Formation of carbon onions with Pd clusters in a high-resolution electron microscope

Abstract

Carbon onions have been produced in a transmission electron microscope by electron irradiation of amorphous carbon in the presence of Pd clusters. High-resolution electron microscopy revealed structural changes of the onion surface, and atom clouds were observed at the pentagonal vertices. In some onions, Pd atoms were intercalated between the graphite onion sheets, and a structural model for the intercalation has been proposed. The present work indicates that electron-beam irradiation of amorphous carbon in the presence of Pd clusters is an effective method for the formation of intercalated onions.