Nano-scale metal cluster deposition using STM

Abstract

A scanning tunneling microscope (STM) has been used to create nano-scale metal clusters on a clean stepped Si(111) surface by applying bias pulses to the tip-sample tunneling junction. The following experimental results have been obtained: (1) For Al deposition, negative sample bias pulses produce well-shaped clusters on the surface, whereas positive sample bias pulses not only produce such clusters but also holes and clusters in holes. This phenomenon can be explained by the differences in the critical evaporation fields for Al and Si ions in terms of the field evaporation deposition mechanism. (2) Al nano-lines can be generated by programming the bias pulses to be applied at the positions desired on the surface. The deposition process was found to be more successful at step edges which are relatively higher than other areas on the surface. (3) Controlled depositions can also be realized using an etched W tip to form pre-defined patterns of W clusters. (4) Using Au clusters deposited by field evaporation, single-electron tunneling effects have been observed at room temperature in an Au tip-Au cluster-Si substrate double junction system.