ELECTRIC-FIELD-INDUCED PHENOMENA IN SCANNING-TUNNELING-MICROSCOPY - TIP DEFORMATIONS AND AU(111) SURFACE PHASE-TRANSITIONS DURING TUNNELINGSPECTROSCOPY EXPERIMENTS

We report electric field induced phase transitions of Au(111) surfaces and electric field stress induced elongation of Au tips during curren t voltage measurements with a scanning tunneling microscope (STM) in a ir. Transitions between the reconstructed square-root 3 x 22 and the u nreconstructed 1 x 1 phase of the Au(111) surface are attributed to ch anges in the electronic surface excess charge density induced by the e lectric field between the tip and sample. Elongations of STM tips duri ng tunneling spectroscopy give rise to a hysteresis in the current-vol tage response at tip-to-sample biases greater than approximately 0.5 V and frequently result in the formation of a mechanical tip-sample con tact.