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Dependence of h-BN film thickness as grown on nickel single crystal substrates of different orientation
摘要： Chemical vapor deposition of 2D materials has been an active area of research in recent years because it is a scalable process for obtaining thin films that can be used to fabricate devices. The growth mechanism for hexagonal boron nitride (h-BN) on metal catalyst substrates has been described to be either surface energy driven or diffusion driven. In this work, h-BN is grown in a CVD system on Ni single crystal substrates as a function of Ni crystallographic orientation to clarify the competing forces acting on the growth mechanism. We observed that the thickness of the h-BN film depends on the Ni substrate orientation, with the growth rate increasing from the (100) surface to the (111) surface, and the highest on the (110) surface. We associate the observed results with surface reactivity and diffusivity differences for different Ni orientations. Boron and nitrogen diffuse and precipitate from the Ni bulk to form thin multilayer h-BN. Our results serve to clarify the h-BN CVD growth mechanism which has been previously ascribed to a surface energy-driven growth mechanism.
关键词： surface diffusion,electron backscatter diffraction,growth mechanism,hexagonal boron nitride
更新于2025-09-23 15:21:01
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Modifying the geometric and electronic structure of hexagonal boron nitride on Ir(111) by Cs adsorption and intercalation
摘要： Epitaxial hexagonal boron nitride on Ir(111) is significantly modified by adsorption and intercalation of alkali-metal atoms. Regarding geometry, intercalation lifts the two-dimensional layer from its substrate and reduces the characteristic corrugation imprinted by direct contact with the metal substrate. Moreover, the presence of charged species in close proximity to the hexagonal boron nitride (hBN) layer strongly shifts the electronic structure (valence bands and core levels). We used scanning tunneling microscopy, low-energy electron diffraction, x-ray photoelectron spectroscopy (XPS), and the x-ray standing wave technique to study changes in the atomic structure induced by Cs adsorption and intercalation. Depending on the preparation, the alkali-metal atoms can be found on top and underneath the hexagonal boron nitride in ordered and disordered arrangements. Adsorbed Cs does not change the morphology of hBN/Ir(111) significantly, whereas an intercalated layer of Cs decouples the two-dimensional sheet and irons out its corrugation. XPS and angle-resolved photoelectron spectroscopy reveal a shift of the electronic states to higher binding energies, which increases with increasing density of the adsorbed and intercalated Cs. In the densest phase, Cs both intercalates and adsorbs on hBN and shifts the electronic states of hexagonal boron nitride by 3.56 eV. As this shift is not sufficient to move the conduction band below the Fermi energy, the electronic band gap must be larger than 5.85 eV.
关键词： hexagonal boron nitride,Cs adsorption,electronic structure,geometric structure,intercalation
更新于2025-09-23 15:21:01
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Probing hyperbolic polaritons using infrared attenuated total reflectance micro-spectroscopy
摘要： Hyperbolic polariton modes are highly appealing for a broad range of applications in nanophotonics, including surfaced enhanced sensing, sub-diffractional imaging, and recon?gurable metasurfaces. Here we show that attenuated total re?ectance (ATR) micro-spectroscopy using standard spectroscopic tools can launch hyperbolic polaritons in a Kretschmann–Raether con?guration. We measure multiple hyperbolic and dielectric modes within the naturally hyperbolic material hexagonal boron nitride as a function of different isotopic enrichments and ?ake thickness. This overcomes the technical challenges of measurement approaches based on nanostructuring, or scattering scanning near-?eld optical microscopy. Ultimately, our ATR approach allows us to compare the optical properties of small-scale materials prepared by different techniques systematically.
关键词： Hyperbolic polaritons,infrared attenuated total re?ectance micro-spectroscopy,hexagonal boron nitride,Kretschmann–Raether con?guration
更新于2025-09-23 15:21:01
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Conversionless efficient and broadband laser light diffusers for high brightness illumination applications
摘要： Laser diodes are efficient light sources. However, state-of-the-art laser diode-based lighting systems rely on light-converting inorganic phosphor materials, which strongly limit the efficiency and lifetime, as well as achievable light output due to energy losses, saturation, thermal degradation, and low irradiance levels. Here, we demonstrate a macroscopically expanded, three-dimensional diffuser composed of interconnected hollow hexagonal boron nitride microtubes with nanoscopic wall-thickness, acting as an artificial solid fog, capable of withstanding ~10 times the irradiance level of remote phosphors. In contrast to phosphors, no light conversion is required as the diffuser relies solely on strong broadband (full visible range) lossless multiple light scattering events, enabled by a highly porous (>99.99%) non-absorbing nanoarchitecture, resulting in efficiencies of ~98%. This can unleash the potential of lasers for high-brightness lighting applications, such as automotive headlights, projection technology or lighting for large spaces.
关键词： high-brightness illumination,solid-state lighting,light diffusers,laser diodes,hexagonal boron nitride
更新于2025-09-23 15:19:57
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van der Waals heterostructures combining graphene and hexagonal boron nitride
摘要： As the first in a large family of 2D van der Waals (vdW) materials, graphene has attracted enormous attention owing to its remarkable properties. The recent development of simple experimental techniques for combining graphene with other atomically thin vdW crystals to form heterostructures has enabled the exploration of the properties of these so-called vdW heterostructures. Hexagonal boron nitride is the second most popular vdW material after graphene, owing to the new physics and device properties of vdW heterostructures combining the two. Hexagonal boron nitride can act as a featureless dielectric substrate for graphene, enabling devices with ultralow disorder that allow access to the intrinsic physics of graphene, such as the integer and fractional quantum Hall effects. Additionally, under certain circumstances, hexagonal boron nitride can modify the optical and electronic properties of graphene in new ways, inducing the appearance of secondary Dirac points or driving new plasmonic states. Integrating other vdW materials into these heterostructures and tuning their new degrees of freedom, such as the relative rotation between crystals and their interlayer spacing, provide a path for engineering and manipulating nearly limitless new physics and device properties.
关键词： quantum Hall effect,graphene,moiré superlattices,polaritons,hexagonal boron nitride,van der Waals heterostructures
更新于2025-09-19 17:15:36
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Thickness-tunable growth of ultra-large, continuous and high-dielectric h-BN thin films
摘要： The outstanding thermal properties, mechanical properties and large optical bandgap of hexagonal boron nitride (h-BN) make it very attractive for various applications in ultrathin 2D microelectronics. However, the synthesis of large lateral size and uniform h-BN thin films with a high breakdown strength still remains a great challenge. Here, we comprehensively investigated the effect of growth conditions on the thickness of h-BN films via low pressure chemical vapor deposition (LPCVD). By optimizing the LPCVD growth parameters with electropolished Cu foils as the deposition substrates and developing customized "enclosure" quartz-boat reactors, we achieved thickness-tunable (1.50–10.30 nm) growth of h-BN thin films with a smooth surface (RMS roughness is 0.26 nm) and an ultra-large area (1.0 cm × 1.0 cm), meanwhile, the as-grown h-BN films exhibited an ultra-high breakdown strength of ~10.0 MV cm?1, which is highly promising for the development of electrically reliable 2D microelectronic devices with an ultrathin feature.
关键词： dielectric breakdown strength,h-BN,thin films,LPCVD,2D microelectronics,hexagonal boron nitride
更新于2025-09-19 17:15:36
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Improved breakdown strength of Poly(vinylidene Fluoride)-based composites by using all ball-milled hexagonal boron nitride sheets without centrifugation
摘要： Hexagonal boron nitride (h-BN) is an ideal candidate to endow ferroelectric polymers with high energy density ((cid:1)(cid:2)) due to its intrinsic high breakdown strength ((cid:3)(cid:4)) of 800 kV/mm. Generally, it is believed that only boron nitride nanosheets (BNNSs) could remarkably improve (cid:3)(cid:4) of composite. Nevertheless, low-yield and time-consuming preparation procedures of BNNSs greatly limits the application of h-BN. To overcome this challenge, in this study, all ball-milled h-BN (B-BN) sheets were entirely used to enhance (cid:3)(cid:4) of poly(vinylidene fluoride) (PVDF) without any further centrifugation. (cid:3)(cid:4) of composites increased as ball-milling time increases at filler content of 8 wt%. Remarkably, PVDF with h-BN ball-milled for 16 h (B16-BN) possesses an impressive (cid:3)(cid:4) value of 506.8 kV/mm, which is 2.86 times that of neat PVDF (272.4 kV/mm) and even 1.33 times higher than that of PVDF/h-BN composites (380.6 kV/mm). (cid:3)(cid:4) of PVDF/B16-BN composites is close to that of PVDF/OH-BNNSs composites at same filler content, suggesting that the centrifugation is not a necessary procedure. Besides, improved dielectric loss, calculated (cid:1)(cid:2), mechanical properties and in-plane thermal conductivity can also be achieved for PVDF/B16-BN composites. These improved properties of PVDF/B16-BN composites indicate that the employment of B16-BN can avoid the weakness of low-yield and time-consuming preparation procedure of BNNSs and broaden its applications in the field of energy storage. Finally, the improved dispersion of OH-BN as well as synergy effect (f) on (cid:3)(cid:4) between OH-BN and OH-BNNSs were discussed to better understand these improved properties of PVDF/B16-BN composites.
关键词： Breakdown strength,No centrifugation,Synergy effect,Hexagonal boron nitride
更新于2025-09-19 17:13:59
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Localized Nanoresonator Mode in Plasmonic Microcavities
摘要： Submicron-thick hexagonal boron nitride crystals embedded in noble metals form planar Fabry-Perot half-microcavities. Depositing Au nanoparticles on top of these microcavities forms previously unidentified angle- and polarization-sensitive nanoresonator modes that are tightly laterally confined by the nanoparticle. Comparing dark-field scattering with reflection spectroscopies shows plasmonic and Fabry-Perot-like enhancements magnify subtle interference contributions, which lead to unexpected redshifts in the dark-field spectra, explained by the presence of these new modes.
关键词： dark-field scattering,plasmonic microcavities,nanoresonator mode,Au nanoparticles,hexagonal boron nitride
更新于2025-09-19 17:13:59
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Hexagonal Boron Nitride Phononic Crystal Waveguides
摘要： Hexagonal boron nitride (h-BN), one of the hallmark van der Waals (vdW) layered crystals with an ensemble of attractive physical properties, is playing increasingly important roles in exploring two-dimensional (2D) electronics, photonics, mechanics, and emerging quantum engineering. Here we report on the demonstration of h-BN phononic crystal waveguides with designed pass and stop bands in the radio frequency (RF) range, and controllable wave propagation and transmission, by harnessing arrays of coupled h-BN nanomechanical resonators with engineerable coupling strength. Experimental measurements validate that these phononic crystal waveguides confine and support 15 to 24 megahertz (MHz) wave propagation over hundreds of micrometers. Analogous to solid-state crystal lattices, phononic bandgaps and dispersive behaviors have been observed and systematically investigated in the h-BN phononic waveguides. Guiding and manipulating acoustic waves on such additively integratable h-BN platform may facilitate multiphysical coupling and information transduction, and open up new opportunities for coherent on-chip signal processing and communication via emerging h-BN photonic and phononic devices.
关键词： integrated phononics,phononic crystal waveguide,nanoelectromechanical systems (NEMS),acoustic wave,Hexagonal boron nitride (h-BN),radio frequency
更新于2025-09-19 17:13:59
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Plasmonically enabled two-dimensional material-based optoelectronic devices
摘要： Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides, black phosphorus and hexagonal boron nitride, have been intensively investigated as building blocks for optoelectronic devices in the past few years. Very recently, significant efforts have been devoted to the improvement of the optoelectronic performances of 2D materials, which are restricted by their intrinsically low light absorption due to the ultrathin thickness. Making use of the plasmonic effects of metal nanostructures as well as intrinsic plasmon excitation in graphene has been shown to be one of the promising strategies. In this minireview, recent progresses in 2D material-based optoelectronics enabled by the plasmonic effects are highlighted. A perspective on more possibilities in plasmon-assisted 2D material-based optoelectronic applications will also be provided.
关键词： Transition metal dichalcogenides,Plasmonic effects,Two-dimensional materials,Black phosphorus,Hexagonal boron nitride,Graphene,Optoelectronic devices
更新于2025-09-19 17:13:59