外场下NBT-KBT100x压电薄膜畴变演化、保持特性及印记的研究

Domain Switching, Retention and Imprint of NBT-KBT100x Piezoelectric Thin Films under Different External Fields

采用金属有机物分解法制备了不同K含量的弛豫型压电薄膜(1-x)Na0.5Bi0.5TiO3-xK0.5Bi0.5TiO3(NBT-KBT100x)。利用压电力显微镜研究了外场条件下纳米级铁电畴翻转,以及保持性能和印记失效。结果表明:(1)不同组分中,NBT-KBT17薄膜单畴态的晶粒个数最多。选取NBT-KBT17薄膜分别测试了其面内极化分量和面外极化分量,该薄膜的面内压电信号较强,这说明薄膜在d31模式下的压电响应明显。(2)选择NBT-KBT17薄膜中较大尺寸的单晶,实现了对弛豫性铁电体的电畴写入。将其在大气环境下放置不同时间,出现了退极化现象,但总的畴态稳定,表明其保持性能较好。(3)制备了NBT-KBT17原理型薄膜电容器,分别测试了加载作用前后NBT-KBT17薄膜电容器的相位和振幅滞后回线图。结果表明外加作用力使相位回线向右发生了一定的移动,且振幅的蝶形曲线均在不同方向上发生了偏移,同时形状也发生了改变。最后,利用空间电荷原理分析了外加力导致薄膜印记产生的机理。

MOD method was used to prepare（1-x）Na 0.5 Bi 0.5 TiO 3-xK 0.5 Bi 0.5 TiO 3（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 d 31 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 but-terfly 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.