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Czajkowski KM, Świtlik D, Langhammer C, Antosiewicz TJ. Effective Optical Properties of Inhomogeneously Distributed Nanoobjects in Strong Field Gradients of Nanoplasmonic Sensors. PLASMONICS (NORWELL, MASS.) 2018; 13:2423-2434. [PMID: 30595678 PMCID: PMC6280852 DOI: 10.1007/s11468-018-0769-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 05/14/2018] [Indexed: 06/09/2023]
Abstract
Accurate and efficient modeling of discontinuous, randomly distributed entities is a computationally challenging task, especially in the presence of large and inhomogeneous electric near-fields of plasmons. Simultaneously, the anisotropy of sensed entities and their overlap with inhomogeneous fields means that typical effective medium approaches may fail at describing their optical properties. Here, we extend the Maxwell Garnett mixing formula to overcome this limitation by introducing a gradient within the effective medium description of inhomogeneous nanoparticle layers. The effective medium layer is divided into slices with a varying volume fraction of the inclusions and, consequently, a spatially varying effective permittivity. This preserves the interplay between an anisotropic particle distribution and an inhomogeneous electric field and enables more accurate predictions than with a single effective layer. We demonstrate the usefulness of the gradient effective medium in FDTD modeling of indirect plasmonic sensing of nanoparticle sintering. First of all, it yields accurate results significantly faster than with explicitly modeled nanoparticles. Moreover, by employing the gradient effective medium approach, we prove that the detected signal is proportional to not only the nanoparticle size but also its size dispersion and potentially shape. This implies that the simple volume fraction parameter is insufficient to properly homogenize these types of nanoparticle layers and that in order to quantify optically the state of the layer more than one independent measurement should be carried out. These findings extend beyond nanoparticle sintering and could be useful in analysis of average signals in both plasmonic and dielectric systems to unveil dynamic changes in exosomes or polymer brushes, phase changes of nanoparticles, or quantifying light absorption in plasmon assisted catalysis.
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Affiliation(s)
- Krzysztof M. Czajkowski
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland
| | - Dominika Świtlik
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland
| | - Christoph Langhammer
- Department of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden
| | - Tomasz J. Antosiewicz
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland
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Majumdar S, Grochowska K, Sawczak M, Śliwiński G, Huhtinen H, Dahl J, Tuominen M, Laukkanen P, Majumdar HS. Interfacial Properties of Organic Semiconductor-Inorganic Magnetic Oxide Hybrid Spintronic Systems Fabricated Using Pulsed Laser Deposition. ACS APPLIED MATERIALS & INTERFACES 2015; 7:22228-22237. [PMID: 26402298 DOI: 10.1021/acsami.5b04840] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report fabrication of a hybrid organic semiconductor-inorganic complex oxide interface of rubrene and La0.67Sr0.33MnO3 (LSMO) for spintronic devices using pulsed laser deposition (PLD) and investigate the interface structure and chemical bonding-dependent magnetic properties. Our results demonstrate that with proper control of growth parameters, thin films of organic semiconductor rubrene can be deposited without any damage to the molecular structure. Rubrene, a widely used organic semiconductor with high charge-carrier mobility and spin diffusion length, when grown as thin films on amorphous and crystalline substrates such as SiO2-glass, indium-tin oxide (ITO), and LSMO by PLD at room temperature and a laser fluence of 0.19 J/cm2, reveals amorphous structure. The Raman spectra verify the signatures of both Ag and Bg Raman active modes of rubrene molecules. X-ray reflectivity measurements indicate a well-defined interface formation between surface-treated LSMO and rubrene, whereas X-ray photoelectron spectra indicate the signature of hybridization of the electronic states at this interface. Magnetic measurements show that the ferromagnetic property of the rubrene-LSMO interface improves by >230% compared to the pristine LSMO surface due to this proposed hybridization. Intentional disruption of the direct contact between LSMO and rubrene by insertion of a dielectric AlOx layer results in an observably decreased ferromagnetism. These experimental results demonstrate that by controlling the interface formation between organic semiconductor and half-metallic oxide thin films, it is possible to engineer the interface spin polarization properties. Results also confirm that by using PLD for consecutive growth of different layers, contamination-free interfaces can be obtained, and this finding is significant for the well-controlled and reproducible design of spin-polarized interfaces for future hybrid spintronics devices.
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Affiliation(s)
- Sayani Majumdar
- Department of Applied Physics, Aalto University School of Science , FI-00076 Aalto, Finland
| | - Katarzyna Grochowska
- Photophysics Department, The Szewalski Institute, Polish Academy of Sciences , 80-231 Gdansk, Poland
| | - Miroslaw Sawczak
- Photophysics Department, The Szewalski Institute, Polish Academy of Sciences , 80-231 Gdansk, Poland
| | - Gerard Śliwiński
- Photophysics Department, The Szewalski Institute, Polish Academy of Sciences , 80-231 Gdansk, Poland
| | - Hannu Huhtinen
- Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku , FI-20014 Turku, Finland
| | - Johnny Dahl
- Materials Research Laboratory, Department of Physics and Astronomy, University of Turku , FI-20014 Turku, Finland
| | - Marjukka Tuominen
- Materials Research Laboratory, Department of Physics and Astronomy, University of Turku , FI-20014 Turku, Finland
| | - Pekka Laukkanen
- Materials Research Laboratory, Department of Physics and Astronomy, University of Turku , FI-20014 Turku, Finland
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Bittencourt C, Ewels C, Krasheninnikov AV. Atomic scale interface design and characterisation. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2015; 6:1708-11. [PMID: 26425422 PMCID: PMC4578409 DOI: 10.3762/bjnano.6.174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 07/28/2015] [Indexed: 05/16/2023]
Affiliation(s)
- Carla Bittencourt
- Chimie des Interactions Plasma-Surface (ChIPS), CIRMAP, Research Institute for Materials Science and Engineering, University of Mons, 7000 Mons, Belgium
| | - Chris Ewels
- Institute des Matériaux Jean Rouxel, IMN, Université de Nantes, CNRS UMR6502 Nantes, France
| | - Arkady V Krasheninnikov
- Department of Applied Physics, Aalto University, Finland
- Institute of Ion Beam Physics and Materials Research, Helmholtz Zentrum Dresden-Rossendorf, Germany
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