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

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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.