FIELD EVAPORATION OF GOLD BY SCANNING-TUNNELING-MICROSCOPY

We demonstrate that the gold surface modification with scanning tunnel ing microscopy is caused mainly by material transfer from the positive electrode to the negative one. On clean Au(lll) surfaces evaporated o n mica, we observe atomic steps and terraces with a 22 X root 3 'herri ngbone' reconstruction in air. Mounds are made by applying positive vo ltage pulses to the gold tip. At a tunneling resistance larger than 20 0 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 adjacen t to the mounds, depressions are often observed in this case. We think that the tip contact and following neck formation play a role in gene rating this structure. The stability of the surface is discussed in re lation to the herringbone reconstruction.