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 {} and height 20 {}, and pits of width 50 {} and depth 10 {} can be produced on a gold surface with nearly equal probabilities by applying voltage pulses to a gold tip in the scanning tunneling microscope. We study the effects of the polarity and the height of the applied voltage pulses, and those of atmospheric environments. Our data show that field evaporation can occur both in positive and negative fields, but in ultrahigh vacuum, a tip can sustain itself only if it is in negative polarity.