Observations of nanoscale properties of ZnO pillars subject to compression

Zinc Oxide (ZnO) nanoscale nanowires (NW) and pillars exhibit substantial size-effects in mechanical properties as a function of diameter D, which enables their exploitation for nanotechnology purposes. Both elastic (i.e. the Young´s Modulus, E) and fracture properties of ZnO nanostructures are key and need to be characterized for the sake of designing MEMS and NEMS, such as nanogenerators based on NWs. Both size-effects in inelastic and inelastic properties were described by distinct power-laws, although less attention has gone to showing another important property in failure mode, which shift from brittle in bulk ZnO to ductile in ZnO nanoscale samples. This aspect is very important as it reinforce the concept of damage tolerance of an otherwise brittle materials system and could enable new fabrication route of MEMS/NEMS by plastic deformation. We report preliminary observations from controlled microcompression tests on pillars of unprecedented small size, with an emphasis on strategy and equipment used to perform such accurate miniaturized nanomechanical tests.