STUDY OF THE IONIZED CLUSTER BEAM TECHNIQUE

The unique aspect of Ionized Cluster Beam (ICB) thin film deposition is that material is deposited in the form of ionized, accelerated atom clusters. Unique film properties have been reported for ICB, including high surface adhesion, low temperature epitaxy, and minimal surface damage. The cluster size in much of the early work was not measured directly but was inferred from theory including the following: (1) Thermodynamic description of beam generation using a nozzle source; (2) cluster embryo formation and subsequent growth due to collisions; (3) scaling laws based on gas dynamics; (4) classical nucleation theory coupled with gas flow equations; (5) classical nucleation theory with time dependence; and (6) condensation of vapor atoms on crucible walls, surface migration to form embryos, and establishment of bonds between atoms and embryos. These theories do predict the formation of clusters using a nozzle source even though they are not in complete agreement and have their detractors. Consequently the issues of cluster formation and direct cluster measurement remain of primary importance in ICB. In this presentation, different cluster measurement theories and measurement methods is described. Results of recent cluster size measurements using gold will be reported.