Residual stress behaviors in sputter-deposited BCC solid solution alloys

Abstract

Metal alloy films are used in many technical applications such as magnetic storage, catalysis, and hard coatings. As with any coating, residual stress is critical to their adhesion and physical properties. While there have been numerous studies of residual stress evolution in elemental metal systems, alloy films are less understood. In this work, we present in situ measurements of the stress in Cr–W and V–Mo alloys of different compositions at different growth rates. The stress is quantitatively analyzed (along with previous results in V–W) using a model for stress in alloys that is based on similar mechanisms invoked for elemental systems. The modeling allows the measured change in stress with composition to be related to the underlying stress-generating mechanisms. Adding a lower-mobility element to a higher mobility, one suppresses surface mobility, leading to less compressive stress from non-energetic growth kinetics. However, it also decreases defect mobility, which enhances the stress due to energetic impacts. Adding heavier, higher-melting-point elements enhances compressive stress generated by energetic particle impacts. As a result, W-containing alloys become increasingly compressive with higher W content, whereas in V–Mo, the competing growth kinetic and energetic impact contributions are comparable, leading to a non-monotonic dependence of stress on composition for different growth rates.