Spatially resolved probing of Preisach density in polycrystalline ferroelectric thin films

Applications of the ferroelectric materials for the information storage necessitate the understanding of local switching behavior on the level of individual grains and microstructural elements. In particular, implementation of multilevel neuromorphic elements requires the understanding of history-dependent polarization responses. Here, we introduce the spatially resolved approach for mapping local Preisach densities in polycrystalline ferroelectrics based on first-order reversal curve (FORC) measurements over spatially resolved grid by piezoresponse force spectroscopy using tip-electrode. The band excitation approach allowed effective use of cantilever resonances to amplify weak piezoelectric signal and also provided insight in position-, voltage-, and voltage history-dependent mechanical properties of the tip-surface contact. Several approaches for visualization and comparison of the multidimensional data sets formed by FORC families or Preisach densities at each point are introduced and compared. The relationship between switching behavior and microstructure is analyzed.