Broadband optical properties of large-area monolayer CVD molybdenum disulfide
Name
PhysRevB.90.195434.pdf
Size
1.85 MB
Format
Adobe PDF
Checksum (MD5)
2169b32648b215d13ae7199ec64a310a
Author(s)
Li, Wei
Birdwell, A. Glen
Amani, Matin
Burke, Robert A.
Ling, Xi
Lee, Yi-Hsien
Liang, Xuelei
Peng, Lianmao
Richter, Curt A.
Kong, Jing
Date Issued
November 2014
Journal
Physical Review B
Publisher
American Physical Society
Citation
Li, Wei et al. “Broadband Optical Properties of Large-Area Monolayer CVD Molybdenum Disulfide.” Physical Review B 90.19 (2014): n. pag. © 2014 American Physical Society
Version
Final published version
Abstract
Recently emerging large-area single-layer MoS[subscript 2] grown by chemical vapor deposition has triggered great interest due to its exciting potential for applications in advanced electronic and optoelectronic devices. Unlike gapless graphene, MoS[subscript 2] has an intrinsic band gap in the visible which crosses over from an indirect to a direct gap when reduced to a single atomic layer. In this paper, we report a comprehensive study of fundamental optical properties of MoS[subscript 2] revealed by optical spectroscopy of Raman, photoluminescence, and vacuum ultraviolet spectroscopic ellipsometry. A band gap of 1.42 eV is determined by the absorption threshold of bulk MoS[subscript 2] that shifts to 1.83 eV in monolayer MoS[subscript 2]. We extracted the high precision dielectric function up to 9.0 eV, which leads to the identification of many unique interband transitions at high symmetry points in the MoS[subscript 2] momentum space. The positions of the so-called A and B excitons in single layers are found to shift upwards in energy compared with those of the bulk form and have smaller separation because of the decreased interactions between the layers. A very strong optical critical point predicted to correspond to a quasiparticle gap is observed at 2.86 eV, which is attributed to optical transitions along the parallel bands between the M and Γ points in the reduced Brillouin zone. The absence of the bulk MoS[subscript 2] spin-orbit interaction peak at ~3.0 eV in monolayer MoS[subscript 2] is, as predicted, the consequence of the coalescence of nearby excitons. A higher energy optical transition at 3.98 eV, commonly occurring in bulk semiconductors, is associated with a combination of several critical points. Additionally, extending into the vacuum ultraviolet energy spectrum are a series of newly observed oscillations representing optical transitions from valence bands to higher conduction bands of the monolayer MoS[subscript 2] complex band structure. These optical transitions herein reported enhance our understanding of monolayer MoS[subscript 2] as well as of two-dimensional systems in general and thus provide informative guidelines for MoS[subscript 2] optical device designs and theoretical considerations.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Research Laboratory of Electronics
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Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1103/PhysRevB.90.195434
