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Unisized two-dimensional platinum clusters on silicon(111)-7×7 surface observed with scanning tunneling microscope

2005; American Institute of Physics; Volume: 123; Issue: 12 Linguagem: Inglês

10.1063/1.2018639

1520-9032

Hisato Yasumatsu, T. Hayakawa, Shinichi Koizumi, Tamotsu Kondow,

Advanced Materials Characterization Techniques

Uni-sized platinum clusters (size range of 5–40) on a silicon(111)-7×7 surface were prepared by depositing size-selected platinum cluster ions on the silicon surface at the collision energy of 1.5 eV per atom at room temperature. The surface thus prepared was observed by means of a scanning tunneling microscope (STM) at the temperature of 77 K under an ambient pressure less than 5×10−9Pa. The STM images observed at different cluster sizes revealed that (1) the clusters are flattened and stuck to the surface with a chemical-bond akin to platinum silicide, (2) every platinum atom occupies preferentially the most reactive sites distributed within a diameter of ∼2nm on the silicon surface at a cluster size up to 20, and above this size, the diameter of the cluster increases with the size, and (3) the sticking probability of an incoming cluster ion on the surface increases with the cluster size and reaches nearly unity at a size larger than 20.