Plastic and Elastic Properties of Compositionally Modulated Thin Films

Abstract

The mechanical properties of thin films with grown-in periodic com­ position modulations, usually referred to as multi layers or superlattices, continue to be actively investigated. Much of the early interest centered on elastic properties and the supermodulus effect, i.e. the observation of unusually large elastic moduli at specific composition-modulation wave­ lengths. While recent experimental evidence contradicting the supcr­ modulus results has dampened interest in this area, there is still con­ siderable activity concerning smaller elastic anomalies observed in superiattices. The interest in the strength and hardness of these materials has increased over the last several years, driven not only by scientific issues, but by possible practical applications in the area of protective and tribological coatings. Recent fundamental advances have improved the understanding of the mechanisms controlling these properties. Multilayer mechanical properties are also of general interest because of the wide use of such structures in semiconductor, magnetic, and superconducting applications. Recent review articles (I, 2) have described the work in this area in considerable detail. The topics covered in this review are thus primarily