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Lifetime Stability and Microstructure Properties of Cr/B <sub/>4</sub> C X-ray Reflective Multilayer Coatings
摘要： This paper demonstrates that highly re?ective Cr/B4C multilayer interference coatings with nanometric layer thicknesses, designed to operate in the soft X-ray photon energy range, have stable re?ective performance for a period of 3 years after deposition. The microstructure and chemical composition of layers and interfaces within Cr/B4C multilayers is also examined, with emphasis on the B4C-on-Cr interface where a signi?cant diffusion layer is formed and on the oxide in the top B4C layer. Multiple characterization techniques (X-ray re?ectivity at different photon energies, X-ray photoelectron spectroscopy, transmission electron microscopy, electron diffraction and X-ray diffraction) are employed and the results reveal a consistent picture of the Cr/B4C layer structure.
关键词： Multilayers,Chrominum,Soft X-rays,Boron Carbide
更新于2025-09-04 15:30:14
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Quantitative determination of a model organic/insulator/metal interface structure
摘要： By combining X-ray photoelectron spectroscopy, X-ray standing waves and scanning tunneling microscopy, we investigate the geometric and electronic structure of a prototypical organic/insulator/metal interface, namely cobalt porphine on monolayer hexagonal boron nitride (h-BN) on Cu(111). Specifically, we determine the adsorption height of the organic molecule and show that the original planar molecular conformation is preserved in contrast to the adsorption on Cu(111). In addition, we highlight the electronic decoupling provided by the h-BN spacer layer and find that the h-BN–metal separation is not significantly modified by the molecular adsorption. Finally, we find indication of a temperature dependence of the adsorption height, which might be a signature of strongly-anisotropic thermal vibrations of the weakly bonded molecules.
关键词： hexagonal boron nitride,X-ray standing waves,X-ray photoelectron spectroscopy,cobalt porphine,Cu(111),scanning tunneling microscopy,organic/insulator/metal interface
更新于2025-09-04 15:30:14
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Primitive and O-functionalized R-graphyne-like BN sheet: Candidates for SO <sub/>2</sub> Sensor with High Sensitivity and Selectivity at Room Temperature
摘要： In recent years, the successful obtained of various boron nitride allotropes have raised exciting prospects of 2D material for nano device area. Herein, two novel two-dimensional boron nitride allotropes, a rectangular graphyne-like sheet (R-BNyne) and an O-functionalized R-BNyne nanosheet (R-BNOyne), are proposed and investigated by first principle calculations. The structural stabilities of metallic R-BNyne and indirect gap semiconducting R-BNOyne are proved through the phonon dispersion and Molecular Dynamic calculations. Furthermore, the adsorptions of CH4, CO, CO2, SO2 and H2 on R-BNyne and R-BNOyne have been calculated to explore the possibilities of being as gas sensors. The significant change of the current-voltage curve with and without SO2 adsorption on R-BNyne and R-BNOyne implies that both of them could be used as candidates for SO2 superior sensor with high sensitivity and selectivity at room temperature. Our studies not only reveal a new solution to modulate the electronic properties of 2D nanosheets, but also are helpful for designing novel boron nitride allotropes for expanding the possibilities of being as gas sensors as well as superior capturer of SO2 with high sensitivity.
关键词： O-functionalized,R-graphyne-like boron nitride sheet,Electronic properties,Sensor,In-plane stiffness
更新于2025-09-04 15:30:14
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Material Reliability of Low-Temperature Boron Deposition for PureB Silicon Photodiode Fabrication
摘要： The chemical-vapor deposition conditions for the growth of pure boron (PureB) layers on silicon at temperatures as low as 400oC were investigated with the purpose of optimizing photodiodes fabricated with PureB anodes for minimal B-layer thickness, low dark current and chemical robustness. The B-deposition is performed in a commercially-available Si epitaxial reactor from a diborane precursor. In-situ methods commonly used to improve the cleanliness of the Si surface before deposition are tested for a deposition temperature of 450oC and PureB layer thickness of 3 nm. Specifically, high-temperature baking in hydrogen, and exposure to HCl are tested. Both material analysis and electrical diode characterization indicate that these extra cleaning steps degrade the properties of the PureB layer and the fabricated diodes.
关键词： silicon,photodiodes,chemical-vapor deposition,Pure boron,diborane
更新于2025-09-04 15:30:14
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monolayers on the hBN-layer thickness
摘要： The optical properties of two-dimensional transition-metal dichalcogenide monolayers, such as MoS2 or WSe2 are dominated by excitons, Coulomb bound electron-hole pairs. Screening effects due to the presence of hexagonal-boron nitride (hBN) surrounding layers have been investigated by solving the Bethe-Salpeter equation on top of GW wave functions in density functional theory calculations. We have calculated the dependence of both the quasiparticle gap and the binding energy of the neutral exciton ground-state Eb as a function of the hBN-layer thickness. This paper demonstrates that the effects of screening at this level of theory are more short ranged than is widely believed. The encapsulation of a WSe2 monolayer by three sheets of hBN (～1 nm) already yields a 20% decrease in Eb, whereas the maximal reduction is 27% for thick hBN. We have performed similar calculations in the case of a WSe2 monolayer deposited on stacked hBN layers. These results are compared to the recently proposed quantum electrostatic heterostructure approach.
关键词： GW wave functions,density functional theory,hexagonal-boron nitride,two-dimensional transition-metal dichalcogenide,Bethe-Salpeter equation,exciton
更新于2025-09-04 15:30:14
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Investigation of Improvement of Electronic Properties and Ductility of RuAl2 Semiconducting Material by Boron Doping Using First-Principles Calculations
摘要： The occupation mechanism and influence of B doping on the electronic and mechanical properties of RuAl2 semiconducting compound have been investigated using first-principles calculations. Four possible B doping sites are considered. The results show that B-doped RuAl2 is thermodynamically stable. In particular, B element prefers to occupy B(4) site in comparison with other sites. Importantly, B doping improves the electronic properties of RuAl2 by shifting the Al 3p and Ru 4d states from the Fermi level (EF) to the valence band. Although B doping weakens the resistance to volume and shear deformation as well as the elastic stiffness of RuAl2, it improves the ductility due to the formation of Ru-B and Al-B bonds. Therefore, it can be concluded that B is a favorable doping element to improve the electronic properties and ductility of RuAl2 semiconducting compound.
关键词： Boron doping,RuAl2,First-principles calculations,Ductility,Electronic properties
更新于2025-09-04 15:30:14
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Ohmic graphite-metal contacts on oxygen-terminated lightly boron-doped CVD monocrystalline diamond
摘要： A process to obtain ohmic contacts on oxygen-terminated lightly boron-doped CVD monocrystalline diamond films was developed. Samples were contacted by Ti/Au metallic pads in the transmission line model (TLM) configuration. The electric contacts were placed onto a mesa structure produced on the CVD boron-doped layer. One of the samples was additionally implanted with helium ions at 10 keV in order to induce the formation of a graphitic layer underneath the diamond surface before contacting so as to improve electrical conduction. The electrical performance of both devices was characterized by the TLM method and compared. As a result, the sample with metallic electrodes exhibited a small and non-linear electrical conduction, while the graphitic/metallic contacts showed an ohmic behaviour with an estimated specific contact resistance as low as 3.3 × 10-4 Ω.cm2 for a doping level of a few 1017 cm-3. This approach opens the way to more efficient ohmic contacts on intrinsic or low-doped diamond that are crucial for the development of electronic devices and detectors.
关键词： oxygen terminations,graphitization,Ohmic graphite-metal contacts,lightly boron-doped CVD diamond film,ion implantation
更新于2025-09-04 15:30:14
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2-Level Quantum Systems in 2-D Materials for Single Photon Emission
摘要： Single photon emission (SPE) by a solid state source requires presence of a distinct two-level quantum system, usually provided by point defects. Here we note that a number of qualities offered by novel, two dimensional materials—their all-surface openness and optical transparence, tighter quantum confinement, and reduced charge screening—are advantageous for achieving an ideal SPE. Based on first principles calculations and point-group symmetry analysis, a strategy is proposed to design paramagnetic defect complex with reduced symmetry, meeting all the requirements for SPE: its electronic states are well isolated from the host material bands, belong to a majority spin eigenstate, and can be controllably excited by polarized light. The defect complex is thermodynamically stable, and appears feasible for experimental realization, to serve as a SPE-source, essential for quantum computing, with ReMoVS in MoS2 as one most practical candidate.
关键词： diamane,boron nitride,ab initio,Photonic qubits,color centers,paramagnetic defects,transition metal dichalcogenides
更新于2025-09-04 15:30:14
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Influence of Boron Antisite Defects on the Electrical Properties of MBE‐Grown GaAs Nanowires
摘要： Nanowires provide a platform for the integration of heterogeneous materials in III–V systems grown on Si. BxGa1(cid:1)xAs is an interesting material for strain applications, which has not yet been studied in nanowire form. The incorporation of boron in GaAs nanowires is investigated via DC-IV measurements. In transmission electron microscopy analysis a high concentration of boron is found at the nanowire edges, indicating surface segregation during growth. Nanowires grown under boron flux are found to exhibit Ohmic contacts and low contact resistances with p-type metallizations such as Au/Zn/Au or Cr/Au. Back-gated measurements confirmed the p-type behavior of such nanowires, indicating that boron is incorporated on antisite defects where it acts as a doubly-charged acceptor. This offers a new route for the inclusion of p-doped layers in GaAs-based nanowire heterostructures and the subsequent formation of Ohmic contacts.
关键词： boron doping,B:GaAs,nanowires,molecular beam epitaxy
更新于2025-09-04 15:30:14
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Tuning the electronic structure of hexagonal boron nitride by carbon atom modification: a feasible strategy to reduce sliding friction
摘要： Essentially, the interlayer interaction of the two-dimensional (2D) layered material is dominant, so it is expected to modify the electronic configuration of the system to change the interlayer interaction for the purpose of reducing interlayer sliding friction. In this paper, using density functional theory (DFT) calculation, we report an effective method to reduce the sliding friction between the two-layer hexagonal boron nitride layers for changing the hexagonal boron nitride electronic structure via introducing carbon. Research results indicate that the increase of the potential energy fluctuation along the sliding path increases with the increase of the load, which is caused by the difference of the degree of interlayer interaction on the sliding path with the increase of the load; at the same time, we found that the appearance of C at the B or N position can promote the interlayer charge transfer to different extents (B position is better than N position) in the BN/BN bilayer, and then produce the effect of reducing the energy barrier on the sliding path between the layers.
关键词： hexagonal boron nitride,charge transfer,friction,electronic configuration,2D material
更新于2025-09-04 15:30:14