Creation of nanometer-scale structures with the scanning tunneling microscope

We used a scanning tunneling microscope to create nanoscale structures on Au surfaces by applying two kinds of voltage pulses. In the case of short rectangular pulses a sequence of identical pulses can lead to a number of different structures ranging from holes to hillocks. To separate the influence of the electric field and the current long triangular pulses have been applied under the condition of constant current. With this technique we are able to create either holes or hillocks, the material transport being from the positive to the negative electrode. We interpret our experiments as field evaporation of positive Au ions.