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DS: Dünne Schichten

DS 23: Nanowires, nanoparticles and nanostructures

DS 23.1: Hauptvortrag

Donnerstag, 30. März 2006, 15:30–16:15, GER 38

Laser-induced diffusion processes on metal nanoparticles — •Andreas Heilmann — Fraunhofer Institute for Mechanics of Materials Halle (Saale)

Although metal nanoparticles embedded in an insulating matrix show sufficient long-term stability, diffusion processes of metal atoms occur at temperatures far below the melting point of the metals. The material transport is driven by the free surface energy of the nanoparticles and associated with lattice defects and grain boundaries. These diffusion processes result in changes of the size and shape distribution of the embedded particles. Therefore, the optical and electrical properties of the nanoparticles change dramatically.

The simplest way to accelerate and to study such diffusion processes is thermal treatment, but also Laser irradiation or electron beam irradiation can cause nanostructural changes inside the beam spot without material ablation. By irradiating nanoparticle assemblies with linearly polarized, ultrashort laser pulses in far field arrangement, parallel arranged line structures of embedded gold or silver nanoparticles were achieved inside the laser spot. These structures are result of diffusion processes induced by the irradiation energy and directed by linear polarization of the laser pulses. The anisotropic structure modification results in anisotropic optical and electrical properties of the nanoparticle assemblies.