Defect-dependent elasticity: Nanoindentation as a probe of stress state

Using an interfacial force microscope, the measured elastic response of 100 -nm-thick Au films was found to be strongly correlated with the films' stre ss state and thermal history. Large, reversible variations (2x) of indentat ion modulus were recorded as a function of applied stress. Low-temperature annealing caused permanent changes in the films' measured elastic propertie s. The measured elastic response was also found to vary in close proximity to grain boundaries in thin films and near surface steps on single-crystal surfaces. These results demonstrate a complex interdependence of stress sta te, defect structure, and elastic properties in thin metallic films.