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Application of the hybrid complex variable method to the analysis of a crack at a piezoelectric-metal interface
摘要： A plane strain problem for an electrically conducting interface crack between linear transversely isotropic piezoelectric and isotropic elastic conductor materials under remote mechanical loading is considered. The attention is focused on a hybrid complex variable method which combines the Stroh formalism for piezoelectric materials with the Muskhelishvili formalism for conducting isotropic elastic materials. This method is illustrated in detail for the open crack model and the contact zone crack model. Using special presentations of mechanical quantities via sectionally analytic functions, a combined Dirichlet–Riemann and Hilbert boundary value problem is formulated and solved analytically. Stress intensity factors as well as the crack tip energy release rate are found in a clear analytical form. Furthermore, transcendental equations for the determination of the realistic contact zone length and the location of the first interpenetration point have been obtained. A significant influence of the external mechanical loading on the crack opening and the stresses as well as the contact zone and interpenetration region lengths is observed. The dependencies of the mentioned values on the intensities of the mechanical loading are presented in tables and associated diagrams.
关键词： electrically conducting interface crack,Piezoelectric-metal joint,contact zone,complex variable method
更新于2025-09-23 15:23:52
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Contactless Optical Characterization of Carrier Dynamics in Free-Standing InAs-InAlAs Core-Shell Nanowires on Silicon
摘要： Contactless time-resolved pump-probe and external quantum efficiency measurements were performed on epitaxially grown free-standing wurtzite indium arsenide/indium aluminum arsenide (InAs-InAlAs) core-shell nanowires on Si (111) substrate from 77K to 293K. The first independent investigation of Shockley-Read-Hall, radiative and Auger recombination in InAs-based NWs is presented. Although the Shockley-Read Hall recombination coefficient was found to be at least two orders of magnitude larger than the average experimental values of other reported InAs materials, the Auger recombination coefficient was reported to be ten-fold smaller. The very low Auger and high radiative rates result in an estimated peak internal quantum efficiency of the core-shell nanowires as high as 22% at 77K, making these nanowires of potential interest for high efficiency mid-infrared emitters. A greater than two-fold enhancement in minority carrier lifetime was observed from capping nanowires with a thin InAlAs shell due to passivation of surface defects.
关键词： Auger recombination rate,radiative,Shockley-Read-Hall,Pump-probe spectroscopy,core-shell nanowires,surface/interface recombination velocity,minority carrier lifetime
更新于2025-09-23 15:23:52
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Interface Engineering of Au(111) for the Growth of 1T′-MoSe <sub/>2</sub>
摘要： Phase-controlled synthesis of two-dimensional transition metal dichalcogenides (TMDCs) is of great interest due to the distinct properties of the different phases. However, it is challenging to prepare metallic phase of group-VI TMDCs due to their metastability. At the monolayer level, interface engineering can be used to stabilize the metastable phase. Here, we demonstrate the selective growth of either single-layer 1H or 1T’-MoSe2 on Au(111) by molecular beam epitaxy; the two phases can be unambiguously distinguished using scanning tunnelling microscopy and spectroscopy. While the growth of 1H-MoSe2 is favourable on pristine Au(111), the growth of 1T’-MoSe2 is promoted by the pre-deposition of Se on Au(111). The selective growth of 1T’-MoSe2 phase on Se-pretreated Au(111) is attributed to Mo intercalation-induced stabilization of the 1T’ phase, which is supported by density functional theory calculations. In addition, 1T’ twin boundaries and 1H-1T’ heterojunctions were observed and found to exhibit enhanced tunnelling conductivity. The substrate pre-treatment approach for phase-controlled epitaxy should be applicable to other group-VI TMDCs grown on Au (111).
关键词： phase control,heterojunction,scanning tunnelling microscopy/spectroscopy,interface engineering,transition metal dichalcogenides,MoSe2
更新于2025-09-23 15:23:52
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Molecular Functionalization of Planar Nanocrystalline and Porous Nanostructured Diamond to Form an Interface with Newborn and Adult Neurons
摘要： This article examines the ability of newly developed nanostructured porous boron-doped diamond (BDD) to form an interface with neural cells and the role of molecular functionalization by a polymer on this interface. Due to its high stability, biocompatibility, and electrical properties, BDD is a promising material for construction of neuroelectrodes. Nanostructuring and an increase in the surface specific area can further improve the sensitivity and performance of such electrodes. Here, porous BDD prepared in a multistep diamond deposition on a porous template consisting of a polymer and electrospun SiO2 fibers is examined. This work shows that this new material is biocompatible and does not exhibit any cytotoxicity on fibroblast cell lines. Further, this work shows that porous BDD supports regeneration of newborn and adult neurons when functionalized with poly-L-lysine.
关键词： nanocrystalline diamond,boron-doped diamond,enhanced surface area,neural interface,chemical functionalization
更新于2025-09-23 15:23:52
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Millimeter-scale single-crystalline semiconducting MoTe <sub/>2</sub> via solid-to-solid phase transformation
摘要： Among the Mo- and W-based two-dimensional (2D) transition metal dichalcogenides (TMDCs), MoTe2 is particularly interesting for phase-engineering applications, because it has the smallest free energy difference between the semiconducting 2H phase and metallic 1T’ phase. In this work, we reveal that, under the proper circumstance, Mo and Te atoms can rearrange themselves to transform from a polycrystalline 1T’ phase into a single-crystalline 2H phase in a large scale. We manifest the mechanisms of the solid-to-solid transformation by conducting the density functional theory calculations, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The phase transformation is well described by the time-temperature-transformation diagram. By optimizing the kinetic rates of nucleation and crystal growth, we have synthesized single-crystalline 2H-MoTe2 domain with a diameter of 2.34 mm, centimeter-scale 2H-MoTe2 thin film with a domain size up to several hundred micrometers, and the seamless 1T’-2H MoTe2 coplanar homojunction. The 1T’-2H MoTe2 homojunction provides an elegant solution for ohmic contact of 2D semiconductors. The controlled solid-to-solid phase transformation in 2D limit provides a new route to realize wafer-scale single-crystalline 2D semiconductor and coplanar heterostructure for 2D circuitry.
关键词： 1T’-2H interface,phase transformation,single crystal,MoTe2 film
更新于2025-09-23 15:23:52
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Dispersion relations of elastic waves in three-dimensional cubical piezoelectric phononic crystal with initial stresses and mechanically and dielectrically imperfect interfaces
摘要： The shape of individual building blocks is an important parameter in bottom-up self-assembly of nano-structured materials. A simple shape change from sphere to spheroid can significantly affect the assembly process due to the modification to the orientational degrees of freedom. When a layer of spheres is placed upon a layer of spheroids, the strain at the interface can be minimized by the spheroid taking a special orientation. C70 fullerenes represent the smallest spheroids, and their interaction with a sphere-like C60 is investigated. We find that the orientation of the C70 within a close-packed C70 layer can be steered by contacting a layer of C60. This orientational steering phenomenon is potentially useful for epitaxial growth of multilayer van der Waals molecular heterostructures.
关键词： interface,self-assembly,epitaxy,scanning tunnelling microscopy,graphene,van der Waals heterostructures,fullerene
更新于2025-09-23 15:23:52
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An adapted method for analyzing 4H silicon carbide metal-oxide-semiconductor field-effect transistors
摘要： Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) are key devices for next-generation power electronics. However, accurate determination of device parameters from 3-terminal characteristics is hampered by the presence of interface traps. Here we present a method that, in contrast to previous evaluation schemes, explicitly considers those defects. A well-tractable parametrization of the SiC/SiO2-specific interface trap spectrum is introduced that reflects the body of known data. With this ingredient, we develop an analysis that targets for an accurate determination of device parameters from simple 3-terminal characteristics. For its validation, we investigate MOSFETs with significantly different defect densities. The resulting parameters – charge carrier density, mobility and threshold voltage – are in excellent agreement with Hall effect investigations on the very same devices, avoiding systematic errors inherent to conventional evaluation techniques. With this adapted scheme, 4H-SiC power MOSFETs, even packaged, can be meaningfully characterized, speeding up innovation cycles in energy-saving power electronics.
关键词： mobility,Silicon carbide,Hall effect,interface traps,threshold voltage,MOSFET
更新于2025-09-23 15:23:52
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Electromagnetic behavior of a non-integer dimensional planar interface located in chiral medium
摘要： Purpose of the present study is to investigate the reflection and transmission characteristics of a non-integer dimensional (NID) planar interface located in an unbounded homogeneous chiral medium. The medium is NID in direction normal to the interface and a parameter, called NID parameter, is used to model the NID characteristics of the medium. Interface exists due to unequal value of the NID parameters characterizing mediums lying on two sides of the interface. It is observed co and cross-components of reflected field have very significant effect of NID parameters. Special cases in which one and neither of the NID parameter is integer order have also been discussed.
关键词： Planar interface and fractal medium,Non-integer dimensional space,Chiral medium
更新于2025-09-23 15:23:52
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Interaction between in-gap states and carriers at the conductive interface between perovskite oxides
摘要： The 2D electron systems of SrTiO3/NdGaO3 (STO/NGO) and amorphous-LaAlO3/SrTiO3/NdGaO3 (a-LAO/STO/NGO) heterojunctions were explored. An obvious interaction between in-gap states (IGSs) and carriers was found. The IGSs can trap a large number of carriers and enhance carrier scattering. As a result of the high density of IGSs in STO, the conductivity of STO/NGO was severely weakened. However, for a-LAO/STO/NGO heterojunctions, the high carrier density can reduce the effect of IGSs through the electrostatic screening effect. The competition between IGSs and the screening effect of carriers results in an insulator–metal transition and a strange temperature dependence of carrier density. We also explored the interaction between IGSs and carriers theoretically. A mathematical description was proposed and the calculated results showed good agreement with experimental findings.
关键词： in-gap states,perovskite oxides interface,2D electron system,electrostatic screening effect
更新于2025-09-23 15:23:52
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Ultrafast dynamics of solvated electrons at anatase TiO<sub>2</sub>/H<sub>2</sub>O interface
摘要： Solvated electrons are known to be the lowest energy charge transfer pathways at oxide/aqueous interface and the understanding of the electron transfer dynamics at the interface is fundamental for photochemical and photocatalytic processes. Taking anatase TiO2/H2O interface as a prototypical system, we perform time-dependent ab initio nonadiabatic molecular dynamics (NAMD) calculations to study the charge transfer dynamics of solvated electrons. For the static electronic properties, we find that the dangling H atoms can stabilize solvated electrons. A solvated electron band can be formed with one monolayer H2O adsorption. The energies of the solvated electron band minimum decrease when H2O adsorbs dissociatively. Moreover, the surface oxygen vacancies are also helpful for stabilizing the solvated electron band. For the dynamics behaviour, we find that the ultrafast charge transfer from solvated electron band minimum to anatase TiO2(101) surface at 100 K is mainly contributed by nonadiabatic mechanism. Comparing with rutile TiO2(110) surface, the lifetime of solvated electron on anatase TiO2 (101) surface is longer, suggesting a better photocatalytic properties. Our results provide essential insights into the understanding of the charge transfer dynamics and the possible photocatalytic mechanism at oxide/aqueous interface.
关键词： nonadiabatic molecular dynamics,solvated electron,oxide/aqueous interface
更新于2025-09-23 15:23:52