Ionized cluster beam deposition and thin insulating films

The ionized cluster beam (ICB) deposition method has been used to obtain high quality films of metals, semiconductors and insulators. A review of the ICB technique is given with a discussion of recent developments and examples of the results obtained with different materials. The characteristics of ICB deposited films of TiO₂, Al₂O₃), and CaF₂ and their dependence on the process parameters are discussed in more detail. Deposition of epitaxial Al-CaF₂-Si heterostructures is also discussed. The crystallographic structure and physical properties of thin films are found to be strongly dependent on the energy of the ionized species, controlled by the acceleration voltage during film deposition. Some of the properties of the films usually associated with high substrate temperature in conventional vacuum depositions can be obtained at low substrate temperature in the ICB technique, which may give it a distinct advantage in device fabrication. While the ICB method has proven to be successful in deposition of high quality thin films, more fundamental studies of the processes are needed. In particular, finding correlations between the ionized beam characteristics and the film properties is most desirable.