Realization of highly efficient hexagonal boron nitride neutron detectors

Maity, Avisek; Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.

doi:10.1063/1.4960522

Cited by 82 publications

(93 citation statements)

References 23 publications

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“…DFT calculations reveal that 10 B isotopic substitution in h-BN yields an upward shift of the phonon bands, which is most marked in the high energy optical modes, whereas the acoustic modes show very little sensitivity to isotopic substitution throughout the Brillouin zone. The uneven shift of the phonon bands has implications on the phonon anharmonic decay channels, which for 10 BN include a relevant decay path into two phonons that has a more prominent role than in 11 BN and natural composition BN because of its closer phonon energy match. The influence of this three-phonon anharmonic decay channel is key to explain the symmetric Raman line shape observed in the experiments on the 10 BN crystal.…”

Section: Discussionmentioning

confidence: 99%

“…7(b). The anharmonic contribution (dashed line) is particularly smaller for 10 BN on account of the more important role that three-phonon anharmonic decay processes play in the decay pathways compared to 11 BN and natural composition h-BN, as inferred from the FWHM analysis presented in Sec. IV C.…”

Section: Phonon Lifetimementioning

confidence: 99%

“…By taking into account all the relevant anharmonic effects as well as the effects of isotopic disorder, a comprehensive understanding of the E high 2g phonon in 10 BN, 11 BN, and natural h-BN is achieved. The model not only describes accurately the temperature dependence of the frequency and FWHM of the E high 2g mode, but also the line-shape alterations observed for different isotopical compositions and temperatures.…”

Section: Phonon Lifetimementioning

confidence: 99%

“…Another area in which isotopic enrichment plays a crucial role is the development of high-efficiency solid-state neutron detectors. The 10 B isotope has a very large capture cross-section for thermal neutrons, and detectors based on 10 B enriched (99.9%) h-BN have demonstrated the highest detection efficiency (51.4%) for solid-state detectors to date [11].…”

Section: Introductionmentioning

confidence: 99%

“…Here we present a Raman scattering study of the in-plane high-energy Raman active mode on isotopically enriched singlecrystal h-BN. Phonon frequency and lifetime are measured in the 80-600-K temperature range for 10 B-enriched, 11 B-enriched, and natural composition high quality crystals. Their temperature dependence is explained in the light of perturbation theory calculations of the phonon self-energy.…”

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Isotopic effects on phonon anharmonicity in layered van der Waals crystals: Isotopically pure hexagonal boron nitride

et al. 2018

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Hexagonal boron nitride (h-BN) is a layered crystal that is attracting a great deal of attention as a promising material for nanophotonic applications. The strong optical anisotropy of this crystal is key to exploit polaritonic modes for manipulating light-matter interactions in 2D materials. h-BN has also great potential for solid-state neutron detection and neutron imaging devices, given the exceptionally high thermal neutron capture cross section of the boron-10 isotope. A good knowledge of phonons in layered crystals is essential for harnessing long-lived phonon-polariton modes for nanophotonic applications and may prove valuable for developing solidstate 10 BN neutron detectors with improved device architectures and higher detection efficiencies. Although phonons in graphene and isoelectronic materials with a similar hexagonal layer structure have been studied, the effect of isotopic substitution on the phonons of such lamellar compounds has not been addressed yet. Here we present a Raman scattering study of the in-plane high-energy Raman active mode on isotopically enriched singlecrystal h-BN. Phonon frequency and lifetime are measured in the 80-600-K temperature range for 10 B-enriched, 11 B-enriched, and natural composition high quality crystals. Their temperature dependence is explained in the light of perturbation theory calculations of the phonon self-energy. The effects of crystal anisotropy, isotopic disorder, and anharmonic phonon-decay channels are investigated in detail. The isotopic-induced changes in the phonon density of states are shown to enhance three-phonon anharmonic decay channels in 10 B-enriched crystals, opening the possibility of isotope tuning of the anharmonic phonon decay processes.

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Section: Discussionmentioning

confidence: 99%

Section: Phonon Lifetimementioning

confidence: 99%

Section: Phonon Lifetimementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Isotopic effects on phonon anharmonicity in layered van der Waals crystals: Isotopically pure hexagonal boron nitride

et al. 2018

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A Review of Scalable Hexagonal Boron Nitride (h‐BN) Synthesis for Present and Future Applications

2022

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Ga-N, In-P, etc. Crystalline BN has typically been perceived as a purely synthetic material, [1] however geological findings provide evidence of structures similar to BN in rocks. [2] BN exhibits several stable crystal forms (see Figure 1A), for example, i) sp 3 bonded cubic and wurtzite forms; and ii) sp 2 bonded hexagonal and rhombohedral forms. [3] The cubic BN (c-BN) form has "zincblende" type crystal structure consisting of overlapping fcc cubic lattices consisting of B and N atoms. The c-BN crystal structure is analogous to that of diamond. The wurtzite form of BN (w-BN) is also sp 3 bonded like c-BN, however the wurtzite form consists of a hexagonal lattice with each ring sitting in a boat configuration. The w-BN crystal structure is analogous to that of the rare lonsdaleite, a carbon allotrope formed from graphite under immense heat and pressure. [4] Hexagonal boron nitride (h-BN) is a layered hexagonal crystal (a = 2.505 Å and c = 6.653 Å) belonging to the P6 3 /mmc space group with a structure analogous to that of graphite. [11,12] Alternating B and N atoms are sp 2 bonded in-plane to form a hexagonal lattice and several such layers are stacked to form the bulk h-BN crystal (Figure 1B). [11,12] The BN sp 2 bonding results in strong in-plane σ bonds leading to high in-plane thermal conductivity, chemical stability and strength, while empty π orbitals make h-BN electrically insulating (bandgap ≈ 5.955 eV). [3,13] The in-plane BN bonds exhibit ionic behavior due to the stronger electronegativity of the N atoms and results in layer to layer interactions between h-BN layers leading to AA′ stacking configuration, that is, each N atom in one layer is directly above the B atoms of the next layer (Figure 1B). [14] In addition to AA′ stacking, AB stacking (Bernal stacking) has also been occasionally observed in thin h-BN films even though this is a higher energy configuration. [15,5] Finally, BN is also observed in rhombohedral form (r-BN). Each layer of r-BN is the same crystal structure as that of h-BN (Figure 1A), however r-BN follows an ABC stacking configuration whereby boron still sits atop nitrogen atoms, except layers are offset such that the 1 and 3 atoms (N and N for example) sit atop the 4 and 6 atoms (B and B in this example) of the ring below. [3] Hexagonal boron nitride (h-BN) is a layered inorganic synthetic crystal exhibiting high temperature stability and high thermal conductivity. As a ceramic material it has been widely used for thermal management, heat shielding, lubrication, and as a filler material for structural composites. Recent scientific advances in isolating atomically thin monolayers from layered van der Waals crystals to study their unique properties has propelled research interest in mono/few layered h-BN as a wide bandgap insulating support for nanoscale electronics, tunnel barriers, communications, neutron detectors, optics, sensing, novel separations, quantum emission from defects, among others. Realizing these futuristic applications hinges on scalable cost-effective high-qual...

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Recent Development of Boron Nitride towards Electronic Applications

Izyumskaya

Demchenko

Das

et al. 2017

Adv Elect Materials

117

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Boron nitride occurs in several polymorphs, among which cubic and hexagonal varieties have been extensively studied over many years and have found numerous practical applications. Although various forms of BN have been used as lubricant and abrasive material for many years, the unique electronic properties of BN have not been yet utilized. Due to their wide optical bandgaps (the widest among nitride semiconductors), cubic and hexagonal polymorphs of BN are promising candidates for optoelectronic devices operating in the deep‐ultraviolet range and for high‐power electronic devices for switching and radio‐frequency applications. The layered structure of hexagonal BN allows preparation of ultrathin nanosheets with very smooth surfaces and low defect density, which are proved to be useful as supporting substrates and gate dielectric layers in graphene‐based structures. The first device demonstrations are very encouraging. In this contribution, the recent progress in properties, fabrication technologies, and emerging applications of BN as a wide‐gap semiconductor material is reviewed.

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Realization of highly efficient hexagonal boron nitride neutron detectors

Cited by 82 publications

References 23 publications

Isotopic effects on phonon anharmonicity in layered van der Waals crystals: Isotopically pure hexagonal boron nitride

Isotopic effects on phonon anharmonicity in layered van der Waals crystals: Isotopically pure hexagonal boron nitride

A Review of Scalable Hexagonal Boron Nitride (h‐BN) Synthesis for Present and Future Applications

Recent Development of Boron Nitride towards Electronic Applications

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