Indium selenide: an insight into electronic band structure and surface excitations

Politano, Antonio; Campi, Davide; Cattelan, Mattia; Amara, Imen Ben; Jaziri, S.; Mazzotti, A.; Barinov, Alexey; Gürbulak, B.; Duman, S.; Agnoli, Stefano; Caputi, Lorenzo; Granozzi, G.; Cupolillo, A.

doi:10.1038/s41598-017-03186-x

Cited by 73 publications

(58 citation statements)

References 64 publications

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“…The inset shows the enlarged HRTEM image, in which the In and Se atoms can be directly identified. Figure S7c (Supporting Information) shows the hexagonal crystal structure with lattice constant, which is performed by the image analysis and concluded to be a = 0.405 nm along (100) direction, which is in agreement with the reported lattice constant of InSe …”

Section: Resultssupporting

confidence: 84%

Synthesis of Large‐Area InSe Monolayers by Chemical Vapor Deposition

Chang

Lin

et al. 2018

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Recently, 2D materials of indium selenide (InSe) layers have attracted much attention from the scientific community due to their high mobility transport and fascinating physical properties. To date, reports on the synthesis of high-quality and scalable InSe atomic films are limited. Here, a synthesis of InSe atomic layers by vapor phase selenization of In O in a chemical vapor deposition (CVD) system, resulting in large-area monolayer flakes or thin films, is reported. The atomic films are continuous and uniform over a large area of 1 × 1 cm , comprising of primarily InSe monolayers. Spectroscopic and microscopic measurements reveal the highly crystalline nature of the synthesized InSe monolayers. The ion-gel-gated field-effect transistors based on CVD InSe monolayers exhibit n-type channel behaviors, where the field effect electron mobility values can be up to ≈30 cm V s along with an on/off current ratio, of >10 at room temperature. In addition, the graphene can serve as a protection layer to prevent the oxidation between InSe and the ambient environment. Meanwhile, the synthesized InSe films can be transferred to arbitrary substrates, enabling the possibility of reassembly of various 2D materials into vertically stacked heterostructures, prompting research efforts to probe its characteristics and applications.

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Section: Resultssupporting

confidence: 84%

Synthesis of Large‐Area InSe Monolayers by Chemical Vapor Deposition

Chang

Lin

et al. 2018

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“…2d, in agreement with the existing literature. 5,6,26 The ARPES spectra of a bulk crystal show broad features with multiple states dispersed in the k z direction, perpendicular to the layers, since µARPES detects photoemitted electrons with a wide (here, undetermined) range of k z .…”

Section: Resultsmentioning

confidence: 99%

Indirect to Direct Gap Crossover in Two-Dimensional InSe Revealed by Angle-Resolved Photoemission Spectroscopy

et al. 2019

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Atomically thin films of III-VI post-transition metal chalcogenides (InSe and GaSe) form an interesting class of two-dimensional semiconductor that feature strong variations of their band gap as a function of the number of layers in the crystal 1-4 and, specifically for InSe, an earlier predicted crossover from a direct gap in the bulk 5,6 to a 1 arXiv:1901.06943v1 [cond-mat.mtrl-sci] 21 Jan 2019 weakly indirect band gap in monolayers and bilayers. 7-11 Here, we apply angle resolved photoemission spectroscopy with submicrometer spatial resolution (µARPES) to visualise the layer-dependent valence band structure of mechanically exfoliated crystals of InSe. We show that for 1 layer and 2 layer InSe the valence band maxima are away from the Γ-point, forming an indirect gap, with the conduction band edge known to be at the Γ-point. In contrast, for six or more layers the bandgap becomes direct, in good agreement with theoretical predictions. The high-quality monolayer and bilayer samples enables us to resolve, in the photoluminescence spectra, the band-edge exciton (A) from the exciton (B) involving holes in a pair of deeper valence bands, degenerate at Γ, with the splitting that agrees with both µARPES data and the results of DFT modelling. Due to the difference in symmetry between these two valence bands, light emitted by the A-exciton should be predominantly polarised perpendicular to the plane of the two-dimensional crystal, which we have verified for few-layer InSe crystals. KeywordsARPES, indium selenide, 2D materials, density functional theory, photoluminescence, spinorbit coupling Two-dimensional materials (2DM) and their van der Waals heterostructures, constructed by the mechanical assembly of individual 2D crystals, have a great potential for optoelectronic applications. 12 The fast growing family of 2DM 13 includes 2D insulators, 2D semiconductors with various band gaps, 2D metals and even 2D superconductors, with electronic and optical properties that often differ from their bulk allotropes. 14 In this family, post-transition metal monochalcogenides (PTMC), III-VI compounds such as GaSe and InSe, are emerging as important materials to study, due to their interesting layer-dependent optical properties and exceptionally high carrier mobility. [1][2][3][4]8,15,16 Both GaSe and InSe display a pronounced quantum confinement effect: an increase of the band gap upon decreasing the number of layers, L, which is stronger in InSe 3,11 than in GaSe 17 films as revealed recently by photolu-

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“…InSe was grown and characterized following experimental methods reported elsewhere. [58] Surface cleanliness for both GaSe and InSe was checked by survey XPS spectra, shown in Figures S3 and S4, Supporting Information, respectively. The LEED pattern of InSe single crystal is shown in the inset to Figure S4, Supporting Information.…”

Section: Methodsmentioning

confidence: 99%

Enhanced Electrocatalytic Activity in GaSe and InSe Nanosheets: The Role of Surface Oxides

D’Olimpio

Nappini

Vorokhta

et al. 2020

Adv Funct Materials

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Gallium selenide (GaSe) is a van der Waals semiconductor widely used for optoelectronic devices, whose performances are dictated by bulk properties, including band-gap energy. However, recent experimental observations that the exfoliation of GaSe into atomically thin layers enhances performances in electrochemistry and photocatalysis have opened new avenues for its applications in the fields of energy and catalysis. Here, it is demonstrated by surface-science experiments and density functional theory (DFT) that the oxidation of GaSe into Ga 2 O 3 , driven by Se vacancies and edge sites created in the exfoliation process, plays a pivotal role in catalytic processes. Specifically, both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are energetically unfavorable in pristine GaSe, due to energy barriers of 1.9 and 5.7-7.4 eV, respectively. On the contrary, energy barriers are reduced concurrently with surface oxidation. Especially, the Heyrovsky step (H ads + H + + e − → H 2) of HER becomes energetically favorable only in sub-stoichiometric Ga 2 O 2.97 (−0.3 eV/H +). It is also discovered that the same mechanisms occur for the case of the parental compound indium selenide (InSe), thus ensuring the validity of the model for the broad class of III-VI layered semiconductors.

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Indium selenide: an insight into electronic band structure and surface excitations

Cited by 73 publications

References 64 publications

Synthesis of Large‐Area InSe Monolayers by Chemical Vapor Deposition

Synthesis of Large‐Area InSe Monolayers by Chemical Vapor Deposition

Indirect to Direct Gap Crossover in Two-Dimensional InSe Revealed by Angle-Resolved Photoemission Spectroscopy

Enhanced Electrocatalytic Activity in GaSe and InSe Nanosheets: The Role of Surface Oxides

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