Stability of Surface Steps on .BETA.-ET2I3 Surfaces and Removal of Molecules by an STM Tip.

We have observed, using the scanning tunneling microscope (STM), that molecules at the β- (ET) 2I3 (001) surface are removed by scanning the STM tip. Such removal of the molecules is followed by a systematic change in the directions and the structures of the surface steps. We discuss the stability of the observed steps, based on the molecular arrangement on (001) surfaces terminated by I3 and ET layers. Both the change of the surface steps and the STM images successively recorded at the same area indicate that the I3 and ET layers are alternately removed by the STM tip.