Block-copolymer-based plasmonic metamaterials Antonio Capretti a,b , Finizia Auriemma c , Claudio De Rosa c , Rocco Di Girolamo c , Carlo Forestiere b , Giovanni Miano b , Giovanni P. Pepe a a Department of Physics & CNR-SPIN, b Department of Electrical Engineering and Information Technology, c Department of Chemistry, Universit`a degli Studi di Napoli Federico II, Italy ABSTRACT Block-copolymer (BCP) self-assembling provides a unique tool for realizing large-area ordered metamaterials, with desired optical properties. The benefits of using BCPs as templates for metamaterials come from two main aspects: first, BCPs show a rich range of available nano-morphologies, whose domains can be conveniently tuned in size, shape and periodicity, by changing molecular parameters; second, the chemical properties of the block polymers can lead to the selective inclusion of functionalized nanoparticles (NPs) of different materials in specific nanodomains, generating periodic arrays of NPs according to the geometry of the BCP acting as template. This approach allows finely modulating the optical properties of NPs and can be used as an intriguing and versatile tool to build useful devices for Optics & Photonics applications, with significant benefits for both fundamental and applied investigations. In this work, we investigate nanostructured thin films of polystyrene-block-poly(methyl methacrylate) BCP (PS-PMMA), characterized by an hexagonal array of PS cylinders in the PMMA matrix. The PS cylindrical domain are selectively filled by functionalized metallic (Au, Ag) NPs. The optical properties of such nano-structures are strongly affected by localized surface plasmons (LSPs) in the NPs, arising from the collective resonances of conduction electrons in the metal at a characteristic spectral range, usually in the visible range. LSPs induce high field enhancement (FE), with respect to an incident light, in proximity of the NP surface, and in particular in the gap between two close NPs (hot-spot). Moreover, LSPs increase the intensity of absorption and scattering of light by the NPs in their range of resonance. Keywords: Metamaterials, Block-copolymers, Self-assembly, Plasmonics 1. INTRODUCTION Metamaterials are re-defining the use of naturally-occurring materials for technological applications. In particu- lar, electromagnetic metamaterials allow for unexpected effects of light ranging from the optical to the microwave spectra. They consist of regular structures made of common media, such as dielectrics and conductors, with geometrical features much smaller than the wavelength of the light interacting with them. As a result, it is possible to control to electromagnetic response of these novel materials by accurately designing their geometries and by selecting the composition of their constitutive bricks. The fabrication of metamaterials is typically achieved by nano-patterning thin films with physical or chemical methods, such as lithography or self-assembly. In particular, nano-scale geometrical features are needed for applications in the optical spectrum of light. Moreover, the use of different materials is necessary to obtain the desired optical response. As a matter of fact, these heterostructures are often characterized by several nano-scale objects of different materials, at very small separations. The effective operation of nano-structured thin films as metamaterials requires that the nano-patterns are regularly repeated on the surface and that the wavelength of the interacting electromagnetic field is much larger than the pattern features. As a consequence, the incident light ’sees’ an effective medium with unexpected optical properties, different from those of the starting materials, and strictly depending on their patterning. It is clear that the establishment of metamaterials in technological applications strictly depends on the ability to fabricate large-area cost-effective films with nanostructured features and selected composite materials. In the present work, we illustrate the use of a self-assembly method based on block-copolymers (BCPs), for Further author information: (Send correspondence to Giovanni P. Pepe) Giovanni P. Pepe: E-mail: gpepe@na.infn.it, Telephone: +39 081 768 2584 Metamaterials VIII, edited by Vladimir Kuzmiak, Peter Markos, Tomasz Szoplik, Proc. of SPIE Vol. 8771, 87710V · © 2013 SPIE · CCC code: 0277-786X/13/$18 · doi: 10.1117/12.2018492 Proc. of SPIE Vol. 8771 87710V-1 DownloadedFrom:http://proceedings.spiedigitallibrary.org/on07/20/2013TermsofUse:http://spiedl.org/terms