SCANNING-TUNNELING-MICROSCOPY ANALYSIS OF A GLASSY-CARBON HEAT-TREATED AT 2500-DEGREES-C

The surface structures obtained by scanning tunneling microscopy (STM) studies of a commercial glassy carbon, heat treated at 2500-degrees-C, are presented and discussed. The observed STM images show at atomic scale featureless amorphous regions that coexist with different types of ordered zones. The disordered regions include four or five membered rings with bonding distance between 2.5 and 3.5 angstrom. The ordered regions are characterized by various topographical features including rows of atoms at distances of 3.40 +/- 0.15 angstrom, a hexagonal graphitic or diamond-type structure with apparent interatomic distances d(i) = 2.50 +/- 0.15 angstrom, a graphite-like structure with d(i) = 2.2 +/- 0.1 angstrom, and finally an unexplained square lattice structure with d(i) = 1.8 +/- 0.1 angstrom.