Regensburg 2010 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 9: Poster: Synthesis of Nanostructured Films by Self-organization, Thermoelectric Thin Films and Nanostructures, High-k and Low-k Dielectrics, Layer Deposition Processes, Layer Growth, Layer Properties, Application of Thin Films, Surface Modification, Hard and Superhard Coatings, Metal Layers

DS 9.4: Poster

Montag, 22. März 2010, 15:00–17:30, Poster D1

Formation mechanism of noble metal nanoparticles in reactively sputtered TiO₂ films — John Okumu¹, Dominik Köhl², Alexander Sprafke², •Hendrik Holzapfel², Gero von Plessen², and Matthias Wuttig² — ¹Department of Physics, Kenyatta University, P. O. Box 43844-00100, Nairobi, Kenya — ²I. Physikalisches Institut (1A), RWTH Aachen University, D-52056 Aachen, Germany

Recently a simple preparation method has been developed to prepare Ag nanoparticles in a TiO₂ matrix [1,2]. In this scheme, silver nanoparticles are formed in a TiO₂ matrix first by sputtering a thin (d=15nm) silver film sandwiched between two reactively sputtered TiO₂ layers (d=30nm); this is followed by an annealing process. To determine the formation mechanism of noble metal nanoparticles in the TiO₂ matrix, we compare the behavior of Ag with that of two similar noble metals, gold and copper, by using x-ray diffraction, x-ray reflectance and optical spectroscopy. Despite the similarity of the three noble metals, we find that no Cu and Au nanoparticles are formed. This is in striking contrast to the behavior observed for Ag. The difference can be explained by a three step process, which involves oxidation of the Ag upon reactive sputter deposition of TiO₂, dissociation of the Ag oxide upon annealing and Ag aggregation to form nanoparticles. These processes do not occur at all in the case of Au, and are much slower in the case of Cu.

[1] J. Okumo et al., J. Appl. Phys., 97, 094305 (2005)

[2] C. Dahmen et al., Appl. Phys. Lett., 88, 011923 (2006)