Current View of Nanoindentation: Recent Developments and Application in Material Characterization.

The first demonstration of qualitative nanoindentation several decades ago sparked enormous research on different types of materials, revealing unprecedented mechanical phenomena and properties. Since mechanical properties are directly linked to many materials' structural and compositional features, nanoindentation has been successfully utilized to explore the coupling between mechanical behavior and functional properties, like electrical conductivity, reaction kinetics in electrodes, and hydrogen charging. Nanoindentation measurements have evolved beyond probing simple bulk metals, extending to complex alloys, nanomaterials, and nanocomposites. This review summarizes recent advancements in the nanoindentation technique, which now expands beyond traditional hardness and Young's modulus measurement. Beginning with the fundamental mechanics and principles of indentation, we explore recent methodological developments. We discuss the interpretation and significance of key mechanical characteristics derived from nanoindentation including elastic strain to failure, resistance to plastic deformation, and elastic recovery. Furthermore, we highlight advanced approaches such as topographic reconstruction of thin films, combinatorial nanoindentation, and