Electronic structure of exfoliated and epitaxial hexagonal boron nitride

Koch, Roland; Katoch, Jyoti; Moser, Simon; Schwarz, Daniel; Kawakami, Roland; Bostwick, Aaron; Rotenberg, Eli; Ulstrup, Søren

doi:10.1103/physrevmaterials.2.074006

Cited by 24 publications

(25 citation statements)

References 51 publications

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“…It consists in an exfoliated monoisotopic h 11 BN crystal transferred onto a graphene/SiC(0001) substrate. It should be pointed out that charging effects in photoemission from a bulk-like flake of an insulating material can be avoided by thinning the material in the exfoliation process and by placing it on a conductive support (38). Indeed, our recent photoemission study showed that it is possible to resolve the π-band of exfoliated hBN on epitaxial graphene (39).…”

Section: Resultsmentioning

confidence: 99%

Structural and electronic transitions in few layers of isotopically pure hexagonal boron nitride

et al. 2020

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Hexagonal boron nitride (hBN) is attracting tremendous interest as an essential component in van der Waals heterostructures due to its ability to provide weakly interacting interfaces and because of its large bandgap. While exfoliated flakes of hBN have been widely investigated using ultraviolet optoelectronics, detailed experimental measurements of the electronic band structure are lacking. In fact, hBN has been predicted to exist in various crystallographic stacking sequences, which can strongly affect its optical and electronic properties. Here, we determine the electronic band structure and stacking order of few-layers of isotopically-pure exfoliated h 11 BN flakes, using nanoscopic angle-resolved photoemission spectroscopy (nano-ARPES) combined with density functional theory (DFT) calculations. Additionally, the high crystalline quality and the thickness of the hBN flakes were determined by means of micro-Raman spectroscopy and atomic force microscopy (AFM), respectively. We demonstrate that hBN presents an AA' stacking in its bulk form and an A'B stacking for 3 and 4 monolayers. Our findings open perspectives in understanding and controlling the stacking orders in hBN, which could be of great interest for applications.

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Section: Resultsmentioning

confidence: 99%

Structural and electronic transitions in few layers of isotopically pure hexagonal boron nitride

et al. 2020

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“…2(d) are obtained by integrating the intensity within the blue and magenta boxes on bare and WS 2 covered hBN shown in panel (c). The expected π * resonance is observed in addition to a shoulder which appears after SL WS 2 transfer [14]. Using secondary electron contrast from the t 2g resonance on the TiO 2 L-edge we are able to distinguish bare and WS 2 covered TiO 2 in Fig.…”

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confidence: 88%

Imaging microscopic electronic contrasts at the interface of single-layer WS2 with oxide and boron nitride substrates

Ulstrup

Koch

Schwarz

et al. 2019

Applied Physics Letters

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The electronic properties of devices based on two-dimensional materials are significantly influenced by interactions with substrate and electrode materials. Here, we use photoemission electron microscopy to investigate the real-and momentum-space electronic structures of electrically contacted single-layer WS2 stacked on hBN, SiO2 and TiO2 substrates. Using work function and X-ray absorption imaging we single-out clean microscopic regions of each interface type and collect the valence band dispersion. We infer the alignments of the electronic band gaps and electron affinities from the measured valence band offsets of WS2 and the three substrate materials using a simple electron affinity rule and discuss the implications for vertical band structure engineering using mixed three-and two-dimensional materials.

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“…This enables us to correlate the real-space (x, y)-dependent features of our sample with the "local" E(k)-dispersion. 34,36,37 This method leads to our observation of the SL WS (g) Summary of band maxima at Γ and K for SL WS 2 (red ticks) and MoS 2 /WS 2 (green ticks). The different VBM between the two regions has been highlighted with thin dashed lines.…”

Section: Resultsmentioning

confidence: 99%

Visualizing band structure hybridization and superlattice effects in twisted MoS$_2$/WS$_2$ heterobilayers

Jones¹,

Muzzio²,

Pakdel³

et al. 2021

Preprint

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A mismatch of atomic registries between single-layer transition metal dichalcogenides (TMDs) in a two dimensional van der Waals heterostructure produces a moiré superlattice with a periodic potential, which can be fine-tuned by introducing a twist angle between the materials. This approach is promising both for controlling the interactions between the TMDs and for engineering their electronic band structures, yet direct observation of the changes to the electronic structure introduced with varying twist angle has so far been missing. Here, we probe heterobilayers comprised of singlelayer MoS 2 and WS 2 with twist angles of (2.0 ± 0.5)• , (13.0 ± 0.5)• , and (20.0 ± 0.5)• and investigate the differences in their electronic band structure using micro-focused angle-resolved photoemission spectroscopy. We find strong interlayer hybridization between MoS 2 and WS 2 electronic states at the Γ-point of the Brillouin zone, leading to a transition from a direct bandgap in the single-layer to an indirect gap in the heterostructure. Replicas of the hybridized states are observed at the centre of twist angle-dependent moiré mini Brillouin zones. We confirm that these replica features arise from the inherent moiré potential by comparing our experimental observations with density functional theory calculations of the superlattice dispersion. Our direct visualization of these features underscores the potential of using twisted heterobilayer semiconductors to engineer hybrid electronic states and superlattices that alter the electronic and optical properties of 2D heterostructures.

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Electronic structure of exfoliated and epitaxial hexagonal boron nitride

Cited by 24 publications

References 51 publications

Structural and electronic transitions in few layers of isotopically pure hexagonal boron nitride

Structural and electronic transitions in few layers of isotopically pure hexagonal boron nitride

Imaging microscopic electronic contrasts at the interface of single-layer WS2 with oxide and boron nitride substrates

Visualizing band structure hybridization and superlattice effects in twisted MoS$_2$/WS$_2$ heterobilayers

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