Large domain-wall current in BiFeO3 epitaxial thin films
Large domain-wall current in BiFeO3 epitaxial thin films
复制标题
BiFeO3 外延薄膜中的大畴壁电流
DOI：
10.1016/j.ceramint.2020.12.161
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发表时间：
2021-02-25
影响因子：
5.2
通讯作者：
Jiang, Anquan
中科院分区：
文献类型：
--
作者：
Jiang, Xu;Sun, Jie;Jiang, Anquan
绝缘铁电薄膜的大畴壁导电性为非易失性铁电畴壁存储器的畴信息无损读出提供了新的思路。然而，它的发展面临着一些挑战，包括泄漏电流过大和导通读电流不足。大量的实验和理论数据都将铁电薄膜畴壁区氧空位的积累作为壁传导的外在贡献。在这项工作中，我们发现壁电流随外加电场与初始极化之间的角度而变化，并且对于氧空位减少的铋铁氧体薄膜器件，壁电流可以增加到1.9 mu A，而对于氧空位丰富的器件，壁电流可以增加到2 nA。通过在5%氢气与氩气和纯氧气混合的两个大气压下对样品进行热处理，可以控制氧空位浓度。对于前者，在还原气氛下退火样品中增强的氧空位使畴壁电流降低了几个数量级以上，而后者在氧化气氛下退火样品的畴壁电流则显著增强。x射线光电子能谱分析揭示了Fe2+ Fe3+跃迁过程中氧空位浓度的变化。这一变化证实了刚性畴壁传导机制以及壁电流的外在不利缺陷补偿，为探索具有足够输出电流的大功率畴壁纳米器件铺平了道路。
Large domain wall conductivity in insulating ferroelectric thin films provides a new idea for non-destructive readout of domain information of a nonvolatile ferroelectric domain wall memory. However, there are several challenges hindering its development, including the excessive leakage current and insufficient on-state read current. A lot of experimental and theoretical data have referred to the accumulation of oxygen vacancies at the domain wall regions of ferroelectric thin films as the extrinsic contribution of the wall conduction. In this work, we found that the wall current varied with the angle between the applied electric field and the initial polarization, and that the wall current could be increased to 1.9 mu A for a bismuth ferrite thin-film device with the reduced oxygen vacancies in contrast to the previous value of 2 nA for the device with rich oxygen vacancies. The oxygen vacancy concentration can be controlled through the thermal annealing of the sample at two atmospheres of 5% hydrogen mixed with argon gas and pure oxygen gas. For the former, the enhanced oxygen vacancies within the annealed sample at the reduced atmosphere decreased the domain wall current by over a few orders of magnitude, in contrast to the significant enhancement of the wall current for the sample in the latter annealed at the oxidizing atmosphere. The change of oxygen vacancy concentration was implied from the Fe2+ Fe3+ transition by the X-ray photoelectron spectroscopy analysis. This change confirmed the rigid domain wall conduction mechanism as well as the extrinsic adverse defect compensation of the wall current, paving the way to the exploration of high-power domain-wall nanodevices with sufficient output currents.