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Lewis Acid Modulation of meso-Pyridyl BODIPY Chromophores
摘要： Two pyridyl-substituted BODIPY compounds are shown to interact with the strong Lewis acid B(C6F5)3. The borane adducts are characterized by multinuclear NMR and in one case by X-ray crystallography. The titration of pyridyl-substituted BODIPYs with B(C6F5)3 results in a bathochromic shift of the UV-vis absorption and emission spectra, with the magnitude of the shift depending on the distance of the bound borane from the BODIPY core. In meso-4-pyridyl-BODIPY, binding of B(C6F5)3 induces a small ca. 230 cm?1 red shift in the UV-vis absorption maximum, with a much larger 1950 cm?1 shift in the photoluminescence maximum. In meso-4-pyridylphenyl-BODIPY, where the pyridine Lewis base is separated from the BODIPY core by a phenyl spacer, smaller shifts of ca. 120 cm?1 in UV-vis absorption and 330 cm?1 in photoluminescence are observed. This work shows that these organic chromophores can interact with Lewis acids as a means of systematically perturbing the electronic structure and excited-state properties.
关键词： Boron,UV/Vis Spectroscopy,Lewis acids,Fluorescence,BODIPY
更新于2025-09-09 09:28:46
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Elastic and thermophysical properties of BAs under high pressure and temperature
摘要： The pseudopotential plane-wave approach in the framework of the density functional theory, and the density functional perturbation theory with the generalized gradient approach for the exchange-correlation functional has been used to calculate the structural phase stability, elastic constants and thermodynamic properties of boron-arsenide (BAs) compound. The BAs compound transforms from the zincblende phase to rock-salt structure; the phase transition pressure was found to be 141.2 GPa with a volume contraction of around 8.2 %. The thermodynamic properties under high pressure and temperature up to 125 GPa and 1200 K respectively were also determined, analyzed and discussed in comparison with other data of the literature. The systematic errors in the static energy were corrected using the bpscal EEC method. Our results agree well with those reported in the literature, where for example, our calculated melting temperature (2116 K) deviates from the theoretical one (2132.83 K) with only 0.8 %, and the deviation between our result (1.86) of the Grüneisen parameter and the theoretical one (1.921) is only around 3.2 %.
关键词： Phase transition,Thermodynamic properties,High-pressure,High-temperature,Boron arsenide
更新于2025-09-09 09:28:46
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Towards epitaxial graphene p-n junctions as electrically programmable quantum resistance standards
摘要： We report the fabrication and measurement of top gated epitaxial graphene p-n junctions where exfoliated hexagonal boron nitride (h-BN) is used as the gate dielectric. The four-terminal longitudinal resistance across a single junction is well quantized at the von Klitzing constant RK with a relative uncertainty of 10?7. After the exploration of numerous parameter spaces, we summarize the conditions upon which these devices could function as potential resistance standards. Furthermore, we offer designs of programmable electrical resistance standards over six orders of magnitude by using external gating.
关键词： p-n junctions,quantum resistance standards,gate dielectric,hexagonal boron nitride,epitaxial graphene
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - A Compact Model of Drift and Diffusion Memristor Applied in Neuron Circuits Design
摘要： A compact model of memristor for unifying two switch characteristics, drift and diffusion has been proposed, based on the ion dynamic transport theory at the oxide interface layer. The model is verified by measured data in different oxide-material-based drift/diffusion memristors, and well fits DC/AC characteristics of both devices, under parameter variations and temperature evolution. Moreover, the applications of this model in neuron circuits design are shown.
关键词： adsorption effect,boron nitride nanotubes,first-principles calculations,small molecule
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - High Voltage Electrical Properties of Epoxy / h-BN Microcomposites
摘要： Two high voltage properties – DC conductivity and AC breakdown strength – of epoxy composites filled with 30 wt% of micron sized hexagonal boron nitride (h-BN) are discussed in comparison to neat epoxy. The influence of h-BN upon the field dependence of DC conductivity has been studied up to 18 kV/mm. The addition of h-BN does not lead to a modification of conduction mechanisms: the J-V characteristics show an ohmic behavior at low fields and a space charge limited current (SCLC) at higher fields for both neat epoxy and composite. However, the addition of 30 wt% h-BN reduces the overall electrical conductivity and increases the threshold voltage between ohmic and SCLC regions, leading to a significant modification of electrical conductivity within the field range compared to neat epoxy. AC breakdown strength is enhanced for epoxy – h-BN composites while generally speaking the addition of micro fillers in an epoxy matrix tends to decrease it.
关键词： DC conductivity,electrical conduction mechanisms,epoxy composites,hexagonal boron nitride,AC breakdown strength
更新于2025-09-09 09:28:46
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Multiphonon Intracenter Relaxation of Boron Acceptor States in Diamond
摘要： The relaxation rates are calculated in the adiabatic approximation, in which the steady-state impurity states are taken to be electronic-vibrational (vibronic) states. The probabilities of transitions between these states with the emission (or absorption) of one or several phonons are calculated in first-order perturbation theory on the assumption that the transitions are a result of the violation of adiabaticity. The electron part of the wave function of the vibronic state is described by a simple Hamiltonian with an isotropic effective mass. The wave function of the ground state is determined by the quantum defect method. According to the calculations, a hole relaxes from the excited boron acceptor state, whose energy is 304 meV higher than the energy of the ground state, to the ground state with the emission of two optical phonons with a rate of ~1011 s–1. This value is an estimate from above, since the model of nondispersive optical phonons used in the study overestimates the number of phonon modes, whose participation in relaxation is allowed by the energy conservation law. However, despite the rough approximation, it can be concluded that the multiphonon relaxation of boron acceptor states in diamond is a fast process.
关键词： diamond,boron acceptor states,multiphonon relaxation,vibronic states,adiabatic approximation
更新于2025-09-09 09:28:46
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A brief overview of RF sputtering deposition of boron carbon nitride (BCN) thin films
摘要： A great part of interest has been paid for fabricating new materials with novel mechanical, optical, and electrical properties. Boron carbon nitride (BCN) ternary system was applied for variable bandgap semiconductors and systems with extreme hardness. The purpose of this literature review is to provide a brief historical overview of B4C and BN, to review recent research trends in the BCN synthesizes, and to summarize the fabrication of BCN thin films by plasma sputtering technique from B4C and BN targets in different gas atmospheres. Pre-set criteria are used to discuss the processing parameters affecting BCN performance which includes the gasses flow ratio and effect of temperature. Moreover, many characterization studies such as mechanical, etching, optical, photoluminescence, XPS, and corrosion studies of the RF sputtered BCN thin films are also covered. We further mentioned the application of BCN thin films to enhance the electrical properties of metal-insulator-metal (MIM) devices according to a previous report of Prakash et al. (Opt. Lett. 41, 4249, 2016).
关键词： Radio frequency sputtering,Gas flow ratio,Boron carbon nitride,Metal-insulator-metal device
更新于2025-09-04 15:30:14
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Photonic Nanostructures from Hexagonal Boron Nitride
摘要： Growing interest in devices based on layered van der Waals (vdW) materials is motivating the development of new nanofabrication methods. Hexagonal boron nitride (hBN) is one of the most promising materials for studies of quantum photonics and phonon polaritonics. A promising nanofabrication process used to fabricate several hBN photonic devices using a hybrid reactive ion etching (RIE) and electron beam-induced etching (EBIE) technique is reported in detail here. The shortcomings and benefits of RIE and EBIE are highlighted and the utility of the hybrid approach for the fabrication of suspended and supported device structures with nanoscale features and highly vertical sidewalls are demonstrated. Functionality of the fabricated devices is proven by measurements of high-quality cavity optical modes (Q ≈ 1500). This nanofabrication approach constitutes an advance toward an integrated, monolithic quantum photonics platform based on hBN and other layered vdW materials.
关键词： hexagonal boron nitride,photonic devices,nanofabrication,nanophotonics,layered materials
更新于2025-09-04 15:30:14
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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) - Hydrothermal assembly of one-dimensional boron nitride nanostructures
摘要： Boron nitride (BN) is a state-of-the-art ultrawide bandgap semiconducting material. One-dimensional (1D) boron nitride nanostructures have high thermal conductivity (~600 W/mK) and wide band gap (5~6eV), which make it a promising thermal interface material. The 1D BN nanostructures were usually synthesized with chemical vapor deposition, restricted by the low yield and the high cost. Herein, we present a facile hydrothermal method to get 1D BN nanostructures. In the hydrothermal process, 2D BN nanosheets were firstly exfoliated from the BN powder, and then curled into 1D BN nanostructure through the chemical etching with sodium hydroxide. The alternative approach exhibited a high yield and a high concentration, which should be meaningful for the fabrication of 1D BN nanostructures.
关键词： One-dimensional nanostructure,Hydrothermal exfoliation,Chemical etching,Boron nitride
更新于2025-09-04 15:30:14
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Synthesis, characterization and photocatalytic activity of boron-doped titanium dioxide nanotubes
摘要： Two-step hydrothermal method was used to prepare undoped and boron-doped one-dimensional titanium dioxide (TiO2) nanotubes. Structural properties, thermal stability and microstructural features of the fabricated undoped titanium dioxide nanotubes (TNTs) and boron-doped titanium dioxide nanotubes (BTNTs) were characterized by Xeray diffraction, Raman, Fourieretransform infrared spectroscopy, nitrogen adsorption-desorption isotherms, scanning and transmission electron microscopy techniques. The photocatalytic activity of the fabricated nanotubes was evaluated by using methylene blue degradation. Boron addition to the titanium dioxide nanotubes up to 5% increased the photocatalytic methylene blue degradation ef?ciency. The achieved highest degradation ef?ciency was 81% and it was determined that higher (>5%) boron doped into the titanium dioxide nanotubes resulted in a decreased degradation ef?ciency.
关键词： Titanium dioxide nanotubes,Photocatalyst,Boron,Hydrothermal synthesis,Spectroscopy
更新于2025-09-04 15:30:14