SURFACE SUPERSTRUCTURES FLUCTUATING IN THE QUASI-ONE-DIMENSIONAL ORGANIC CONDUCTOR BETA-(BEDT-TTF)(2)PF6 OBSERVED BY SCANNING-TUNNELING-MICROSCOPY

Two types of surface structures were observed at similar to 280 K by s canning tunneling microscopy on a crystal surface of beta-(BEDT-TTF)(2 )PF6. One is a structure which corresponds to the expected crystal str ucture determined by X-ray diffraction measurement, and the other is a modulated structure with two-fold periodicity perpendicular to the on e-dimensional conductive axis. Fluctuation between these two types of structures in the same area was observed by scanning tunneling microsc opy, with a surface defect used as a positional marker. Occurrence of a double tip effect was considered but concluded not to be responsible for the observed change.