Single Crystal Growth of Millimeter-Sized Monoisotopic Hexagonal Boron Nitride

Liu, Song; He, Rui; Xue, Lianjie; Li, Jiahan; Liu, Bin; Edgar, James H.

doi:10.1021/acs.chemmater.8b02589

Cited by 130 publications

(131 citation statements)

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“…The Hall devices were made from graphene encapsulated between two hBN crystals using the standard dry transfer technique and polypropylene carbonate (PPC) coated polydimethylsiloxane (PDMS) films as stamps. The hBN crystals used in this work were produced by the atmospheric pressure metal-flux method 31 . The metal contacts (5 nm Cr/ 50-70 nm Au) and the Hall bar mesa were fabricated as in the previous reports 32,33 .…”

Section: Device Fabricationmentioning

confidence: 99%

Micromagnetometry of two-dimensional ferromagnets

et al. 2019

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The recent advent of atomically-thin ferromagnetic crystals has allowed experimental studies of two-dimensional (2D) magnetism 1-9 that not only exhibits novel behavior due to the reduced dimensionality but also often serves as a starting point for understanding of the magnetic properties of bulk materials 10-17 . Here we employ ballistic Hall micromagnetometry 18,19 to study magnetization of individual 2D ferromagnets. Our devices are multilayer van der Waals (vdW) heterostructures 20 comprising of an atomically-thin ferromagnetic crystal placed on top of a Hall bar made from encapsulated 21 graphene. 2D ferromagnets can be replaced repeatedly, making the graphene-based Hall magnetometers reusable and expanding a range of their possible applications. The technique is applied for the quantitative analysis of magnetization and its behavior in atomically thin CrBr 3 . The compound is found to remain ferromagnetic down to a monolayer thickness and exhibit high out-of-plane anisotropy. We report how the critical temperature changes with the number of layers and how domain walls propagate through the ultimately thin ferromagnets. The temperature dependence of magnetization varies little with thickness, in agreement with the strongly layered nature of CrBr 3 . The observed behavior is markedly different from that given by the simple 2D Ising model normally expected to describe 2D easy-axis ferromagnetism. Due to the increasingly common usage of vdW assembly, the reported approach offers vast possibilities for investigation of 2D magnetism and related phenomena.Research on magnetism in strongly layered (vdW) materials is only a couple of years old but has already revealed a number of interesting phenomena including, for example, unexpected changes in magnetic properties as a function of the number of layers 2,17 and the possibility to control magnetism by electric and chemical doping [12][13][14][15][16]22 . Of particular interest are ferromagnetic semiconductors such as Cr 2 Ge 2 Te 6 and CrI 3 , in which a magnetization-dependent optical response and switching of a magnetization direction by applied electric field have been reported [12][13][14][15][16] . A number of different techniques have been employed to study magnetic properties of the above compounds at a few-layer thickness, including magneto-optical Kerr effect 1,2,15 , circular dichroism

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Section: Device Fabricationmentioning

confidence: 99%

Micromagnetometry of two-dimensional ferromagnets

et al. 2019

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“…Only recently have isotopically engineered h-BN crystals become available [23][24][25] . To date, investigations have focused on fundamental isotope effects related to Raman phonon lifetimes and the electronic bandgap 23,24 .…”

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Modulating the thermal conductivity in hexagonal boron nitride via controlled boron isotope concentration

et al. 2019

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Hexagonal boron nitride (h-BN) has been predicted to exhibit an in-plane thermal conductivity as high as~550 W m −1 K −1 at room temperature, making it a promising thermal management material. However, current experimental results (220-420 W m −1 K −1) have been well below the prediction. Here, we report on the modulation of h-BN thermal conductivity by controlling the B isotope concentration. For monoisotopic 10 B h-BN, an in-plane thermal conductivity as high as 585 W m −1 K −1 is measured at room temperature,~80% higher than that of h-BN with a disordered isotope concentration (52%:48% mixture of 10 B and 11 B). The temperature-dependent thermal conductivities of monoisotopic h-BN agree well with first principles calculations including only intrinsic phonon-phonon scattering. Our results illustrate the potential to achieve high thermal conductivity in h-BN and control its thermal conductivity, opening avenues for the wide application of h-BN as a next-generation thin-film material for thermal management, metamaterials and metadevices.

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“…For the purposes of these experiments, we employed isotopically pure hBN flakes (>99% h 10 BN) to minimize the intrinsic polariton losses. 12,49 These were grown as described in reference, 50 then subsequently exfoliated and transferred onto the appropriate substrate. Single crystals of VO2 were grown on quartz from vanadium pentoxide powder (V2O5) by physical vapor transport.…”

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confidence: 99%