The National Academy of Sciences of Belarus The State Scientific Institution "B.I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus" Scientific Council of NAS Belarus "Plasma Physics and Plasma Technology" Russian Academy of Sciences The Federal State Budget Institution of Science "Joint Institute for High Temperatures RAS" Scientific Council of RAS "Physics of Low Temperature Plasma" The al-Farabi Kazakh National University
PLASMA PHYSICS AND PLASMA TECHNOLOGY (PPPT-8)
VIII International Conference Minsk, Belarus, September 14 – 18, 2015 CONTRIBUTED PAPERS In two volumes Volume I (Sections 1-3) Minsk “Kovcheg” 2015
UDC 533.9(082)
EDITORIAL BOARD: V.S. Burakov, I.I. Filatova, M.S. Usachonak
SPONSORED BY: The A.V. Luikov Heat and Mass Transfer Institute of NAS of Belarus The Belarusian Republican Foundation for Fundamental Research The Belarusian Physical Society SOLAR LS «Laser Systems & Spectral Instruments» SOL instruments Ltd. Standa Ltd. The Research Institute of Experimental and Theoretical Physics, al-Farabi Kazakh National University The National Nanotechnological Laboratory of Open Type, al-Farabi Kazakh National University
The reports in these Contributed Papers are presented by the individual authors. The views expressed are their own and do not necessarily represent the views of the Publishers or Sponsors. Whilst every effort has been made to ensure the accuracy of the information contained in this book, the Publisher or Sponsors cannot be held liable for any errors or omissions however caused. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the copying owner.
ISBN 978-985-7137-18-3(Vol 1) ISBN 978-985-7137-17-6
© B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 2015 © Registration, “Kovcheg LTD”, 2015
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STRUCTURE AND PLASMONIC PROPERTIES OF PMMA LAYERS WITH ION-IMPLANTED SILVER NANOPARTICLES FOR DIFFRACTION GRATING SENSORS A.L. Stepanov1, V.I. Nuzhdin1, V.F. Valeev1, T.S. Kavetskyy2,3 1
Kazan Physical-Technical Institute of the Russian Academy of Sciences, Sibirsky Trakt 10/7, 420029 Kazan, Russian Federation
[email protected] 2 Drohobych Ivan Franko State Pedagogical University, 82100 Drohobych, Ukraine 3 The John Paul II Catholic University of Lublin, 20-950 Lublin, Poland
Metal-polymer nanocomposites attract considerable attention due to a number of practical applications. In particular, optical properties of polymers with noble metal nanoparticles (MNPs) are of interest due to strong localized surface plasmon resonance (LSPR). Such materials are considered to be promising for nanoscale plasmonics, fabrication of non-linear optical devices and optical sensors. The aim of this study is to form the visible range diffraction surface grids for optical plasmonic sensor applications based on transparent polymer matrix, in particular, polymethylmethacrylate (PMMA) in which periodic areas nanoparticles of noble metals could be synthesized using lowenergy high-dose ion implantation /1/. Polymeric materials are now extensively used for the construction of various types of optical waveguides and photonic light control elements such as prisms, lenses and others. For the synthesis of metal nanoparticles to form diffraction grid polymer structures is offered to use the mask ion implantation technology /2/. Earlier in our work in 2000 [3] for the first time in practice it has been experimentally demonstrated the principle possibility for the formation of Ag-nanoparticles in PMMA matrix (Ag:PMMA) using Ag-ion implantation. Electron microscopy and optical absorption study of Ag:PMMA were presented in /3/. Detailed modeling of optical extinction spectra of Ag-nanoparticles with different sizes in PMMA and carbon-PMMA surrounding were also realized /4/. However, at the same time, it must be note that in a number of recent publications, for example in [5], the priority for the creation of Ag:PMMA composite material in the same way under similar ion implantation parameters and conditions unfairly attributed exclusively to their own research without correct truthful references. The present study reports the further development for our methodology of low-energy ion implantations of polymers, which was presented in /3/, for a sensor application in the field of optoelectronics, namely, to create the plasmonic diffractive microstructures with Ag:PMMA material. The implantation of PMMA plates with a thickness of 1 mm was performed
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by an ILU-3 ion implanter (Kazan, Russia) with doses from 5.0⋅1014 to 1.5⋅1017 ion/cm2 and Ag+-ion energy of 30 keV at a current density 2 µA/cm2 in residual vacuum of 10-2 Pa as it was suggested in /3/. To avoid thermal degradation and polycrystallization of the polymer, the sample holder was cooled with running water and temperature of the target under the irradiation did not exceed ~ 70°C, which is below the glass transition temperature of PMMA ~ 100°C. For fabrication of a periodic diffraction structure on the PMMA Agion implantation was used through the mask – nickel grid with a mesh size of 20 µm. The grid was attached to the polymer surface and implantation was performed at normal incidence to the substrate. Simulation of concentration depth profiles of implanted Ag-ions in PMMA using a computer algorithm SRIM-2013 for 30 keV, showed that most of Ag-atoms are collected near the polymer surface. Such accumulation of silver in the local layer leads to a supersaturation of the metal atoms, the nucleation and growth of Agnanoparticles. The total thickness of the implanted layer, and hence the thickness of the active layer of diffraction grid with formed silver nanoparticles in polymer, for the given conditions of implantation does not exceed 100 nm. Fig. 1, left shows the spectra of optical transmittance for the virgin PMMA and implanted Ag:PMMA with different doses. As seen from the figure, during of the irradiation the transmittance of the composites is monotonically decrease in the shorter wavelength spectral range (curves 1 and 2) due to the destruction of the polymer structure, radical creation and the formation of carbon fragments (carbonization) /4, 6/. Formation of Ag-nanoparticles in the implanted PMMA was evident by the optical transmittance showing an appearance of the characteristic band with a maximum of about 500 nm (curve 3) for the sample created with a dose of 1.0⋅1016 ion/cm2 that is attributed to the LSPR absorption of metal nanoparticles. With increasing Ag-ion dose a shift of LSPR maximum to longer wavelengths, which corresponds a raise of the silver concentration in the implanted polymer layer and an increase of the Agnanoparticle size, was observed. Similar patterns are detected in the case of ionsynthesis of noble metal nanoparticles in various inorganic glasses and crystals, and repeatedly demonstrated in the literature /1/. Earlier simulations of the extinction coefficient of Ag-nanoparticles placed in the PMMA matrix by the Mie theory /4/, also indicate a shift of the plasmon peak of Ag-nanoparticles toward longer wavelengths with an increase of their size. Note, that during incorrect measurements of optical transmittance and the primitive corrections of the experimental spectra for the same our Ag:PMMA samples, which were analyzed by the authors of the work /5/ as a secret from us, they were not recognized the spectral shift of LSPR maximum, and therefore made the wrong conclusion about the immutability of the Ag-nanoparticles size formed in PMMA with increasing of implantation dose.
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Fig. 1. Optical transmission spectra of PMMA and PMMA implanted by Ag-ions with different doses (left) and AFM image of PMMA surface with implanted Agnanoparticles (right)
For the formation of plasmonic diffraction grid the sample with the dose of 2.5⋅1016 ion/cm2, containing definitely the ion-synthesized Ag-nanoparticles in implanted PMMA layer, was selected. AFM image of the Ag:PMMA surafce in areas which was not protected by the mask is shown in Fig. 1, rigth. In contrast to the relatively smooth surface of the non-irradiated PMMA with roughness not exceeding 1.5 nm, the morphology of the Ag:PMMA implanted region is characterized by the semi-spherical hillocks as a result of partial exposure of spherical Ag-nanoparticles at the surface, similar to that was previously observed for ion-synthesized metal nanoparticles of silicate glasses and sapphire /1/. Such surface structure is explained by the polymer sputtering and patial towering of the spherical-shaped Ag-nanoparticles nucleated in the near-surface irradiated layer.
Fig. 2. Optical microscope image of grid structure on the PMMA surface implanted by Agions (left) and optical diffraction pattern from grid structure on the PMMA implanted by Ag-ions (right)
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Surface periodic microstructure on Ag:PMMA implanted through the mask PMMA was observed with an optical microscope (Fig. 2, left). As the figure shows, the entire surface of the sample was an ordered lattice with a mesh size of 20 µm. These squares are a cell area of implanted PMMA, i.e. polymer structure with Ag-nanoparticles exhibiting LSPR absorption in the visible range (Fig. 1, left). The walls between the square mesh lattice consist of a nonirradiated polymer. Details of the sample in the cell edge of a square mask were analysed by ContourGT profiler. It was clearly indicated that during the Ag-ion implantation of PMMA a periodic structure was formed by the effective surface sputtering of the polymer substrate. Note, that this result is the direct experimental evidence on the spraying the surface of PMMA by low-energy metal-ion implantation. It is known that implantation of the metal-ions of the dielectric increases its refractive index to ~ 1.7 - 1.9 in the visible region of the spectrum (especially at frequencies of nanoparticles LSPR) /1/. Therefore, it is evident that by mask implantation of the PMMA a microstructure with periodically variable optical constants of the material (nPMMA = 1.5), i.e., between the cells of the lattice and its walls, was caried out. Fig. 2, right shows the diffraction image recorded by plasmonic grid by probing the semiconductor laser at a wavelength of 527 nm. Note that the diffraction image was obtained in visible range wavelengths of LSPR absorption of Ag-nanoparticles. Therefore, it is obvious that by changing modes of ion implantation and synthesizing nanoparticles of various sizes, thereby changing the effective refractive index of the individual elements in the diffraction grid, one can control the optical and diffraction characteristics in a sufficiently wide range. Acknowledgements. This work was supported by the Russian Foundation for Basic Research (grant No. 15-48-02525). References 1. Stepanov A.L. Ion-synthesis of silver nanoparticles and their optical properties. New York: Nova Sci. Publ. (2010). 2. Stepanov A.L., Galyautdinov M.F., Evlyukhin A.B., Nuzhdin V.I., Valeev V.F., Osin Y.N., Evlyukhin E.A., Kiyan R., Kavetskyy T.S. and Chichkov B.N. Appl. Phys. A, 111 (2013) 261-264. 3. Stepanov A.L., Abdullin S.N., Petukhov V.Y., Osin Y.N., Khaibullin R.I. and Khaibullin I.B. Phil. Mag. B, 80 (2000) 23-28. 4. Stepanov A.L. and Khaibullin R.I. Rev. Adv. Mat. Sci. 7 (2004) 108-125. 5. Popok V.V. and Hanif M. J. Polym. Sci., (2015) in press. 6. Sviridov D.V. Russian Chem. Rev., 71 (2002) 315-327.
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