Purity-dependent structures of Al nanoclusters on HOPG observed by STM

Nanoclusters with a diameter of 2–10 nm were deposited from highly pure Al and Al–50%Cu targets onto highly oriented pyrolitic graphite (HOPG) by pulsed laser ablation. The structures and atomic configurations of these nanoclusters were then investigated with atomic resolution using a scanning tunneling microscope. On the pure Al nanoclusters, hexagonal two-dimensional configurations were found over a large area around a three-dimensional nanocluster. These two-dimensional structures were oriented at 30° to the graphite lattice and the atomic distance was estimated to be 0.424 nm. On the other hand, two-dimensional atomic configurations were not observed around the Al–50%Cu nanoclusters and the atomic distance was almost the same as that of highly oriented pyrolytic graphite visible in the STM. Thus, the initial growth and structures were completely different between the two materials.