The influence of ion bombardment on the adhesion of thin films to substrates

Abstract

Ion bombardment has been used for several years to improve the adhesion of metallic films to ceramic substrates. Many studies have demonstrated such an improvement in film adhesion but no single mechanism is considered responsible. This paper discusses the mechanisms that can contribute to adhesion and the supporting experimental evidence. For example, intermediate phase formations, structure changes, and stress relief as the result of ion beam mixing are discussed. Ion bombardment can also result in changes in film and substrate hardness, friction characteristics, and film thickness (due to sputtering), which can affect the measurement of adhesion in a mechanical test. While the scratch test and the peel test (both commonly used adhesion tests) are useful for comparisons of the adhesion strength for specimens within the same film/substrate system, the ion beam may cause sufficient changes in the character of the system so as to make straightforward comparisons between mixed and unmixed specimens difficult.