Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 69: Nanostructures at Surfaces: Dots, Particles, Clusters

O 69.4: Poster

Wednesday, March 9, 2016, 18:15–20:30, Poster A

Manipulating the nucleation behavior of MoO_x on Al₂O₃/NiAl(110) — •Rik Mom¹, Marcel J. Rost¹, Joost W.M. Frenken^1,2, and Irene M.N. Groot³ — ¹Huygens-Kamerlingh Onnes Laboratory, Niels Bohrweg 2, Leiden, The Netherlands — ²Advanced Research Center for Nanolithography, Science Park 104, Amsterdam, The Netherlands — ³Gorlaeus Laboratories, Einsteinweg 55, Leiden, The Netherlands

Understanding and manipulation of the nucleation behavior of metals and metal oxides on oxidic substrates is essential for the production of catalysts and nanodevices. Due to the large number of non-equivalent sites typically available on an oxidic substrate [1], prediction of such behavior remains challenging. Here, we studied the nucleation of Mo and MoO_x on Al₂O₃/NiAl(110) using scanning tunneling microscopy. In both cases we find 3D growth, yet there are clear differences in the particle dispersion. The larger diffusion speed of Mo leads to larger particles and nucleation on domain boundaries and step edges, whereas for MoOx the dispersion depends on the preparation method. Manipulation of the MoO_x dispersion is possible through the choice of evaporant (Mo or MoO_x). When Mo is evaporated in a mild 5x10⁻⁷ mbar O₂ atmosphere, the resulting MoO_x shows wetting of domain boundaries and step edges. In contrast, preparation using MoO_x as evaporant, yields a random distribution of particles. The observed differences are explained by a large diffusion length of Mo before oxidation on the surface.

[1] G. Kresse et al., Science 308, 1440 (2005)