Surface superstructure on fullerenes annealed at elevated temperatures

Scanning tunneling microscopy images of fullerenes annealed at elevated temperatures are investigated. Three types of ringlike superstructures of (√3× √3)R30° of graphite, the circular type, the U type, and the semicircular type, are observed on the curved surface of the fullerenes annealed in the temperature range from 2073 to 2673 K. A new modified interference model, in which both the α and β site atoms contribute to the tunneling current caused by the curved surface, is proposed. The model well simulates the three types of the ringlike superstructure of graphite and the continuous change from the triangular structure of graphite to the ringlike superstructure of graphite.