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Nanomaterials
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Nanomaterials for Terahertz Technology Applications
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Nanomaterials for Terahertz Technology Applications

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanoelectronics, Nanosensors and Devices".

Deadline for manuscript submissions: 30 June 2024 | Viewed by 6382

Special Issue Editors

Prof. Dr. Xunjun He

E-Mail Website
Guest Editor
Key Laboratory of Engineering Dielectric and Applications, School of Electrical and Electronic Engineering, Harbin University of Science and Technology, Harbin 150080, China
Interests: terahertz devices; terahertz metamaterials/metasurfaces; terahertz technology applications
Dr. Ying Zhang

E-Mail Website
Guest Editor
School of Sciences, Harbin University of Science and Technology, Harbin 150080, China
Interests: terahertz devices; terahertz metamaterials; terahertz wave excitation and detection techniques

Special Issue Information

Dear Colleagues,

Over the past several decades, terahertz technology has achieved considerable progress with the development of nanoscience and nanotechnology. In particular, nanomaterials for terahertz technology applications are also attracting extensive attention in various areas, such as national defense, military, chemistry, medicine, pharmaceutical, communications, and many other fields. In order to utilize terahertz technology flexibly and efficiently, it is currently important and necessary to develop novel terahertz devices and systems via the versatility of nanomaterials and nanostructures.

This Special Issue of Nanomaterials aims to explore nanomaterials for terahertz technology applications. The format of welcomed articles includes full papers, communications, and reviews. Potential topics include, but are not limited to, nanomaterials and nanostructures for terahertz technology applications (terahertz devices; terahertz generation and propagation; terahertz imaging; terahertz sources, detectors and receivers; terahertz sensing and diagnostics; terahertz nanoelectronics; terahertz spectroscopy; terahertz metamaterials/metasurfaces; etc.).

Prof. Dr. Xunjun He
Dr. Ying Zhang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • terahertz
  • metamaterials
  • metasurfaces
  • sensing
  • imaging
  • detecting
  • devices

Published Papers (7 papers)

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Research

11 pages, 2098 KiB  
Article
Enhancing Multi-Spectral Fingerprint Sensing for Trace Explosive Molecules with All-Silicon Metasurfaces
by Jie Lin, Ying Xue, Weijin Wang, Mingjun Sun, Shengnan Shi, Shan Zhang and Yanpeng Shi
Nanomaterials 2024, 14(9), 738; https://doi.org/10.3390/nano14090738 - 23 Apr 2024
Viewed by 392
Abstract
Spectroscopy is a powerful tool to identify the specific fingerprints of analytes in a label-free way. However, conventional sensing methods face unavoidable barriers in analyzing trace-amount target molecules due to the difficulties of enhancing the broadband molecular absorption. Here, we propose a sensing [...] Read more.
Spectroscopy is a powerful tool to identify the specific fingerprints of analytes in a label-free way. However, conventional sensing methods face unavoidable barriers in analyzing trace-amount target molecules due to the difficulties of enhancing the broadband molecular absorption. Here, we propose a sensing scheme to achieve strong fingerprint absorption based on the angular-scanning strategy on an all-silicon metasurface. By integrating the mid-infrared and terahertz sensing units into a single metasurface, the sensor can efficiently identify 2,4-DNT with high sensitivity. The results reveal that the fingerprint peak in the enhanced fingerprint spectrum is formed by the linked envelope. It exhibits a significant enhancement factor exceeding 64-fold in the terahertz region and more than 55-fold in the mid-infrared region. Particularly, the corresponding identification limit of 2,4-DNT is 1.32 µg cm−2, respectively. Our study will provide a novel research idea in identifying trace-amount explosives and advance practical applications of absorption spectroscopy enhancement identification in civil and military security industries. Full article
(This article belongs to the Special Issue Nanomaterials for Terahertz Technology Applications)
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10 pages, 4507 KiB  
Article
Graphene-Tuned, Tightly Coupled Hybrid Plasmonic Meta-Atoms
by Kai Chen, Ke Li, Yiming Wang, Zihao Zhang, Yanpeng Shi, Aimin Song and Yifei Zhang
Nanomaterials 2024, 14(8), 713; https://doi.org/10.3390/nano14080713 - 19 Apr 2024
Viewed by 386
Abstract
Tightly coupled meta-atoms (TCMAs) are densely packed metamaterials with unnatural refractive indexes. Actively modulated TCMAs with tunable optical properties have found many applications in beam shaping, holography, and enhanced light–matter interactions. Typically, TCMAs are studied in the classic Bloch theory. Here, tightly coupled [...] Read more.
Tightly coupled meta-atoms (TCMAs) are densely packed metamaterials with unnatural refractive indexes. Actively modulated TCMAs with tunable optical properties have found many applications in beam shaping, holography, and enhanced light–matter interactions. Typically, TCMAs are studied in the classic Bloch theory. Here, tightly coupled H-shaped meta-atoms are proposed with an ultra-high permittivity of ~6000, and their active modulation with graphene is designed by using the tightly coupled dipole array (TCDA) theory. The H-shaped meta-atoms are used as dipole arms, and the graphene strips function as the dipole loads. By tuning the chemical potential of graphene, the resonant amplitude, frequency, and permittivity are dynamically modulated. The simulations indicate that the real and imaginary parts of permittivity change from 6854 to 1522 and from 7356 to 2870, respectively. The experimental validation demonstrates a modulation depth of 11.6% in the resonant frequency, i.e., from 219.4 to 195 GHz, and a substantial 52.5% modulation depth in transmittance under a bias voltage of less than 1.5 V. Full article
(This article belongs to the Special Issue Nanomaterials for Terahertz Technology Applications)
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16 pages, 10393 KiB  
Article
Migration-Enhanced Epitaxial Growth of InAs/GaAs Short-Period Superlattices for THz Generation
by Ruolin Chen, Xuefei Li, Hao Du, Jianfeng Yan, Chongtao Kong, Guipeng Liu, Guangjun Lu, Xin Zhang, Shuxiang Song, Xinhui Zhang and Linsheng Liu
Nanomaterials 2024, 14(3), 294; https://doi.org/10.3390/nano14030294 - 31 Jan 2024
Viewed by 706
Abstract
The low-temperature-grown InGaAs (LT-InGaAs) photoconductive antenna has received great attention for the development of highly compact and integrated cheap THz sources. However, the performance of the LT-InGaAs photoconductive antenna is limited by its low resistivity and mobility. The generated radiated power is much [...] Read more.
The low-temperature-grown InGaAs (LT-InGaAs) photoconductive antenna has received great attention for the development of highly compact and integrated cheap THz sources. However, the performance of the LT-InGaAs photoconductive antenna is limited by its low resistivity and mobility. The generated radiated power is much weaker compared to the low-temperature-grown GaAs-based photoconductive antennas. This is mainly caused by the low abundance of excess As in LT-InGaAs with the conventional growth mode, which inevitably gives rise to the formation of As precipitate and alloy scattering after annealing. In this paper, the migration-enhanced molecular beam epitaxy technique is developed to grow high-quality (InAs)m/(GaAs)n short-period superlattices with a sharp interface instead of InGaAs on InP substrate. The improved electron mobility and resistivity at room temperature (RT) are found to be 843 cm2/(V·s) and 1648 ohm/sq, respectively, for the (InAs)m/(GaAs)n short-period superlattice. The band-edge photo-excited carrier lifetime is determined to be ~1.2 ps at RT. The calculated photocurrent intensity, obtained by solving the Maxwell wave equation and the coupled drift–diffusion/Poisson equation using the finite element method, is in good agreement with previously reported results. This work may provide a new approach for the material growth towards high-performance THz photoconductive antennas with high radiation power. Full article
(This article belongs to the Special Issue Nanomaterials for Terahertz Technology Applications)
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15 pages, 16631 KiB  
Article
Full-Space Wavefront Shaping of Broadband Vortex Beam with Switchable Terahertz Metasurface Based on Vanadium Dioxide
by Xueying Li, Ying Zhang, Jiuxing Jiang, Yongtao Yao and Xunjun He
Nanomaterials 2023, 13(23), 3023; https://doi.org/10.3390/nano13233023 - 26 Nov 2023
Cited by 1 | Viewed by 983
Abstract
Currently, vortex beams are extensively utilized in the information transmission and storage of communication systems due to their additional degree of freedom. However, traditional terahertz metasurfaces only focus on the generation of narrowband vortex beams in reflection or transmission mode, which is unbeneficial [...] Read more.
Currently, vortex beams are extensively utilized in the information transmission and storage of communication systems due to their additional degree of freedom. However, traditional terahertz metasurfaces only focus on the generation of narrowband vortex beams in reflection or transmission mode, which is unbeneficial for practical applications. Here, we propose and design terahertz metasurface unit cells composed of anisotropic Z-shaped metal structures, two dielectric layers, and a VO2 film layer. By utilizing the Pancharatnam–Berry phase theory, independent control of a full 2π phase over a wide frequency range can be achieved by rotating the unit cell. Moreover, the full-space mode (transmission and reflection) can also be implemented by utilizing the phase transition of VO2 film. Based on the convolution operation, three different terahertz metasurfaces are created to generate vortex beams with different wavefronts in full-space, such as deflected vortex beams, focused vortex beams, and non-diffraction vortex beams. Additionally, the divergences of these vortex beams are also analyzed. Therefore, our designed metasurfaces are capable of efficiently shaping the wavefronts of broadband vortex beams in full-space, making them promising applications for long-distance transmission, high integration, and large capacity in 6G terahertz communications. Full article
(This article belongs to the Special Issue Nanomaterials for Terahertz Technology Applications)
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12 pages, 2783 KiB  
Article
Strain versus Tunable Terahertz Nanogap Width: A Simple Formula and a Trench below
by Hwanhee Kim, Mahsa Haddadi Moghaddam, Zhihao Wang, Sunghwan Kim, Dukhyung Lee, Hyosim Yang, Myongsoo Jee, Daehwan Park and Dai-Sik Kim
Nanomaterials 2023, 13(18), 2526; https://doi.org/10.3390/nano13182526 - 09 Sep 2023
Cited by 1 | Viewed by 935
Abstract
A flexible zerogap metallic structure is periodically formed, healing metal cracks on a flexible substrate. Zerogap is continuously tunable from nearly zero to one hundred nanometers by applying compressive strains on the flexible substrate. However, there have been few studies on how the [...] Read more.
A flexible zerogap metallic structure is periodically formed, healing metal cracks on a flexible substrate. Zerogap is continuously tunable from nearly zero to one hundred nanometers by applying compressive strains on the flexible substrate. However, there have been few studies on how the gap width is related to the strain and periodicity, nor the mechanism of tunability itself. Here, based on atomic force microscopy (AFM) measurements, we found that 200 nm-deep nano-trenches are periodically generated on the polymer substrate below the zerogap owing to the strain singularities extant between the first and the second metallic deposition layers. Terahertz and visible transmission properties are consistent with this picture whereby the outer-bending polyethylene terephthalate (PET) substrate controls the gap size linearly with the inverse of the radius of the curvature. Full article
(This article belongs to the Special Issue Nanomaterials for Terahertz Technology Applications)
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13 pages, 5684 KiB  
Article
Switchable and Tunable Terahertz Metamaterial Based on Vanadium Dioxide and Photosensitive Silicon
by Xin Zhang, Guan Wang, Jia Liu, Shiyi Zuo, Meichen Li, Shuang Yang, Yang Jia and Yachen Gao
Nanomaterials 2023, 13(14), 2144; https://doi.org/10.3390/nano13142144 - 24 Jul 2023
Cited by 6 | Viewed by 1240
Abstract
A switchable and tunable terahertz (THz) metamaterial based on photosensitive silicon and Vanadium dioxide (VO2) was proposed. By using a finite-difference time-domain (FDTD) method, the transmission and reflective properties of the metamaterial were investigated theoretically. The results imply that the metamaterial [...] Read more.
A switchable and tunable terahertz (THz) metamaterial based on photosensitive silicon and Vanadium dioxide (VO2) was proposed. By using a finite-difference time-domain (FDTD) method, the transmission and reflective properties of the metamaterial were investigated theoretically. The results imply that the metamaterial can realize a dual electromagnetically induced transparency (EIT) or two narrow-band absorptions depending on the temperature of the VO2. Additionally, the magnitude of the EIT and two narrow-band absorptions can be tuned by varying the conductivity of photosensitive silicon (PSi) via pumping light. Correspondingly, the slow-light effect accompanying the EIT can also be adjusted. Full article
(This article belongs to the Special Issue Nanomaterials for Terahertz Technology Applications)
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17 pages, 42229 KiB  
Article
Coexistence of Bloch and Parametric Mechanisms of High-Frequency Gain in Doped Superlattices
by Vladislovas Čižas, Natalia Alexeeva, Kirill N. Alekseev and Gintaras Valušis
Nanomaterials 2023, 13(13), 1993; https://doi.org/10.3390/nano13131993 - 01 Jul 2023
Cited by 1 | Viewed by 765
Abstract
The detailed theoretical study of high-frequency signal gain, when a probe microwave signal is comparable to the AC pump electric field in a semiconductor superlattice, is presented. We identified conditions under which a doped superlattice biased by both DC and AC fields can [...] Read more.
The detailed theoretical study of high-frequency signal gain, when a probe microwave signal is comparable to the AC pump electric field in a semiconductor superlattice, is presented. We identified conditions under which a doped superlattice biased by both DC and AC fields can generate or amplify high-frequency radiation composed of harmonics, half-harmonics, and fractional harmonics. Physical mechanisms behind the effects are discussed. It is revealed that in a general case, the amplification mechanism in superlattices is determined by the coexistence of both the phase-independent Bloch and phase-dependent parametric gain mechanisms. The interplay and contribution of these gain mechanisms can be adjusted by the sweeping AC pump strength and leveraging a proper phase between the pump and strong probe electric fields. Notably, a transition from the Bloch gain to the parametric gain, often naturally occurring as the amplitude of the amplified signal field grows, can facilitate an effective method of fractional harmonic generation in DC–AC-driven superlattices. The study also uncovers that the pure parametric generation of the fractional harmonics can be initiated via their ignition by switching the DC pump electric field. The findings open a promising avenue for the advancement of new miniature GHz–THz frequency generators, amplifiers, and dividers operating at room temperature. Full article
(This article belongs to the Special Issue Nanomaterials for Terahertz Technology Applications)
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