Cross-Sectional Imaging of Polarization Reversal in Ferroelectric Films

Polarization reversal in Pb(Zr,Ti)O₃ ferroelectric films was followed by a novel technique of cross-sectional piezoelectric force microscopy (PFM). Instead of the traditional scanning of the top surface of ferroelectric thin films, the domain structure across the cross section is visualized. The probing AC electric field is applied to the capacitor structure between top and bottom electrodes resulting in a homogenous field throughout the film while the atomic force microscope (AFM) tip is only used to sense the piezoelectric vibration. In the cases of the studied (111)-oriented tetragonal and rhombohedral PZT films, the sequence of imaged domain configurations taken at increasing poling voltages puts forward a sideways growth of oblique domains. Additionally, the considered domain growth model could explain the gradual variation of the piezoelectric response amplitude, which is commonly observed in planar PFM images. The cross-sectional PFM setup looks promising for gaining new insights into reversal mechanisms and may be used as a tool for studying phenomena of switching deterioration in ferroelectric film devices.