Measurement of adhesion of thin films

Abstract

Methods of measuring adhesion are considered and an analysis is presented of a method which is particularly suitable for thin films. In this method a rounded steel point of smooth contour is drawn across the film surface and the load on the point is gradually increased until the film is removed, leaving a clear channel. It is shown experimentally that the load required depends upon the nature of the interface between film and substrate without being directly dependent upon the mechanical properties of either. The method is analyzed in detail and a suitable mechanism is proposed. This mechanism is examined both theoretically and experimentally and it is shown that an absolute value of the shearing force required to remove a film can be calculated from the critical load required, the tip radius of the point and the identation hardness of the substrate. Applications have been restricted so far to metal films on transparent substrates.