Cluster beams from liquid alloy ion sources
Liquid Alloy Ion Sources (LAIS), especially Cobalt-Neodymium LAIS as well as Au containing sources (AuGe, AuSi, AuGeSi) were investigated with respect to their cluster emission behaviour. Clusters, complex and molecular ions were found. The influence of the source emission current on the cluster emission intensity and also on the cluster mass distribution were studied. The Co-Nd LAIS was used for writing patterning (implantation, sputtering) in a mass-selecting Focused Cluster Beam (FCB) system (cluster size up to 5). Theoretical estimations were carried out concerning the use of the FCB for direct deposition at landing energies of about 100 eV / atom. At present a mass resolved retarding field energy distribution analyser for FCB - LAIS was put into operation and is now used to investigate different LAIS with different alloy source materials from the needle as well as the capillary type. The energy spread of a certain emitted component is an important parameter which determines the obtainable cluster beam spot size. Another parameter is the energy deficit e.g. the energy shift of some eV to a lower energy as the extraction potential which allows to study the physics of the emission process itself. For calibrating the system a gallium LMIS was used where all parameters are well known. The system energy resolution is smaller than 1.5 eV and the mass resolution is about 100.