Coatings and films are often used to enhance performance and reliability of micro and nanoscale devices fabricated using micosystem technologies. In all environments, performance depends on adhesion. Variations in surface topology are used to great advantage in improving film and coating adhesion at the micron and sub-micron scales. However, limitations in test capabilities have prevented a direct measure of surface topology contributions to adhesion at the nanoscale. Understanding these contributions to adhesion is a key factor to enhancing performance and reliability of nanostructured materials and devices especially in active environments. As a result, we are combining nanomechanical tests and finite element-based simulations to develop an understanding of how patterns of small-scale interfacial heterogeneities affect interfacial crack nucleation and crack propagation. The nanomechanical tests show that the nanopatterns alter film fracture morphology while markedly increasing interfacial fracture energies. The simulations show that the increased resistance to interfacial film fracture is controlled by pattern morphology and mode mixity. In this presentation, we will use the test results and finite element simulations to show how small-scale variations in topology affect resistance to fracture thereby providing a means to tailor nanoscale film device performance and reliability.

This work is supported by Sandia National Laboratories, a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.