Plasmonic behaviour of laser processed Pd-Ag layered films

Resumen del trabajo presentado en el E-MRS Spring Meeting 2012: Simposio V Laser materials processing for micro and nano applications, celebrado en Estrasburgo (Francia), del 14 al 17 de mayo de 2012Metal nanostructures are known to have unique properties such as enhanced absorption associated to their surface plasmon resonance (SPR), reactivity or catalytic activity. While noble metals such as Ag or Au typically have their SPR in the visible part of the spectrum that of most transition metals appears in the UV. However, to enhance the chemical reaction or catalytic capabilities, metals such as Pt or Pd are very attractive. An interesting approach that allows tuning the SPR as well as creates new catalysts with improved properties with respect to single metal ones is the production of bimetallic nanostructures, which exhibit characteristics that are not just the addition of the properties of the two constituent metals. In this work, we aim to produce bimetallic Pd-Ag nanostructures with tunable optical response. We produce layered films prepared by magnetron sputtering that have similar total thickness but different relative Pd to Ag layer thickness in order to change the overall composition. We have used an excimer laser operating at λ=193 nm and pulse duration of τ=20 ns to expose large homogeneous areas (≈4x4 mm²). The structural features of the irradiated areas will be discussed in terms of melting followed by diffusion and partial dewetting of the films and related to the changes observed in their absorption and reflection spectra. The evolution of the SPR wavelength as a function of the Pd to Ag ratio is finally discussed