Periodic cracks and temperature-dependent stress in Mo/Si multilayers on Si substrates

Abstract

This work examines formation of the peculiar periodic crack patterns observed in the thermally loaded Mo/Si multilayers. Using the substrate curvature measurements, the macroscopic film stress evolution during thermal cycling was investigated. Then high-speed microscopic observation of crack propagation in the annealed Mo/Si multilayers was presented providing experimental evidence of the mechanism underlying formation of the periodic crack patterns. The origin of the peculiar periodic crack patterns was determined. They were observed to form by the slow crack propagation under quasi-static conditions as a result of the interaction between the channelling crack propagation and the advance of the delamination front.

Keywords:

• Fracture
• cracks
• crack growth
• pattern dynamics
• multilayers
• Mo/Si

Acknowledgements

The authors would like to acknowledge support for this research from National Science Foundation under the 0600266 and 1358088 grants. Dr. Dirk Meyers group members help at Technical University Dresden is greatly appreciated. In particular, we would like to thank Dr. Tilmann Leisegang and Dr. Alexandr Levin. The authors also thank Dr. Stefan Braun from the Fraunhofer Institute for Material and Beam Technology in  Dresden for providing the Mo/Si samples and the stress  data.