Elucidating the mechanism for indentation size-effect in dielectrics

Recent work presented experimental evidence of a strong elastic indentation size-effect in ferroelectric BaTiO3. The apparent elastic modulus was shown to exhibit significant stiffening with decreasing contact size and this was attributed to the phenomenon of flexoelectricity. There is however room for debate whether domain wall movement, nucleation, and related phenomena are responsible for the size-effect in BaTiO3. In this work, we present a nanoindentation study of paraelectric SrTiO3 and argue that indeed flexoelectricity rather than ferroelectric-specific effects cause the observed size dependent behavior.