Al2O3(110) surface as a template for the ordered growth of Ni and Co nanoclusters

The morphology and thermal stability of Ni and Co nanoclusters grown by physical vapour deposition on a reconstructed (110) surface of α-Al2O3 is investigated using non-contact atomic force microscopy (NC-AFM). NC-AFM images reveal that the clean α-Al2O3(110) substrate adopts a characteristic (12 × 4) reconstruction when prepared in vacuum at high temperature. Subsequent deposition of Ni and Co onto this substrate at room temperature facilitates the growth of well-ordered metal nanocluster arrays with a preferred inter-cluster distance determined by the (12 × 4) periodicity of the substrate surface. The order in the cluster arrangement remains intact even upon annealing the system to temperatures up to 500 °C indicating a high resistance against sintering. The reconstructed α-Al2O3(110) surface can, therefore, serve as an appropriate insulating template for studies of size-dependent magnetic or catalytic effects in a well-defined ensemble of metallic nanoclusters.