Efficient technique for producing high-brightness, size-selected cluster beams

An efficient technique for producing size-selected cluster beams from a magnetron cluster source is described. In this technique the clusters are ejected from a laminar gas expansion nozzle and the resulting size selection is achieved with a simple parallel-plate electrostatic separator. Using this method we have been able to select gold clusters in the size range from 250 to 16 000 atoms. The limiting size resolution is around 2% and because up to 40% of the clusters from the source are negatively charged the beam intensity is higher than many other sources. Furthermore, the angular divergence of the beam can be kept below 3° full width at half maximum for a 3-nm-diam exit nozzle so that it is possible to soft land size-selected clusters on surfaces by the simple expedient of applying a retarding voltage to the substrate.