Self-organized growth of Mn nanocluster arrays on Si(111)-(7x7) surfaces

We demonstrate the formation of well-ordered arrays of Mn nanoclusters of nearly identical sizes on a Si(111)-(7x7) surface. The Mn atoms are found not to react with the Si substrate at temperatures below similar to 260 degrees C. At room temperature, the Mn clusters occupy both halves of the (7x7) unit cell and arrange themselves into a honeycomb structure, whereas at a temperature of 258 degrees C, they exclusively occupy the faulted half of the unit cell and form an array with hexagonal symmetry. The self-organization process of the nanocluster array of Mn is different from that previously reported for the group-IIIA metals, due to stronger Mn-substrate and Mn-Mn interactions.