外延PbZr0.4Ti0.6O3薄膜厚度对其铁电性能的影响

从Landau-Devonshire唯象理论出发，考虑到晶格失配导致的NFDA3位错应力场与极化场的耦合，研究了在SrTiO₃衬底上外延生长的PbZr_0.4Ti_0.6O₃薄膜厚度对其自发极化强度、电滞回线的影响. 结果表明，产生刃位错的PbZr_0.4Ti_0.6O₃薄膜临界厚度为～1.27nm，当薄膜厚度大于临界厚度时，在所形成的位错附近，极化强度出现急剧变化，形成自发极化强度明显减弱的“死层”；随着薄膜厚度的减小，位错间距增大，“死层”厚度与薄膜总厚度之比增加. 由薄膜电滞回线的变化情况可知，其剩余极化强度随着薄膜厚度的减小而逐渐减小. 关键词： 铁电薄膜 自发极化强度 电滞回线 位错

Effect of thickness of epitaxial PbZr0.4Ti0.6O3 film on the physical properties

The thickness dependence of the spontaneous polarization and the hysteresis loop of epitaxial PbZr_0.4Ti_0.6O₃ thin films deposited on (001) SrTiO₃ substrate was investigated via the Landau-Devonshire's phenomenological theory considering the coupling of the stress field of the edge dislocation and the polarization. The results show that the critical thickness for the formation of misfit dislocation is ～1.27nm, and there is a drastic variation in the polarization near the dislocation in films with thickness greater than the critical value, which results in the formation of the dead layer that severely degrades ferroelectric properties. With decreasing the film thickness, both the dislocation spacing and the ratio of the dead layer to film total thickness increase. The thickness dependence of the hysteresis loop indicates that the remnant polarization decreases as the thickness decreases.