Platinum nanodot formation by atomic point contact with a scanning tunneling microscope platinum tip

Using a platinum tip of a scanning tunneling microscope, ultrasmall nanodots of about 1 to 2 nm in diameter are reproducibly created on the Si(111)7×7 surface at room temperature by applying appropriate voltage pulses between tip and sample. Dynamic processes of the nanodot formation have been monitored by means of the displacement of the tip and the current through the tip. The experimental data suggest that a nanometer-scale bridge is formed between tip and sample, and that the created nanodot is a part of the nanobridge left on the surface. We have also observed relaxation of the tip apex and the created nanodots after the nanobridge is broken.