Tuning Coupling Behavior of Stacked Heterostructures Based on MoS2, WS2, and WSe2

Wang, Fang; Wang, Junyong; Guo, Shuang; Zhang, Jinzhong; Hu, Zhigao; Chu, Junhao

doi:10.1038/srep44712

Cited by 62 publications

(64 citation statements)

References 50 publications

(63 reference statements)

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“…E E E = E e e e x . As the valence band maximum and conduction band minimum at the K point are primarily composed of the d orbitals of the metal atoms 49,50 , electrons and holes will, to a good approximation, reside in the middle of their respective layers. We are therefore able to freeze their out-of-plane motion, which effectively makes solving Eq.…”

Section: Interlayer Excitonsmentioning

confidence: 99%

Interlayer excitons in van der Waals heterostructures: Binding energy, Stark shift, and field-induced dissociation

Kamban

Pedersen

2020

Sci Rep

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Photoexcited intralayer excitons in van der Waals heterostructures (vdWHs) with type-II band alignment have been observed to tunnel into interlayer excitons on ultrafast timescales. Such interlayer excitons have sufficiently long lifetimes that inducing dissociation with external in-plane electric fields becomes an attractive option of improving efficiency of photocurrent devices. In the present paper, we calculate interlayer exciton binding energies, Stark shifts, and dissociation rates for six different transition metal dichalcogenide (TMD) vdWHs using a numerical procedure based on exterior complex scaling (ECS). We utilize an analytical bilayer Keldysh potential describing the interaction between the electron-hole pair, and validate its accuracy by comparing to the full multilayer Poisson equation. Based on this model, we obtain an analytical weak-field expression for the exciton dissociation rate. The heterostructures analysed are MoS 2 /MoSe 2 , MoS 2 /WS 2 , MoS 2 /WSe 2 , MoSe 2 /WSe 2 , WS 2 /MoSe 2 , and WS 2 /WSe 2 in various dielectric environments. For weak electric fields, we find that WS 2 /WSe 2 supports the fastest dissociation rates among the six structures. We, furthermore, observe that exciton dissociation rates in vdWHs are significantly larger than in their monolayer counterparts.Naturally occurring layered materials held together by van-der-Waals-like forces have been intensely studied in recent years. Peeling graphite layer-by-layer and forming graphene 1 , a task thought impossible, turned researchers on to two-dimensional materials. Realizing that these layers may be used as building blocks of artificially layered materials, so-called van der Waals heterostructures, provides an endless array of possible combinations 2, 3 . The extraordinary electronic and optical properties of TMDs 4-11 have made them one of the most interesting classes of building blocks for vdWHs. Potential electro-optical applications of TMDs include photodetectors 12-14 , light-emitting diodes 15-17 , and solar cells 16,18,19 . It is well known that the optical properties of TMD monolayers are dominated by excitons 2,3,6,8,20 , as such two-dimensional excitons can have giant binding energies 6,8,[21][22][23] . Strongly bound excitons, in turn, make generation of photocurrents difficult, as excitons must first be dissociated into free electrons and holes. This is one of the challenges facing the use of monolayer TMDs in efficient photocurrent devices. A further complication is the fast recombination rates of excitons in these monolayers [24][25][26] . Without inducing dissociation in some way, excitons will typically recombine before they are dissociated. Applying an in-plane electric field to the excitons, however, enhances generation of photocurrents for two reasons: (i) the electric field counteracts recombination by pulling electrons and holes in opposite directions, and (ii) the electric field assists dissociation of excitons [27][28][29][30] .When two TMD monolayers are brought together with a type-II band align...

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Section: Interlayer Excitonsmentioning

confidence: 99%

Interlayer excitons in van der Waals heterostructures: Binding energy, Stark shift, and field-induced dissociation

Kamban

Pedersen

2020

Sci Rep

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“…26 The characteristics of van der Waals heterostructures are represented not only by the constituent monolayers but also by the interactions among the layers. Recently, various types of van der Waals heterostructures based on MoS 2 have exhibited several interesting electrical, optical, and magnetic properties, [27][28][29][30][31][32][33][34][35][36][37][38][39] but none has reported the mechanism of interface interactions (vdW heterostructures) between MoS 2 and Si 2 BN. We have chosen a 2D Si 2 BN (ref.…”

Section: Introductionmentioning

confidence: 99%

Impact of edge structures on interfacial interactions and efficient visible-light photocatalytic activity of metal–semiconductor hybrid 2D materials

Singh

Panda

Khossossi

et al. 2020

Catal. Sci. Technol.

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The present work systematically investigates the structural, electronic, and optical properties of a MoS 2 / Si 2 BN heterostructure based on first-principles calculations. Firstly, the charge transport and optoelectronic properties of MoS 2 and Si 2 BN heterostructures are computed in detail. We observed that the positions of the valence and conduction band edges of MoS 2 and Si 2 BN change with the Fermi level and form a Schottky contact heterostructure with superior optical absorption spectra. Furthermore, the charge density difference profile and Bader charge analysis indicated that the internal electric field would facilitate the separation of electron-hole (e − /h + ) pairs at the MoS 2 /Si 2 BN interface and restrain the carrier recombination.This work provides an insightful understanding about the physical mechanism for the better photocatalytic performance of this new material system and offers adequate instructions for fabricating superior Si 2 BNbased heterostructure photocatalysts.

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“…WS 2 /MoS 2 is known to form a so‐called type II heterostructure, as shown in Figure , which can effectively separate electron–hole pairs at the interface . Theoretical calculations showed that the valence band maximum was mainly occupied by the d orbital of W in the WS 2 layer, whereas the conduction band minimum primarily originated from the d orbital of Mo in the MoS 2 layer . As a result, the Fermi level of the WS 2 /MoS 2 heterostructure was shifted and appeared between the CBM of MoS 2 and the VBM of WS 2 .…”

Section: Resultsmentioning

confidence: 99%

Internal Fields in Multilayer WS₂/MoS₂ Heterostructures Epitaxially Grown on Sapphire Substrates

Kim

Tsai

et al. 2020

Physica Status Solidi (a)

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In conventional 3D heterostructures, a gradual potential gradient in constituent layers and an abrupt potential discontinuity at heterointerfaces can appear. Studies of the electrostatic potential in 2D heterostructures require careful characterizations and analyses because the 2D materials have distinct physical characteristics compared with their 3D counterparts. Herein, three kinds of samples are prepared using sulfurization of metal layers on single‐crystalline sapphire substrates: WS2, MoS2, and WS2/MoS2. The surface potential (VS) of the samples is measured using Kelvin probe force microscopy. The light‐induced VS change in the stand‐alone trilayer (3L‐) WS2 (−63 mV) is much more notable than that in the 3L‐WS2/3L‐MoS2 heterostructure (−12 mV). In contrast, the light‐induced VS change in the stand‐alone 3L‐MoS2 is positive and very large (≈200 mV). To explain these results, the potential and internal field distributions are proposed for both the stand‐alone (WS2 and MoS2) and heterostructure (WS2/MoS2) samples. The polarity and magnitude of the internal field depend on the electronic interaction and screening from neighboring 2D layers and underlying substrates. Relative peak shifts of the Raman spectra of the samples are obtained and discussed, with consideration of the internal field effects.

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Tuning Coupling Behavior of Stacked Heterostructures Based on MoS2, WS2, and WSe2

Cited by 62 publications

References 50 publications

Interlayer excitons in van der Waals heterostructures: Binding energy, Stark shift, and field-induced dissociation

Interlayer excitons in van der Waals heterostructures: Binding energy, Stark shift, and field-induced dissociation

Impact of edge structures on interfacial interactions and efficient visible-light photocatalytic activity of metal–semiconductor hybrid 2D materials

Internal Fields in Multilayer WS₂/MoS₂ Heterostructures Epitaxially Grown on Sapphire Substrates

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Tuning Coupling Behavior of Stacked Heterostructures Based on MoS2, WS2, and WSe2

Cited by 62 publications

References 50 publications

Interlayer excitons in van der Waals heterostructures: Binding energy, Stark shift, and field-induced dissociation

Interlayer excitons in van der Waals heterostructures: Binding energy, Stark shift, and field-induced dissociation

Impact of edge structures on interfacial interactions and efficient visible-light photocatalytic activity of metal–semiconductor hybrid 2D materials

Internal Fields in Multilayer WS2/MoS2 Heterostructures Epitaxially Grown on Sapphire Substrates

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Internal Fields in Multilayer WS₂/MoS₂ Heterostructures Epitaxially Grown on Sapphire Substrates