO scattering is the most important scattering mechanism, and specifically channel alloy disorder gets severer than barrier alloy disorder except for InGaN channels with very low indium content (near 0) or extremely high indium mole fraction (near 1). The variations of the barrier strain, two-dimensional electron gas (2DEG) density, 2DEG mobility, and conductivity in AlInGaN/In0.04Ga0.96N heterostructure with full barrier alloy composition are summarized. The results indicate that relatively large aluminum content and small indium mole fraction are desired for higher conductivity. By comparing the temperature-dependent transport properties of Al0.83In0.13Ga0.04N/InGaN heterostructures with different InGaN compositions, we find that it is the ADO scattering and PO scattering that determine 2DEG mobility change and the mobility exhibits a weaker dependence on temperature with increasing indium mole fraction in InGaN channel.
关键词： scattering mechanisms,mobility,temperature,two-dimensional electron gas
更新于2025-09-23 15:23:52
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Graphene-like Monolayer Yttrium Nitride: A Moderate Semiconductor and Pronounced Electronic Insensitivity to Strain
摘要： It is extremely important to explore two-dimensional materials with excellent properties due to their potential applications in future electronic devices. In the present study, a 2D hexagonal YN (h-YN) is predicted based on theoretical calculations. By assessing the phonon spectrum, ab initio molecule dynamics and elastic constants, the h-YN monolayer is proved to own satisfying thermal, dynamic and mechanical stability. Distinguishing from the most reported 2D transition metal mononitrides which exhibit metallic, monolayer h-YN presents a semiconducting characteristic with a indirect bandgap of 1.144 eV. In particular, h-YN presents unusually insensitive responses of electronic structures to tensile or compressive strain due to the valence orbital hybridization. Moderate bandgap together with insensitive electronic responses to strain endow h-YN a promising candidate in future nanoscale electronic devices in high-strain conditions.
关键词： nano-electronics,strain condition,band structure,two-dimensional
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Two-dimensional Spectrum for Diving Stage SAR Processing with High-order Equivalent Range Model
摘要： For airborne synthetic aperture radar (SAR) processing in its diving stage, the diving velocity brings additional range variance to the range history in the synthetic aperture time. The traditional hyperbolic range model is not accurate enough to approximate the actual range equation and the precise two-dimensional spectrum cannot be achieved. In order to address this problem, a highly accurate spectrum deduction based on high-order equivalent range model is proposed in this paper. By introducing the high-order terms, more degrees-of-freedom are obtained for the equivalent range model and the actual range history can be accurately fitted. Based on the achieved range model, the two-dimensional spectrum for diving stage SAR can be accessed. Simulation experiments are carried out to validate the effectiveness of proposed spectrum.
关键词： two-dimensional spectrum,diving stage,range model,Synthetic aperture radar (SAR)
更新于2025-09-23 15:22:29
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Dual frequency-comb spectroscopy of chromophores in condensed phases
摘要： Femtosecond time-resolved spectroscopy and frequency-comb spectroscopy have been individually developed to achieve better time and frequency resolutions, respectively. The two spectroscopic techniques have been developed for different systems, even though they use mode-locked laser in common. Recently, there was an interesting merge of the two techniques into a dual frequency-comb (DFC) spectroscopy, resulting in a new femtosecond spectroscopy with simple instrumentation and high data acquisition speed compared to conventional femtosecond spectroscopic techniques. By slightly detuning the repetition rates of two phase-locked frequency-comb lasers, both automatic time-delay scanning and parallel data recording with single point detectors are possible. Thus, we anticipate that the DFC spectroscopy would allow one to expand the application limits of the conventional femtosecond spectroscopic methods. In this Perspective article, we provide reviews of linear and nonlinear DFC spectroscopy theory and applications with a perspective on the development of coherent multidimensional frequency-comb spectroscopy.
关键词： nonlinear spectroscopy,optical frequency-comb,time-resolved spectroscopy,coherent two-dimensional spectroscopy,solvation dynamics,dual comb spectroscopy
更新于2025-09-23 15:22:29
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Optimal Hexagonal Constellations Based on A Two-Dimensional Signal Space for Peak-Limited Intensity-Modulated Channels
摘要： For high-rate peak-limited intensity-modulated optical systems, the two-dimensional time-disjoint signal space (TDSS) is proposed. Based on the TDSS, the optimal hexagonal constellations (OHCs) are proposed analytically under a peak optical power constraint. Both analytical and simulation results show our proposed OHCs based on TDSS have asymptotical peak optical power gain of 0.753 dB over the baseline schemes at no extra bandwidth cost.
关键词： two-dimensional,peak-limited,IM/DD,signal space,Hexagonal lattice,AWGN
更新于2025-09-23 15:22:29
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From pentagonal geometries to two-dimensional materials
摘要： Hexagons are dominating building blocks in the atomic structures of existing and predicted two-dimensional (2D) materials. A wealth of properties possessed by numerous 2D materials are attributed to their hexagonal, structural units. Although many review articles exist for 2D hexagonal materials, this review focus on a less common building block, pentagon, of 2D materials. We start with introducing 15 types of convex pentagons that can tile an infinite plane without creating a gap. We connect one of these pentagonal geometries (type 2 pentagon) with 2D materials via density functional theory (DFT) calculations, resulting in predictions of 2D pentagonal materials that could be synthesized in experiments. We summarize the experimental and theoretical efforts in this burgeoning subfield of 2D materials research. We also suggest several issues that DFT calculations can continue to address to develop the subfield. We expect this brief review to stimulate further experimental and computational interests in synthesizing and designing new 2D pentagonal materials.
关键词： Density functional theory calculations,Pentagonal geometries,Two-dimensional materials
更新于2025-09-23 15:22:29
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Unusual Electric and Optical Tuning of KTaO <sub/>3</sub> -Based Two-Dimensional Electron Gases with 5d Orbitals
摘要： Controlling electronic processes in low dimension electron system is centrally important for both fundamental and applied researches. While most of the previous works focused on SrTiO3-based two-dimensional electron gases (2DEGs), here we report on a comprehensive investigation in this regard for amorphous-LaAlO3/KTaO3 2DEGs with the Fermi energy ranging from ~13 meV to ~488 meV. The most important observation is the dramatic variation of the Rashba spin-orbit coupling (SOC) as Fermi energy sweeps through 313 meV: The SOC effective field first jumps and then drops, leading to a cusp of ~2.6 T. Above 313 meV, an additional species of mobile electrons emerges, with a 50-fold enhanced Hall mobility. A relationship between spin relaxation distance and the degree of band filling has been established in a wide range. It indicates that the maximal spin precession length is ~70.1 nm and the maximal Rashba spin splitting energy is ~30 meV. Both values are much larger than the previously reported ones. As evidenced by density functional theory calculation, these unusual phenomena are closely related to the distinct band structure of the 2DEGs composed of 5d electrons. The present work further deepens our understanding of perovskite conducting interfaces, particularly those composed of 5d transition metal oxides.
关键词： oxide interfaces,spin-orbital coupling,two-dimensional electron gas,optical gating,gating effect
更新于2025-09-23 15:22:29
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Quantum Calligraphy: Writing Single-Photon Emitters in a Two-Dimensional Materials Platform
摘要： We present a paradigm for encoding strain into two dimensional materials (2DM) to create and deterministically place single photon emitters (SPEs) in arbitrary locations with nanometer-scale precision. Our material platform consists of a 2DM placed on top of a deformable polymer film. Upon application of sufficient mechanical stress using an atomic force microscope tip, the 2DM/polymer composite deforms, resulting in formation of highly localized strain fields with excellent control and repeatability. We show that SPEs are created and localized at these nanoindents, and exhibit single photon emission up to 60K, the highest temperature reported in these materials. This quantum calligraphy allows deterministic placement and real time design of arbitrary patterns of SPEs for facile coupling with photonic waveguides, cavities and plasmonic structures. In addition to enabling versatile placement of SPEs, these results present a general methodology for imparting strain into 2DM with nanometer-scale precision, providing an invaluable tool for further investigations and future applications of strain engineering of 2DM and 2DM devices.
关键词： tungsten disulfide,atomic force microscopy,two-dimensional materials,single photon emitter,strain engineering
更新于2025-09-23 15:22:29
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Two-dimensional-related catalytic materials for solar-driven conversion of CO <sub/>x</sub> into valuable chemical feedstocks
摘要： The discovery of improved chemical processes for CO and CO2 hydrogenation to valuable hydrocarbon fuels and alcohols is of paramount importance for the chemical industry. Such technologies have the potential to reduce anthropogenic CO2 emissions by adding value to a waste stream, whilst also reducing our consumption of fossil fuels. Current thermal catalytic technologies available for CO and CO2 hydrogenation are demanding in terms of energy input. Various alternative technologies are now being developed for COx hydrogenation, with solar-driven processes over two-dimensional (2D) and 2D-related composite materials being particularly attractive due to the abundance of solar energy on Earth and also the high selectivity of defect-engineered 2D materials towards specific valuable products under very mild reaction conditions. This review showcases recent advances in the solar-driven COx reduction to hydrocarbons over 2D-based materials. Optimization of 2D catalyst performance demands interdisciplinary research that embraces catalyst electronic structure manipulation and morphology control, surface/interface engineering, reactor engineering and density functional theory modelling studies. Through improved understanding of the structure–performance relationships in 2D-related catalysts which is achievable through the application of modern in situ characterization techniques, practical photo/photothermal/photoelectrochemical technologies for CO and CO2 reduction to high-valuable products such as olefins could be realized in the not-too-distant future.
关键词： hydrocarbons,feedstocks,two-dimensional materials,solar-driven conversion,catalysis,COx reduction
更新于2025-09-23 15:22:29
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Electric-Field Control of Dirac Two-Dimensional Electron Gas in PbTe/CdTe Heterostructures
摘要： Two-dimensional electron gases (2DEGs) confined to quantum wells trigger rich emergent phenomena and serve as a host for high-speed electronics. 2DEG in PbTe/CdTe heterostructure was predicted to be Dirac electrons and confirmed by recent experiments. Here, we demonstrate the manipulation of electrical transport properties of this 2DEG with extremely high mobility and unique electron structure by ionic liquid-gating. The extreme capacitance of carrier modulation enables to tune the band structure. With a change of the gate voltage, the Fermi level moves to the conduction band and crosses the Dirac Point, leading to the shift of quantum oscillation. Our results may offer new insight toward electronic application with on-demand properties.
关键词： Fermi surface,molecular beam epitaxy,ionic liquid gating,quantum oscillation,two-dimensional electron gas
更新于2025-09-23 15:22:29