Toughness Assessment and Fracture Mechanism of Brittle Thin Films Under Nano-Indentation

The nano-indentation technique is an effective tool for assessing the fracture toughness of brittle thin film. In this chapter, a comprehensive and systematic review of toughness measurement methods and fracture mechanisms in brittle film by indentation are presented. The classic method, the energy method, and the stress-based method are three major approaches for determining fracture toughness using the nano-indentation technique. The limits and application ranges of these methods are discussed in detail. In particular, the stress-based method depends highly on the fracture mechanism of cracking. This chapter also reviews different types of crack patterns induced by nano-indentation, such as radial cracks, ring cracks, picture-frame cracks, spiral cracks, and spalling. The possible mechanisms of the crack patterns are investigated considering the substrate effect, the indenter shape effect, and the load level effect. Understanding the fracture mechanism provides guidance in developing a more accurate stress-based model