SCANNING TUNNELING MICROSCOPE AND ATOMIC-FORCE MICROSCOPE STUDY OF EPITAXIALLY GROWN PALLADIUM CRYSTALLITES ON GRAPHITE

Scanning tunneling microscope (STM) and atomic force microscope (AFM) have been applied to the study of an epitaxial growth of Pd on graphite. Pd deposited at 450-degrees-C nucleates to crystallize and grow epitaxially along the [111] direction. The STM images of the topmost layer of the (111) face exhibited a long periodic structure with a periodic distance of about 2.7 nm. Codeposition of Pd and Cu on graphite at 550-degrees-C created clear images of the atomic arrangement together with the periodic structure. The periodic length was found to exactly correspond to a distance of 10 atoms. Auger measurements of each crystallite showed that its surface layer mostly contains Pd atoms although almost equal amount of Pd and Cu was deposited. The AFM observations also showed images with similar periodicity to those from the STM. On the basis of the STM and the AFM results, the possibility of the reconstruction of the surface is discussed.