Adhesion measurement of a buried Cr interlayer on polyimide

Abstract

A fundamental knowledge and understanding of the adhesion behaviour of metal–polymer systems is important as interface failure leads to a complete breakdown of flexible devices. A combination of in situ atomic force microscopy for studying topological changes and in situ synchrotron based stress measurements both during film tensile testing were used to estimate the adhesion energy of a thin bilayer film. The film systems consisted of 50–200 nm Cu with a 10 nm Cr adhesion layer on 50 μm thick polyimide. If the Cu film thickness is decreased to 50 nm the Cr interlayer starts dominating the system behaviour. An apparent transition from plastic to predominantly brittle deformation behaviour of the Cu can be observed. Then, compressive stresses in the transverse direction are high enough to cause delamination and buckling of the Cr interlayer from the substrate. This opens a new route to induce buckling of a brittle interlayer between a ductile film and a compliant substrate which is used to determine the interfacial adhesion energy.

Keywords:

• thin films
• buckling
• atomic force microscopy
• synchrotron radiation
• tensile testing

Acknowledgements

Partial funding of the research study has been provided by the Austrian Science Fund FWF (project no. P22648-N20) and by the Helmholtz-Zentrum Berlin (project no. 2011_2_110211 and 2012_1_111115). J. Schalko, Research Unit for Integrated Sensor Systems of the Austrian Academy of Sciences (Wiener Neustadt, Austria) is acknowledged for providing films.