Observation of HCI-induced nanostructures with a scanning probe microscope

Abstract

We present scanning tunneling microscope (STM) images, atomically resolved, of the nanostructures on various kinds of surfaces bombarded with highly charged ions (HCIs). In the STM image of a highly oriented pyrolytic graphite surface (Xe29+-impact), a protrusion structure was observed with √3 × √3 R30° surface reconstruction around the impact site. A crater-like structure was formed on a Si(111)-(7×7) surface by an I50+-HCI impact. An atomic image of ∼0.1 nm in height was also observed around the missing topmost layers of the crater. In the case of a TiO2(110) surface, a typical nanostructure induced by a single I51+-HCI impact, relatively larger crater structure than that on the Si surface was observed; the height (∼1 nm) was higher than the atomic step of the TiO2(110)-(1×1) surface (∼0.3 nm) and the depth reached at least 1.5 nm. This implies that the degree of the HCI-radiation effect on the TiO2 surface is higher than that of the Si(111) case.