Generation and analysis of nano-scale Al islands by STM

Abstract

Metallic nanoclusters on suitable substrates are of particular interest when studying thermally activated island decay processes and single-electron tunneling effects. By ap- plication of voltage pulses to the STM tip-sample junction, well-defined Al clusters ranging from 3 to a few hundred nm in diameter have been generated on a clean Si(111) surface in ultra-high vacuum (UHV). The voltage thresholds determined are about 5V for negative sample pulses andC 6V for posi- tive sample pulses under the current experimental conditions. Thermal decay rates of two Al islands (10 nm and 30 nm in diameter) at room temperature have been studied as a func- tion of time using STM. It is found that Al clusters on clean Si(111) are stable in UHV. Deposition mechanisms in terms of tip melting, point contact, and field evaporation have been discussed.