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Light Emission from Self‐Assembled and Laser‐Crystallized Rapid #: -16480465 CROSS REF ID: 1104701 LENDER: ZCU :: Electronic BORROWER: PUL :: Interlibrary Services, Firestone TYPE: Article CC:CCG JOURNAL TITLE: Advanced optical materials USER JOURNAL TITLE: Advanced Optical Materials ARTICLE TITLE: Light Emission from Self-Assembled and Laser-Crystallized Chalcogenide Metasurface ARTICLE AUTHOR: Feifan Wang, Zi Wang, Dun Mao, Mingkun Chen, Qiu L VOLUME: 8 ISSUE: 8 MONTH: April YEAR: 2020 PAGES: NA ISSN: 2195-1071 OCLC #: Processed by RapidX: 8/17/2020 9:02:16 AM This material may be protected by copyright law (Title 17 U.S. Code) FULL PAPER www.advopticalmat.de Light Emission from Self-Assembled and Laser-Crystallized Chalcogenide Metasurface Feifan Wang, Zi Wang, Dun Mao, Mingkun Chen, Qiu Li, Thomas Kananen, Dustin Fang, Anishkumar Soman, Xiaoyong Hu, Craig B. Arnold,* and Tingyi Gu* demonstrated to improve the light emis- Subwavelength periodic confinement can collectively and selectively sion efficiency through enhancing light enhance local light intensity and enable control over the photoinduced phase outcoupling efficiency[1,2] and sponta- [3–5] transformations at the nanometer scale. Standard nanofabrication process neous emission rate. Nanophotonic engineering can lead to narrowband can result in geometrical and compositional inhomogeneities in optical phase and directive light emission.[6–8] Chal- change materials, especially chalcogenides, as those materials exhibit poor cogenide materials with unique phase chemical and thermal stability. Here the self-assembled planar chalcogenide change properties have been explored nanostructured array is demonstrated with resonance-enhanced light for tunable thermal emission[9] or reflec- [10] emission to create an all-dielectric optical metasurface, by taking advantage tion in infrared wavelength ranges. of the fluid properties associated with solution-processed films. A patterned PhC waveguide has been demonstrated on thin-film chalcogenide by e-beam silicon membrane serves as a template for shaping the chalcogenide lithography, showing slow light and res- metasurface structure. Solution-processed arsenic sulfide metasurface onance-enhanced parametric nonlinear structures are self-assembled in the suspended 250 nm silicon membrane process in material.[11,12] To reduce cost templates. The periodic nanostructure dramatically manifests the local light– and improve scalability, solution-processed matter interaction such as absorption of incident photons, Raman emission, chalcogenide nanostructure is recently reported through solution process and and photoluminescence. Also, the thermal distribution is modified by the self-assembling.[13] In this work, we dem- boundaries and thus the photothermal crystallization process, leading to the onstrate the first active chalcogenide formation of anisotropic nanoemitters within the field enhancement area. This metasurface fabricated by self-assembling hybrid structure shows wavelength-selective anisotropic photoluminescence, with tunable dimensions. The nanopho- which is a characteristic behavior of the collective response of the resonant- tonic structure is tailored to enhance the guided modes in a periodic nanostructure. The resonance-enhanced Purcell light emission efficiency through reso- nance-enhanced absorption of excitation, effect can manifest the quantum efficiency of localized light emission. suppressing guided mode at emission wavelength and Purcell enhancement.[14–17] The 2D hexagonal chalcogenide nanorod 1. Introduction arrays are self-assembled[13] on a silicon template through solu- tion processing.[18–24] Silicon nanophotonic structure with a few Periodic perturbation of refractive index in subwavelength nanometer surface roughness enables delamination of top and dimensions can boost efficiency of light emission device. Many bottom bulk chalcogenides during solvent evaporation leaving nanophotonic structures, such as photonic crystals (PhCs), only a filled nanorod array. Nanophotonic confinement can plasmonic structures, gratings, and resonators, have been simultaneously manifest local photon density for enhanced F. Wang, Z. Wang, D. Mao, M. Chen, Dr. Q. Li, T. Kananen, D. Fang, Dr. Q. Li A. Soman, Dr. T. Gu Tianjin Key Laboratory of High Speed Cutting and Precision Machining Electrical and Computer Engineering School of Mechanical Engineering University of Delaware Tianjin University of Technology and Education Newark, DE 19716, USA Tianjin 300222, P. R. China E-mail: [email protected] Dr. C. B. Arnold F. Wang, Dr. X. Hu Princeton Institute for the Science and Technology of Materials State Key Laboratory for Mesoscopic Physics & Department Princeton University of Physics Collaborative Innovation Center of Quantum Matter Princeton, NJ 08544, USA Peking University E-mail: [email protected] Beijing 100871, P. R. China The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.201901236. DOI: 10.1002/adom.201901236 Adv. Optical Mater. 2020, 8, 1901236 1901236 (1 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.advancedsciencenews.com www.advopticalmat.de Figure 1. Self-assembled chalcogenide metasurface with the solution process. a) Fabrication process: i) Suspended planar silicon nanostructure; ii) drop-casting As2S3 solution; iii) reflow and delamination; and iv) top illuminated optical excitation. b) Scanning electron microscope of delaminated As2S3–silicon interface after step (iii). The silicon nanostructured template has hole radii from 80 to 150 nm, with 10 nm per step. Scale bars: 1 µm. c) Atomic force microscope image of the self-assembled surface topology. resonance absorption[25] and nonlinear process.[26] The guided on a 250 nm thick silicon-on-insulator device layer via ultravi- mode with a concentration in the light-emitting materials can olet lithography and etching for reduced disorder scattering[30] significantly enhance the quantum efficiency of both stimulated (Figure S1, Supporting Information). The lattice constant of Raman emission and spontaneous photoluminescence (PL) the periodic structure is 415 nm, and we vary the hole radii process, which plays a major role in the device compared to the from 80 to 150 nm with 10 nm per step (Figure 1b). The sup- leaky mode enhancement of light outcoupling efficiency.[27–29] porting silicon oxide buffer layer is removed via buffered oxide wet etching. As2S3 solution is prepared by uniformly dissolving the powder into n-propylamine solvent according to recipes [14,18] 2. Localized Photon and Heat Distribution in the prior literature. The solution is then drop-casted in the Hybrid Metasurface onto the suspended silicon membrane, forming a thick As2S3 film on top of the Si layer. The sample is kept in the oxygen-free Fabrication of the light-emitting device is composed of two glove box environment for several days at room temperature to steps: 1) assembling the As2S3 nanostructures in the silicon evaporate out excess solvent. As2S3 dissolved in alkyl amines template; and 2) local laser annealing for enhanced PL. The can be described as a nanocolloidal solution consisting of flat first step is for shaping the chalcogenide nanostructures and clusters that internally retain the structure of the layer-like the second step removes the solvent-related atomic defects and starting material but capped by ionic pairs of sulfide dangling induces phase transitions in chalcogenide for effective light bonds and alkyl ammonium molecules.[31] Without annealing, emission. those solvent-related atomic defect states suppress light emis- [14] sion from As2S3. Due to the fluid nature of the drop-casted materials, the 2.1. Self-Assembled Chalcogenide Metasurface solution will accumulate in the hollow region[13] with excess chalcogenide material above and below the silicon membrane. Here we demonstrate a simple and scalable way of producing The sample is left in the glove box at room temperature over- chalcogenide nanostructures, combining advanced silicon night. Upon evaporating the excess solvent, the dried bulk nanofabrication and solution processing. Figure 1 shows the chalcogenide cleanly delaminates from the smooth, flat silicon fabrication process and scanning electron microscope (SEM) surface (Figure S2, Supporting Information). Our previous images of a self-assembled chalcogenide–silicon metasurface work shows that the room-temperature dried chalcogenide structures. The silicon patterns (triangular lattice) are fabricated nanorods still contain solvent-related residue (CH/NH Adv. Optical Mater. 2020, 8, 1901236 1901236 (2 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.advancedsciencenews.com www.advopticalmat.de Figure 2. Device geometry. a) Side and b) top views of self-assembled chalcogenide metasurface in a silicon matrix. The yellow region indicates the intensity distribution of the top incident Gaussian beam profile, which is a continuous-wave light centered at 532 nm. c) Top view of the temperature distribution, with its z-axis marked in panel (d). d) Temperature distribution on the cross section, with its y-axis marked in panel (e). e) Temperature distribution near the bottom plane of the hybrid metasurface, with its z-axis marked in panel (d). f) Photoluminescence of As2S3 and laser-crystallized As4S4. bond),[32] which can be removed by hot plate annealing (170 °C) mode profile leads to localized heating in plane (Figure S4, or laser annealing.[14] Energy-dispersive X-ray spectroscopy Supporting Information) and out of the plane (Figure S5,
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