Hong, Jinhua, Li, Kun, Jin, Chuanhong et al. (3 more authors) (2016) Layer-dependent anisotropic electronic structure of freestanding quasi-two dimensional MoS2. Physical Review B. 075440. ISSN 2469-9969
Abstract
The anisotropy of the electronic transition is a well-known characteristic of low-dimensional transition-metal dichalcogenides, but their layer-thickness dependence has not been properly investigated experimentally until now. Yet, it not only determines the optical properties of these low-dimensional materials, but also holds the key in revealing the underlying character of the electronic states involved. Here we used both angle-resolved electron energy-loss spectroscopy and spectral analysis of angle-integrated spectra to study the evolution of the anisotropic electronic transition involving the low-energy valence electrons in the freestanding MoS2 layers with different thicknesses. We are able to demonstrate that the well-known direct gap at 1.8 eV is only excited by the in-plane polarized field while the out-of-plane polarized optical gap is 2.4 ± 0.2 eV in monolayer MoS2. This contrasts with the much smaller anisotropic response found for the indirect gap in the few-layer MoS2 systems. In addition, we determined that the joint density of states associated with the indirect gap transition in the multilayer systems and the corresponding indirect transition in the monolayer case has a characteristic three-dimensional-like character. We attribute this to the soft-edge behavior of the confining potential and it is an important factor when considering the dynamical screening of the electric field at the relevant excitation energies. Our result provides a logical explanation for the large sensitivity of the indirect transition to thickness variation compared with that for the direct transition, in terms of quantum confinement effect.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | ©2016, American Physical Society. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details |
Dates: |
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Institution: | The University of York |
Academic Units: | The University of York > Faculty of Sciences (York) > Physics (York) |
Funding Information: | Funder Grant number THE ROYAL SOCIETY Woflson Lab Refurbishment |
Depositing User: | Pure (York) |
Date Deposited: | 12 Oct 2016 13:21 |
Last Modified: | 16 Oct 2024 12:52 |
Published Version: | https://doi.org/10.1103/PhysRevB.93.075440 |
Status: | Published |
Refereed: | Yes |
Identification Number: | 10.1103/PhysRevB.93.075440 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:105938 |