Preparation and properties of noble metal clusters (Rh, Ir) on TiO2(110)-(1x2) surface are studied by scanning tunneling microscopy and spectroscopy. Formation of 12 nm of 3D clusters begins already at 300 K for 1 % monolayer (ML) noble metal coverage. The terrace edges are not preferred centres in this case. By enhancement of the deposited metal up to 1-2 ML the cluster size increases above 5 nm. The effect of annealing below 700 K results in a moderate increase of the cluster size. Above 900 K, however, the metal clusters agglomerate and collapse resulting in separated larger crystallites, which are bonded mainly at the crosspoints of terrace edges. By exploiting the large difference in the diffusion coefficient between noble metal atoms and crystallites larger than 1-2 nm, we suggest a method (called "seeding + growing") by which an independent control of average cluster size and interparticle distance is attainable. The applicability of this method in the studies of some important processes (cluster size dependence of the treatments in different gases, decoration phenomena, etc.) in the field of heterogeneous catalysis are demonstrated in this work.
|Number of pages||14|
|Journal||Magyar Kemiai Folyoirat, Kemiai Kozlemenyek|
|Publication status||Published - Dec 1 2000|
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