In situ transmission electron microscopy of degradation phenomena of Pb(Zrx Ti_<l-x>)O_3 thin films

利用透射电子显微镜进行原位和实时观察是揭示材料结构改性动态行为的最有前途的技术之一。本工作主要研究铁电器件中广泛应用的PbO_3薄膜的疲劳现象，即剩余极化退化现象，旨在发展一种可以在原子尺度上揭示薄膜在电场应力作用下结构变化的透射电子显微镜观察技术。我们新开发了一种可以在观察过程中对样品进行可控偏置的透射电子显微镜样品夹持器。还开发了样品制备工艺，其中使用了光刻和聚焦离子束方法。此外，我们还对具有PZT电容结构的加工样品进行了透射电子显微镜观察和铁电性能测量，证实了样品表面局部形成的损伤层对PZT剩余极化性能的退化有重要影响。这项工作使我们不仅可以获得铁电薄膜在电场应力作用下疲劳现象的静态信息，而且可以获得动态信息。

In situ and real-time observation using transmission electron microscopy (TEM) is one of the most promising-techniques which reveal dynamic behavior of structural modification of materials. In this work, we focus on the fatigue phenomenon, i.e., degradation of remnant polarization, of Pb(Zr_xTi_<1-x>)O_3 thin films which are widely used for ferroelectric devices and aim at the development of a TEM observation technique by which structural changes of the films under electric field stresses can be revealed on an atomic scale. We have newly developed a TEM sample holder which can controllably bias the samples during observation. Sample preparation processes have been also developed, in which photo lithography and focused ion beam methods were employed. Furthermore, we have carried out TEM observation and measurement of ferroelectric properties for the processed samples having PZT capacitor structures and confirmed that damaged layers formed locally on the sample surface critically influence the degradation of remnant polarization of PZT. This work allows us to obtain not only static information but also dynamic information on the fatigue phenomena of the ferroelectric films under electric field stresses.