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arXiv · 2412.17195

Growth of hexagonal BN crystals by traveling-solvent floating zone

Eli Zoghlin·Juliette Plo·Gaihua Ye·Cynthia Nnokwe·Reina Gomez·Austin Ferrenti·Satya Kushwaha·Rui He·Stephen D. Wilson·Pierre Valvin·Bernard Gil·Guillaume Cassabois·James H. Edgar·Tyrel M. McQueen
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Abstract

Large, high-purity single-crystals of hexagonal BN (h-BN) are essential for exploiting its many desirable and interesting properties. Here, we demonstrate via X-ray tomography, X-ray diffraction and scanning electron microscopy that h-BN crystals can be grown by traveling-solvent floating-zone (TSFZ). The diameters of grown boules range from 3 - 5 mm with lengths from 2 - 10 mm. Tomography indicates variable grain sizes within the boules, with the largest having areas of $\approx$ 1 mm $\times$ 2 mm and thickness $\approx$ 0.5 mm. Although the boules contain macroscale flux inclusions, the h-BN lattice itself is of high quality for samples grown under optimized conditions. The currently optimized growth procedure employs an Fe flux, moderate N$_2$ pressure ($P_{N2} \approx$ 6 bar), and a growth rate of 0.1 mm/h. Raman spectroscopy for an optimized sample gives an average linewidth of 7.7(2) cm$^{-1}$ for the E$_{\mathrm{2g}}$ intralayer mode at 1365.46(4) cm$^{-1}$ and 1.0(1) cm$^{-1}$ for the E$_{\mathrm{2g}}$ interlayer shear mode at 51.78(9) cm$^{-1}$. The corresponding photoluminescence spectrum shows sharp phonon-assisted free exciton peaks and minimal signal in the energy range corresponding to carbon-related defects ($E$ = 3.9 4.1 eV). Our work demonstrates the viability of growing h-BN by the TSFZ technique, thereby opening a new route towards larger, high-quality crystals and advancing the state of h-BN related research.

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Eli Zoghlin, Juliette Plo, Gaihua Ye, Cynthia Nnokwe, Reina Gomez, Austin Ferrenti, Satya Kushwaha, Rui He, Stephen D. Wilson, Pierre Valvin, Bernard Gil, Guillaume Cassabois, James H. Edgar, Tyrel M. McQueen. 2024-12-23. Growth of hexagonal BN crystals by traveling-solvent floating zone. https://doi.org/10.1016/j.jcrysgro.2025.128164

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