Sputtered copper and tungsten thin films both with and without tungsten and chromium superlayers were tested by using nanoindentation probing to initiate and drive delamination. The adhesion energies of the films were calculated from the induced delaminations using the analysis presented in `Quantitative adhesion measures of multilayer films: Part I. Indentation mechanics.' Copper films ranging in thickness from 150 to 1500 nm in the as-sputtered condition had measured adhesion energies ranging from 0.2 to 2 J/m2, commensurate with the thermodynamic work of adhesion. Tungsten films ranging in thickness from 500 to 1000 nm in the as-sputtered condition had measured adhesion energies ranging from 5 to 15 J/m2. The superlayer was shown to induce radial cracking when under residual tension, resulting in underestimation of the adhesion energy when the film was well adhered. Under conditions of weak adherence or residual compression, the superlayer provided an excellent means to induce a delamination and allowed an accurate and reasonably precise quantitative measure of thin film adhesion.
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The authors gratefully acknowledge support for this work by the Center for Interfacial Engineering at the University of Minnesota under grant NSF/CDR-8721551, the Department of Energy under DOE/DE-FG02/96ER45574, and the Department of Energy under DOE contract DE-AC04-94AL85000. The valuable assistance of Dr. Maarten de Boer, Joshua S. Robach, and William Schildgen were also greatly appreciated in the development of this work.