Bright Luminescence from Indirect and Strongly Bound Excitons in h-BN

Schue, Léonard; Sponza, Lorenzo; Plaud, Alexandre; Bensalah, H.; Watanabe, Kenji; Taniguchi, Takashi; Ducastelle, F.; Loiseau, Annick; Barjon, Julien

doi:10.1103/physrevlett.122.067401

Cited by 88 publications

(106 citation statements)

References 54 publications

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“…By comparing these two dispersion curves, it is found that excitonic effects tend to flatten the dispersion of the noninteracting electron–hole pair due to the change of exciton effective mass as a function of q . [ 26 ] As a result, the binding energy of the lowest‐energy indirect exciton

E_{b}^{i}

(0.16 eV) is different from that of the lowest‐energy direct exciton

E_{b}^{d}

(0.29 eV) shown in Figure 4d. In traditional indirect‐gap semiconductors [ 7a,8b,27 ] and 2D transition metal dichalcogenides, [ 10a–c,28 ] the EHL critical temperature T c has been predicted to be a fraction of the the lowest indirect exciton binding energy (

k_{B} T_{c} \approx 0.1 E_{b}^{i}, k_{B}

is the Boltzmann constant).…”

Section: Resultsmentioning

confidence: 92%

Excitons and Electron–Hole Liquid State in 2D γ‐Phase Group‐IV Monochalcogenides

Luo

Duan

Yakobson

et al. 2020

Adv Funct Materials

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Different dispersion near the electronic band edge of a semiconductor can have great influence on its transport, thermoelectric, and optical properties. Using first-principles calculations, it is demonstrated that a new phase of group-IV monochalcogenides (γ-MX, M = Ge, Sn; X = S, Se, or Te) can be stabilized in monolayer limit. γ-MXs are shown to possess a unique band dispersion-that is, camel's back like structure-in the top valence band. The band nesting effect near the camel's back region induces a large excitonic absorbance and significantly different exciton behaviors from other 2D materials. Importantly, the small effective mass and the indirect characteristics of lowest-energy exciton render it advantageous for the generation of electron-hole liquid state. After careful evaluation of the electron-hole dissociation temperature and the Mott critical density, it is predicted that a high-temperature exciton gas to electron-hole liquid phase transition can be achieved in these materials with a low excitation power density. The findings open up new opportunities for both the fundamental research on exciton physics and design of excitonic devices based on 2D materials with distinct band dispersion.

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E_{b}^{i}

(0.16 eV) is different from that of the lowest‐energy direct exciton

E_{b}^{d}

k_{B} T_{c} \approx 0.1 E_{b}^{i}, k_{B}

is the Boltzmann constant).…”

Section: Resultsmentioning

confidence: 92%

Excitons and Electron–Hole Liquid State in 2D γ‐Phase Group‐IV Monochalcogenides

Luo

Duan

Yakobson

et al. 2020

Adv Funct Materials

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“…The wavelength of the excitation-light source must be shorter than that corresponding to the band-gap energy of h-BN, that is, about 6 eV (206 nm), to excite the exciton PL band. 17,18 The optimal excitation wavelength must be sufficiently different from the wavelength of exciton luminescence at 215 nm to separate the PL component from the excitation by a far-UV interference filter. Designing the filter for a suitable transmission characteristic in this wavelength range is extremely difficult because the combinations of optical materials in the far-UV region (wavelength <230 nm) are limited.…”

Section: Resultsmentioning

confidence: 99%

Far-UV photoluminescence microscope for impurity domain in hexagonal-boron-nitride single crystals by high-pressure, high-temperature synthesis

Watanabe

Taniguchi

2019

npj 2D Mater Appl

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Hexagonal-boron-nitride single crystals grown by high-pressure, high-temperature (HPHT) synthesis are commonly used as the insulated substrate dielectric for two-dimensional (2D) atomic-layered materials like graphene and transition metal dichalcogenides (TMDs) to improve the flatness of the 2D materials atomically without disturbing the 2D electronic characteristics. However, HPHT single crystals often contain impure regions, which can hold subtle clues in regard to the 2D atomic-layered materials for new discoveries in the physics of 2D materials. To identify the position of the impure domains and to avoid them when the 2D devices are prepared, a far-ultraviolet photoluminescence microscope was developed. This microscope makes it possible to visualize the impure-growth region with ease in a no-contact and non-destructive manner. npj 2D Materials and Applications (2019) 3:40; https://doi.

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“…Additionally, hBN has been demonstrated as a promising material for ultraviolet light emission [8,9]. Despite the indirect character of its bandgap, hBN exhibits highly efficient radiative recombination through phononmediated transitions due to strong electron-phonon interactions [6,7,[10][11][12][13]. It has also recently been shown to host point defects that function as bright, room temperature single photon sources, which can enable technologies such as quantum cryptography and precision sensing [14,15].…”

Section: Introductionmentioning

confidence: 99%

Rotationally aligned hexagonal boron nitride on sapphire by high-temperature molecular beam epitaxy

Page

Casamento

Cho

et al. 2019

Phys. Rev. Materials

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Hexagonal boron nitride (hBN) has been grown on sapphire substrates by ultrahigh-temperature molecular beam epitaxy (MBE). A wide range of substrate temperatures and boron fluxes have been explored, revealing that high crystalline quality hBN layers are grown at high substrate temperatures, >1600℃ , and low boron fluxes, ∼1 × 10 %& Torr beam equivalent pressure. In situ reflection high-energy electron diffraction revealed the growth of hBN layers with 60° rotational symmetry and the [112 + 0] axis of hBN parallel to the [11 + 00] axis of the sapphire substrate. Unlike the rough, polycrystalline films previously reported, atomic force microscopy and transmission electron microscopy characterization of these films demonstrate smooth, layered, few-nanometer hBN films on a nitridated sapphire substrate. This demonstration of high-quality hBN growth by MBE is a step toward its integration into existing epitaxial growth platforms, applications, and technologies.

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Bright Luminescence from Indirect and Strongly Bound Excitons in h-BN

Cited by 88 publications

References 54 publications

Excitons and Electron–Hole Liquid State in 2D γ‐Phase Group‐IV Monochalcogenides

Excitons and Electron–Hole Liquid State in 2D γ‐Phase Group‐IV Monochalcogenides

Far-UV photoluminescence microscope for impurity domain in hexagonal-boron-nitride single crystals by high-pressure, high-temperature synthesis

Rotationally aligned hexagonal boron nitride on sapphire by high-temperature molecular beam epitaxy

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