Colored porous silicon as support for plasmonic nanoparticles

Colored porous silicon as support for plasmonic nanoparticles M. Lublow,1,2,a S. Kubala,1,2 J. F. Veyan,3 and Y. J. Chabal3 1Helmholtz Centre Berlin for Materials and Energy, Institute for Heterogeneous Materials Systems, Berlin, Germany 2Department of Physical Chemistry, Fritz Haber Institute, Berlin, Germany 3Department of Materials Science and Engineering, University of Texas at Dallas, Texas, USA Received 15 November 2011; accepted 9 March 2012; published online 16 April 2012 Colored nanoporous silicon thin films were employed as dielectric spacing layers for the enhancement of localized surface plasmon LSP polaritons. Upon formation of Au nanoparticles Au NPs on these layers, a visible color change is observed due to multiple LSP resonance excitations. Far field effects were assessed by angle resolved reflectometry. Resonance enhancements, particularly for s polarized light, account for the observed color change and are discussed in terms of effective medium and Mie scattering theory. Enhancements of the electric field strengths in the near field and of the absorption in the substrate were deduced from finite difference time domain calculations and exceed considerably those of the non porous Au NP Si interface. First results of improved photoelectrocatalytic hydrogen evolution at these interfaces are discussed. Samples were prepared by varied procedures of metal assisted etching and dry etching with XeF2. Structural and chemical properties were investigated by scanning electron and atomic force microscopy as well as energy dispersive x ray analysis. VC 2012 American Institute of Physics. [http dx.doi.org 10.1063 1.370346