Temporal behaviour of nanofeatures on Au

Tip-crash techniques allow dents of 5-10 nm dimension to be written with a W tip on bulk Au. These features subsequently decay as a result of surface diffusion of Au atoms. Voltage pulses 5 V high and 5 ms wide applied to a Au-coated W tip enable mounds of 10-20 nm lateral dimension to be formed. The height of these features may be built up by sequential pulsing at one location with an approximate growth rate of 4 nm per pulse. Interestingly, the mounds do not, in general, suffer subsequent decay. They can, however, change shape and be affected somewhat by further mound deposition in their vicinity. An explanation of the persistence of the mounds, as compared with the dents, is offered in terms of inhibition of surface diffusion processes at the base of the mounds where there are atomic sites of increased co-ordination number.