Ordered arrays of Au nanoclusters by TiOx ultrathin templates on Pt(111)

Ultrathin ordered films of TiOx (x approximate to 1) on Pt(111) have been investigated by scanning tunneling microscopy (STM) to test their capability as templates for growing ordered and monodispersed Au nanocluster arrays. The ordered array of parallel black troughs spaced by 1.44 nm, observed in the STM data of the zigzag-like TiOx ultrathin film, was revealed to be a good template for growing a linear array of Au clusters, with a mean size of 1.3 nm and a narrow dispersion. The wagon-wheel-like TiOx film, having a similar chemical composition but without a nanostructured array of defects, does not show templating effects, thus leading to nucleation of disordered and larger Au clusters (mean size of 3.4 nm with a large dispersion). Hence, this work shows that the ordering of the deposited Au nanoclusters is strongly dependent on the actual defectivity of the film. Annealing the Au cluster arrays at high temperature produces drastic changes in the spatial arrangement of the clusters, which has been interpreted as the consequence of the changes in the ultrathin film template.