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Microstructure-Induced Anisotropic Optical Properties of YF 3 Columnar Thin Films Prepared by Glancing Angle Deposition. NANOMATERIALS 2020; 10:nano10122413. [PMID: 33287123 PMCID: PMC7761633 DOI: 10.3390/nano10122413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 11/30/2020] [Accepted: 11/30/2020] [Indexed: 11/17/2022]
Abstract
Yttrium fluoride (YF3) columnar thin films (CTFs) were fabricated by electron beam evaporation with the glancing angle deposition method. The microstructures and optical properties of YF3 CTFs were studied systematically. The YF3 films grown at different deposition angles are all amorphous. As the deposition angle increases, the columns in YF3 CTFs become increasingly separated and inclined, and the volume fraction of YF3 decreases, resulting in lower refractive indices. This phenomenon is attributed to the self-shadowing effect and limited adatom diffusion. The YF3 CTFs are optically biaxial anisotropic with the long axis (c-axis) parallel to the columns, the short axis (b-axis) perpendicular to the columns, and the other axis (a-axis) parallel to the film interface. The principal refractive index along the b-axis for the 82°-deposited sample is approximately 1.233 at 550 nm. For the 78°-deposited sample, the differences of principal refractive indices between the c-axis and the b-axis and between the a-axis and the b-axis reach the maximum 0.056 and 0.029, respectively. The differences of principal refractive indices were affected by both the deposition angle and the volume fraction of YF3.
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Ge B, Larson S, Tu H, Zhao Y, Fei Y. Generalized ellipsometry characterization of Ag nanorod arrays prepared by oblique angle deposition. NANOTECHNOLOGY 2020; 31:075705. [PMID: 31675750 DOI: 10.1088/1361-6528/ab53ae] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Silver nanorods arrays (AgNRs) prepared by oblique angle deposition were characterized by the generalized ellipsometry method in the spectral range from 370 to 950 nm. Three structure models were used to fit the ellipsometry data, the uniaxial model, the biaxial orthorhombic model, and the biaxial monoclinic model. Unlike the uniaxial model reported in most literature, the biaxial models are found to give better fitting results. The optical properties along the three principle axes are different: along long axis it displays predominantly metallic behavior; along one short axis it approaches to a lossless dielectric while along the other it behaves as an absorbance dielectric. The AgNRs also demonstrate epsilon-near-zero property with the real part of dielectric constant along the rod being very close to zero at wavelength of 416 nm, which is expected to be tuned with changing of the vapor incident angles.
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Affiliation(s)
- Bilin Ge
- Department of Optical Science and Engineering, Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, Shanghai, 200433, People's Republic of China
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Wang Y, Zhang Z, Zhao Y. The IR plasmonic properties of sub-wavelength ITO rod arrays predicted by anisotropic effective medium theory. NANOTECHNOLOGY 2020; 31:075203. [PMID: 31661675 DOI: 10.1088/1361-6528/ab5275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Simple three-layer Fresnel equations combined with Maxwell-Garnett approximation were applied to study the IR plasmonic properties of indium-tin-oxide (ITO) nanorods. By treating the anisotropic nanorod layer as a layer with an effective dielectric constant, and using anisotropic effective medium theory, we were able to accurately predict the surface plasmon resonance behavior of ITO nanorods with different nanorod length, spacing, and tilt angle. This model allows a fast and computationally inexpensive calculation to predict the plasmonic properties of arrayed nanorods.
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Affiliation(s)
- Yanfeng Wang
- Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, People's Republic of China. Department of Physics and Astronomy, and Nanoscale Science and Engineering Center, University of Georgia, Athens, GA 30602, United States of America
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Zang R, Hu H, Li X, Gao J, Liang L, Zhang H, Zhuge F, Luo J, Cao H. Broadband hyperbolic metamaterial covering the whole visible-light region. OPTICS LETTERS 2019; 44:2970-2973. [PMID: 31199358 DOI: 10.1364/ol.44.002970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 05/08/2019] [Indexed: 06/09/2023]
Abstract
Nanowire-based hyperbolic metamaterials (HMMs) with rich optical dispersion engineering capabilities are promising for use in miniaturization devices, such as nanophotonic chips and circuits. Herein, based on a one-step and template-free sputtering method, we are capable of precisely tuning the microstructural parameters of Ag nanowires (with a diameter <10 nm) in silica matrix, offering plenty of opportunities to perform hyperbolic dispersion engineering. Thus, the effective plasma frequency of the designed HMMs was shifted into the near-ultraviolet region (∼350 nm), leading to a broadband hyperbolic dispersion feature covering the whole visible-light region. This demonstration could pave the way for the development of metamaterial-based flat lenses, deep-subwavelength waveguiding, and broadband perfect absorbers and sensing, etc.
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Silver-Nanoparticle-Decorated Gold Nanorod Arrays via Bioinspired Polydopamine Coating as Surface-Enhanced Raman Spectroscopy (SERS) Platforms. COATINGS 2019. [DOI: 10.3390/coatings9030198] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The controlled deposition of nanoparticles onto 3-D nanostructured films is still facing challenges due to the uncontrolled aggregation of colloidal nanoparticles. In the context of this study, a simple yet effective approach is demonstrated to decorate the silver nanoparticles (AgNP) onto the 3-D and anisotropic gold nanorod arrays (GNAs) through a bioinspired polydopamine (PDOP) coating to fabricate surface-enhanced Raman spectroscopy (SERS) platforms. Since the Raman reporter molecules (methylene blue, MB, 10 µM) were not adsorbed directly on the surface of the plasmonic material, a remarkable decrease in SERS signals was detected for the PDOP-coated GNAs (GNA@PDOP) platforms. However, after uniform and well-controlled AgNP decoration on the GNA@PDOP (GNA@PDOP@AgNP), huge enhancement was observed in SERS signals from the resultant platform due to the synergistic action which originated from the interaction of GNAs and AgNPs. I also detected that PDOP deposition time (i.e., PDOP film thickness) is the dominant parameter that determines the SERS activity of the final system and 30 min of PDOP deposition time (i.e., 3 nm of PDOP thickness) is the optimum value to obtain the highest SERS signal. To test the reproducibility of GNA@PDOP@AgNP platforms, relative standard deviation (RSD) values for the characteristic peaks of MB were found to be less than 0.17, demonstrating the acceptable reproducibility all over the proposed platform. This report suggests that GNA@PDOP@AgNP system may be used as a robust platform for practical SERS applications.
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Lattery DM, Kim M, Choi J, Lee BJ, Wang X. Effective Radiative Properties of Tilted Metallic Nanorod Arrays Considering Polarization Coupling. Sci Rep 2018; 8:13896. [PMID: 30224764 PMCID: PMC6141545 DOI: 10.1038/s41598-018-32265-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 09/05/2018] [Indexed: 11/29/2022] Open
Abstract
With the advent of new nanomanufacturing techniques has come the rise of the field of nanophotonics and an increased need to determine optical properties of novel structures. Commercial software packages are able to estimate the behavior, but require large resources and heavy computational time. By combining coordinate transforms and Effective Medium Theory (EMT), an effective relative permittivity tensor is defined and further exploited to calculate the polarization-coupled Fresnel coefficients through Maxwell’s equations. A uniaxial simplification is made to show the case of tilted nanorod arrays. To demonstrate the flexibility of this system, the interfacial reflectance has been calculated for both s- and p-polarizations as well as the coupled case with the volume filling fractions of f = 0.10 and 0.30 for silver (Ag) and titanium (Ti) nanorods, and a scenario of a Ag nanorod array with polymethyl methacrylate (PMMA) as the surrounding medium. The exact results computed by the finite-difference time-domain method justify the validity of EMT with polarization coupling taken into account. The effects of incidence angle and azimuthal angle on reflectance are also discussed. The relatively simple nature of this approach allows for fast estimations of the optical properties of various nanostructures.
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Affiliation(s)
- Dustin M Lattery
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Mingeon Kim
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 34141, South Korea
| | - Jongin Choi
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 34141, South Korea
| | - Bong Jae Lee
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 34141, South Korea.
| | - Xiaojia Wang
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
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Zhou K, Cheng Q, Song J, Lu L, Jia Z, Li J. Broadband perfect infrared absorption by tuning epsilon-near-zero and epsilon-near-pole resonances of multilayer ITO nanowires. APPLIED OPTICS 2018; 57:102-111. [PMID: 29328120 DOI: 10.1364/ao.57.000102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 11/30/2017] [Indexed: 06/07/2023]
Abstract
We numerically investigate the broadband perfect infrared absorption by tuning epsilon-near-zero (ENZ) and epsilon-near-pole (ENP) resonances of multilayer indium tin oxide nanowires (ITO NWs). The monolayer ITO NWs array shows intensive absorption at ENZ and ENP wavelengths for p polarization, while only at the ENP wavelength for s polarization. Moreover, the ENP resonances are almost omnidirectional and the ENZ resonances are angularly dependent. Therefore, the absorption bandwidth is broader for p polarization than that for s polarization when polarized waves are incident obliquely. The ENZ resonances can be tuned by altering the doping concentration and volume filling factor of ITO NWs. However, the ENP resonances only can be tuned by changing the doping concentration of ITO NWs, and volume filling factor impacts little on the ENP resonances. Based on the strong absorption properties of each layer at their own ENP and ENZ resonances, the tuned absorption of the bilayer ITO NWs with the different doping concentrations can be broader and stronger. Furthermore, multilayer ITO NWs can achieve broadband perfect absorption by controlling the doping concentration, volume filling factor, and length of the NWs in each layer. This study has the potential to apply to applications requiring efficient absorption and energy conversion.
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Zhao Y, Fu C. Multiband selective absorbers made of 1D periodic Ag/SiO 2/Ag core/shell coaxial cylinders horizontally lying on a planar substrate. OPTICS EXPRESS 2017; 25:A208-A222. [PMID: 28437916 DOI: 10.1364/oe.25.00a208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this paper, we present a one-dimensional periodic microstructure for multiband selective absorbers of thermal radiation. The microstructure is made of Ag/SiO2/Ag core/shell coaxial cylinders horizontally lying on top of a SiO2 dielectric spacer and an opaque silver substrate. The spectral-directional absorptivity of the proposed structure was numerically investigated with the finite element based Comsol Multiphysics software. Multiband selective absorption in the wavenumber range from 2500 to 20000 cm-1 for TM-wave incidence was obtained. Physical mechanisms responsible for the multiband selective absorption were elucidated due to the resonance of magnetic polaritons in the SiO2 spacer shell, excitation of surface plasmon polaritons at the SiO2/Ag interface, and the effect of Wood's anomaly. Furthermore, the effects of a silver core radius, spacer shell thickness, a confocal elliptical core/shell cylinder on the property of multiband absorption, and the absorptivity of the structure with one core/four shells coaxial cylinders were explored.
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Yilmaz M, Senlik E, Biskin E, Yavuz MS, Tamer U, Demirel G. Combining 3-D plasmonic gold nanorod arrays with colloidal nanoparticles as a versatile concept for reliable, sensitive, and selective molecular detection by SERS. Phys Chem Chem Phys 2014; 16:5563-70. [DOI: 10.1039/c3cp55087g] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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