Increasing energy storage capabilities of space-charge dominated ferroelectric thin films using interlayer coupling

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• 作者：Hanfei Zhu^a ; ^b ; Menglin Liu^a ; ^b ; Yunxiang Zhang^a ; ^b ; Zhenghai Yu^a ; ^b ; Jun Ouyang^a ; ^b ; ^c ; ^{ouyangjun@sdu.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Wei Pan^d
• 关键词：Ferroelectric ; Bilayer ; Electrical properties ; Interface ; Energy storage
• 刊名：Acta Materialia
• 出版年：2017
• 出版时间：1 January 2017
• 年：2017
• 卷：122
• 期：Complete
• 页码：252-258
• 全文大小：1753 K

文摘

In our previous work (W. Zhang et al., Space-charge dominated epitaxial BaTiO₃ heterostructures, Acta Mater. 85 (2015) 207–215), it was demonstrated that a space charge dominated BaTiO₃ thin film can have much improved energy storage characteristics when compared with a regular insulating film of ferroelectric BaTiO₃. However, the improved recoverable electric energy density (discharged energy per unit volume), W_re, is still constrained by the maximum/saturated polarization (P_s) of the BaTiO₃ thin film. Here we propose a novel method to further improve W_re in ferroelectric thin film heterostructures by using interlayer coupling in an epitaxial ferroelectric bilayer. In our model structure, a ferroelectric BiFeO₃ layer with a large remnant polarization (P_r ∼70 μC/cm²) was deposited in-situ on top of a BaTiO₃/SrRuO₃ heterostructure which shows a small remnant polarization (P_r ∼ 3 μC/cm²). The resulted bilayer structure showed a slim P-E hysteresis loop characterized by a small remnant polarization and a large saturated one (P_s ≫ P_r), which can be well explained by a competition between the effect of space charges (dominant at low field) and that of the interlayer charge coupling (dominant at high field). The large difference, i.e. P_s − P_r, increases the recoverable electric energy density by about 85% (from ∼28 J/cm³ to ∼51 J/cm³).