The Investigation of PFM Method for Characterization of Ultra-thin Piezoelectric Films

Piezoresponse force microscopy (PFM) offers a non-destructive, fast, and cost-effective approach for characterizing the longitudinal piezoelectric coefficient (d33) of piezoelectric films. However, it is challenges to accurately measure d33 in ultrathin and multilayer piezoelectric films due to non-uniform electric field distribution at the tip of PFM cantilevers. In this study, the staircase voltage method was demonstrated to effectively characterize the d33 of AlN piezoelectric films as thin as 100nm. For the polarity-inverted AlN multilayers, we employed an ultrathin metal electrode to improve electric field uniformity, achieving a measured d33 of 0.91 pm/V that matches the expected near-zero material design and experimental device performance. The results demonstrate the effectiveness of the staircase voltage method and the introduction of ultrathin metal electrode in mitigating tip-induced field inhomogeneity. This work highlights the potential of PFM for d33 characterization in ultrathin and multilayer piezoelectric films.