GENERATION AND ANALYSIS OF NANO-SCALE AL ISLANDS BY STM

Metallic nanoclusters on suitable substrates are of particular interes t when studying thermally activated island decay processes and single- electron tunneling effects. By application of voltage pulses to the ST M tip-sample junction, well-defined Al clusters ranging from 3 to a fe w hundred nm in diameter have been generated on a clean Si(111) surfac e in ultra-high vacuum (UHV). The voltage thresholds determined are ab out -5 V for negative sample pulses and +6 V for positive sample pulse s under the current experimental conditions. Thermal decay rates of tw o Al islands (10 nm and 30 nm in diameter) at room temperature have be en studied as a function of time using STM. It is found that Al cluste rs on clean Si(111) are stable in UHV. Deposition mechanisms in terms of tip melting, point contact, and field evaporation have been discuss ed.