Introduction

The bombardment of a growing film with energetic particles has been observed to change for the better a number of characteristics and properties, critical to the performance of thin films and coatings, such as adhesion, densification of films grown at low substrate temperatures, modification of residual stresses, control of texture (orientation), modification of grain size and morphology, modification of optical properties, and modification of hardness and ductility.

The process of simultaneous thin-film deposition and directed ion bombardment from an ion source has been labeled by a variety of terms including: ion assisted coating (IAC); ion assisted deposition (IAD); ion vapor deposition (IVD); ion beam enhanced deposition (IBED); dynamic recoil mixing (DRM) at high energies; and ion beam assisted deposition (IBAD). This term, ion beam assisted deposition, or IBAD, will be used here in favor of its growing acceptance by the energetic-particle–solid interaction research community.

The important role of ions in thin-film deposition techniques has long been realized by the coating community. It is difficult, however, in many of the plasma based coating techniques, to separate out the degree to which ion and neutral particle fluxes as well as ion energies affect resultant coating properties. Mattox (1982) showed as early as 1963 that energetic ions within plamsa had an important influence on coating properties in his early development of ion plating. In addition, other plasma-based deposition processes, such as activated reactive evaporation (ARE), developed by R. F. Bunshah and co-workers (Bunshah, 1982), employ ionization to promote film properties.