Mechanical deformation of PZT thin films for MEMS applications

The mechanical properties of solution deposited lead zirconate titanate (PZT) thin films; including the hardness, modulus, and fracture behavior, have been studied using continuous indentation methods. Comparisons are made between the behavior of the thin films and a bulk PZT ceramic. The thin films exhibit a hardness between 5 and 8 GPa, slightly lower than the hardness measured in a bulk PZT, ≈9 GPa. The increased grain boundary area in the thin films, which have 100 nm grain sizes, may act to accommodate plastic deformation. Fracture caused by indentations appears to be constrained to the sub-surface regions of the film, and no evidence of indentation induced delamination was observed. Traditional indentation analysis cannot accurately determine the elastic modulus of thin film PZT materials due to non-linear elastic behavior. The apparent modulus of the thin film PZT is insensitive to processing methods that alter the electrical properties of the film.