Nanoscale investigation of side wall and surface domain structures in multilayer PbTiO₃/PbZr_0.3Ti_0.7O₃/PbTiO₃thin films

Abstract

Nanoscale domain structures of multilayer PbTiO3/PbZr0.3Ti0.7O3/PbTiO3 (PT/PZT/PT) thin films are investigated by three-dimensional piezoresponse force microscopy (PFM) in the side wall and on the bare surface. Topography images of the side wall show that the thin films have a compact columnar grain microstructure, and two or three grains stacked in the direction normal to the thin film plane can be observed clearly. The nanoscale three-dimensional piezoresponse images of the side wall and the surface exhibit a random distribution of the domains' orientation in the PT/PZT/PT thin films, but that all the grains in the side wall have a piezoresponse and the various changes in the magnitude of the piezoresponse obtained by the polarized voltage indicate that no a domains, amorphous or nonferroelectric structure can be detected on the thin films' surface. The fine and clear PFM images with various contrasts in the side wall exhibit that the stacked grains also have a random polarization direction. These stacked grains with a random polarization direction result in the reduction of the integral piezoresponse; therefore, various grey contrasts can be shown in the PFM images detected on the bare surface of the thin films.