Tunable Tunneling Electroresistance in Ferroelectric Tunnel Junctions by Mechanical Loads
Tunable Tunneling Electroresistance in Ferroelectric Tunnel Junctions by Mechanical Loads
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通过机械负载调节铁电隧道结中的隧道电阻
DOI：
10.1021/nn1031438
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发表时间：
2011-03-01
期刊：
影响因子：
17.1
通讯作者：
Zheng, Yue
中科院分区：
文献类型：
--
作者：
Luo, Xin;Wang, Biao;Zheng, Yue
将非平衡格林函数方法与密度泛函理论相结合，研究了所施加的机械载荷对铁电隧道结 (FTJ) 的极化、静电势和隧道电导的影响。使用第一性原理计算，我们表明压缩应变可以诱导和增强铁电隧道势垒的极化，并且在-2.2%压缩应变下实际上实现了两个晶胞厚度的铁电性。更重要的是，机械应变可以显着改变FTJ中的有效静电势，从而控制其隧道电导，这被定义为巨压电电阻（GPR）效应。我们的计算表明，探地雷达效应在顺电/铁电相变附近尤其显着，并且随着势垒厚度呈指数增加。此外，还发现氧空位和氮掺杂缺陷对应变FTJ的GPR比影响不大。由于其对外部机械负载的高敏感性，具有探地雷达效应的 FTJ 应足以适用于敏捷机械传感器、传感器和其他多功能设备。
Combining nonequilibrium Green function's approach with density functional theory, effects of the applied mechanical loads on polarization, electrostatic potential, and tunneling conductance of a,ferroelectric tunneling junction (FTJ) have been investigated. Using the first principle calculations, we show that compressive strains can induce and enhance the polarization in ferroelectric tunnel barriers, and practically achieve ferroelectricity in two unit cell thickness under a -2.2% compressive strain. More importantly, mechanical strains can significantly change the effective electrostatic potential in FTJ and thus control its tunneling conductance, which is defined as giant piezoelectric resistance (GPR) effect. Our calculations indicate that GPR effect is particularly significant near the paraelectric/ferroelectric phase transition, and increases exponentially with the barrier thickness. Furthermore, it is also found that defects of oxygen vacancies and nitrogen doping have little impact on GPR ratio of strained FTJ. Because of its high sensitivity to external mechanical loads, FTJ with GPR effect should be adequate for applications in agile mechanical sensors, transducers, and other Multifunctional devices.