Compact sputter source for deposition of small size-selected clusters

We report on the development of a caesium ion sputter source for the production of small mass-selected atomic clusters. It has been designed to be compact and portable, enabling it to be attached to ultrahigh vacuum (UHV) systems for use in deposition experiments. The sputter source, developed from a high energy (similar to 20 keV) atomic ion beam source, has been modified by introducing a beam extraction section, resulting in a cluster beam energy of 1.5 kV. This allows mass selection to be performed with a compact Wien velocity filter, greatly reducing the dimensions of the source. The source produces sufficient intensities of small clusters (1 - 15 atoms/cluster) for UHV deposition experiments, for example, a deposition rate of 0.002 monolayers/min for Al-7(-) focused onto a 1 cm(2) area has been obtained. It is possible to produce beams of many materials, especially the noble metals and carbon. We show mass spectra for Ag-n(-), Al-n(-), and C-n(-) clusters. (C) 1997 American Institute of Physics.