Electronic structure of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">WSe</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>: A combined photoemission and inverse photoemission study

Traving, M.; Boehme, M.; Kipp, L.; Skibowski, M.; Starrost, F.; Krasovskii, E. E.; Perlov, A. Ya.; Schattke, W.

doi:10.1103/physrevb.55.10392

Cited by 82 publications

(48 citation statements)

References 15 publications

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“…The absence of interlayer interaction leads to strong modifications of the electronic and optical properties in all the monolayer systems. They are found to be direct-band-gap semiconductors with the VBM and CBM at the K point of the Brillouin zone, in contrast to the indirect band gaps of the bulk materials with the VBM at the point and the CBM at about 0.55 -K. 15,[25][26][27][28][29][30] An indirect-directband-gap crossover with decreasing sample thickness has been exemplified for MoS 2 experimentally. 12 While the CBM of a WS 2 monolayer has not been studied, a shift of the VBM from the to the K point due to the absence of interlayer interaction has been demonstrated by angle-resolved photoelectron spectroscopy.…”

Section: Resultsmentioning

confidence: 99%

Giant spin-orbit-induced spin splitting in two-dimensional transition-metal dichalcogenide semiconductors

2011

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Fully relativistic first-principles calculations based on density functional theory are performed to study the spin-orbit-induced spin splitting in monolayer systems of the transition-metal dichalcogenides MoS 2 , MoSe 2 , WS 2 , and WSe 2 . All these systems are identified as direct-band-gap semiconductors. Giant spin splittings of 148-456 meV result from missing inversion symmetry. Full out-of-plane spin polarization is due to the two-dimensional nature of the electron motion and the potential gradient asymmetry. By suppression of the Dyakonov-Perel spin relaxation, spin lifetimes are expected to be very long. Because of the giant spin splittings, the studied materials have great potential in spintronics applications.

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Section: Resultsmentioning

confidence: 99%

Giant spin-orbit-induced spin splitting in two-dimensional transition-metal dichalcogenide semiconductors

2011

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“…The electronic band structure of WSe 2 have been calculated by Sharma et al [13] within LDA using the linear muffin-tin orbital (LMTO) method in the atomic sphere approximation (ASA) and also using the full potential linearised augmented plane-wave (FP-LAPW) method. Coehoorn et al [14] have reported the electronic structure of WSe 2 by using augmented spherical wave (ASW) method, while for the same objectives Traving et al [15] have employed the relativistic LMTO and the expanded LAPW methods within the LDA scheme. The FP-LAPW (LDA) calculations to compute electronic band structure of WSe 2 were also performed by Finteis et al [16] and Straub et al [17].…”

Section: Introductionmentioning

confidence: 99%

“…Till date, no one has attempted the generalized gradient approximation (GGA) approach for WX 2 compounds which is supposed to be more accurate in determination of the electronic properties. On the experimental point of view, mainly photoemission studies have been reported by several workers [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Electronic structure of layer type tungsten metal dichalcogenides WX2 (X=S, Se) using Compton spectroscopy: Theory and experiment

Arora¹,

Sharma²,

Sharma

et al. 2009

Journal of Alloys and Compounds

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“…Our µ-ARPES spectra show that the valence band maximum is at K for 1ML WSe 2 and shifts to Γ for multilayer WSe 2 . Previous reports [35][36][37] [38][39] using traditional ARPES and inverse photoemission instruments have confirmed that the location of the VBM in bulk WSe 2 to be at Γ ; note that for bulk WSe 2 , ARPES measurements over a large enough photon energy range are required in order to take into account the k z dependence of the observed states. To fully quantify the VBM transition as a function of thickness, we used curvature analysis, [40] or the second-derivative method, to help delineate the electronic band structure, as shown in Fig.…”

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confidence: 99%

Layer-dependent electronic structure of an atomically heavy two-dimensional dichalcogenide

et al. 2015

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We report angle-resolved photoemission spectroscopic measurements of the evolution of the thickness-dependent electronic band structure of the heavy-atom two-dimensional layered, dichalcogenide, tungsten-diselenide (WSe 2 ). Our data, taken on mechanically exfoliated WSe 2 singlecrystals, provide direct evidence for shifting of the valence-band maximum from Γ (multilayer WSe 2 ), to K , (single-layer WSe 2 ). Further, our measurements also set a lower bound on the energy of the direct band-gap and provide direct measurement of the hole effective mass.Single layers of two-dimensional metal dichalcogenides (TMDCs) such as MoS 2 , have emerged as a new class of non-centrosymmetric direct-bandgap materials with potential photonic and spintronic applications.[ [4] . In addition, ML WSe 2 has been demonstrated to be the first TMDC material possessing ambipolar, i.e., both p-type and n-type conducting behavior, [4][12] thus making it possible to design additional electronic functionality, such as p-n junctions or complementary logic circuits.Despite these intriguing characteristics, measurements of ML WSe 2 have generally been limited to probing of optical and transport properties. [4][5] [6] In this paper, we report thickness-dependent measurements of the surface and electronic structure of exfoliated WSe 2, using low-energy electron microscopy (LEEM), diffraction (LEED), and micrometer-scale angle-resolved photoemission spectroscopy (µ-ARPES) of samples supported on a native-oxide terminated silicon substrate. Our experimental results provide direct evidence for a predicted valence-band maximum (VBM) symmetrypoint change, which leads to an indirect-to-direct bandgap transition. Because TMDCs have a large carrier effective mass and reduced screening in two dimensions, electron-hole interactions are much stronger than in conventional semiconductors. [13][14] [15] Our results allow us to obtain a direct measurement of the hole effective mass. Finally, our measurements allow us to directly infer a lower bound on the energy of the direct band gap. 2Our measurements were performed using the spectroscopic photoemission and low-energy electron microscope (SPE-LEEM) system at the National Synchrotron Light Source (NSLS) beamline U5UA.[16] [17] The spectrometer energy resolution of this instrument was set to 100 meV at 33 eV incident photon energy with a beam spot size of 1 μm in diameter. The momentum resolution is ~0.02 Å -1. Exfoliated WSe 2 samples were transferred to a native-oxide covered Si substrate; prior to measurements, these samples were annealed at 350 o C for ~12 hours under UHV conditions. The layer number of the sample is determined by Raman and photoluminescence spectroscopy.[18] [19] Additional experimental details can be found in the Supplemental Materials section.Sample quality and crystal orientation were examined using both LEEM and µ-LEED (Fig. 1). Diffraction patterns (at a primary electron energy of 48eV) of exfoliated WSe 2 flakes of 1-3ML and bulk are shown in Fig. 2a-d, respectively, and cl...

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Electronic structure ofWSe2: A combined photoemission and inverse photoemission study

Cited by 82 publications

References 15 publications

Giant spin-orbit-induced spin splitting in two-dimensional transition-metal dichalcogenide semiconductors

Giant spin-orbit-induced spin splitting in two-dimensional transition-metal dichalcogenide semiconductors

Electronic structure of layer type tungsten metal dichalcogenides WX2 (X=S, Se) using Compton spectroscopy: Theory and experiment

Layer-dependent electronic structure of an atomically heavy two-dimensional dichalcogenide

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