Book of Abstracts Book of Abstracts - Universität Konstanz

Self-Assembly of Metal Nanoclusters on Oxide Surfaces
N. Berdunov 1 , G. Mariotto 1 , S. Murphy 1 , K. Balakrishnan 1 , Y. M. Mukovskii 2 , I. V. Shvets 1
1 SFI Laboratories, Physics Dept., Trinity College Dublin, Ireland
2 MISIS, Leninsky Prospect 4, Moscow 119991, Russia
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The self-assembly of ordered arrays of metal nanoclusters is a fascinating scientific
phenomenon as well as a particularly promising subject for technological applications, such as
microelectronics, ultra-high density recording, corrosion and catalysis. For example, magnetite
and iron play an important role in industrial processes such as the production of hydrogen and
the synthesis of ammonia. The ability of controlling the size and arrangement of Fe
nanostructures may influence the way catalytic processes take place.
We have studied the formation of Fe nanostructures on the magnetite (111) surface of single
crystals and thin films. The Fe3O4(111) surface exhibits an hexagonal 42 Å superstructure, when
annealed in oxygen atmosphere [1]. We have shown that this highly regular pattern is useful as
a template for the self-assembly of nanostructures.
We have deposited Fe films of 0.2, 0.5, 1 and 2 Å thickness at room temperature by means of
electron beam evaporation. STM images prove that ordered nucleation of nanoclusters takes
place only on the patterned regions of the surface, while random nucleation takes place on the
unpatterned regions (see Fig. 1). These results have been reproduced in the case of a 0.5 Å Cr
film. The metal nanostructures are characterized by a very regular size distribution over a length
of several hundreds nanometers.
Our results demonstrate that the self-assembly of crystalline Fe and Cr nanostructures takes
place on the preferential nucleation sites provided by the nanopatterned Fe3O4(111) surface. We
suggest that ordered arrays of nanostructures could be grown on different oxides displaying
long-range surface reconstruction, as recently demonstrated by the growth of ordered Pd
clusters on Al2O3 [2].
Figure 1. 80 nm × 80 nm STM image of 0.5 Å Fe deposited onto the Fe3O4(111) surface. Self-assembly of Fe
nanostructures takes place only on the patterned areas of the crystal (terrace A), while Fe nucleates randomly onto the
unpatterned areas (terrace B).
References
[1] N. Berdunov, S. Murphy, G. Mariotto and I.V. Shvets, Phys. Rev. B 70, 085404 (2004).
[2] S. Degen, C. Becker and K. Wandelt, Faraday Discuss. 125, 343 (2004).
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