The use of ion beams in thin film deposition

Bombardment of growing films with energetic ions has become an established method of improving or, at least, changing, many of the important structural, optical and electrical properties of thin films. Although the techniques used to achieve the desired bombardment vary quite dramatically from high pressure plasma processing to irradiation with mono-energetic, mass-analysed ion beams in ultrahigh vacuum environments, the ion-surface interaction processes which lead to the deposition, removal and relocation of surface and near surface atoms form the basis of all the ion assisted processing techniques. The purpose of this paper is to review the rates of penetration and entrapment, recoil particle and defect generation, and sputtering processes in determining the formation kinetics and characterization of films deposited under ion bombardment conditions. Consideration of these processes enables the deposition parameters to be optimized from the point of view of the relative contributions of energy and material deposition and the design and performance of experimental systems capable of realizing the specified conditions will be discussed.