Layer-dependent anisotropic electronic structure of freestanding quasi-two-dimensional Mo S 2

Handle URI:
http://hdl.handle.net/10754/600665
Title:
Layer-dependent anisotropic electronic structure of freestanding quasi-two-dimensional Mo S 2
Authors:
Hong, Jinhua; Li, Kun; Jin, Chuanhong; Zhang, Xixiang ( 0000-0002-3478-6414 ) ; Zhang, Ze; Yuan, Jun
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.
KAUST Department:
Advanced Nanofabrication and Thin Film Core Lab; Imaging and Characterization Core Lab; Physical Sciences and Engineering (PSE) Division
Citation:
Layer-dependent anisotropic electronic structure of freestanding quasi-two-dimensional Mo S 2 2016, 93 (7) Physical Review B
Publisher:
American Physical Society (APS)
Journal:
Physical Review B
Issue Date:
29-Feb-2016
DOI:
10.1103/PhysRevB.93.075440
Type:
Article
ISSN:
2469-9950; 2469-9969
Sponsors:
This work is financially supported by the National Basic Research Program of China (Grants No. 2014CB932500 and No. 2015CB921004) and National Science Foundation of China (GrantsNo. 51222202 and No. 51472215). The research reported in this paper was partially supported by King Abdullah University of Science and Technology (KAUST). J.Y. acknowledges Pao Yu-Kong International Foundation for a visiting Chair Professorship in ZJU and EPSRC and Royal Society for partial support. Dr. Ray Egerton and Dr. He Tian are kindly acknowledged for critical reading, comments, and revisions. J.H. and K.L. contributed equally to this work.
Additional Links:
http://link.aps.org/doi/10.1103/PhysRevB.93.075440
Appears in Collections:
Articles; Advanced Nanofabrication, Imaging and Characterization Core Lab; Physical Sciences and Engineering (PSE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorHong, Jinhuaen
dc.contributor.authorLi, Kunen
dc.contributor.authorJin, Chuanhongen
dc.contributor.authorZhang, Xixiangen
dc.contributor.authorZhang, Zeen
dc.contributor.authorYuan, Junen
dc.date.accessioned2016-03-06T13:13:40Zen
dc.date.available2016-03-06T13:13:40Zen
dc.date.issued2016-02-29en
dc.identifier.citationLayer-dependent anisotropic electronic structure of freestanding quasi-two-dimensional Mo S 2 2016, 93 (7) Physical Review Ben
dc.identifier.issn2469-9950en
dc.identifier.issn2469-9969en
dc.identifier.doi10.1103/PhysRevB.93.075440en
dc.identifier.urihttp://hdl.handle.net/10754/600665en
dc.description.abstractThe 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.en
dc.description.sponsorshipThis work is financially supported by the National Basic Research Program of China (Grants No. 2014CB932500 and No. 2015CB921004) and National Science Foundation of China (GrantsNo. 51222202 and No. 51472215). The research reported in this paper was partially supported by King Abdullah University of Science and Technology (KAUST). J.Y. acknowledges Pao Yu-Kong International Foundation for a visiting Chair Professorship in ZJU and EPSRC and Royal Society for partial support. Dr. Ray Egerton and Dr. He Tian are kindly acknowledged for critical reading, comments, and revisions. J.H. and K.L. contributed equally to this work.en
dc.language.isoenen
dc.publisherAmerican Physical Society (APS)en
dc.relation.urlhttp://link.aps.org/doi/10.1103/PhysRevB.93.075440en
dc.rightsArchived with thanks to Physical Review Ben
dc.titleLayer-dependent anisotropic electronic structure of freestanding quasi-two-dimensional Mo S 2en
dc.typeArticleen
dc.contributor.departmentAdvanced Nanofabrication and Thin Film Core Laben
dc.contributor.departmentImaging and Characterization Core Laben
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalPhysical Review Ben
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.institutionState Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, People's Republic of Chinaen
dc.contributor.institutionDepartment of Physics, University of York, Heslington, York, YO10 5DD, United Kingdomen
dc.contributor.affiliationKing Abdullah University of Science and Technology (KAUST)en
kaust.authorLi, Kunen
kaust.authorZhang, Xixiangen
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