Abstract: MOD method was used to prepare (1-x)Na_0.5Bi_0.5TiO_3-xK_0.5Bi_0.5TiO₃ (NBT-KBT100x) relaxor piezoelectric thin films. The surface morphology, the initial domain structures, domain switching, retention and imprint of NBT-KBT100x thin films were observed by PFM under different external fields. The results show that the NBT-KBT17 thin film presents the most single domain grains. Moreover, the LPFM phase and amplitude images of NBT-KBT17 thin film are also obtained, which indicates that the piezoelectric response is significant at d31 mode. The single grain with larger size of NBT-KBT17 thin film is selected to write the domain by opposite DC voltages. The written single grain is then placed in environment for different duration to detect the domain evolution and retention of the thin film. Although the depolarization phenomenon is observed in small area, the original domain states are still stable, showing low retention loss. The phase and amplitude-electric voltage hysteresis loops of NBT-KBT17 thin film capacitor are observed by PFM under the mechanical force. The observations indicate that the hysteresis loop and butterfly curve has a migration, which means the imprint is produced by the external force. Finally, the formation mechanism of imprint is explained by space charge principle.

Key words: PFM, domain switching, retention, imprint