Effect of Film Microstructure on Domain Nucleation and Intrinsic Switching in Ferroelectric Y:HfO2 Thin Film Capacitors
Effect of Film Microstructure on Domain Nucleation and Intrinsic Switching in Ferroelectric Y:HfO2 Thin Film Capacitors
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DOI：
10.1002/adfm.202108876
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发表时间：
2021-11-20
影响因子：
19
通讯作者：
Gruverman, Alexei
中科院分区：
文献类型：
--
作者：
Buragohain, Pratyush;Erickson, Adam;Gruverman, Alexei
铁电系统的一般特征之一是极化反转的复杂性质，其中涉及磁畴成核和磁畴壁的运动。在这里，时间分辨纳米级成像与积分开关电流测量相结合，研究了钇掺杂 HfO2 (Y:HfO2) 中极化反转的机制，这是目前研究最活跃的铁电系统之一。更具体地说，通过对外延和多晶 Y:HfO2 薄膜电容器的偏振切换行为进行比较研究，研究了薄膜微观结构对成核过程的影响。研究发现，虽然外延 Y:HfO2 电容器的开关速度往往比多晶电容器慢，但它们表现出明显更高的成核密度和速率，表明这是一种速率限制机制。此外，据观察，在接近激活场值的外部场下，两种类型电容器的开关动力学可以通过成核限制开关和 Kolmogorov-Avrami-Ishibashi 模型同样好地描述。这意味着两种不同机制的收敛，意味着极化反转通过不受薄膜微观结构影响的均匀成核过程进行，这可以被认为接近本征转换极限。
One of the general features of ferroelectric systems is a complex nature of polarization reversal, which involves domain nucleation and motion of domain walls. Here, time-resolved nanoscale domain imaging is applied in conjunction with the integral switching current measurements to investigate the mechanism of polarization reversal in yttrium-doped HfO2 (Y:HfO2)-currently one of the most actively studied ferroelectric systems. More specifically, the effect of film microstructure on the nucleation process is investigated by performing a comparative study of the polarization switching behavior in the epitaxial and polycrystalline Y:HfO2 thin film capacitors. It is found that although the epitaxial Y:HfO2 capacitors tend to switch slower than their polycrystalline counterparts, they exhibit a significantly higher nucleation density and rate, suggesting that this is a rate-limiting mechanism. In addition, it is observed that under the external fields approaching the activation field value, the switching kinetics can be described equally well by the nucleation limited switching and the Kolmogorov-Avrami-Ishibashi models for both types of capacitors. This signifies convergence of two different mechanisms implying that the polarization reversal proceeds via a homogeneous nucleation process unaffected by the film microstructure, which can be considered as approaching the intrinsic switching limit.