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Wafer-scale single-crystal hexagonal boron nitride film via self-collimated grain formation
摘要： Although polycrystalline hexagonal boron nitride (PC-hBN) has been realized, defects and grain boundaries still cause charge scatterings and trap sites, impeding high-performance electronics. Here, we report a method of synthesizing wafer-scale single-crystalline hBN (SC-hBN) monolayer films by chemical vapor deposition. The limited solubility of boron (B) and nitrogen (N) atoms in liquid gold promotes high diffusion of adatoms on the surface of liquid at high temperature to provoke the circular hBN grains. These further evolve into closely packed unimodal grains by means of self-collimation of B and N edges inherited by electrostatic interaction between grains, eventually forming an SC-hBN film on a wafer scale. This SC-hBN film also allows for the synthesis of wafer-scale graphene/hBN heterostructure and single-crystalline tungsten disulfide.
关键词： single-crystalline,hexagonal boron nitride,wafer-scale,tungsten disulfide,chemical vapor deposition,graphene/hBN heterostructure
更新于2025-09-10 09:29:36
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Angular Optical Transparency Induced by Photonic Topological Transition in Hexagonal Boron Nitride
摘要： The transmission property of hexagonal boron nitride at its four photonic topological transitions has been studied. An interesting result is revealed that the angular optical transparency can be achieved at wavelength 12.0494 μm. The numerical results indicate that the transparency window has an angular full width at half maximum of 4° with an optical transmission higher than 0.9 at normal incidence. Besides, corresponding to an angular full width at half maximum narrower than 20°, the wavelength span is about 230 nm. These features may make the hexagonal boron nitride holds promise for applications in private screens and optical detectors.
关键词： Hexagonal boron nitride,Photonic topological transition,Angular transparency
更新于2025-09-10 09:29:36
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Interface States in Bilayer Graphene Encapsulated by Hexagonal Boron Nitride
摘要： The threshold voltages at the onset of conduction for electron and hole branches can provide information on band gap values or the interface states in a gap. We measured conductivity of bilayer graphene encapsulated by hexagonal boron nitride as a function of back and top gates, where another bilayer graphene is used as a top gate. From the measured conductivity the transport gap values were extracted assuming zero interface trap states, and they are close to the theoretically expected gap values. From a little discrepancy an average density of interface states per energy within a band gap (Dit) is also estimated. The data clearly show that Dit decreases as a bilayer graphene band gap increases rather than being constant. Despite the decreasing trend of Dit, interestingly the total interface states within a gap increases linearly as a band gap increases. This is because of ~ 2 × 1010 cm-2 interface states localized at band edges even without a band gap, and other gap states are equally spread over the gap.
关键词： band gap,hexagonal boron nitride,bilayer graphene,transport gap,interface states
更新于2025-09-10 09:29:36
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A Novel Transparent pH Sensor Based on a Nanostructured ITO Electrode Coated with [3,3′-Co(1,2-C2B9H11)2]-Doped Poly(pyrrole)
摘要： A novel transparent and nanostructured ion-sensitive electrode based on indium tin oxide (ITO) coated with cobaltbis(dicarbollide)-doped poly(pyrrole) (PPy) is presented in this work. This metallacarborane-doped PPy was used as conducting polymer due to its high stability and chemical resistance. The ion-sensitive electrode was coupled to a miniaturized and low-cost potentiostat, in a final autonomous kit for potentiometric determination of pH. Qualitative calibration of the system revealed Nernstian behavior, resulting promising for novel point-of-care biomedical applications.
关键词： indium tin oxide (ITO),intrinsically conducting polymer (ICP),poly(pyrrole) (PPy),pH sensor,potentiometry,potentiometric sensor,boron compounds,nanoscience,metallacarboranes
更新于2025-09-10 09:29:36
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Strength and toughness anisotropy in hexagonal boron nitride: An atomistic picture
摘要： Strength and toughness are two crucial mechanical properties of a solid that determine its ability to function reliably without undergoing failure in extreme conditions. While hexagonal boron nitride (hBN) is known to be elastically isotropic in the linear regime of mechanical deformation, its directional response to extreme mechanical loading remains less understood. Here, using a combination of density functional theory calculations and molecular dynamics simulations, we show that strength and crack nucleation toughness of pristine hBN are strongly anisotropic and chirality dependent. They vary nonlinearly with the chirality of the lattice under symmetry breaking deformation, and the anisotropic behavior is retained over a large temperature range with a decreasing trend at higher temperatures. An atomistic analysis reveals that bond deformation and associated distortion of electron density are nonuniform in the nonlinear regime of mechanical deformation, irrespective of the loading direction. This nonuniformity forms the physical basis for the observed anisotropy under static conditions, whereas reduction in nonuniformity and thermal softening reduce anisotropy at higher temperatures. The chirality-dependent anisotropic effects are well predicted by inverse cubic polynomials.
关键词： chirality,anisotropy,hexagonal boron nitride,molecular dynamics simulations,density functional theory,strength,toughness
更新于2025-09-10 09:29:36
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A universal method for large-yield and high-concentration exfoliation of two-dimensional hexagonal boron nitride nanosheets
摘要： Hexagonal boron nitride (hBN) is an ultra-wide bandgap insulating material, which possesses a graphite-like layered structure, and the two-dimensional (2D) hexagonal boron nitride nanosheets (hBNNS), exfoliated from the bulk hBN, have promising applications in electronic packaging and high-power devices, due to the high thermal conductivity, excellent thermal/chemical stability as well as the ultra-wide band gap. However, the exfoliation of hBNNS is still a challenge with respect to high cost, time consuming, and low yield. Herein, a facile hydrothermal exfoliation method was proposed for the first time to exfoliate the hBNNS in a large yield and high concentration. In the optimized hydrothermal conditions, the lithium ion (Li+) intercalation, isopropanol (IPA) solvent, and the strong stirring could give rise to a large exfoliation yield up to (cid:1)55% and a high concentration (cid:1)4.13 mg/mL. In addition, the exfoliated hBNNS could enhance the methyl orange (MO) photodegradation efficiency of TiO2 from 91% to 96.4 %. Most importantly, this hydrothermal exfoliation method could be a universal approach for the exfoliation of 2D materials.
关键词： Hydrothermal exfoliation,Nanosheets,2D materials,Hexagonal boron nitride,Solubility parameters theory,Universal approach
更新于2025-09-10 09:29:36
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Impacts of in-plane strain on commensurate graphene/hexagonal boron nitride superlattices
摘要： Due to atomically thin structure, graphene/hexagonal boron nitride (G/hBN) heterostructures are intensively sensitive to the external mechanical forces and deformations being applied to their lattice structure. In particular, strain can lead to the modification of the electronic properties of G/hBN. Furthermore, moiré structures driven by misalignment of graphene and hBN layers introduce new features to the electronic behavior of G/hBN. Utilizing ab initio calculation, we study the strain-induced modification of the electronic properties of diverse stacking faults of G/hBN when applying in-plane strain on both layers, simultaneously. We observe that the interplay of few percent magnitude in-plane strain and moiré pattern in the experimentally applicable systems leads to considerable valley drifts, band gap modulation and enhancement of the substrate-induced Fermi velocity renormalization. Furthermore, we find that regardless of the strain alignment, the zigzag direction becomes more efficient for electronic transport, when applying in-plane non-equibiaxial strains.
关键词： strain,graphene/hexagonal boron nitride,moiré pattern,electronic properties
更新于2025-09-10 09:29:36
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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) - Effect of Catalysts on Hydrothermal Preparation of boron nitride nanostructures
摘要： Boron nitride (BN) has attracted intense interests due to its excellent thermal conductivity and electrical insulation, which make it a promising thermal interface material for electronic packaging. Conventionally, the BN nanostructures were made from high cost method, e.g. chemical vapor deposition (CVD), which was restricted by the extremely high reaction temperature as well as the expensive instruments. Herein, a facile hydrothermal method was presented, where the catalysts were used to tune the phase and morphologies of the BN products starting from the boron and nitrogen sources. With different catalysts, the phase of the products could be changed from the orthorhombic to cubic BN, and the morphology underwent an evolution from nanorods to nanoflowers. The results are of great significance for the large-scale fabrication of BN nanostructures in a low cost.
关键词： Nanoflowers,Hydrothermal synthesis,Morphology evolution,Nanorods,Boron nitride,Catalyst
更新于2025-09-10 09:29:36
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Probing the nanoscale origin of strain and doping in graphene-hBN heterostructures
摘要： We use confocal Raman microscopy and a recently proposed vector analysis scheme to investigate the nanoscale origin of strain and carrier concentration in exfoliated graphene-hexagonal boron nitride (hBN) heterostructures on silicon dioxide (SiO2). Two types of heterostructures are studied: graphene on SiO2 partially covered by hBN, and graphene fully encapsulated between two hBN flakes. We extend the vector analysis method to produce separated spatial maps of the strain and doping variation across the heterostructures. This allows us to visualise and directly quantify the much-speculated effect of the environment on carrier concentration in graphene. Moreover, we demonstrate that variations in strain and carrier concentration in graphene arise from nanoscale features of the heterostructures such as fractures, folds and bubbles trapped between layers. For bubbles in hBN-encapsulated graphene, hydrostatic strain is shown to be greatest at bubble centres, whereas the maximum carrier concentration is localised at bubble edges. Raman spectroscopy is shown to be a non-invasive tool for probing strain and doping in graphene, which could prove useful for engineering of two-dimensional devices.
关键词： hexagonal boron nitride,Raman,strain,van der Waals heterostructures,graphene,hBN,doping
更新于2025-09-09 09:28:46
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Solution processed boron doped ZnO thin films: Influence of different boron complexes
摘要： ZnO is one of the most investigated semiconductor material in optoelectronic applications. Its eco-friendly, abundance and superior physical properties, makes it quite remarkable for researchers. In this study, we have shown that a new type of salen-phenyl boron complex (L2BPh2) can strongly affect the physical properties of the ZnO nanostructured samples. To prepare the doped and undoped ZnO thin film samples on glass substrates a popular solution and non-vacuum based sol-gel method was used. By adding of critical 0.5 % molar ratio of new type salen-phenyl boron complex (L2BPh2) in ZnO solution, ZnO nanorod arrays were formed on the surface of the films. A decrease in the visible region of optical transmittance was also observed due to the formation of nanorods. Further increasing of doping ratio causes disappearing of nanorods. Resistivity values are found to decrease from 11 ?cm to ~10-3 ?cm for undoped and 0.5 % boron doped samples.
关键词： sol-gel,BZO,phenyl boron complex (L2BPh2),ZnO
更新于2025-09-09 09:28:46