Vanishing critical thickness in asymmetric ferroelectric tunnel junctions: First principle simulations
Vanishing critical thickness in asymmetric ferroelectric tunnel junctions: First principle simulations
复制标题
非对称铁电隧道结中临界厚度消失：第一原理模拟
DOI：
10.1063/1.3532000
复制
发表时间：
2011-01-15
影响因子：
3.2
通讯作者：
Woo, C. H.
中科院分区：
文献类型：
--
作者：
Cai, Meng-Qiu;Zheng, Yue;Woo, C. H.
铁电势垒层中残余极化的稳定性是涉及铁电隧道结 (FTJ) 或电容器的应用的先决条件。寻求该领域进一步发展的最重要问题之一是克服临界厚度造成的限制，低于该厚度铁电极化就会消失。在本文中，我们报告了非对称 FTJ（A-FTJ）（即具有不同电极的电极）中电荷分布和极化的第一原理密度泛函计算。我们发现，Pt 和 SrRuO3 电极之间的 BaTiO3 薄膜可以在厚度小至 0.8 nm（两个晶胞）的情况下保持显着且稳定的极化，这与对称 FTJ 的情况完全不同。我们将这个令人惊讶的结果追溯到电极之间由于不同的电子环境而引起的电荷转移产生的大电场，该电场对抗去极化场并增强铁电性，导致去极化场减少甚至完全消除，从而导致临界厚度消失。我们推测这是 A-FTJ 的一般结果，这对于铁电薄膜和隧道结或电容器的应用非常重要，其中临界厚度的存在是一个限制因素。 (C) 2011 年美国物理研究所。 [doi:10.1063/1.3532000]
The stability of the remnant polarization in the ferroelectric barrier layer is a prerequisite to applications involving ferroelectric tunnel junctions (FTJs) or capacitors. One of the most important issues in the pursuit of further developments in this area is to overcome the limitations due to the critical thickness, below which the ferroelectric polarization disappears. In this paper we report first-principle density-functional calculations of the charge distribution and polarization in an asymmetric FTJ (A-FTJ), i.e., one with dissimilar electrodes. We found that a significant and stable polarization can be retained down to thicknesses as small as 0.8 nm (two unit-cells) in a BaTiO3 thin film between Pt and SrRuO3 electrodes, quite unlike the case of symmetric FTJs. We trace this surprising result to the large electric field produced by the charge transfer between the electrodes caused by their different electronic environments, which acts against the depolarization field and enhances the ferroelectricity, leading to the reduction, or even the complete elimination of the depolarization field, leading to the vanishing of the critical thickness. We speculate that this is a general result for A-FTJs, which could be of importance to applications of ferroelectric thin films and tunneling junctions or capacitors where the presence of the critical thickness is a limiting factor. (C) 2011 American Institute of Physics. [doi:10.1063/1.3532000]