Laser-Induced Formation of Periodic Structures in Plasma Deposited Polymer Films Containing Au, Ag, and Cu Nanoparticles
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0960-N03-01
Laser-Induced Formation of Periodic Structures in Plasma Deposited Polymer Films Containing Au, Ag, and Cu Nanoparticles Katrin Loeschner, Andreas Kiesow, and Andreas Heilmann Fraunhofer Institute for Mechanics of Materials, Heideallee 19, Halle/Saale, 06120, Germany
ABSTRACT Thin polymer films containing metal nanoparticles were irradiated with linearly polarized femtosecond laser pulses. The resulting laser-induced periodic modification of the nanoparticle assemblies was studied by using scanning and transmission electron microscopy. The structure period Λ is correlated with the applied laser wavelength λ by Λ = 0.7 λ. The effect was observed for gold, silver and copper nanoparticles. Optical spectra of the laser-irradiated films show a clear dichroism. INTRODUCTION Polymer films with embedded metal nanoparticles offer unique optical and electrical properties. Methods which allow a controlled modification of the nanostructure of these films and their properties are of interest because they will further increase the spectrum of possible applications in optical and electronic industries. A way to modify thin polymer films containing metal nanoparticles by linear polarized femtosecond laser pulses has been introduced in former studies [1,2]. The laser irradiation induces periodic arrangements of the nanoparticles within the irradiated area. This leads to anisotropic optical and electrical properties of the films. First experiments had shown the formation of periodic structures for plasma polymer films with embedded gold nanoparticles at a wavelength of 800 nm and for films with embedded silver nanoparticles at 400 nm [1]. Further systematic investigations were carried out for films containing gold nanoparticles to understand the complex process of evolution of these periodic structures [2,3]. The dependence of the periodic structure formation on several laser irradiation parameters (laser polarization, wavelength, intensity, number of pulses) was presented in [3]. The aim of this study is to demonstrate that the laser-induced formation of periodic structures can also be obtained for plasma polymer films with silver and copper nanoparticles as well as for gold nanoparticles embedded in another matrix material. The spontaneous formation of periodic surface structures due to laser irradiation with a single laser beam was observed on a broad variety of material surfaces, e.g., semiconductors, metals and dielectrics, within certain ranges of laser parameters [4,5]. The dependence of the structure period and structure orientation on laser wavelength and laser polarization, respectively, is characteristic for these structures. Their formation is described as a result of a self-enhanced interference process between incident and scattered laser light [5]. Theoretical considerations concerning this process have been made by several authors, e.g., [6,7].
Materials and Methods The investigated polymer-metal nanocomposites were produced by plasma polymerization of hexamethyldisilazane (HMDSN) or sputtering of poly
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