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考虑衬底应力、畴壁运动和畴结构变化,建立了修正的Landau-Devonshire热力学模型,计算了生长在不同衬底上的含有纳米晶粒的PbZr0.4Ti0.6O3(PZT)薄膜的电滞回线,研究了矫顽场、剩余极化强度和相对介电常数对晶粒尺寸以及薄膜厚度的依赖关系.结果表明,矫顽场和相对介电常数对晶粒尺寸的依赖关系呈类抛物线状;衬底压应力使矫顽场和剩余极化强度增大,使相对介电常数减小;随着厚度增加,矫顽场先缓慢增加,到200nm急剧增加,到310nm再缓慢增加,这一结果主要取决于介电常数对厚度的依赖.
The modified Landau-Devonshire thermodynamic model was established considering the substrate stress, domain wall motion and domain structure changes. The electrical hysteresis of PbZr0.4Ti0.6O3 (PZT) thin films containing nanocrystalline grains grown on different substrates was calculated The dependence of coercive field, remanent polarization and relative permittivity on grain size and film thickness was studied.The results show that the dependence of coercive field and relative permittivity on grain size is parabolic ; The substrate compressive stress increases the coercive field and remanent polarization so that the relative permittivity decreases; as the thickness increases, the coercive field increases slowly and increases sharply to 200 nm and then slowly increases to 310 nm The result depends mainly on the dependence of the dielectric constant on the thickness.