ATOMIC-STRUCTURE OF LONGITUDINAL SECTIONS OF A PITCH-BASED CARBON-FIBER STUDIED BY STM

Longitudinal sections of pitch-based carbon fibers have been studied with scanning tunneling microscopy. A hexagonal superstructure due to a rotation of 9.5-degrees of the top graphitic plane with respect to the underlying bulk was observed. Remarkably this superstructure was modulated near defects by a (square-root 3 X square-root 3)R30-degrees modulation. The same modulation was found on the images with atomic resolution. It was concluded that the atomic structure of the fiber resembles the hexagonal structure of graphite. But locally this structure is disturbed. From the modulation of the superstructure it is deduced that this disturbance extends at least two layers into the bulk.