SCANNING-TUNNELING-MICROSCOPY STUDY OF TIP-INDUCED TRANSITIONS OF DISLOCATION-NETWORK STRUCTURES ON THE SURFACE OF HIGHLY ORIENTED PYROLYTIC-GRAPHITE

Scanning-tunneling-microscopy observations of a reversible, tip-induce d transition between triangular- and star-shaped networks of partial d islocations on the basal (0001) plane of highly oriented pyrolytic gra phite are reported. The transition between network geometries results from small variations (0.14 V) in the tip-to-substrate voltage bias an d is attributed to shear-induced motion of partial dislocations. The s hear stress required for the transition is estimated to be 5 MPa. Disl ocation motion occurs over distances of tens of nanometers on the time scale of several minutes, allowing the dynamics of the transition bet ween the two networks to be observed in real time. Atomically resolved images near a dislocation show distortions of the atomic lattice that are consistent with glide of the surface basal plane. Analysis of the separation distance between pairs of dislocations yields a surface st acking-fault energy of 2.1-4.5 mJ/m2.