CAREER: Study of the Mechanical Properties of Thin Metal Films and Shape Memory Alloy Coatings

Harvard University, Cambridge MA

Investigators

Abstract

This project aims at greater understanding of deformation and fracture mechanisms of thin films. It has been known that these mechanisms interact with microstructural features such as grain size, grain orientation, interfaces and surfaces, and dislocation substructure albeit the nature of these interactions is not well established. The project investigates the stress-strain behavior of freestanding films using bulge test technique while films on substrates will be studied using the substrate curvature method. Another goal of the project is to investigate the precipitation hardening and the shape memory effects in Ni-Ti thin films. Third objective of the project is to develop micromechanical techniques for measuring thin film fracture toughness. These techniques are used to investigate sub-critical crack growth under cyclical loading conditions and to determine how factors like film thickness, chemical environment, and process conditions affect the fracture toughness of thin metal and alloy films. A new undergraduate Introductory Materials Science course along with a special topics course will serve as the main vehicles for some of the educational activities. %%% This research develops new and improved understanding of the deformation mechanisms that operate in thin films, resulting in better models for thin film mechanical behavior that will have an impact on many engineering applications where thin films are used, such as integrated circuits, MEMS devices, and wear resistant coatings. The fracture toughness and fatigue resistance of thin films are applicable from reliability concerns for MEMS devices in non-hermetic packaging that is more cost-effective than traditional hermetic packaging.