Optical spectroscopy of boron nitride heterostructures

Abstract : Hexagonal boron nitride (h-BN) is a wide bandgap (~ 6 eV) semiconductor with a very high thermal and chemical stability often used in devices operating under extreme conditions. The indirect nature of the bandgap in h-BN is investigated by both theoretical calculations and experiments. An indirect excion and phonon-assisted reombinations in h-BN are observed in photoluminescene spectroscopy.This thesis focus on the optical properties of bulk and epilayers of h-BN. We investigated samples from different sources grown different methods in order to confirm the intrinsic optical properties of h-BN. We report the impact of the phonon symmetry on the optical response of h-BN by performing polarization-resolved PL measurements. From them, we will measure the contribution of all the phonon-assisted recombination which was not detected before this thesis. We follow by addressing the origin of the fine structure of the phonon-assisted recombinations in h-BN. It arises from overtones involving up to six low-energy interlayer shear phonon modes, with a characteristic energy of about 6.8 meV.Raman and photoluminescence measurements are recorded to quantify the influence of isotope effects on optical properties of h-BN as well as the modifications of van de Waals interactions linked to utilization of 10B and 11B or natural Boron for the growth of bulk h-BN crystals.Finally, we study h-BN thin epilayers grown by Molecular Beam Epitaxy at Nottingham University, atomic force microscopy (AFM) images and photoluminescence features are combined to confirm the first observation of phonon-assisted recombination in high quality thin h-BN epilayers grown on c-plane sapphire and Highly Ordered Pyrolitic Graphite. This demontrates that large scale growth of h-BN by epitaxy is getting a technologically required maturity.
Keywords : Optics Boron nitride Uv
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Phuong Vuong. Optical spectroscopy of boron nitride heterostructures. Physics [physics]. Université Montpellier, 2018. English. ⟨NNT : 2018MONTS075⟩. ⟨tel-02152566⟩

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