ABSTRACT
A thin solid film grown on a much thicker solid substrate is generally deposited in a state of stress. This stress can be quite large, often exceeding the yield stress of the material in bulk form, and can lead to deleterious effects such as cracking, spalling, and deadhesion. As a result, attempts are often made to control and to minimize the stress levels during growth, or to relieve the stress after deposition. However, it is sometimes necessary or even desirable for a thin film to be under stress. It is generally required for electronic material applications that a semiconductor film be grown epitaxially, that is, as a single crystal deposited on a single crystal substrate with defect-free lattice matching at the film-substrate interface. If the in-plane equilibrium lattice spacings of the film and the substrate are different, the film will be under stress to achieve this lattice matching. The deposition of a magnetical film with a certain stress state can lead to an enhanced magnetical anisotropy that may be exploited in certain device applications. A material that has a thin film coating in a state of compressive stress can result in enhanced fracture and fatigue resistance compared to an uncoated material.
