Monolayer Boron Nitride: Hyperspectral Imaging in the Deep Ultraviolet

Rousseau, Adrien; Ren, Lei; Durand, A.; Valvin, Pierre; Gil, Bernard; Watanabe, Kenji; Taniguchi, Takashi; Urbaszek, B.; Marie, X.; Robert, Cédric; Cassabois, Guillaume

doi:10.1021/acs.nanolett.1c02531

Cited by 29 publications

(30 citation statements)

References 35 publications

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“…[ 48–50 ] Recently, the emissions with higher peak energies (above 5.96 eV) were attributed to the carrier transition and recombination processes in monolayer hBN with a direct bandgap. [ 32,33,51 ] However, there is a large difference between the experimentally measured emission (6–6.15 eV) [ 32,33 ] and the theoretically predicted bandgap (8 eV) for a monolayer hBN. [ 34–36 ] To explain the 6.12 eV emission resonance from a monolayer hBN/HOPG heterostructure, we use first‐principles calculations based on density functional theory (DFT) and many‐body perturbation theory.…”

Section: Resultsmentioning

confidence: 99%

Scalable Synthesis of Monolayer Hexagonal Boron Nitride on Graphene with Giant Bandgap Renormalization

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as fundamental building blocks of such 2D devices. Specifically, vertically stacked hBN/ graphene (hBN/G) van der Waals (vdW) heterostructures have been successfully employed to produce emergent properties, such as quantum Hall effect, [8] Hofstadter butterfly spectrum, [9] and plasmon and phonon polaritons. [10] Complementary to the vertical hBN/G vdW heterostructure, the in-plane version forms a covalent hBN/G heterostructure with equally attractive properties, such as transitions between semiconducting, half-metallic, and metallic phases, spin polarization magnetism, and exotic electronic states, [11][12][13][14][15] or even the possibility to reconstruct electronic interfaces similar to those observed in oxide heterostructures. [16,17] The scope of these fascinating properties could be radically expanded by demonstrating epitaxially grown monolayer hBN on graphene with superior structural, electrical, and optical properties, as well as precise control of both the hBN/G out-ofplane and in-plane monolayer interfaces.Recently, intensive efforts have been devoted to the epitaxial growth of hBN on metals, [18][19][20] sapphire, [21] and graphene substrates [22] by using sputtering, [23] chemical vapor deposition (CVD), [24] metal-organic chemical vapor deposition (MOCVD), [25] and molecular beam epitaxy (MBE). [26] Due to the Monolayer hexagonal boron nitride (hBN) has been widely considered a fundamental building block for 2D heterostructures and devices. However, the controlled and scalable synthesis of hBN and its 2D heterostructures has remained a daunting challenge. Here, an hBN/graphene (hBN/G) interface-mediated growth process for the controlled synthesis of high-quality monolayer hBN is proposed and further demonstrated. It is discovered that the in-plane hBN/G interface can be precisely controlled, enabling the scalable epitaxy of unidirectional monolayer hBN on graphene, which exhibits a uniform moiré superlattice consistent with single-domain hBN, aligned to the underlying graphene lattice. Furthermore, it is identified that the deep-ultraviolet emission at 6.12 eV stems from the 1s-exciton state of monolayer hBN with a giant renormalized direct bandgap on graphene. This work provides a viable path for the controlled synthesis of ultraclean, wafer-scale, atomically ordered 2D quantum materials, as well as the fabrication of 2D quantum electronic and optoelectronic devices.

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Section: Resultsmentioning

confidence: 99%

Scalable Synthesis of Monolayer Hexagonal Boron Nitride on Graphene with Giant Bandgap Renormalization

et al. 2022

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“…In BN, theoretical calculations including the Coulomb correlation predict a direct bandgap at K for the monolayer and an indirect or marginally direct bandgap for stackings of two or more layers [124,[147][148][149]. Photoluminescence experiments [150][151][152] combined with reflectance measurements [150,151] have jointly confirmed using monolayers, deposited by molecular beam epitaxy on highly ordered pyrolytic graphite (HOPG) [150,151] and on suspended membranes [152], that it is a direct bandgap. The photoluminescence of the BN monolayer emits at 6.085 eV at low temperature, which was recently confirmed by the direct measurement of the density of states of a single monolayer of h-BN epitaxially grown on HOPG.…”

Section: Linear Optical Properties Of the Bn Monolayermentioning

confidence: 96%

Polytypes of sp2-Bonded Boron Nitride

et al. 2022

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The sp2-bonded layered compound boron nitride (BN) exists in more than a handful of different polytypes (i.e., different layer stacking sequences) with similar formation energies, which makes obtaining a pure monotype of single crystals extremely tricky. The co-existence of polytypes in a similar crystal leads to the formation of many interfaces and structural defects having a deleterious influence on the internal quantum efficiency of the light emission and on charge carrier mobility. However, despite this, lasing operation was reported at 215 nm, which has shifted interest in sp2- bonded BN from basic science laboratories to optoelectronic and electrical device applications. Here, we describe some of the known physical properties of a variety of BN polytypes and their performances for deep ultraviolet emission in the specific case of second harmonic generation of light.

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“…Even if the thickness variations result in different optical contrast in the hBN and bBN crystals shown in Figure , there is, at this stage, no way to identify the stacking order and to differentiate the crystalline phases from one crystal to another, whatever the operating mode of the optical microscope (bright-field, dark-field, polarization-contrast). The combination of SHG and PL mappings in a scanning confocal cryomicroscope operating in the deep-ultraviolet range , is necessary to unravel the existence of different BN polytypes in Figure .…”

Section: Resultsmentioning

confidence: 99%

Bernal Boron Nitride Crystals Identified by Deep-Ultraviolet Cryomicroscopy

et al. 2022

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The presence of metastable Bernal stacking boron nitride is verified by combining second harmonic generation (SHG) and photoluminescence (PL) spectroscopy. The scanning confocal cryomicroscope, operating in the deep-ultraviolet range, shows a one-to-one correlation between inversion symmetry breaking probed by SHG and the detection of an intense PL line at ∼6.035 eV, the specific signature of the noncentrosymmetric Bernal stacking. The coherent character of the Bernal phase in boron nitride crystals is demonstrated by two-photon excitation spectroscopy. Direct and indirect excitons are simultaneously detected in the emission spectrum; they are quasi-degenerate, in agreement with theoretical predictions for Bernal boron nitride. The transition from AA′ to AB stacking is characterized by an intense emission from stacking faults at the grain boundaries of hexagonal and Bernal boron nitride crystals.

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Monolayer Boron Nitride: Hyperspectral Imaging in the Deep Ultraviolet

Cited by 29 publications

References 35 publications

Scalable Synthesis of Monolayer Hexagonal Boron Nitride on Graphene with Giant Bandgap Renormalization

Scalable Synthesis of Monolayer Hexagonal Boron Nitride on Graphene with Giant Bandgap Renormalization

Polytypes of sp2-Bonded Boron Nitride

Bernal Boron Nitride Crystals Identified by Deep-Ultraviolet Cryomicroscopy

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