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Conrads L, Schüler L, Wirth KG, Wuttig M, Taubner T. Direct programming of confined surface phonon polariton resonators with the plasmonic phase-change material In 3SbTe 2. Nat Commun 2024; 15:3472. [PMID: 38658601 PMCID: PMC11043413 DOI: 10.1038/s41467-024-47841-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 04/12/2024] [Indexed: 04/26/2024] Open
Abstract
Tailoring light-matter interaction is essential to realize nanophotonic components. It can be achieved with surface phonon polaritons (SPhPs), an excitation of photons coupled with phonons of polar crystals, which also occur in 2d materials such as hexagonal boron nitride or anisotropic crystals. Ultra-confined resonances are observed by restricting the SPhPs to cavities. Phase-change materials (PCMs) enable non-volatile programming of these cavities based on a change in the refractive index. Recently, the plasmonic PCM In3SbTe2 (IST) was introduced which can be reversibly switched from an amorphous dielectric state to a crystalline metallic one in the entire infrared to realize numerous nanoantenna geometries. However, reconfiguring SPhP resonators to modify the confined polaritons modes remains elusive. Here, we demonstrate direct programming of confined SPhP resonators by phase-switching IST on top of a polar silicon carbide crystal and investigate the strongly confined resonance modes with scanning near-field optical microscopy. Reconfiguring the size of the resonators themselves result in enhanced mode confinements up to a value of λ / 35 . Finally, unconventional cavity shapes with complex field patterns are explored as well. This study is a first step towards rapid prototyping of reconfigurable SPhP resonators that can be easily transferred to hyperbolic and anisotropic 2d materials.
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Affiliation(s)
- Lukas Conrads
- Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany.
| | - Luis Schüler
- Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Konstantin G Wirth
- Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Matthias Wuttig
- Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Thomas Taubner
- Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany.
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2
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Criswell SG, Mahadik NA, Gallagher JC, Barnett J, Kim L, Ghorbani M, Kamaliya B, Bassim ND, Taubner T, Caldwell JD. Nanoscale Infrared Spectroscopic Characterization of Extended Defects in 4H-Silicon Carbide. Nano Lett 2024; 24:114-121. [PMID: 38164942 DOI: 10.1021/acs.nanolett.3c03369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Extended defects in wide-bandgap semiconductors have been widely investigated using techniques providing either spectroscopic or microscopic information. Nano-Fourier transform infrared spectroscopy (nano-FTIR) is a nondestructive characterization method combining FTIR with nanoscale spatial resolution (∼20 nm) and topographic information. Here, we demonstrate the capability of nano-FTIR for the characterization of extended defects in semiconductors by investigating an in-grown stacking fault (IGSF) present in a 4H-SiC epitaxial layer. We observe a local spectral shift of the mid-infrared near-field response, consistent with the identification of the defect stacking order as 3C-SiC (cubic) from comparative simulations based on the finite dipole model (FDM). This 3C-SiC IGSF contrasts with the more typical 8H-SiC IGSFs reported previously and is exemplary in showing that nanoscale spectroscopy with nano-FTIR can provide new insights into the properties of extended defects, the understanding of which is crucial for mitigating deleterious effects of such defects in alternative semiconductor materials and devices.
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Affiliation(s)
- Scott G Criswell
- Department of Electrical Engineering, Vanderbilt University, 2400 Highland Avenue, Nashville, Tennessee 37212, United States
- Electro-Optic Technology Division, Naval Surface Warfare Center, Crane, Indiana 47522, United States
| | - Nadeemullah A Mahadik
- US Naval Research Laboratory, 4555 Overlook Avenue, S.W., Washington, D.C. 20375, United States
| | - James C Gallagher
- US Naval Research Laboratory, 4555 Overlook Avenue, S.W., Washington, D.C. 20375, United States
| | - Julian Barnett
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - Luke Kim
- Department of Mechanical Engineering, Vanderbilt University, 2400 Highland Avenue, Nashville, Tennessee 37212, United States
| | - Morvarid Ghorbani
- Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L8, Canada
| | - Bhaveshkumar Kamaliya
- Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L8, Canada
- Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario L8S 4L8, Canada
| | - Nabil D Bassim
- Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L8, Canada
- Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario L8S 4L8, Canada
| | - Thomas Taubner
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - Joshua D Caldwell
- Department of Electrical Engineering, Vanderbilt University, 2400 Highland Avenue, Nashville, Tennessee 37212, United States
- Electro-Optic Technology Division, Naval Surface Warfare Center, Crane, Indiana 47522, United States
- Department of Mechanical Engineering, Vanderbilt University, 2400 Highland Avenue, Nashville, Tennessee 37212, United States
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3
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Conrads L, Heßler A, Völkel L, Wilden K, Strauch A, Pries J, Wuttig M, Taubner T. Infrared Resonance Tuning of Nanoslit Antennas with Phase-Change Materials. ACS Nano 2023; 17:25721-25730. [PMID: 38085927 DOI: 10.1021/acsnano.3c11121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
Phase-change materials (PCMs) have been established as prime candidates for nonvolatile resonance tuning of nanophotonic components based on a large optical contrast between their amorphous and crystalline states. Recently, the plasmonic PCM In3SbTe2 was introduced, which can be switched from an amorphous dielectric state to a crystalline metallic one over the entire infrared spectral range. While locally switching the PCM around metallic nanorod antennas has already been demonstrated, similar tuning of inverse antenna structures (nanoslits) has not yet been investigated. Here, we demonstrate optical resonance tuning of nanoslit antennas with dielectric and plasmonic PCMs. We compare two geometries with fundamentally different resonance tuning mechanisms: tuning the resonance of aluminum slit antennas by change of the refractive index (dielectric PCM Ge3Sb2Te6), and creating slit-like volumes of amorphous In3SbTe2 and modifying the slit geometry directly (plasmonic PCM In3SbTe2). While the tuning range with the plasmonic PCM is about 3.4 μm and only limited by fabrication, the resonances with the dielectric PCM feature a three times larger quality factor compared to resonances obtained with the plasmonic PCM.
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Affiliation(s)
- Lukas Conrads
- Institute of Physics (IA), RWTH Aachen University, Aachen D-52056, Germany
| | - Andreas Heßler
- Institute of Physics (IA), RWTH Aachen University, Aachen D-52056, Germany
| | - Lukas Völkel
- Institute of Physics (IA), RWTH Aachen University, Aachen D-52056, Germany
| | - Kilian Wilden
- Institute of Physics (IA), RWTH Aachen University, Aachen D-52056, Germany
| | - Achim Strauch
- Institute of Physics (IA), RWTH Aachen University, Aachen D-52056, Germany
| | - Julian Pries
- Institute of Physics (IA), RWTH Aachen University, Aachen D-52056, Germany
| | - Matthias Wuttig
- Institute of Physics (IA), RWTH Aachen University, Aachen D-52056, Germany
| | - Thomas Taubner
- Institute of Physics (IA), RWTH Aachen University, Aachen D-52056, Germany
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Taubner T, Skřivan M, Englmaierová M, Malá L. Effects of hemp seed and flaxseed on enzyme activity in the broiler chicken digestive tract. Animal 2023; 17:100765. [PMID: 36965210 DOI: 10.1016/j.animal.2023.100765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 02/24/2023] [Accepted: 02/27/2023] [Indexed: 03/08/2023] Open
Abstract
The activity of enzymes in the digestive tract is an important parameter for appropriate digestive tract function. Feed mixtures can be adjusted to support enzymatic activity in different parts of the digestive tract. Flaxseed and hemp seed are commodities and significant sources of nutrition, and their addition to feed could change enzymatic activity in the digestive tract and improve nutritional intake. The aim of this study was to determine the effects of flaxseed, hemp seed and a combination of both on basic enzymes in the polysaccharidase group, such as amylase, cellulase, pectinase, xylanase and inulinase; basic enzymes in the disaccharidase group, including maltase, invertase and lactase; proteinases and lipases in the digestive tract of broiler chickens. During the experiment, the control group was fed a diet without flaxseed or hemp seed. The diet of the second group contained 80 g/kg flaxseed, the diet of the third group contained 40 g/kg hemp seed, and the diets of the fourth to sixth groups contained 80 and 30 g/kg, 80 and 40 g/kg and 80 and 50 g/kg flaxseed and hemp seed, respectively. Enzyme activity was found to depend on the location in the digestive tract and the composition of the feed mixture (P < 0.05). Most enzymatic conversion occurs in the ileum, where the addition of flaxseed and hemp seed to the diet increased most enzyme activities, namely, amylase, cellulase, pectinase, xylanase, maltase, invertase, proteinase and lipase activities. The highest values of enzyme activity were found in groups IV-VI fed a combination of flaxseed and hempseed, especially in chickens fed diet VI (flaxseed and hemp seed at 80 and 50 g/kg). Growth performance results confirmed the enzyme activity results, as the weights of the chickens increased after the addition of flaxseed and/or hemp seed. The findings have economic implications, suggesting that feeding a diet with a combination of flaxseed and hemp seed is beneficial.
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Affiliation(s)
- T Taubner
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Přátelství 815, 104 00 Prague-Uhříněves, Czech Republic.
| | - M Skřivan
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Přátelství 815, 104 00 Prague-Uhříněves, Czech Republic
| | - M Englmaierová
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Přátelství 815, 104 00 Prague-Uhříněves, Czech Republic
| | - L Malá
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Přátelství 815, 104 00 Prague-Uhříněves, Czech Republic
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5
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Zeebone YY, Kovács M, Bóta B, Zdeněk V, Taubner T, Halas V. Dietary fumonisin may compromise the nutritive value of feed and distort copper and zinc digestibility and retention in weaned piglets. J Anim Physiol Anim Nutr (Berl) 2023; 107:504-517. [PMID: 35534935 DOI: 10.1111/jpn.13724] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 03/23/2022] [Accepted: 04/10/2022] [Indexed: 11/26/2022]
Abstract
Fumonisins (FUM) have been reported to impede gut functioning in pigs. However, investigations into the possible effect on mineral metabolism are limited. Thus, the trial studied the apparent total tract digestibility (ATTD) and retention of dietary nitrogen and minerals, intestinal architecture, digestive enzymes activity and heat-shock protein 70 (Hsp70) activity. Eighteen weaned piglets of 7 weeks old were assigned to three groups and their feed either contained 0, 15 or 30 mg FUM/kg for 21 days. ATTD and retention of dietary N and minerals were measured in a 5- day long balance trial between Day 17 and Day 21. The digestible and metabolisable energy (DE and ME) content of the feeds were also determined. The body weights, cumulative feed intake, relative organ weights, digestive enzymes activity and intestinal morphology were not affected (p > 0.05) by dietary treatments. The DE content was significantly lower (p < 0.05) when the feed contained 15 mg/kg FUM, but no statistically reliable treatment effect was confirmed for ME content. Dietary FUM significantly lowered (p < 0.05) the ATTD of Ca and P but not (p > 0.05) N, K, Mg and Na. The relative retention rate of N, Ca, P, K, Mg and Na in all groups were not impacted (p > 0.05) by treatments. The ATTD and relative retention of Cu and Zn were remarkably (p < 0.05) lower in piglets fed FUM-contaminated feed. In addition, the expression of Hsp70 activity in the liver was significantly elevated (p < 0.05) in the highest treatment group. These findings suggest that a dietary dose of 15 or 30 mg FUM/kg diet distorts the nutritive value of the mixed feed, results in poor ATTD and retention rates of Zn and Cu, and elevate Hsp70 activity in the liver without altering intestinal architecture or digestive enzymes' activity in weaned piglets.
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Affiliation(s)
- Y Y Zeebone
- Department of Physiology and Animal Health, Hungarian University of Agriculture and Life Sciences Kaposvár Campus, Kaposvár, Hungary.,MTA-KE-SZIE Mycotoxins in the Food Chain Research Group, Kaposvár, Hungary
| | - M Kovács
- Department of Physiology and Animal Health, Hungarian University of Agriculture and Life Sciences Kaposvár Campus, Kaposvár, Hungary.,MTA-KE-SZIE Mycotoxins in the Food Chain Research Group, Kaposvár, Hungary
| | - B Bóta
- MTA-KE-SZIE Mycotoxins in the Food Chain Research Group, Kaposvár, Hungary
| | - V Zdeněk
- Department of Nutritional Physiology and Animal Product Quality, Institute of Animal Science, Prague, Czechia
| | - T Taubner
- Department of Microbiology, Nutrition and Dietetics, Czech University of Life Sciences, Prague, Czechia
| | - V Halas
- Department of Farm Animal Nutrition, Hungarian University of Agriculture and Life Sciences Kaposvár Campus, Kaposvár, Hungary
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6
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Wirth KG, Hauck JB, Rothstein A, Kyoseva H, Siebenkotten D, Conrads L, Klebl L, Fischer A, Beschoten B, Stampfer C, Kennes DM, Waldecker L, Taubner T. Experimental Observation of ABCB Stacked Tetralayer Graphene. ACS Nano 2022; 16:16617-16623. [PMID: 36205460 DOI: 10.1021/acsnano.2c06053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
In tetralayer graphene, three inequivalent layer stackings should exist; however, only rhombohedral (ABCA) and Bernal (ABAB) stacking have so far been observed. The three stacking sequences differ in their electronic structure, with the elusive third stacking (ABCB) being unique as it is predicted to exhibit an intrinsic bandgap as well as locally flat bands around the K points. Here, we use scattering-type scanning near-field optical microscopy and confocal Raman microscopy to identify and characterize domains of ABCB stacked tetralayer graphene. We differentiate between the three stacking sequences by addressing characteristic interband contributions in the optical conductivity between 0.28 and 0.56 eV with amplitude and phase-resolved near-field nanospectroscopy. By normalizing adjacent flakes to each other, we achieve good agreement between theory and experiment, allowing for the unambiguous assignment of ABCB domains in tetralayer graphene. These results establish near-field spectroscopy at the interband transitions as a semiquantitative tool, enabling the recognition of ABCB domains in tetralayer graphene flakes and, therefore, providing a basis to study correlation physics of this exciting phase.
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Affiliation(s)
- Konstantin G Wirth
- 1st Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany
| | - Jonas B Hauck
- Institute for Theory of Statistical Physics, RWTH Aachen University and JARA Fundamentals of Future Information Technology, 52062 Aachen, Germany
| | - Alexander Rothstein
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Hristiyana Kyoseva
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, 52074 Aachen, Germany
| | - Dario Siebenkotten
- 1st Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany
| | - Lukas Conrads
- 1st Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany
| | - Lennart Klebl
- Institute for Theory of Statistical Physics, RWTH Aachen University and JARA Fundamentals of Future Information Technology, 52062 Aachen, Germany
| | - Ammon Fischer
- Institute for Theory of Statistical Physics, RWTH Aachen University and JARA Fundamentals of Future Information Technology, 52062 Aachen, Germany
| | - Bernd Beschoten
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, 52074 Aachen, Germany
| | - Christoph Stampfer
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Dante M Kennes
- Institute for Theory of Statistical Physics, RWTH Aachen University and JARA Fundamentals of Future Information Technology, 52062 Aachen, Germany
- Center for Free Electron Laser Science, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
| | - Lutz Waldecker
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, 52074 Aachen, Germany
| | - Thomas Taubner
- 1st Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany
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7
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Lu J, Wirth KG, Gao W, Heßler A, Sain B, Taubner T, Zentgraf T. Observing 0D subwavelength-localized modes at ~100 THz protected by weak topology. Sci Adv 2021; 7:eabl3903. [PMID: 34851678 PMCID: PMC8635428 DOI: 10.1126/sciadv.abl3903] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Accepted: 10/13/2021] [Indexed: 05/31/2023]
Abstract
Topological photonic crystals (TPhCs) provide robust manipulation of light with built-in immunity to fabrication tolerances and disorder. Recently, it was shown that TPhCs based on weak topology with a dislocation inherit this robustness and further host topologically protected lower-dimensional localized modes. However, TPhCs with weak topology at optical frequencies have not been demonstrated so far. Here, we use scattering-type scanning near-field optical microscopy to verify mid-bandgap zero-dimensional light localization close to 100 THz in a TPhC with nontrivial Zak phase and an edge dislocation. We show that because of the weak topology, differently extended dislocation centers induce similarly strong light localization. The experimental results are supported by full-field simulations. Along with the underlying fundamental physics, our results lay a foundation for the application of TPhCs based on weak topology in active topological nanophotonics, and nonlinear and quantum optic integrated devices because of their strong and robust light localization.
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Affiliation(s)
- Jinlong Lu
- Department of Physics, Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany
| | | | - Wenlong Gao
- Department of Physics, Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany
| | - Andreas Heßler
- I. Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany
| | - Basudeb Sain
- Department of Physics, Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany
| | - Thomas Taubner
- I. Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany
- Jülich Aachen Research Alliance Fundamentals of Future Information Technology (JARA-FIT), 52074 Aachen, Germany
| | - Thomas Zentgraf
- Department of Physics, Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany
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8
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Barnett J, Wehmeier L, Heßler A, Lewin M, Pries J, Wuttig M, Klopf JM, Kehr SC, Eng LM, Taubner T. Far-Infrared Near-Field Optical Imaging and Kelvin Probe Force Microscopy of Laser-Crystallized and -Amorphized Phase Change Material Ge 3Sb 2Te 6. Nano Lett 2021; 21:9012-9020. [PMID: 34665620 DOI: 10.1021/acs.nanolett.1c02353] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Chalcogenide phase change materials reversibly switch between non-volatile states with vastly different optical properties, enabling novel active nanophotonic devices. However, a fundamental understanding of their laser-switching behavior is lacking and the resulting local optical properties are unclear at the nanoscale. Here, we combine infrared scattering-type scanning near-field optical microscopy (SNOM) and Kelvin probe force microscopy (KPFM) to investigate four states of laser-switched Ge3Sb2Te6 (as-deposited amorphous, crystallized, reamorphized, and recrystallized) with nanometer lateral resolution. We find SNOM to be especially sensitive to differences between crystalline and amorphous states, while KPFM has higher sensitivity to changes introduced by melt-quenching. Using illumination from a free-electron laser, we use the higher sensitivity to free charge carriers of far-infrared (THz) SNOM compared to mid-infrared SNOM and find evidence that the local conductivity of crystalline states depends on the switching process. This insight into the local switching of optical properties is essential for developing active nanophotonic devices.
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Affiliation(s)
- Julian Barnett
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - Lukas Wehmeier
- Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
- ct.qmat, Dresden-Würzburg Cluster of Excellence-EXC 2147, Technische Universität Dresden, 01062 Dresden, Germany
| | - Andreas Heßler
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - Martin Lewin
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - Julian Pries
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - Matthias Wuttig
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
| | - J Michael Klopf
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Susanne C Kehr
- Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Lukas M Eng
- Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
- ct.qmat, Dresden-Würzburg Cluster of Excellence-EXC 2147, Technische Universität Dresden, 01062 Dresden, Germany
| | - Thomas Taubner
- I. Institute of Physics (IA), RWTH Aachen, 52074 Aachen, Germany
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Rose MA, Barnett J, Wendland D, Hensling FVE, Boergers JM, Moors M, Dittmann R, Taubner T, Gunkel F. Local inhomogeneities resolved by scanning probe techniques and their impact on local 2DEG formation in oxide heterostructures. Nanoscale Adv 2021; 3:4145-4155. [PMID: 36132831 PMCID: PMC9419657 DOI: 10.1039/d1na00190f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 06/02/2021] [Indexed: 06/16/2023]
Abstract
Lateral inhomogeneities in the formation of two-dimensional electron gases (2DEG) directly influence their electronic properties. Understanding their origin is an important factor for fundamental interpretations, as well as high quality devices. Here, we studied the local formation of the buried 2DEG at LaAlO3/SrTiO3 (LAO/STO) interfaces grown on STO (100) single crystals with partial TiO2 termination, utilizing in situ conductive atomic force microscopy (c-AFM) and scattering-type scanning near-field optical microscopy (s-SNOM). Using substrates with different degrees of chemical surface termination, we can link the resulting interface chemistry to an inhomogeneous 2DEG formation. In conductivity maps recorded by c-AFM, a significant lack of conductivity is observed at topographic features, indicative of a local SrO/AlO2 interface stacking order, while significant local conductivity can be probed in regions showing TiO2/LaO interface stacking order. These results could be corroborated by s-SNOM, showing a similar contrast distribution in the optical signal which can be linked to the local electronic properties of the material. The results are further complemented by low-temperature conductivity measurements, which show an increasing residual resistance at 5 K with increasing portion of insulating SrO-terminated areas. Therefore, we can correlate the macroscopic electrical behavior of our samples to their nanoscopic structure. Using proper parameters, 2DEG mapping can be carried out without any visible alteration of sample properties, proving c-AFM and s-SNOM to be viable and destruction-free techniques for the identification of local 2DEG formation. Furthermore, applying c-AFM and s-SNOM in this manner opens the exciting prospect to link macroscopic low-temperature transport to its nanoscopic origin.
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Affiliation(s)
- M-A Rose
- Institute of Electronic Materials (IWE II), RWTH Aachen University Aachen Germany
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - J Barnett
- I. Institute of Physics (IA), RWTH Aachen University Aachen Germany
| | - D Wendland
- I. Institute of Physics (IA), RWTH Aachen University Aachen Germany
| | - F V E Hensling
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - J M Boergers
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - M Moors
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - R Dittmann
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - T Taubner
- I. Institute of Physics (IA), RWTH Aachen University Aachen Germany
| | - F Gunkel
- Institute of Electronic Materials (IWE II), RWTH Aachen University Aachen Germany
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
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10
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Englmaierová M, Skřivan M, Taubner T, Skřivanová V, Čermák L. Effect of housing system and feed restriction on meat quality of medium-growing chickens. Poult Sci 2021; 100:101223. [PMID: 34157561 PMCID: PMC8237347 DOI: 10.1016/j.psj.2021.101223] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 04/14/2021] [Accepted: 04/18/2021] [Indexed: 12/02/2022] Open
Abstract
The aim of the study was to evaluate the differences in meat quality of 420 Hubbard JA757 cockerels in relation to the housing system (litter and mobile box) and level of mixed feed (ad libitum [AL], reducing the level by 20% [R20] and 30% [R30]). Three groups of chickens were housed in litter boxes for the entire fattening period (stocking density: 0.094 m2/bird). The other 3 groups were housed in litter boxes until 28 d of age and then relocated into mobile boxes (stocking density: 0.154 m2/bird) on pasture until the end of the experiment at 57 d of age. Restricted groups received a reduced diet level from 29th to 57th d of age. Feed mixture restriction increased the pasture vegetation intake of chickens from 2.63 to 3.50 (R20) and 3.94 g of dry matter/bird/d (R30). Restriction adversely affected the dressing percentage (P < 0.001) and breast yield (P < 0.001), while the leg yield (P < 0.001) was increased with increasing restriction levels. Meat of chickens housed in mobile boxes on a pasture showed lower cooking loss (P < 0.001) and higher redness and yellowness values in the skin (P = 0.030 and P = 0.026; respectively) and meat (P = 0.008 and P < 0.001; respectively). The fragile meat after cooking was observed in chickens reared on litter (P = 0.001). As the level of restriction increased, the number of muscle fibres (P = 0.001) increased, and their cross-sectional area (P = 0.001) and diameter (P = 0.002) decreased. The highest contents of lutein (P = 0.002) and zeaxanthin (P = 0.006) in breast muscle were found in chickens housed in mobile boxes and fed 80% and 70% AL. However, the concentrations of α- and γ-tocopherol (P = 0.006 and P = 0.003) were negatively affected by feed restriction. A 30% reduction in feed level in outdoor housed chickens led to a decrease in oxidative stability (P = 0.024). Feed restriction (R20) in chickens housed in mobile boxes significantly increased the n3 fatty acids content (P = 0.002) and h/H index (P = 0.005) and reduced the n6/n3 ratio (P < 0.001) and atherogenic (P < 0.001) and thrombogenic index (P = 0.003), which possess a health benefits for human. In addition, restriction of mixed feed decreased cholesterol content in breast meat (P = 0.042). It might be concluded that, in terms of meat quality, cereal diet restriction of 20% in medium-growing cockerels housed in mobile boxes on a pasture is beneficial. The higher level of restriction does not lead to further improvement in meat quality indicators.
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Affiliation(s)
- M Englmaierová
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Czech Republic.
| | - M Skřivan
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Czech Republic
| | - T Taubner
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Czech Republic
| | - V Skřivanová
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Czech Republic
| | - L Čermák
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Czech Republic
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11
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Wirth KG, Linnenbank H, Steinle T, Banszerus L, Icking E, Stampfer C, Giessen H, Taubner T. Tunable s-SNOM for Nanoscale Infrared Optical Measurement of Electronic Properties of Bilayer Graphene. ACS Photonics 2021; 8:418-423. [PMID: 33763503 PMCID: PMC7976599 DOI: 10.1021/acsphotonics.0c01442] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Indexed: 05/31/2023]
Abstract
Here we directly probe the electronic properties of bilayer graphene using s-SNOM measurements with a broadly tunable laser source over the energy range from 0.3 to 0.54 eV. We tune an OPO/OPA system around the interband resonance of Bernal stacked bilayer graphene (BLG) and extract amplitude and phase of the scattered light. This enables us to retrieve and reconstruct the complex optical conductivity resonance in BLG around 0.39 eV with nanoscale resolution. Our technique opens the door toward nanoscopic noncontact measurements of the electronic properties in complex hybrid 2D and van der Waals material systems, where scanning tunneling spectroscopy cannot access the decisive layers.
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Affiliation(s)
| | - Heiko Linnenbank
- 4th
Physics Institute and Research Center SCoPE, University of Stuttgart, 70569 Stuttgart, Germany
- SI
Stuttgart Instruments GmbH, 70771 Leinfelden-Echterdingen, Germany
| | - Tobias Steinle
- 4th
Physics Institute and Research Center SCoPE, University of Stuttgart, 70569 Stuttgart, Germany
- SI
Stuttgart Instruments GmbH, 70771 Leinfelden-Echterdingen, Germany
| | - Luca Banszerus
- 2nd
Institute of Physics (IIA), RWTH Aachen
University, 52074 Aachen, Germany
| | - Eike Icking
- 2nd
Institute of Physics (IIA), RWTH Aachen
University, 52074 Aachen, Germany
| | - Christoph Stampfer
- 2nd
Institute of Physics (IIA), RWTH Aachen
University, 52074 Aachen, Germany
- Jülich
Aachen Research Alliance - Fundamentals of Future Information Technology
(JARA-FIT), 52074 Aachen, Germany
| | - Harald Giessen
- 4th
Physics Institute and Research Center SCoPE, University of Stuttgart, 70569 Stuttgart, Germany
- SI
Stuttgart Instruments GmbH, 70771 Leinfelden-Echterdingen, Germany
| | - Thomas Taubner
- I.
Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany
- Jülich
Aachen Research Alliance - Fundamentals of Future Information Technology
(JARA-FIT), 52074 Aachen, Germany
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12
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Heßler A, Wahl S, Leuteritz T, Antonopoulos A, Stergianou C, Schön CF, Naumann L, Eicker N, Lewin M, Maß TWW, Wuttig M, Linden S, Taubner T. In 3SbTe 2 as a programmable nanophotonics material platform for the infrared. Nat Commun 2021; 12:924. [PMID: 33568636 PMCID: PMC7876017 DOI: 10.1038/s41467-021-21175-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 01/13/2021] [Indexed: 11/24/2022] Open
Abstract
The high dielectric optical contrast between the amorphous and crystalline structural phases of non-volatile phase-change materials (PCMs) provides a promising route towards tuneable nanophotonic devices. Here, we employ the next-generation PCM In3SbTe2 (IST) whose optical properties change from dielectric to metallic upon crystallization in the whole infrared spectral range. This distinguishes IST as a switchable infrared plasmonic PCM and enables a programmable nanophotonics material platform. We show how resonant metallic nanostructures can be directly written, modified and erased on and below the meta-atom level in an IST thin film by a pulsed switching laser, facilitating direct laser writing lithography without need for cumbersome multi-step nanofabrication. With this technology, we demonstrate large resonance shifts of nanoantennas of more than 4 µm, a tuneable mid-infrared absorber with nearly 90% absorptance as well as screening and nanoscale “soldering” of metallic nanoantennas. Our concepts can empower improved designs of programmable nanophotonic devices for telecommunications, (bio)sensing and infrared optics, e.g. programmable infrared detectors, emitters and reconfigurable holograms. Here, the authors introduce In3SbTe2 (IST) as a programmable material platform for plasmonics and nanophotonics in the infrared. They demonstrate direct optical writing, modifying and erasing of metallic crystalline IST nanoantennas, tuning their resonances, as well as nanoscale screening and soldering.
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Affiliation(s)
- Andreas Heßler
- Institute of Physics (IA), RWTH Aachen University, Aachen, Germany.
| | - Sophia Wahl
- Institute of Physics (IA), RWTH Aachen University, Aachen, Germany
| | - Till Leuteritz
- Physikalisches Institut, University of Bonn, Bonn, Germany
| | | | | | | | - Lukas Naumann
- Physikalisches Institut, University of Bonn, Bonn, Germany
| | - Niklas Eicker
- Institute of Physics (IA), RWTH Aachen University, Aachen, Germany
| | - Martin Lewin
- Institute of Physics (IA), RWTH Aachen University, Aachen, Germany
| | - Tobias W W Maß
- Institute of Physics (IA), RWTH Aachen University, Aachen, Germany
| | - Matthias Wuttig
- Institute of Physics (IA), RWTH Aachen University, Aachen, Germany
| | - Stefan Linden
- Physikalisches Institut, University of Bonn, Bonn, Germany
| | - Thomas Taubner
- Institute of Physics (IA), RWTH Aachen University, Aachen, Germany.
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13
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Marounek M, Volek Z, Taubner T, Czauderna M. Metabolic Effects of a Hydrophobic Alginate Derivative and Tetrahydrolipstatin in Rats Fed a Diet Supplemented with Palm Fat and Cholesterol. Folia Biol (Praha) 2021; 67:143-149. [PMID: 35151239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The effects of octadecylamide of alginic acid (amidated alginate) and tetrahydrolipstatin on serum and hepatic cholesterol, and the faecal output of fat and sterols, were investigated in rats. Amidated alginate is a sorbent of lipids, tetrahydrolipstatin is an inhibitor of pancreatic lipase. Rats were fed diets containing cholesterol and palm fat at 10 and 70 g/kg, respectively. Palm fat was provided by coconut meal. Amidated alginate at 40 g/kg diet significantly decreased serum total cholesterol, low-density lipoprotein and hepatic cholesterol, and hepatic lipids and increased the faecal output of fat and coprostanol. Tetrahydrolipstatin at 300 mg/kg diet significantly decreased low-density lipoprotein cholesterol and hepatic lipids and increased the faecal output of fat. The intake of feed was not significantly influenced; however, the weight gains in rats fed amidated alginate were lower than in rats of the control group. Both amidated alginate and tetrahydrolipstatin modified the fatty acid profile in excreta lipids. Concentrations of saturated fatty acids were decreased and those of unsaturated fatty acids increased. Despite different modes of action, amidated alginate and tetrahydrolipstatin were equally efficient in removing the dietary fat from the body.
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Affiliation(s)
- M Marounek
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Prague, Czech Republic
- Department of Microbiology, Nutrition and Dietetics, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences, Prague, Czech Republic
| | - Z Volek
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Prague, Czech Republic
- Department of Microbiology, Nutrition and Dietetics, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences, Prague, Czech Republic
| | - T Taubner
- Department of Nutrition Physiology and Animal Product Quality, Institute of Animal Science, Prague, Czech Republic
| | - M Czauderna
- The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Jablonna, Poland
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14
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Deuter V, Grochowicz M, Brose S, Biller J, Danylyuk S, Taubner T, Siemion A, Grützmacher D, Juschkin L. Computational proximity lithography with extreme ultraviolet radiation. Opt Express 2020; 28:27000-27012. [PMID: 32906962 DOI: 10.1364/oe.398805] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 08/18/2020] [Indexed: 06/11/2023]
Abstract
The potential of extreme ultraviolet (EUV) computational proximity lithography for fabrication of arbitrary nanoscale patterns is investigated. We propose to use a holographic mask (attenuating phase shifting mask) consisting of structures of two phase levels. This approach allows printing of arbitrary, non-periodic structures without using high-resolution imaging optics. The holographic mask is designed for a wavelength of 13.5 nm with a conventional high-resolution electron beam resist as the phase shifting medium (pixel size 50 nm). The imaging performance is evaluated by using EUV radiation with different degrees of spatial coherence. Therefore exposures on identical masks are carried out with both undulator radiation at a synchrotron facility and plasma-based radiation at a laboratory setup.
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15
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Michel AKU, Heßler A, Meyer S, Pries J, Yu Y, Kalix T, Lewin M, Hanss J, De Rose A, Maß TWW, Wuttig M, Chigrin DN, Taubner T. Advanced Optical Programming of Individual Meta-Atoms Beyond the Effective Medium Approach. Adv Mater 2019; 31:e1901033. [PMID: 31131947 DOI: 10.1002/adma.201901033] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/30/2019] [Indexed: 06/09/2023]
Abstract
Nanometer-thick active metasurfaces (MSs) based on phase-change materials (PCMs) enable compact photonic components, offering adjustable functionalities for the manipulation of light, such as polarization filtering, lensing, and beam steering. Commonly, they feature multiple operation states by switching the whole PCM fully between two states of drastically different optical properties. Intermediate states of the PCM are also exploited to obtain gradual resonance shifts, which are usually uniform over the whole MS and described by effective medium response. For programmable MSs, however, the ability to selectively address and switch the PCM in individual meta-atoms is required. Here, simultaneous control of size, position, and crystallization depth of the switched phase-change material (PCM) volume within each meta-atom in a proof-of-principle MS consisting of a PCM-covered Al-nanorod antenna array is demonstrated. By modifying optical properties locally, amplitude and light phase can be programmed at the meta-atom scale. As this goes beyond previous effective medium concepts, it will enable small adaptive corrections to external aberrations and fabrication errors or multiple complex functionalities programmable on the same MS.
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Affiliation(s)
- Ann-Katrin U Michel
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Andreas Heßler
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Sebastian Meyer
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Julian Pries
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Yuan Yu
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Thomas Kalix
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Martin Lewin
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Julian Hanss
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Angela De Rose
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Tobias W W Maß
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Matthias Wuttig
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Dmitry N Chigrin
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
- DWI - Leibniz Institute for Interactive Materials, Forckenbeckstr. 50, D-52056, Aachen, Germany
| | - Thomas Taubner
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
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16
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Maß TWW, Nguyen VH, Schnakenberg U, Taubner T. Tailoring grating strip widths for optimizing infrared absorption signals of an adsorbed molecular monolayer. Opt Express 2019; 27:10524-10532. [PMID: 31052910 DOI: 10.1364/oe.27.010524] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 02/26/2019] [Indexed: 06/09/2023]
Abstract
Metal structures with resonances in the mid-infrared spectral range enable an increased sensitivity for detecting molecular vibrational signals. 1D gold strip gratings have already proven potential in surface-enhanced infrared absorption (SEIRA) experiments, as grating resonances and local electric field enhancement can be spectrally tuned by changing the grating period. Here, we identify the grating strip width as another important design parameter, which is investigated for further optimization of molecular absorption signal enhancement in SEIRA experiments. Previous literature used gratings to increase light absorption in relatively thick polymer layers. Here, we demonstrate the capability of gold strip gratings fabricated on a CaF2 substrate to enhance the CH2 vibrational modes of a thiol-based monolayer of MHDA. An optimal choice of the strip width w = 1.33 μm enables a maximum vibrational signal enhancement factor of around 84, when normalized to microscopic GIR measurements of an MHDA monolayer on an extended gold surface. Numerical simulations demonstrate the broadband local field enhancement of gold strip gratings, which are suitable for enhancing multiple vibrational modes in a large hot-spot volume.
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17
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Sumikura H, Wang T, Li P, Michel AKU, Heßler A, Jung L, Lewin M, Wuttig M, Chigrin DN, Taubner T. Highly Confined and Switchable Mid-Infrared Surface Phonon Polariton Resonances of Planar Circular Cavities with a Phase Change Material. Nano Lett 2019; 19:2549-2554. [PMID: 30920839 DOI: 10.1021/acs.nanolett.9b00304] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Mid-infrared (MIR) photonics demands highly confined optical fields to obtain efficient interaction between long-wavelength light and nanomaterials. Surface polaritons excited on polar semiconductor and metallic material interfaces exhibit near-fields localized on subwavelength scales. However, realizing a stronger field concentration in a cavity with a high quality ( Q) factor and a small mode volume is still challenging in the MIR region. This study reports MIR field concentration of surface phonon polaritons (SPhPs) using planar circular cavities with a high Q factor of ∼150. The cavities are fabricated on a thin film of the phase change material Ge3Sb2Te6 (GST) deposited on a silicon carbide (SiC) substrate. Scattering-type scanning near-field optical microscopy visualizes the near-field distribution on the samples and confirms directly that the SPhP field is strongly concentrated at the center of the centrosymmetric cavities. The smallest concentrated field size is 220 nm in diameter which corresponds to 1/50 of the wavelength of the incident light that is far below the diffraction limit. The thin GST film enhances the SPhP confinement, and it is used to switch the confinement off by tuning the cavity resonance induced by the phase change from the amorphous to the crystalline phase. This subwavelength and switchable field concentration within a high- Q polariton cavity has the potential to greatly enhance the light-matter interaction for molecular sensing and emission enhancement in MIR systems.
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Affiliation(s)
- Hisashi Sumikura
- Institute of Physics (IA) , RWTH Aachen University , 52074 Aachen , Germany
- NTT Basic Research Laboratories and Nanophotonics Center , Nippon Telegraph and Telephone Corporation , Atsugi , Kanagawa 243-0198 , Japan
| | - Tao Wang
- Institute of Physics (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Peining Li
- Institute of Physics (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | | | - Andreas Heßler
- Institute of Physics (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Lena Jung
- Institute of Physics (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Martin Lewin
- Institute of Physics (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Matthias Wuttig
- Institute of Physics (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Dmitry N Chigrin
- Institute of Physics (IA) , RWTH Aachen University , 52074 Aachen , Germany
- DWI - Leibniz Institute for Interactive Materials , 52076 Aachen , Germany
| | - Thomas Taubner
- Institute of Physics (IA) , RWTH Aachen University , 52074 Aachen , Germany
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18
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Richter J, Nezhad MP, Hadam B, Taubner T, Knoch J, Merget F, Moscoso-Mártir A, Witzens J. High-Q inverted silica microtoroid resonators monolithically integrated into a silicon photonics platform. Opt Express 2018; 26:27418-27440. [PMID: 30469810 DOI: 10.1364/oe.26.027418] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 09/16/2018] [Indexed: 06/09/2023]
Abstract
We report on the monolithic integration of a new class of reflown silica microtoroid resonators with silicon nanowaveguides fabricated on top of the silica film. Connectivity with other silicon photonics devices is enabled by inversion of the toroid geometry, defined by etching a circular opening rather than a disk in an undercut silica membrane. Intrinsic quality factors of up to 2 million are achieved and several avenues of process improvement are identified that can help attain the higher quality factors (> 108) that are possible in reflown microtoroids. Moreover, due to the microtoroid being formed by standard microfabrication and post-processing by local laser induced heating, these devices are in principle compatible with monolithic co-fabrication with other electro-optic components.
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19
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Yin X, Steinle T, Huang L, Taubner T, Wuttig M, Zentgraf T, Giessen H. Beam switching and bifocal zoom lensing using active plasmonic metasurfaces. Light Sci Appl 2017; 6:e17016. [PMID: 30167272 PMCID: PMC6062225 DOI: 10.1038/lsa.2017.16] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 02/13/2017] [Accepted: 02/14/2017] [Indexed: 05/03/2023]
Abstract
Compact nanophotonic elements exhibiting adaptable properties are essential components for the miniaturization of powerful optical technologies such as adaptive optics and spatial light modulators. While the larger counterparts typically rely on mechanical actuation, this can be undesirable in some cases on a microscopic scale due to inherent space restrictions. Here, we present a novel design concept for highly integrated active optical components that employs a combination of resonant plasmonic metasurfaces and the phase-change material Ge3Sb2Te6. In particular, we demonstrate beam switching and bifocal lensing, thus, paving the way for a plethora of active optical elements employing plasmonic metasurfaces, which follow the same design principles.
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Affiliation(s)
- Xinghui Yin
- 4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550 Stuttgart, Germany
- Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Tobias Steinle
- 4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550 Stuttgart, Germany
| | - Lingling Huang
- Beijing Institute of Technology, No. 5 South Zhongguancun Street, Beijing 100081, China
| | - Thomas Taubner
- I. Institute of Physics (IA), RWTH Aachen University, 52056 Aachen, Germany
| | - Matthias Wuttig
- I. Institute of Physics (IA), RWTH Aachen University, 52056 Aachen, Germany
| | - Thomas Zentgraf
- Department of Physics, University of Paderborn, Warburger Straße 100, 33098 Paderborn, Germany
| | - Harald Giessen
- 4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550 Stuttgart, Germany
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20
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Li P, Yang X, Maß TWW, Hanss J, Lewin M, Michel AKU, Wuttig M, Taubner T. Reversible optical switching of highly confined phonon-polaritons with an ultrathin phase-change material. Nat Mater 2016; 15:870-5. [PMID: 27213955 DOI: 10.1038/nmat4649] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Accepted: 04/27/2016] [Indexed: 05/14/2023]
Abstract
Surface phonon-polaritons (SPhPs), collective excitations of photons coupled with phonons in polar crystals, enable strong light-matter interaction and numerous infrared nanophotonic applications. However, as the lattice vibrations are determined by the crystal structure, the dynamical control of SPhPs remains challenging. Here, we realize the all-optical, non-volatile, and reversible switching of SPhPs by controlling the structural phase of a phase-change material (PCM) employed as a switchable dielectric environment. We experimentally demonstrate optical switching of an ultrathin PCM film (down to 7 nm, <λ/1,200) with single laser pulses and detect ultra-confined SPhPs (polariton wavevector kp > 70k0, k0 = 2π/λ) in quartz. Our proof of concept allows the preparation of all-dielectric, rewritable SPhP resonators without the need for complex fabrication methods. With optimized materials and parallelized optical addressing we foresee application potential for switchable infrared nanophotonic elements, for example, imaging elements such as superlenses and hyperlenses, as well as reconfigurable metasurfaces and sensors.
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Affiliation(s)
- Peining Li
- Institute of Physics (IA), RWTH Aachen University, Aachen 52056, Germany
| | - Xiaosheng Yang
- Institute of Physics (IA), RWTH Aachen University, Aachen 52056, Germany
| | - Tobias W W Maß
- Institute of Physics (IA), RWTH Aachen University, Aachen 52056, Germany
| | - Julian Hanss
- Institute of Physics (IA), RWTH Aachen University, Aachen 52056, Germany
| | - Martin Lewin
- Institute of Physics (IA), RWTH Aachen University, Aachen 52056, Germany
| | | | - Matthias Wuttig
- Institute of Physics (IA), RWTH Aachen University, Aachen 52056, Germany
| | - Thomas Taubner
- Institute of Physics (IA), RWTH Aachen University, Aachen 52056, Germany
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21
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Jung L, Hauer B, Li P, Bornhöfft M, Mayer J, Taubner T. Exploring the detection limits of infrared near-field microscopy regarding small buried structures and pushing them by exploiting superlens-related effects. Opt Express 2016; 24:4431-4441. [PMID: 29092272 DOI: 10.1364/oe.24.004431] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We present a study on subsurface imaging with an infrared scattering-type scanning near-field optical microscope (s-SNOM). The depth-limitation for the visibility of gold nanoparticles with a diameter of 50 nm under Si3N4 is determined to about 50 nm. We first investigate spot size and signal strength concerning their particle-size dependence for a dielectric cover layer with positive permittivity. The experimental results are confirmed by model calculations and a comparison to TEM images. In the next step, we investigate spectroscopically also the regime of negative permittivity of the capping layer and its influence on lateral resolution and signal strength in experiment and simulations. The explanation of this observation combines subsurface imaging and superlensing, and shows up limitations of the latter regarding small structure sizes.
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22
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Kunkemöller G, Mass TWW, Michel AKU, Kim HS, Brose S, Danylyuk S, Taubner T, Juschkin L. Extreme ultraviolet proximity lithography for fast, flexible and parallel fabrication of infrared antennas. Opt Express 2015; 23:25487-25495. [PMID: 26480066 DOI: 10.1364/oe.23.025487] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present a method for fabrication of large arrays of nano-antennas using extreme-ultraviolet (EUV) illumination. A discharge-produced plasma source generating EUV radiation around 10.88 nm wavelength is used for the illumination of a photoresist via a mask in a proximity printing setup. The method of metallic nanoantennas fabrication utilizes a bilayer photoresist and employs a lift-off process. The impact of Fresnel-diffraction of EUV light in the mask on a shape of the nanostructures has been investigated. It is shown how by the use of the same rectangular apertures in the transmission mask, antennas of various shapes can be fabricated. Using Fourier transform infrared spectroscopy, spectra of antennas reflectivity were measured and compared to FDTD simulations demonstrating good agreement.
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Tittl A, Michel AKU, Schäferling M, Yin X, Gholipour B, Cui L, Wuttig M, Taubner T, Neubrech F, Giessen H. A Switchable Mid-Infrared Plasmonic Perfect Absorber with Multispectral Thermal Imaging Capability. Adv Mater 2015; 27:4597-603. [PMID: 26173394 DOI: 10.1002/adma.201502023] [Citation(s) in RCA: 171] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Indexed: 05/14/2023]
Abstract
A switchable perfect absorber with multispectral thermal imaging capability is presented. Aluminum nanoantenna arrays above a germanium antimony telluride (GST) spacer layer and aluminum mirror provide efficient wavelength-tunable absorption in the mid-infrared. Utilizing the amorphous-to-crystalline phase transition in GST, this device offers switchable absorption with strong reflectance contrast at resonance and large phase-change-induced spectral shifts.
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Affiliation(s)
- Andreas Tittl
- 4th Physics Institute and Research Center Scope, University of Stuttgart, D-70569, Stuttgart, Germany
| | - Ann-Katrin U Michel
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Martin Schäferling
- 4th Physics Institute and Research Center Scope, University of Stuttgart, D-70569, Stuttgart, Germany
| | - Xinghui Yin
- 4th Physics Institute and Research Center Scope, University of Stuttgart, D-70569, Stuttgart, Germany
| | - Behrad Gholipour
- Centre for Disruptive Photonic Technologies, Nanyang Technological University, 637371, Singapore, Singapore
| | - Long Cui
- Centre for Disruptive Photonic Technologies, Nanyang Technological University, 637371, Singapore, Singapore
| | - Matthias Wuttig
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Thomas Taubner
- I. Institute of Physics (IA), RWTH Aachen University, D-52056, Aachen, Germany
| | - Frank Neubrech
- 4th Physics Institute and Research Center Scope, University of Stuttgart, D-70569, Stuttgart, Germany
| | - Harald Giessen
- 4th Physics Institute and Research Center Scope, University of Stuttgart, D-70569, Stuttgart, Germany
- Centre for Disruptive Photonic Technologies, Nanyang Technological University, 637371, Singapore, Singapore
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Abstract
Active control over the handedness of a chiral metamaterial has the potential to serve as key element for highly integrated polarization engineering approaches, polarization sensitive imaging devices, and stereo display technologies. However, this is hard to achieve as it seemingly involves the reconfiguration of the metamolecule from a left-handed into a right-handed enantiomer and vice versa. This type of mechanical actuation is intricate and usually neither monolithically realizable nor viable for high-speed applications. Here, enabled by the phase change material Ge3Sb2Te6 (GST-326), we demonstrate a tunable and switchable mid-infrared plasmonic chiral metamaterial in a proof-of-concept experiment. A large tunability range of the circular dichroism response from λ = 4.15 to 4.90 μm is achieved, and we experimentally demonstrate that the combination of a passive bias-type chiral layer with the active chiral metamaterial allows for switchable chirality, that is, the reversal of the circular dichroism sign, in a fully planar, layered design without the need for geometrical reconfiguration. Because phase change materials can be electrically and optically switched, our designs may open up a path for highly integrated mid-IR polarization engineering devices that can be modulated on ultrafast time scales.
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Affiliation(s)
- Xinghui Yin
- †4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550, Stuttgart, Germany
- §Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Martin Schäferling
- †4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550, Stuttgart, Germany
| | - Ann-Katrin U Michel
- ‡I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
| | - Andreas Tittl
- †4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550, Stuttgart, Germany
| | - Matthias Wuttig
- ‡I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
| | - Thomas Taubner
- ‡I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
| | - Harald Giessen
- †4th Physics Institute and Research Center SCoPE, University of Stuttgart, 70550, Stuttgart, Germany
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25
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Hauer B, Saltzmann T, Simon U, Taubner T. Solvothermally Synthesized Sb2Te3 Platelets Show Unexpected Optical Contrasts in Mid-Infrared Near-Field Scanning Microscopy. Nano Lett 2015; 15:2787-2793. [PMID: 25868047 DOI: 10.1021/nl503697c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report nanoscale-resolved optical investigations on the local material properties of Sb2Te3 hexagonal platelets grown by solvothermal synthesis. Using mid-infrared near-field microscopy, we find a highly symmetric pattern, which is correlated to a growth spiral and which extends over the entire platelet. As the origin of the optical contrast, we identify domains with different densities of charge carriers. On Sb2Te3 samples grown by other means, we did not find a comparable domain structure.
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Affiliation(s)
- Benedikt Hauer
- †Institute of Physics (IA) and JARA - Fundamentals of Future Information Technologies, RWTH Aachen University, 52056 Aachen, Germany
| | - Tobias Saltzmann
- ‡Institute of Inorganic Chemistry (IAC) and JARA - Fundamentals of Future Information Technologies, RWTH Aachen University, 52056 Aachen, Germany
| | - Ulrich Simon
- ‡Institute of Inorganic Chemistry (IAC) and JARA - Fundamentals of Future Information Technologies, RWTH Aachen University, 52056 Aachen, Germany
| | - Thomas Taubner
- †Institute of Physics (IA) and JARA - Fundamentals of Future Information Technologies, RWTH Aachen University, 52056 Aachen, Germany
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26
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Shang D, Li P, Wang T, Carria E, Sun J, Shen B, Taubner T, Valov I, Waser R, Wuttig M. Understanding the conductive channel evolution in Na:WO(3-x)-based planar devices. Nanoscale 2015; 7:6023-6030. [PMID: 25766380 DOI: 10.1039/c4nr07545e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO(3-x)) films on a soda-lime glass substrate, from which Na(+) diffuses into the WO(3-x) films during the deposition. The entire process of Na(+) migration driven by an alternating electric field is visualized in the Na-doped WO(3-x) films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na(+) mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices.
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Affiliation(s)
- Dashan Shang
- I. Physikalisches Institut (IA), RWTH Aachen University, 52074 Aachen, Germany.
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27
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Bensmann S, Gaußmann F, Lewin M, Wüppen J, Nyga S, Janzen C, Jungbluth B, Taubner T. Near-field imaging and spectroscopy of locally strained GaN using an IR broadband laser. Opt Express 2014; 22:22369-22381. [PMID: 25321708 DOI: 10.1364/oe.22.022369] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Scattering-type scanning near-field optical microscopy (SNOM) offers the possibility to analyze material properties like strain in crystals at the nanoscale. In this paper we introduce a SNOM setup employing a newly developed tunable broadband laser source with a covered spectral range from 9 µm to 16 µm. This setup allows for the first time optical analyses of the crystal structure of gallium nitride (GaN) at the nanometer scale by excitation of a near-field phonon resonance around 14.5 µm. On the example of an artificially induced stress field within a GaN wafer, we present a method for a 2D visualization of small deviations in the crystal structure, which allows for fast qualitative characterizations. Subsequently, the stress levels at chosen points were quantified by recording complex near-field spectra and correlating them with theoretical model calculations. Applied to the cross-section of a heteroepitaxially grown GaN wafer, we finally demonstrate the capability of our setup to analyze the relaxation of the crystal structure along the growth axis with a nanometer spatial resolution.
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Abstract
Graphene is a promising two-dimensional platform for widespread nanophotonic applications. Recent theories have predicted that graphene can also enhance evanescent fields for subdiffraction-limited imaging. Here, for the first time we experimentally demonstrate that monolayer graphene offers a 7-fold enhancement of evanescent information, improving conventional infrared near-field microscopy to resolve buried structures at a 500 nm depth with λ/11-resolution.
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Affiliation(s)
- Peining Li
- 1st Institute of Physics (IA), RWTH Aachen University , 52056 Aachen, Germany
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29
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Hoffmann JM, Janssen H, Chigrin DN, Taubner T. Enhanced infrared spectroscopy using small-gap antennas prepared with two-step evaporation nanosphere lithography. Opt Express 2014; 22:14425-32. [PMID: 24977539 DOI: 10.1364/oe.22.014425] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We use nanosphere lithography in combination with two evaporation steps to create bow-tie like infrared antennas with small gaps. The angle of the sample with respect to the evaporation source is changed between two evaporation steps resulting in a displacement of the respective antenna arrays and, therefore, in decreased antenna-gaps. Furthermore, we demonstrate the gap-dependency of surface-enhanced infrared absorption (SEIRA) spectroscopy using the absorption band of the natural SiO(2)-layer of the silicon substrate and antennas with different gap size. A multi-oscillator-model is used to describe the Fano-like spectral coupling of the antenna resonances with the SiO(2) absorption band.
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30
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Reininghaus M, Wortmann D, Cao Z, Hoffmann JM, Taubner T. Fabrication and spectral tuning of standing gold infrared antennas using single fs-laser pulses. Opt Express 2013; 21:32176-32183. [PMID: 24514811 DOI: 10.1364/oe.21.032176] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Upright standing gold monopole nanoantennas are fabricated by irradiation of thin gold films with single pulses of fs-laser radiation. The resulting antennas exhibit extinction resonances in the mid infrared spectral rage for p-polarized light under grazing incidence. Due to the free charge carriers in the surrounding gold film of the antenna, the resonance condition of the thin-wire monopole antenna can be explained by introducing image charges yielding an observable resonance wavelength of four times the antenna length. The antenna length is controlled coarsely by the focusing numerical aperture and fine by the pulse energy of the laser pulse producing the structure. An additional ultrafine tuning of the resonance wavelength with a sub-10 nm resolution is realized by an additional coating process subsequent to the laser structuring.
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31
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Wang T, Li P, Hauer B, Chigrin DN, Taubner T. Optical properties of single infrared resonant circular microcavities for surface phonon polaritons. Nano Lett 2013; 13:5051-5055. [PMID: 24117024 DOI: 10.1021/nl4020342] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Plasmonic antennas are crucial components for nano-optics and have been extensively used to enhance sensing, spectroscopy, light emission, photodetection, and others. Recently, there is a trend to search for new plasmonic materials with low intrinsic loss at new plasmon frequencies. As an alternative to metals, polar crystals have a negative real part of permittivity in the Reststrahlen band and support surface phonon polaritons (SPhPs) with weak damping. Here, we experimentally demonstrate the resonance of single circular microcavities in a thin gold film deposited on a silicon carbide (SiC) substrate in the mid-infrared range. Specifically, the negative permittivity of SiC leads to a well-defined, size-tunable SPhP resonance with a Q factor of around 60 which is much higher than those in surface plasmon polariton (SPP) resonators with similar structures. These infrared resonant microcavities provide new possibilities for widespread applications such as enhanced spectroscopy, sensing, coherent thermal emission, and infrared photodetectors among others throughout the infrared frequency range.
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Affiliation(s)
- Tao Wang
- First Institute of Physics (IA), RWTH Aachen University , Aachen 52056, Germany
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32
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Michel AKU, Chigrin DN, Maß TWW, Schönauer K, Salinga M, Wuttig M, Taubner T. Using low-loss phase-change materials for mid-infrared antenna resonance tuning. Nano Lett 2013; 13:3470-3475. [PMID: 23742151 DOI: 10.1021/nl4006194] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We show tuning of the resonance frequency of aluminum nanoantennas via variation of the refractive index n of a layer of phase-change material. Three configurations have been considered, namely, with the antennas on top of, inside, and below the layer. Phase-change materials offer a huge index change upon the structural transition from the amorphous to the crystalline state, both stable at room temperature. Since the imaginary part of their permittivity is negligibly small in the mid-infrared spectral range, resonance damping is avoided. We present resonance shifting to lower as well as to higher wavenumbers with a maximum shift of 19.3% and a tuning figure of merit, defined as the resonance shift divided by the full-width at half-maximum (FWHM) of the resonance peak, of 1.03.
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Abstract
We investigate surface enhanced infrared absorption (SEIRA) spectroscopy with gold strip gratings made by standard optical lithography. By exciting surface plasmon polaritons on both air-gold and gold-substrate interfaces, the resonance of the 1D gratings is linearly tunable with the grating period. With the field enhancement at the edge of the gold strips, a SEIRA enhancement factor more than 6000 for PMMA molecules is achieved. The strong SEIRA enhancement together with the easy fabrication makes the gold strip grating a promising candidate for SEIRA experiments.
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Affiliation(s)
- Tao Wang
- 1st Institute of Physics (1A), RWTH Aachen University, 52056 Aachen, Germany
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34
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Engelhardt AP, Hauer B, Taubner T. Visibility of weak contrasts in subsurface scattering near-field microscopy. Ultramicroscopy 2012; 126:40-3. [PMID: 23376405 DOI: 10.1016/j.ultramic.2012.12.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 12/07/2012] [Indexed: 11/29/2022]
Abstract
We present a systematic study of the effect of the tip vibration amplitude in scattering-type scanning near-field optical microscopy (s-SNOM) on the visibility of buried structures in terms of image contrast, signal strength, and noise. When varying the tip vibration amplitude the visibility of structures and the image contrast change in opposite directions. We address the question how to optimize the tip vibration amplitude in practice and discuss the respective advantages of either high contrast or low noise. Besides for subsurface imaging, our findings can also be applied to the imaging of structures with a low material contrast on the surface.
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35
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Abstract
Graphene as a one-atom-thick planar sheet can support surface plasmons at infrared (IR) and terahertz (THz) frequencies, opening up exciting possibilities for the emerging research field of graphene plasmonics. Here, we theoretically report that a layered graphene-lens (GL) enables the enhancement of evanescent waves for near-field subdiffractive imaging. Compared to other resonant imaging devices like superlenses, the nonresonant operation of the GL provides the advantages of a broad intrinsic bandwidth and a low sensitivity to losses, while still maintaining a good subwavelength resolution of better than λ/10. Most importantly, thanks to the large tunability of the graphene, we show that our GL is a continuously frequency-tunable subwavelength-imaging device in the IR and THz regions, thus allowing for ultrabroadband spectral applications.
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Affiliation(s)
- Peining Li
- 1st Institute of Physics (IA), RWTH Aachen University, 52056 Aachen, Germany
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36
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Hauer B, Engelhardt AP, Taubner T. Quasi-analytical model for scattering infrared near-field microscopy on layered systems. Opt Express 2012; 20:13173-13188. [PMID: 22714345 DOI: 10.1364/oe.20.013173] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present a quantitative quasi-analytical model to predict and analyze signals on layered samples measured by infrared scattering-type scanning near-field optical microscopy. Our model predictions are compared to experimental data and to fully retarded calculations based on a point dipole approximation of the tip. The model is used to study the influence of the tip vibration amplitude and of the tip radius on the near-field contrasts of samples with particularly small variations in the layer thickness. Additionally the influence of a dielectric capping layer on the tip-substrate coupling is analyzed. When inversely applied, our calculation opens the possibility to extract the local layer thickness of thin films or the dielectric functions that allow one to draw conclusions on the material composition, conductivity or crystal structure on the nanoscale.
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Affiliation(s)
- Benedikt Hauer
- Institute of Physics (IA), JARA – Fundamentals of Future Information Technologies RWTH Aachen University, 52056 Aachen, Germany
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37
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Abstract
We theoretically propose a multilayered polar-dielectric superlens system capable of sub-diffraction limited imaging simultaneously at different wavelengths. Our theory and simulation results show that this multilayered lens can fulfill a superlensing condition at multiple different wavelengths due to phonon resonances of polar dielectrics, and the number of superlensing wavelengths of the lens can be easily tuned by controlling the number of polar dielectrics. Ideally, by suitably choosing polar dielectrics, our lens can cover wavelengths ranging from infrared to THz frequencies.
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Affiliation(s)
- Peining Li
- 1st Institute of Physics, IA, RWTH Aachen University, 52056 Aachen, Germany
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38
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Abstract
We study the amplitude and phase signals detected in infrared scattering-type near field optical microscopy (s-SNOM) when probing a thin sample layer on a substrate. We theoretically describe this situation by solving the electromagnetic scattering of a dipole near a planar sample consisting of a substrate covered by thin layers. We perform calculations to describe the effect of both weakly (Si and SiO(2)) and strongly (Au) reflecting substrates on the spectral s-SNOM signal of a thin PMMA layer. We theoretically predict, and experimentally confirm an enhancement effect in the polymer vibrational spectrum when placed on strongly reflecting substrates. We also calculate the scattered fields for a resonant tip-substrate interaction, obtaining a dramatic enhancement of the signal amplitude and spectroscopic contrast of the sample layer, together with a change of the spectral line shape. The enhanced contrast opens the possibility to perform ultra-sensitive near field infrared spectroscopy of monolayers and biomolecules.
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Affiliation(s)
- Javier Aizpurua
- Donostia International Physics Center, P. Manuel Lardizabal 4, 20018 San Sebastián, Spain.
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39
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Schuller JA, Zia R, Taubner T, Brongersma ML. Dielectric metamaterials based on electric and magnetic resonances of silicon carbide particles. Phys Rev Lett 2007; 99:107401. [PMID: 17930407 DOI: 10.1103/physrevlett.99.107401] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2007] [Indexed: 05/25/2023]
Abstract
Silicon carbide particles exhibit both electric and magnetic optical resonances, allowing unexplored dielectric metamaterial designs. Experimental extinction spectra and Mie theory calculations of single microscale rod-shaped particles reveal three observable midinfrared resonant modes. Two of the modes are degenerate, with a frequency that can be tuned according to a resonance condition derived within the Letter. The existence of both electric and magnetic resonances may enable a novel negative refractive index metamaterial design.
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Affiliation(s)
- Jon A Schuller
- Geballe Laboratory for Advanced Materials, 476 Lomita Mall, Stanford, California 94305, USA
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40
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Abstract
The wave nature of light limits the spatial resolution in classical microscopy to about half of the illumination wavelength. Recently, a new approach capable of achieving subwavelength spatial resolution, called superlensing, was invented, challenging the already established method of scanning near-field optical microscopy (SNOM). We combine the advantages of both techniques and demonstrate a novel imaging system where the objects no longer need to be in close proximity to a near-field probe, allowing for optical near-field microscopy of subsurface objects at sub-wavelength-scale lateral resolution.
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Affiliation(s)
- Thomas Taubner
- Nano-Photonics Group, Max-Planck-Institut für Biochemie, Am Klopferspitz 18, D-82152 Martinsried, Germany
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41
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Brehm M, Taubner T, Hillenbrand R, Keilmann F. Infrared spectroscopic mapping of single nanoparticles and viruses at nanoscale resolution. Nano Lett 2006; 6:1307-10. [PMID: 16834401 DOI: 10.1021/nl0610836] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We demonstrate that scattering near-field microscopy (s-SNOM) can determine infrared "fingerprint" spectra of individual poly(methyl methacrylate) nanobeads and viruses as small as 18 nm. Amplitude and phase spectra are found surprisingly strong, even at a probed volume of only 10(-20) l, and robust in regard to particle size and substrate. This makes infrared spectroscopic s-SNOM a versatile tool for chemical and-in the case of protein-secondary-structure identification.
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Affiliation(s)
- Markus Brehm
- Max-Planck-Institut für Biochemie & Center for NanoScience (CeNS), München, Germany
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42
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Huber A, Ocelic N, Taubner T, Hillenbrand R. Nanoscale resolved infrared probing of crystal structure and of plasmon-phonon coupling. Nano Lett 2006; 6:774-8. [PMID: 16608282 DOI: 10.1021/nl060092b] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We show that slight variations of a crystal lattice cause significant spectral modifications of phonon-polariton resonant near-field interaction between polar semiconductor crystals and a scanning metal tip. Exploiting the effect for near-field imaging a SiC polytype boundary, we establish infrared mapping of crystal structure and crystal defects at 20 nm spatial resolution (lambda/500). By spectroscopic probing of doped SiC polytypes, we find that phonon-polariton resonant near-field interaction is also sensitive to electronic properties due to plasmon-phonon coupling in the crystals.
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Affiliation(s)
- A Huber
- Nano-Photonics Group, Max-Planck-Institut für Biochemie & Center for Nanoscience, Am Klopferspitz 18, 82152 Martinsried, Germany
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43
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Taubner T, Keilmann F, Hillenbrand R. Nanoscale-resolved subsurface imaging by scattering-type near-field optical microscopy. Opt Express 2005; 13:8893-8899. [PMID: 19498922 DOI: 10.1364/opex.13.008893] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We demonstrate that scattering-type scanning near-field optical microscopy (s-SNOM) allows nanoscale-resolved imaging of objects below transparent surface layers at both visible and mid-infrared wavelengths. We show topography-free subsurface imaging at lambda=633 nm. At lambda=10.7 microm, gold islands buried 50 nm below a polymer surface are imaged with a lateral resolution < 120 nm, corresponding to lambda/90. Studying oxide layers with systematically varied thicknesses we provide experimental evidence of mid-infrared near-field probing in depths > 80 nm.
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44
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Abstract
We describe the principles of two scattering-type near-field optical microscopes (s-SNOMs), one operating at 633 nm wavelength, the other at selectable wavelengths in the range 7.3-11.3 micro m, and compare the measurement experience. Both use interferometric detection of scattered radiation, and are therefore capable of amplitude and phase-contrast imaging. In this study both instruments use the same or even identical commercial probe tips, and measure a single, three-component, test sample. Our results show that the imaging process of s-SNOM is wavelength-independent, namely, that the resolution is determined by the properties of the tip only, and that the contrast is given by the complex refractive index of the sample, predictable from a simple, analytical model of tip-sample interaction. A novel, 'edge-darkening' artefact is described which may appear in s-SNOM and that is wavelength-independent.
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Affiliation(s)
- T Taubner
- Max-Planck-Institut für Biochemie, 82152 Martinsried, Germany.
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45
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Abstract
Optical near fields exist close to any illuminated object. They account for interesting effects such as enhanced pinhole transmission or enhanced Raman scattering enabling single-molecule spectroscopy. Also, they enable high-resolution (below 10 nm) optical microscopy. The plasmon-enhanced near-field coupling between metallic nanostructures opens new ways of designing optical properties and of controlling light on the nanometre scale. Here we study the strong enhancement of optical near-field coupling in the infrared by lattice vibrations (phonons) of polar dielectrics. We combine infrared spectroscopy with a near-field microscope that provides a confined field to probe the local interaction with a SiC sample. The phonon resonance occurs at 920 cm(-1). Within 20 cm(-1) of the resonance, the near-field signal increases 200-fold; on resonance, the signal exceeds by 20 times the value obtained with a gold sample. We find that phonon-enhanced near-field coupling is extremely sensitive to chemical and structural composition of polar samples, permitting nanometre-scale analysis of semiconductors and minerals. The excellent physical and chemical stability of SiC in particular may allow the design of nanometre-scale optical circuits for high-temperature and high-power operation.
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Affiliation(s)
- R Hillenbrand
- Max-Planck-Institut für Biochemie, Abteilung Molekulare Strukturbiologie, 82152 Martinsried, Germany
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