期刊
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS
卷 23, 期 1, 页码 -出版社
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/JSTQE.2016.2616839
关键词
Terahertz; metamaterials; optoelectronics; 2D materials; graphene; MoS2
资金
- National Science Foundation through Materials Research Science and Engineering Center [DMR 1121252]
- CAREER Award [ECCS 1351389]
- Div Of Electrical, Commun & Cyber Sys
- Directorate For Engineering [1351389] Funding Source: National Science Foundation
In this study, we extend recent investigations on graphene/metal hybrid tunable terahertz metamaterials to other two-dimensional (2-D) materials beyond graphene. For the first time, use of a nongraphitic 2-D material, molybdenum disulfide (MoS2), is reported as the active medium on a terahertz metamaterial device. For this purpose, high-quality few atomic layer MoS2 films with controlled numbers of layers were deposited on host substrates by means of pulsed laser deposition methods. The terahertz conductivity swing in those films is studied under optical excitation. Although no-appreciable conductivity modulation is observed in single-layer MoS2 samples, a substantial conductivity swing, i.e., 0 to similar to 0.6 mS, is seen in samples with similar to 60 atomic layers. Therefore, although exhibiting much smaller maximum terahertz conductivity than that in graphene, which is a consequence of much smaller carrier mobility, MoS2 can still be employed for terahertz applications by means of utilizing multilayer films. With this in mind, we design and demonstrate optically actuated terahertz metamaterials that simultaneously exhibit a large modulation depth (i.e., > 2x larger than the intrinsic modulation depth by a bare MoS2 film) and low insertion loss (i.e., <3 dB). The advantages of using a 2-D material with a bandgap, such as MoS2, rather than a gapless material, such as graphene, are: 1) a reduced insertion loss, which is owed to the possibility of achieving zero minimum conductivity, and 2) an enhanced modulation depth for a given maximum conductivity level, which is due to the possibility of placing the active material in a much closer proximity to the metallic frequency selective surface, thus allowing us to take full advantage of the near-field enhancement. These results indicate the promise of layered 2D materials beyond graphene for terahertz applications.
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