Ordering of monodisperse Ni nanoclusters by templating on high-temperature reconstructed α-Al2O3(0001)

We demonstrate that the characteristic √31x√31 R9o reconstructed surface of α-alumina (Al2O3) acts as a nanotemplate for the growth of well-ordered monodisperse arrays of Ni nanoclusters. Due to the insulating nature of the substrate we use dynamic scanning force microscopy operated in the non-contact mode (NC-AFM) to characterize the nanotemplate, to examine the size and distribution of metallic clusters on the surface and to investigate their position with respect to the surface atomic structure. The present NC-AFM results for the interaction of Ni with α-Al2O3 are supported by density functional theory (DFT) calculations. The ability of α-Al2O3(0001) to act as a nanotemplate is attributed to a spatially modulated affinity towards the accommodation of Ni into the top layer by substituting the surface Al atoms at certain sites on the √31x√31 R9o reconstructed surface formed by high-temperature annealing. The insulating template, demonstrated for Al2O3, may be a generally attractive system for the study of nanostructures which need to be isolated from a conducting bulk.