STM-INDUCED ANNEALING AND NANOEXTRUSION IN NM-PERIOD MULTILAYERS

Nanometre-period nickel-carbon multilayers were used as a writing medi um for nanostructure fabrication induced by gap voltage manipulations in a scanning tunnelling microscope. The choice of immiscible sample m aterials provided high-stability written metallic structures. Two well -distinguished hillock-like nanostructure types were observed, dependi ng on the tip-sample separation, polarity and interaction time. Relati vely slow local annealing under positive sample potential without a di rect tip-sample contact resulted in the formation of nanostructures of <20 nm wide and a few nanometres high. Rapid melting followed by meta l melt extrusion was observed if the tip contacted the sample during t he nanostructure formation, independent of the polarity of the applied voltage. These metallic-like structures were tens of nanometres high and had a good electronic contrast to the initial carbon-coated surfac e. No traces of tip material were found in the processed areas. The sh ape of the nanostructures and the threshold voltage of their formation were strongly dependent on the tip condition. Possible courses of nan ostructure formation are discussed. (C) 1997 by John Wiley & Sons, Ltd .