Large-grain MBE-grown GaSe on GaAs with a Mexican hat-like valence band dispersion

Chen, Luyang; Kim, Hokwon; Ovchinnikov, Dmitry; Kuc, Agnieszka; Heine, Thomas; Renault, O.; Kis, András

doi:10.1038/s41699-017-0047-x

Cited by 58 publications

(42 citation statements)

References 36 publications

(55 reference statements)

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“…Here, we find that the band inversion is (48 ± 12) meV, which compares well with a value of 80 meV obtained from recent DFT calculations 40 . The value is substantially smaller than 120 meV found for single-layer GaSe grown on graphene on silicon carbide 41 and than the value of (150 +/-10) meV that we determine for the similar dispersion at k z = 3.15Å −1 in Fig. 3(c).…”

Section: Potassium Deposition Of Gasecontrasting

confidence: 73%

“…4(b). The modified dispersion strongly resembles the "bow-shape" or"inverted sombrero" dispersion of single-layer GaSe, where the inversion of the VB is characterized by the energy difference between the VBM and the local energy minimum at Γ 13,22,[39][40][41] . Here, we find that the band inversion is (48 ± 12) meV, which compares well with a value of 80 meV obtained from recent DFT calculations 40 .…”

Section: Potassium Deposition Of Gasementioning

confidence: 99%

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Tunable electronic structure in gallium chalcogenide van der Waals compounds

et al. 2019

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Transition metal monochalcogenides comprise a class of two-dimensional materials with electronic band gaps that are highly sensitive to material thickness and chemical composition. Here, we explore the tunability of the electronic excitation spectrum in GaSe using angle-resolved photoemission spectroscopy. The electronic structure of the material is modified by in-situ potassium deposition as well as by forming GaSxSe1−x alloy compounds. We find that potassium-dosed samples exhibit a substantial change of the dispersion around the valence band maximum (VBM). The observed band dispersion resembles that of a single tetralayer and is consistent with a transition from the direct gap character of the bulk to the indirect gap character expected for monolayer GaSe. Upon alloying with sulfur, we observe a phase transition from AB to AA stacking. Alloying also results in a rigid energy shift of the VBM towards higher binding energies which correlates with a blue shift in the luminescence. The increase of the band gap upon sulfur alloying does not appear to change the dispersion or character of the VBM appreciably, implying that it is possible to engineer the gap of these materials while maintaining their salient electronic properties.

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Section: Potassium Deposition Of Gasecontrasting

confidence: 73%

Section: Potassium Deposition Of Gasementioning

confidence: 99%

Tunable electronic structure in gallium chalcogenide van der Waals compounds

et al. 2019

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“…This height is attributed to a GaSe flake with less than four layers. In fact, the AFM thickness of a GaSe monolayer generally lies between 0.8 and 1 nm, depending on the substrate/GaSe interaction and the AFM instrumentation), and the GaSe interlayer distance is ≈0.8 nm). Statistical TEM analysis (Figure f) indicates that the lateral size data of the flakes follows a log‐normal distribution peaking at ≈45 nm, with most of the measured values above 0.5 µm.…”

Section: Resultsmentioning

confidence: 99%

Solution‐Processed GaSe Nanoflake‐Based Films for Photoelectrochemical Water Splitting and Photoelectrochemical‐Type Photodetectors

Zappia

Bianca

Bellani

et al. 2020

Adv Funct Materials

104

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Gallium selenide (GaSe) is a layered compound, which has been exploited in nonlinear optical applications and photodetectors due to its anisotropic structure and pseudodirect optical gap. Theoretical studies predict that its 2D form is a potential photocatalyst for water splitting reactions. Herein, the photoelectrochemical (PEC) characterization of GaSe nanoflakes (single‐/few‐layer flakes), produced via liquid phase exfoliation, for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both acidic and alkaline media is reported. In 0.5 m H2SO4, the GaSe photoelectrodes display the best PEC performance, corresponding to a ratiometric power‐saved metric for HER (Φsaved,HER) of 0.09% and a ratiometric power‐saved metric for OER (Φsaved,OER) of 0.25%. When used as PEC‐type photodetectors, GaSe photoelectrodes show a responsivity of ≈0.16 A W−1 upon 455 nm illumination at a light intensity of 63.5 µW cm−2 and applied potential of −0.3 V versus reversible hydrogen electrode (RHE). Stability tests of GaSe photodetectors demonstrated a durable operation over tens of cathodic linear sweep voltammetry scans in 0.5 m H2SO4 for HER. In contrast, degradation of photoelectrodes occurred in both alkaline and anodic operation due to the highly oxidizing environment and O2‐induced (photo)oxidation effects. The results provide new insight into the PEC properties of GaSe nanoflakes for their exploitation in photoelectrocatalysis, PEC‐type photodetectors, and (bio)sensors.

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“…The in‐plane geometry of GaSe has a honeycomb‐like hexagonal structure (fourfold layer with the unique Se–Ga–Ga–Se sequence) ( Figure a). The atomically thin (2D layer) exhibits unique valance band dispersion which makes it an interesting material for optoelectronic applications . The investigation of SERS effect of GaSe on the CuPc probe molecule demonstrated a 14‐fold increase in the Raman signal compared to a SiO 2 substrate (Figure b) .…”

Section: D‐transition Metal Chalcogenides For Sensingmentioning

confidence: 99%

Section: D‐transition Metal Chalcogenides For Sensingmentioning

confidence: 99%

Recent Advances in 2D Inorganic Nanomaterials for SERS Sensing

et al. 2019

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Surface‐enhanced Raman spectroscopy is a powerful and sensitive analytical tool that has found application in chemical and biomolecule analysis and environmental monitoring. Since its discovery in the early 1970s, a variety of materials ranging from noble metals to nanostructured materials have been employed as surface enhanced Raman scattering (SERS) substrates. In recent years, 2D inorganic materials have found wide use in the development of SERS‐based chemical sensors owing to their unique thickness dependent physico‐chemical properties with enhanced chemical‐based charge‐transfer processes. Here, recent advances in the application of various 2D inorganic nanomaterials, including graphene, boron nitride, semiconducting metal oxides, and transition metal chalcogenides, in chemical detection via SERS are presented. The background of the SERS concept, including its basic theory and sensing mechanism, along with the salient features of different nanomaterials used as substrates in SERS, extending from monometallic nanoparticles to nanometal oxides, is comprehensively discussed. The importance of 2D inorganic nanomaterials in SERS enhancement, along with their application toward chemical detection, is explained in detail with suitable examples and illustrations. In conclusion, some guidelines are presented for the development of this promising field in the future.

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Large-grain MBE-grown GaSe on GaAs with a Mexican hat-like valence band dispersion

Cited by 58 publications

References 36 publications

Tunable electronic structure in gallium chalcogenide van der Waals compounds

Tunable electronic structure in gallium chalcogenide van der Waals compounds

Solution‐Processed GaSe Nanoflake‐Based Films for Photoelectrochemical Water Splitting and Photoelectrochemical‐Type Photodetectors

Recent Advances in 2D Inorganic Nanomaterials for SERS Sensing

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