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Ionized cluster beam (ICB) deposition has been used to form thin films of metals, insulators, semiconductors and organic materials which have unique characteristics when compared to films formed using other techniques. In addition, the use of gas-phase atoms in the form of accelerated clusters has recently shown promise for surface modification applications. A fundamental understanding of ICB deposition and related techniques requires investigations of (1) the mechanisms which lead to the growth of large vapor phase clusters, (2) techniques for determining the size distribution of large vapor clusters, (3) the initial stages of film nucleation, (4) film growth morphology related to lattice mismatch and ion beam parameters. Clarification of the role of clusters in ICB deposition has been greatly aided by atomic scale imaging by transmission electron microscopy and scanning tunnel microscopy in the early stages of film growth. Emphasis is given to the formation of high-quality, epitaxial metallic films. Several applications of ICB films with respect to microelectronics, optical mirrors, compound materials and organic materials are discussed with emphasis on the special characteristics of ICB films. Applications for gas-cluster processing are reviewed.

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Molecular dynamics simulations of various Ar clusters, with the size ranging 1 to 50000 and the energy up to totally 50keV, impacting on Si surfaces were performed. The cluster size and incident energy dependence on damage formation was examined. Two cluster-size depending parameters, the threshold energy to cause displacements and displacement yield, were proposed and modeled. These two parameters showed non-linearity depending on cluster size. The model function using above parameters reproduced the characteristics of damage formation by cluster ion impact. Two specific cluster sizes to cause maximum and no displacements on the surface were discussed, which is expected to provide useful information about optimized cluster ion beam conditions for various surface modification and thin film formation processes.

We developed a polyatomic cluster ion beam system for materials processing, and polyatomic clusters of materials such as alcohol and water were produced by an adiabatic expansion phenomenon. In this article, cluster formation is discussed using thermodynamics and fluid dynamics. To investigate the interactions of polyatomic cluster ions with solid surfaces, various kinds of substrates such as Si (100), SiO 2 , mica, polymethyl methacrylate, and metals were irradiated by ethanol, methanol, and water cluster ion beams. To be specific, chemical reactions between radicals of polyatomic molecules and surface Si atoms were investigated, and low-irradiation damage as well as high-rate sputtering was carried out on the Si(100) surfaces. Furthermore, materials processing methods including high-rate sputtering, surface modification, and micropatterning were demonstrated with ethanol and water cluster ion beams.