Effect of Zr Content on the Wake-Up Effect in Hf1–xZrxO2 Films

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• 作者：Min Hyuk Park ; Han Joon Kim ; Yu Jin Kim ; Young Hwan Lee ; Taehwan Moon ; Keum Do Kim ; Seung Dam Hyun ; Franz Fengler ; Uwe Schroeder ; Cheol Seong Hwang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：June 22, 2016
• 年：2016
• 卷：8
• 期：24
• 页码：15466-15475
• 全文大小：636K
• 年卷期：0
• ISSN：1944-8252

文摘

In this study, the changes in the structural and electrical properties of ferroelectric Hf_1–xZr_xO₂ films with various Zr contents (0.26–0.70) were systematically examined during electric field cycling, resulting in a “wake-up” effect. To quantify the degree of wake-up effect, a “variable” polarization as the difference between remanent and saturation polarization was suggested as a new parameter, which could be calculated by excluding the linear dielectric contribution from the total electric displacement. Here, the variable polarization value could be minimized for an optimized Zr content of 0.43, which was slightly lower than the value for the largest remanent polarization. The polymorphism in Hf_1–xZr_xO₂ thin films is known to be complicated due to the relatively small energy differences between various phases, such as the monoclinic, tetragonal, and orthorhombic phases. The variations in the polarization-electric field characteristics and dielectric constant values could be qualitatively and quantitatively understood based on the competition of various polymorphs that are dependent on the Zr content. Furthermore, a schematic model for the spatial distribution of mixed phases was suggested for Hf_1–xZr_xO₂ films with various Zr contents based on the experimental observations.