Irradiation of a substrate by an energetic ion beam during film deposition can drastically change the substrate surface, its structure, the surface chemistry, the nucleation processes and the type of coating which is produced. A wide range of novel coatings and improved adhesion to the substrate are possible as a result of the added energy and the incorporation of the ion species into the film. Ion-assisted deposition leads to changes in the film density, structure, crystal-amorphous state, grain size, orientation and defect density. Where coatings comprise more than one element, new metastable phases can be formed and conventional phases, normally formed at much higher temperatures, can be produced.
More recent developments include the application of ion beams to induce chemical reactions at the bombarded surface so that components of gaseous species may be deposited on the irradiated substrate. Because the deposit only occurs along the ion path, precise patterns of coatings can be obtained.
The present paper reviews the physical processes occurring during ion-beam-assisted deposition, describes the main techniques and selectively cites recent studies which demonstrate the different types of film produced. Utilization of these improved surface coatings to treat surfaces for a variety of different applications is discussed and future areas requiring further development are proposed.