Al2o3(11(2)Over-Bar0) Surface As A Template For The Ordered Growth Of Ni And Co Nanoclusters
PHYSICAL CHEMISTRY CHEMICAL PHYSICS(2012)
摘要
The morphology and thermal stability of Ni and Co nanoclusters grown by physical vapour deposition on a reconstructed (11 (2) over bar0) surface of alpha-Al2O3 is investigated using non-contact atomic force microscopy (NC-AFM). NC-AFM images reveal that the clean alpha-Al2O3(11 (2) over bar0) substrate adopts a characteristic (12 X 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 X 4) periodicity of the substrate surface. The order in the cluster arrangement remains intact even upon annealing the system to temperatures up to 500 degrees C indicating a high resistance against sintering. The reconstructed alpha-Al2O3(11 (2) over bar0) surface can, therefore, serve as an appropriate insulating template for studies of size-dependent magnetic or catalytiWc effects in a well-defined ensemble of metallic nanoclusters.
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