Scanning tunneling microscope induced nanostructuring of a Si(111)/Ag(3×3)R30° surface

An atomically flat Si(111)/Ag(3×3)R30° surface has been modified using a scanning tunneling microscope in ultrahigh vacuum. Mesoscopic pits have been created by applying negative voltage pulses to the sample, while at opposite voltage polarity mounds were formed. Moreover, lines could be written by moving the scanner at elevated voltages. The threshold voltage for pit formation increases almost linearly with the distance of the tip to the surface and drops to a value below 2 V for the closest approach. At sufficiently high voltages the depth extends beyond the silver layer height. The lateral pit size is well below 8 nm and can be reduced to values between 2 nm and 5 nm for voltages slightly above the threshold. Even selective top layer Ag atom removal has been achieved.