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Solution-Based Property Tuning of Black Phosphorus
摘要： The air instability of black phosphorus (BP) severely hinders the development of its electronic and optoelectronic applications. Although a lot of effort has been made to passivate it against degradation in ambient conditions, approaches to further manipulate the properties of passivated BP are still very limited. Herein, we report a simple and low-cost chemical method that can achieve BP passivation and property tailoring simultaneously. The method is conducted by immersing a BP sample in the solution containing both 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) and triphenylcarbenium tetrafluorobor in a mixture of water and acetone (v/v = 1:1). After the treatment, the BP sample is functionalized with TEMPO, which not only efficiently passivates BP but also p-dopes BP to a degenerated density level of 1013 cm?2. The performance of the BP field effect transistor is improved after functionalization with a high Ion/Ioff ratio of 106 and carrier mobility of 881.5 cm2/(V·s). The functionalization-induced doping also significantly reduces the contact resistance between BP and the Cr/Au electrode to 0.97 kΩ·μm. Additionally, we observe a great reduction of BP electrical and optical anisotropies after functionalization. This chemical functionalization method provides a viable route to simultaneously passivate and tune the properties of BP.
关键词： p-type doping,anisotropy,functionalization,black phosphorus,contact resistance
更新于2025-09-23 15:21:01
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Near-field observation of guided-mode resonances on a metasurface via dielectric nanosphere excitation
摘要： We study laser-induced guided-mode resonances on an ultra-thin anisotropic metallic metasurface using direct near-field mapping. Coupling of the incident light to the surface waves is provided by a resonant laser-printed silicon nanosphere placed on the metasurface using nano-manipulation under electron-beam supervision. To visualize the propagation of the guided modes, we employ scattering-type scanning near-field optical microscopy in the near-infrared region (850 nm). The guided-mode resonances excited by the nanosphere demonstrate vanishing anisotropy due to weak confinement at the metasurface/air interface. We also extract the wavenumber of the observed modes through Fourier transformation of the measured near-field maps and find it to be in good agreement with numerical calculations.
关键词： Metasurface,Surface waves,Anisotropy,s-SNOM,Guided-mode resonance,Nano-Optics
更新于2025-09-23 15:21:01
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films
摘要： We report proximity effects of spin-orbit coupling in EuO1?x ?lms capped with a Pt overlayer. Transport measurements suggest that current ?ows along a conducting channel at the interface between the Pt and EuO. The temperature dependence of the resistivity picks up the critical behaviors of EuO, i.e., the metal-to-insulator transition. We also ?nd an unusual enhancement of the magnetic anisotropy in this structure from its bulk value, which results from strong spin-orbit coupling across the Pt/EuO1?x interface.
关键词： magnetic anisotropy,Pt/EuO interface,spin-orbit coupling,transport properties
更新于2025-09-23 15:21:01
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Raman spectrum of nanocrystals: Phonon dispersion splitting and anisotropy
摘要： The effects of anisotropy and splitting of the phonon dispersions in the Raman spectrum of nanocrystals are investigated. We describe the different branches of the optical phonon dispersion curves along each high-symmetry direction by fitting a simple empirical model to experimental data. These curves are then used to calculate the Raman spectrum in the framework of the phonon confinement model and the results are compared with a wide range of available experimental data as well as with the spectra predicted by currently available models based on a single isotropic dispersion curve. We show that by considering the anisotropy and splitting of rigorously obtained optical phonon dispersions, the commonly observed deviations between experimental and theoretical data are strongly reduced. Our work enables the extraction of significantly more accurate information about relevant physical properties of nanocrystals from Raman spectroscopy.
关键词： splitting,anisotropy,nanocrystals,phonon dispersion,Raman spectrum
更新于2025-09-23 15:21:01
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Extreme asymmetry of Néel domain walls in multilayered films of the dilute magnetic semiconductor (Ga,Mn)(As,P)
摘要： We report on unconventional perfectly shaped, fully asymmetric ～90? Néel domain walls in multilayered ?lms of the diluted ferromagnetic semiconductor (Ga,Mn)(As,P) with a stepwise variation of P doping. Our results contradict micromagnetic calculations, which favor symmetric domain walls due to crystallographic anisotropy and stray ?eld energy. We demonstrate that both the puzzling uniaxial in-plane anisotropy in the tetragonal multilayered ?lm and the asymmetry of the domain walls could result from Dzyaloshinskii-Moriya interactions that are enhanced by the multiple sharp interfaces between the layers and from anisotropic nonrelativistic exchange coupling. Our ?nding shows that digital variations of composition during the molecular beam epitaxy can be used to tune the anisotropy and chirality of magnetic multilayers.
关键词： diluted magnetic semiconductor,Dzyaloshinskii-Moriya interactions,magnetic anisotropy,Néel domain walls,molecular beam epitaxy
更新于2025-09-23 15:21:01
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Crystallographic Orientation Control of 316L Austenitic Stainless Steel via Selective Laser Melting
摘要： In recent years, additive manufacturing has attracted attention as a technology that enables control of the crystallographic texture of metallic materials. We achieved successful control of the crystallographic texture of 316L austenitic stainless steel using selective laser melting (SLM). Three distinguished textures were achieved by changing the laser scan speed, namely: the single crystalline-like texture with {001} orientation in the build direction, the crystallographic lamellar texture in which two kinds of grains with {011} and {001} orientations in the build direction are alternately stacked, and polycrystalline with relatively random orientation. The melt pool shape and the solidification behavior (thermal gradient and migration velocity of solid/liquid interface) in a melt pool could be important controlling factors for the evolution of the crystallographic texture under the SLM process.
关键词： anisotropy,crystallographic texture,metal additive manufacturing (AM),selective laser melting (SLM),melt pool
更新于2025-09-23 15:19:57
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Orientational competition in quantum dot growth in Si-Ge heteroepitaxy on pit-patterned Si(001) substrates
摘要： Towards precisely controlled nanostructure growth, patterned substrates are used as templates to direct heteroepitaxial self–assembly. This affects the size, shape and ordering of nanostructures which are formed as a consequence of the mismatch strain. In the well–studied case of Si–Ge heteroepiaxy on Si, the lattice mismatch leads to spontaneous formation of quantum dots. On patterned substrates, the competition between the length scale of the pattern and the intrinsic quantum dot size leads to rich behavior where the localization of dots can be modi?ed with respect to the features of the patterns. We show by continuum modeling that, in cubic elastic materials such as silicon and germanium, there is also a competition between the pattern orientation and the elastically soft directions of the ?lm which affects the precise location of quantum dots on the surface. When the pattern is between the elastically soft directions, the quantum dots can form purely in the narrow region directly between two neighboring pits, referred to as the saddle region. On the other hand, when the pattern is along the elastically soft directions, the quantum dots prefer to form in the region at the centre of four pits, referred to as the crown region. This resolves a discrepancy between theory and experiments and gives another dimension to control quantum dot formation in strained nanocrystalline systems.
关键词： elastic anisotropy,Si–Ge,quantum dots,patterned substrates,heteroepitaxy
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International Electron Devices Meeting (IEDM) - San Francisco, CA, USA (2019.12.7-2019.12.11)] 2019 IEEE International Electron Devices Meeting (IEDM) - Area-Selective-CVD Technology Enabled Top-Gated and Scalable 2D-Heterojunction Transistors with Dynamically Tunable Schottky Barrier
摘要： Neurological or biomechanical disorders may distort ankle mechanical impedance and thereby impair locomotor function. This paper presents a quantitative characterization of multivariable ankle mechanical impedance of young healthy subjects when their muscles were relaxed, to serve as a baseline to compare with pathophysiological ankle properties of biomechanically and/or neurologically impaired patients. Measurements using a highly backdrivable wearable ankle robot combined with multi-input multi-output stochastic system identification methods enabled reliable characterization of ankle mechanical impedance in two degrees-of-freedom (DOFs) simultaneously, the sagittal and frontal planes. The characterization included important ankle properties unavailable from single DOF studies: coupling between DOFs and anisotropy as a function of frequency. Ankle impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness in both seated (knee flexed) and standing (knee straightened) postures. Stiffness in the sagittal plane was greater than in the frontal plane and furthermore, was greater when standing than when seated, most likely due to the stretch of bi-articular muscles (medial and lateral gastrocnemius). Very low off-diagonal partial coherences implied negligible coupling between dorsiflexion-plantarflexion and inversion-eversion. The directions of principal axes were tilted slightly counterclockwise from the original joint coordinates. The directional variation (anisotropy) of ankle impedance in the 2-D space formed by rotations in the sagittal and frontal planes exhibited a characteristic “peanut” shape, weak in inversion-eversion over a wide range of frequencies from the stiffness dominated region up to the inertia dominated region. Implications for the assessment of neurological and biomechanical impairments are discussed.
关键词： multivariable impedance,stiffness anisotropy,ankle stiffness,Ankle joint,human ankle,ankle joint stiffness,impedance structure,multivariable stiffness
更新于2025-09-23 15:19:57
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Particle Size Distribution of Natural Clayey Soils: A Discussion on the Use of Laser Diffraction Analysis (LDA)
摘要： Particle size distribution is one of the most significant factors determining physical soil properties. Laser diffraction analysis (LDA) is an alternative method to the traditional hydrometric methods (HM) used to determine particle size distribution in soils. However, significant differences in fraction content are found in relation to the applied methods of a particle size test. Above all, measurements performed by LDA for clayey soils usually produce different results to those based on Stokes’ equation. Methodical problems, such as an appropriate method of dispersing the sample and the selection of LDA calculation theory, also play a significant role in fine soils. This paper contains the results of analyses of Neogene clays from Poland, which are characterized by differentiation with regard to the content of clay fraction particles. In this article, the validity of using laser diffraction analysis (LDA) for the identification and characterization of clayey sediments with common genesis is assessed. The possibility of finding reliable pedotransfer functions to the convert LDA results to a hydrometric analysis is discussed.
关键词： Stokes’ equation,clay soils,shape anisotropy,hydrometric method,particle size analysis,laser diffraction analysis (LDA)
更新于2025-09-23 15:19:57
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Self-assembled nanorods in YBCO matrix a?? a computational study of their effects on critical current anisotropy
摘要： In order to understand how the doping with self-assembled nanorods of different sizes and concentrations as well as applied magnetic fields affect the critical current anisotropy in YBa2Cu3O7?x (YBCO) thin films close to YBCO c-axis, we present an extensive and systematic computational study done by molecular dynamics simulation. the simulations are also used to understand experimentally measured Jc(θ) curves for BaHfO3, BaZrO3 and BaSnO3 doped YBCO thin films with the help of nanorod parameters obtained from transmission electron microscopy measurements. our simulations reveal that the relation between applied and matching field plays a crucial role in the formation of Jc(θ)-peak around YBCO c-axis (c-peak) due to vortex-vortex interactions. We also find how different concentrations of different size nanorods effect the shape of the c-peak and explain how different features, such as double c-peak structures, arise. In addition to this, we have quantitatively explained that, even in an ideal superconductor, the overdoping of nanorods results in decrease of the critical current. our results can be widely used to understand and predict the critical current anisotropy of YBco thin films to improve and develop new pinscapes for various transport applications.
关键词： critical current anisotropy,molecular dynamics simulation,YBCO,flux pinning,self-assembled nanorods
更新于2025-09-23 15:19:57