Isotopic purification allows to improve some intrinsic properties of hexagonal boron nitride (hBN), such as the phonon-polariton lifetime [1] and the thermal conductivity [2], however the impact of isotopic purification on the defects properties has been scarcely studied.
Here, we extend the class of isotopically-purified hBN crystals to 15N and report experimental results obtained by UV-photoluminescence spectroscopy on the intrinsic band-edge and the 4.1 eV emissions in isotopically purified hBN crystals. The isotopic bandgap shift has been estimated to -4.4 meV for 10B14N and +3.9 meV for 11B15N [3], whereas, we evaluate the ZPL shift to -1.8 meV for 10B14N and +1.1 meV for 11B15N. Moreover, the LO3(Γ) phonon mode is shifted by +4.5 meV for 10B14N and -3.9 meV for 11B15N compared to NatBN, while we estimate the splitting between the ZPL and the 1st phonon replica is shifted to +0.9 meV for 10B14N and -1.3 meV for 11B15N.
[1] Giles et al, Nature Mat. 17, 134. (2018).
[2] Cai et al, Phys. Rev. Lett. 125, 085902 (2020)
[3] Janzen et al, Advanced Materials, submitted (June 2023) arXiv:2306.13358
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