Nanoindentation characterization of ErT2 thin films

The properties of ErT2 films change as the tritium decays into 3He, which has important implications for long-term film stability in applications such as neutron generators. Ultra-low load nanoindentation, analyzed using finite-element modeling to separate the nanomechanical properties of 500 nm ErT2 layers from those of the underlying substrates, has been used to examine the films as they age. The 3He bubbles which form as the film ages act as barriers to dislocation movement, hardening the material, but not dramatically affecting the elastic properties. By modeling the layer as an isotropic, elastic–plastic solid with the Mises yield criterion, the nanoindentation data is shown to correspond to an increase of nearly 2× in strength after aging for over a year.