铁电性
材料科学
哈夫尼亚
表面能
电介质
相界
纳米尺度
相(物质)
纳米技术
凝聚态物理
化学物理
立方氧化锆
光电子学
复合材料
陶瓷
化学
有机化学
物理
作者
Min Hyuk Park,Young Hwan Lee,Han Joon Kim,Tony Schenk,Woongkyu Lee,Keum Do Kim,Franz P. G. Fengler,Thomas Mikolajick,Uwe Schroeder,Cheol Seong Hwang
出处
期刊:Nanoscale
[The Royal Society of Chemistry]
日期:2017-01-01
卷期号:9 (28): 9973-9986
被引量:240
摘要
The unexpected ferroelectric properties of nanoscale hafnia-zirconia are considered to be promising for a wealth of applications including ferroelectric memory, field effect transistors, and energy-related applications. However, the reason why the unexpected ferroelectric Pca21 phase can be stabilized has not been clearly understood although numerous extensive theoretical and experimental results have been reported recently. The ferroelectric orthorhombic phase is not a stable phase under processing conditions from the viewpoint of bulk free energy. Although the possibility of stabilization of the ferroelectric phase due to the surface energy effect has been theoretically suggested, such a theoretical model has not been systematically compared with actual experimental results. In this study, the experimental observations on polymorphism in nanoscale HfO2-ZrO2 solid solution thin films of a wide range of film compositions and thicknesses are comprehensively related to the theoretical predictions based on a thermodynamic surface energy model. The theoretical model can semi-quantitatively explain the experimental results on the phase-evolution, but there were non-negligible discrepancies between the two results. To understand these discrepancies, various factors such as the film stress, the role of a TiN capping layer, and the kinetics of crystallization are systematically studied. This work also reports on the evolution of electrical properties of the film, i.e. dielectric, ferroelectric, anti-ferroelectric, and morphotropic phase changes, as a function of the film composition and thickness. The in-depth analyses of the phase change are expected to provide an important guideline for subsequent studies.
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