FIELD EVAPORATION OF GOLD BY SCANNING-TUNNELING-MICROSCOPY

We demonstrate that the gold surface modification with scanning tunneling microscopy is caused mainly by material transfer from the positive electrode to the negative one. On clean Au(lll) surfaces evaporated on mica, we observe atomic steps and terraces with a 22 X root 3 'herringbone' reconstruction in air. Mounds are made by applying positive voltage pulses to the gold tip. At a tunneling resistance larger than 200 M Omega, application of negative pulses makes depressions. When the initial tunneling gap is smaller, i.e., at a resistance less than 100 M Omega, mounds can be created by negative pulses as well, but adjacent to the mounds, depressions are often observed in this case. We think that the tip contact and following neck formation play a role in generating this structure. The stability of the surface is discussed in relation to the herringbone reconstruction.