Self-assembled Au nanoparticles on heated Corning glass by dc magnetron sputtering: size-dependent surface plasmon reson
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RESEARCH PAPER
Self-assembled Au nanoparticles on heated Corning glass by dc magnetron sputtering: size-dependent surface plasmon resonance tuning S. Grammatikopoulos • S. D. Pappas • V. Dracopoulos • P. Poulopoulos • P. Fumagalli M. J. Velgakis • C. Politis
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Received: 2 November 2012 / Accepted: 17 January 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract We report on the growth of Au nanoparticles on Corning glass by direct current magnetron sputtering and on the optical absorption of the films. The substrate temperature was kept to relatively high temperatures of 100 or 450 °C. This lead to the growth of Au nanoparticles instead of smooth Au films as the surface energy of Au is much larger than the one of glass. The size of the particles depended on the substrate temperature and deposition time and was shown to follow a logarithmic normal distribution S. Grammatikopoulos S. D. Pappas P. Poulopoulos M. J. Velgakis C. Politis Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras, Greece V. Dracopoulos Foundation for Research and Technology, Hellas-Institute of Chemical Engineering and High Temperature Chemical Processes, (FORTH/ICE-HT), P.O. Box 1414, 26504 Patras, Greece P. Poulopoulos Materials Science Department, University of Patras, 26504 Patras, Greece P. Poulopoulos (&) P. Fumagalli Institut fu¨r Experimentalphysik, Freie Universita¨t Berlin, Arnimallee 14, 14195 Berlin-Dahlem, Germany e-mail: [email protected] C. Politis Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, TX 76019, USA
function. Both, the surface plasmon resonance position and bandwidth, were found to depend upon the average particle size. The surface plasmon resonance position showed a 75 nm continuous blue shift from 14 nm down to 2.5 nm average particle size. Thus, we have shown how to tune the nanoparticle size and surface plasmon resonance of Au by varying the substrate temperature and deposition time. The experimental results are reproduced reasonably using a method which is based on the size- and wavelengthdependent complex dielectric function of Au within the framework of the Mie theory for the optical properties of metallic nanospheres. Keywords Au Nanoparticles Magnetron sputtering Optical properties Absorption Surface plasmon resonance
Introduction Nanostructuring of metals results in the appearance of surface plasmon resonances (SPR), which are strong collective oscillations of the free electrons on the surface of the conducting nanostructures (Mie 1908). These give rise to peaks in the light absorption spectra of the materials, which depend on the nanostructure geometry and on the dielectric properties of the metal and the surrounding material. Many applications are related to SPR, like fabrication of energy efficient
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coatings, involvement in cancer therapy, biological imaging and biomedicine, cholesterol sensing, lithography, surface enhanced Raman spectroscopy, fabrication of negative p
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