Enhancement of Dielectric Properties in Epitaxial Bismuth Ferrite-Bismuth Samarium Ferrite Superlattices
Enhancement of Dielectric Properties in Epitaxial Bismuth Ferrite-Bismuth Samarium Ferrite Superlattices
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外延铁氧体铋-钐铁氧体超晶格介电性能的增强
DOI：
10.1002/aelm.201600170
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
and Nagarajan Valanoor
中科院分区：
文献类型：
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作者：
Ronald Maran;Shintaro Yasui;Eugene Eliseev;Anna Morozovska;Hiroshi Funakubo;Ichiro Takeuchi;and Nagarajan Valanoor
研究了人工层状铋铁氧体(BiFeO3)/铋钐铁氧体（Bi1-xSmx） feo3超晶格（SLs）的介电性能。在短周期（5-10 nm）的单晶格层中，由于层间耦合机制的作用，非相应调制的纳米级混合物在1 MHz时具有较大的介电常数（ε33≈170），降低了损耗正切，并在钐浓度范围内提高了可调性（τ≈37%），远高于单层（Bi1-xSmx） feo3薄膜。在较大的频率和温度范围内观察到增强的介电可调性。增加SL层厚度会降低层间耦合强度，导致介电常数（ε33≈150）降低，介电损耗正切增大，可调性（τ≈14%）降低。一个现象学模型证实，在短周期SLs中，在较宽的温度和频率范围内，更高的Sm3+浓度增强了极性相的介电性能、可调性和稳定性，这是由于静电耦合。因此，外延短周期SLs作为一种高度可调的无铅（Pb）材料系统在低至中频应用中具有显著的潜力。因此，SL结构中极性/非极性层之间的静电耦合效应可能是实现增强介电性能的通用方法。
Artificially layered bismuth ferrite (BiFeO3)/bismuth samarium ferrite (Bi1–xSmx)FeO3superlattices (SLs) are investigated for their dielectric properties. In short‐period (5–10 nm) SLs, the stabilization of an incommensurately modulated nanoscale mixture due to a strong interlayer coupling mechanism results in a large dielectric permittivity (ε33≈ 170 at 1 MHz), reduced loss tangent, and increased tunability (τ≈ 37%) for a samarium concentration range much larger than that for single‐layer (Bi1–xSmx)FeO3thin‐films. The enhanced dielectric tunability is observed across a large frequency and temperature range. Increasing the thickness of the SL layers reduces the strength of the interlayer coupling, which results in reductions in dielectric permittivity (ε33≈ 150), increases in dielectric loss tangent and decreased tunability (τ≈ 14%). A phenomenological model confirms that the enhanced dielectric properties, tunability and stabilization of the polar phase to higher Sm3+concentrations over a wide range of temperatures and frequencies in the short period SLs is due to electrostatic coupling. Thus, the epitaxial short‐period SLs have significant potential as a highly tunable lead (Pb)‐free materials system in low‐to‐medium frequency applications. Electrostatic coupling effect between polar/non‐polar layers in SL structures could thus be a universal method to achieve enhanced dielectric properties.