Atomistic study of cluster collision on solid surfaces

Abstract

New surface modification processes have been demonstrated using gas cluster ion irradiations, because of the unique interaction between cluster ions and surface atoms, atomistic mechanisms of cluster ion bombardment must be understood for the further developments of this technology. Variable temperature scanning tunneling microscope in ultra high vacuum allows us to study ion bombardment effects on surfaces and nucleation growth at various temperatures. In the STM image of cluster-irradiated surface, large craters with diameter of about 10 nm were observed on Si(1 1 1)7 × 7 surfaces. The structure and size of the traces agree well with theoretical calculation. When the sample irradiated with Ar cluster was annealed at 600 °C, the hole remained, but the outer rim of the crater disappeared and the surface structure was reconstructed at the site of the rim. The depth of damage region in the target became shallower with decrease of the impact energy. These results indicate that low damage and useful surface modification can be realized using the cluster ion beam.