Film Formation and Structure Control by Ionized Cluster Beam

Abstract

The ionized cluster beam (ICB) method is one of the novel ion-assisted techniques for film formation, which enables formation and transportation of low energy and equivalently high current ion beams. The clusters, large size macro-aggregates of 100-2000 atoms, are formed by condensing pure vapor of normally solid materials in an adiabatic expansion process. The ICB causes special film formation mechanism due to the peculiar properties of clusters in addition to the effects of kinetic energy and electric charge of ions. This technique allows unique film formations, such as low temperature epitaxy, hetero-epitaxy with large misfit combinations, formation of ultra-thin films and very smooth film surfaces, and enables control on crystal structure, chemical composition, and miscellaneous electrical properties of the film. This paper includes room temperature epitaxy of thermally stable Al on Si substrate, surface morphology control of epitaxial CaF₂ films, formation of CdTe-PbTe multilayered structure, and crystal structure control of TiO₂ films by reactive ICB method. ICB method is also effective for organic film formation with high crystallinity and improved electrical characteristics. Some results for Cu-phthalocyanine and polyethylene thin films are given.