Electronic Structure, Surface Doping, and Optical Response in Epitaxial WSe<sub>2</sub> Thin Films

Zhang, Yi; Ugeda, Miguel M.; Choi, Jin; Shi, Su‐Fei; Bradley, Aaron J.; Martín-Recio, Ana; Ryu, Hyejin; Kim, Jonghwan; Tang, Shujie; Kim, Yeongkwan; Zhou, Bo; Hwang, Choongyu; Chen, Yulin; Wang, Feng; Crommie, Michael F.; Hussain, Zahid; Shen, Z.‐X.; Mo, S.-K.

doi:10.1021/acs.nanolett.6b00059

Cited by 160 publications

(190 citation statements)

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“…Only the SARPES spectra measured with 55eV are shown in this paper. [20,21]. Second, there exists a clear splitting in the valence band at the K-point.…”

Section: Methodsmentioning

confidence: 99%

“…The details of the growth condition and the sample characterization were the same as described in Ref. [20] and [21]. The samples were then capped with amorphous Se with thickness ∼ 100Å for the transfer to SARPES system.…”

Section: Methodsmentioning

confidence: 99%

“…The size of these splitting is much larger in WSe 2 ∼ 470 meV compared to that in MoSe 2 ∼ 180 meV, due to the stronger SOC induced by heavier element W. Third, the band maximum at the Γ-point locates at the higher binding energy than that at the K-point, leaving the valence band maximum at the K-point. Combining this with the conduction band minimum being at the K-point in the unoccupied state [20,21,26], the 1ML MoSe 2 and WSe 2 are direct band gap semiconductors.…”

Section: Methodsmentioning

confidence: 99%

“…There have been a number of ARPES studies either on bulk MX 2 samples [26,27,28] or a few layer samples [20,21,29,30] prepared by various methods such as exfoliation, chemical vapor deposition (CVD), and epitaxial growth. They all observe sizable splitting in VB at the K-point, with size ∼ 170 meV for MoS 2 and MoSe 2 and ∼ 450 meV for WS 2 and WSe 2 as W induces larger SOC.…”

Section: Introductionmentioning

confidence: 99%

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Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films

Mo¹,

Hwang²,

Zhang³

et al. 2016

J. Phys.: Condens. Matter

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Abstract. MoSe 2 and WSe 2 with a few layer thickness possess non-trivial spin texture with sizable spin splitting due to the inversion symmetry breaking embedded in the crystal structure and strong spin-orbit coupling. We report spinresolved photoemission study of the MoSe 2 and WSe 2 thin film samples epitaxially grown on bilayer graphene substrate. We found spin polarization only in singleand tri-layer samples, but not in bi-layer sample, mostly along the out-of-plane direction of the sample surface. The measured spin polarization is found to be strongly dependent on the light polarization as well as the measurement geometry, which reveals intricate coupling between spin and orbital degrees of freedom in this material class.

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“…Only the SARPES spectra measured with 55eV are shown in this paper. [20,21]. Second, there exists a clear splitting in the valence band at the K-point.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films

Mo¹,

Hwang²,

Zhang³

et al. 2016

J. Phys.: Condens. Matter

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“…16 ) and single-layer WSe 2 (ref. 17 ) grown on doped multilayer graphene, and single-layer MoS 2 grown on a metal surface 18 . On such conductive substrates, the interfacial interactions and screening are known to strongly influence the electronic properties of the single-layer TMD 9 .…”

mentioning

confidence: 99%

Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures

et al. 2018

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In two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs), new electronic phenomena such as tunable bandgaps 1-3 and strongly bound excitons and trions emerge from strong many-body effects [4][5][6] , beyond the spin and valley degrees of freedom induced by spin-orbit coupling and by lattice symmetry 7 . Combining single-layer TMDs with other 2D materials in van der Waals heterostructures offers an intriguing means of controlling the electronic properties through these many-body effects, by means of engineered interlayer interactions [8][9][10] . Here, we use micro-focused angle-resolved photoemission spectroscopy (microARPES) and in situ surface doping to manipulate the electronic structure of single-layer WS 2 on hexagonal boron nitride (WS 2 /h-BN). Upon electron doping, we observe an unexpected giant renormalization of the spin-orbit splitting of the single-layer WS 2 valence band, from 430 meV to 660 meV, together with a bandgap reduction of at least 325 meV, attributed to the formation of trionic quasiparticles. These findings suggest that the electronic, spintronic and excitonic properties are widely tunable in 2D TMD/h-BN heterostructures, as these are intimately linked to the quasiparticle dynamics of the materials [11][12][13] . Coulomb interactions in 2D materials are several times stronger than in their 3D counterparts. In 2D TMDs, this is most directly evidenced by the presence of excitons with binding energies an order of magnitude higher than in the bulk 4 . Although the excitons in these 2D materials have been widely studied by optical techniques 13 , the impact of strong electron-electron interactions on the quasiparticle band structure remains unclear. Theory predicts that many-body effects will influence the spin-orbit splitting around the valenceband maximum (VBM) and conduction-band minimum (CBM) 14 . Although these should be observable by ARPES, a direct probe of many-body effects 15 , measurements so far have mainly focused on the layer-dependence of the single-particle spectrum and the direct bandgap transition in 2D TMD systems, including epitaxial single- . Unfortunately, the lateral size of mechanically assembled heterostructures is usually of the order of 10 μ m, much smaller than the beam spot of typical ARPES setups (≳ 100 μ m). Furthermore, sample charging on insulating bulk h-BN substrates would complicate ARPES experiments.We overcome these challenges as follows. We realize a high-quality 2D semiconductor-insulator interface by mechanically transferring a relatively large (~100 μ m) single-layer WS 2 crystal onto a thin flake of h-BN that has itself been transferred onto a degenerately doped TiO 2 substrate, as depicted in Fig. 1a. Sample charging is avoided because there is electrical contact from the continuous single-layer WS 2 flake to both the h-BN and the conductive TiO 2 . Figure 1b is an optical microscope image of the sample, including a flake of h-BN, approximately 100 μ m wide, surrounded by several transferred flakes of single-layer WS 2 on the Ti...

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Biomimetic Artificial Tetrachromatic Photoreceptors Based on Fully Light‐Controlled 2D Transistors

Liu

Yuan

et al. 2023

Adv Funct Materials

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Artificial photoreceptors offer a promising solution for developing biomimetic vision systems that incorporate in‐sensor processing, which can greatly reduce power consumption and operation latency compared to traditional machine vision systems. This work presents a tetrachromatic optical synaptic device based on a 2D tungsten diselenide optoelectronic p‐type transistor with a unique UV light‐activated surface electron doping layer. Fully light‐controlled bidirectional synaptic excitation and inhibition are demonstrated with visible and UV light stimuli, respectively, with a reasonable power density of <10 mW cm−2 that matches the imaging condition of a biological vision. The weight updates of up to 64 states, high dynamic range, and low nonlinearity are demonstrated for long‐term potentiation and depression behaviors. This artificial tetrachromatic photoreceptor can mimic the alert and foraging behaviors of a reindeer with low power consumption and enhanced signal contrast. Furthermore, it can be employed as an intelligent collision detection solution with in‐sensor processing capabilities. This bioinspired tetrachromatic photoreceptor offers a low‐cost, energy‐efficient, and low‐latency solution for future artificial machines.

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Electronic Structure, Surface Doping, and Optical Response in Epitaxial WSe₂ Thin Films

Cited by 160 publications

References 64 publications

Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films

Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films

Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures

Biomimetic Artificial Tetrachromatic Photoreceptors Based on Fully Light‐Controlled 2D Transistors

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Electronic Structure, Surface Doping, and Optical Response in Epitaxial WSe2 Thin Films

Cited by 160 publications

References 64 publications

Spin-resolved photoemission study of epitaxially grown MoSe2and WSe2thin films

Spin-resolved photoemission study of epitaxially grown MoSe2and WSe2thin films

Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures

Biomimetic Artificial Tetrachromatic Photoreceptors Based on Fully Light‐Controlled 2D Transistors

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Product

Resources

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Electronic Structure, Surface Doping, and Optical Response in Epitaxial WSe₂ Thin Films

Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films

Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films