Nanometer-Scale Characterization of Ferroelectric Polymer Thin Films by Variable-Temperature Atomic Force Microscopy

The morphological changes of ferroelectric polymer thin films during the annealing process were directly imaged by variable-temperature atomic force microscopy (AFM). The growing process of the crystallites underlying the surface amorphous layer was observed as well as the morphological changes using intermittent-contact AFM. We found that fine structures appeared in the rod like grains at a temperature corresponding to the Curie point of the bulk copolymer in the cooling process. In addition, local piezoelectric response was mapped in order to investigate the relationship between the structural change and the ferroelectric phase transition. The local polarization prepared at room temperature disappeared after the film was heated above 120°C, which agreed with both the Curie temperature and the temperature of the observed structural change.