FIELD EVAPORATION BETWEEN A GOLD TIP AND A GOLD SURFACE IN THE SCANNING TUNNELING MICROSCOPE CONFIGURATION

Mounds of gold atoms of horizontal size less than 200 angstrom and hei ght < 20 angstrom, and pits of width < 50 angstrom and depth < 10 angs trom can be produced on a gold surface with nearly equal probabilities by applying voltage pulses to a gold tip in the scanning tunneling mi croscope. We study the effects of the polarity and the height of the a pplied voltage pulses, and those of the atmospheric environments. Our data show that field evaporation can occur both in positive and negati ve fields, but in ultrahigh vacuum, a tip can sustain itself only if i t is in negative polarity.