Lee Kyoungjun, Park Kunwoo, Lee Hyun-Jae, Song Myeong Seop, Lee Kyu Cheol, Namkung Jin, Lee Jun Hee, Park Jungwon, Chae Seung Chul
Department of Physics Education, Seoul National University, Seoul, 08826, Korea.
School of Chemical and Biological Engineering, Institute of Chemical Process, Seoul National University, Seoul, 08826, Korea.
Sci Rep. 2021 Mar 18;11(1):6290. doi: 10.1038/s41598-021-85773-7.
Investigations concerning oxygen deficiency will increase our understanding of those factors that govern the overall material properties. Various studies have examined the relationship between oxygen deficiency and the phase transformation from a nonpolar phase to a polar phase in HfO thin films. However, there are few reports on the effects of oxygen deficiencies on the switching dynamics of the ferroelectric phase itself. Herein, we report the oxygen- deficiency induced enhancement of ferroelectric switching properties of Si-doped HfO thin films. By controlling the annealing conditions, we controlled the oxygen deficiency concentration in the ferroelectric orthorhombic HfO phase. Rapid high-temperature (800 °C) annealing of the HfO film accelerated the characteristic switching speed compared to low-temperature (600 °C) annealing. Scanning transmission electron microscopy and electron energy-loss spectroscopy (EELS) revealed that thermal annealing increased oxygen deficiencies, and first-principles calculations demonstrated a reduction of the energy barrier of the polarization flip with increased oxygen deficiency. A Monte Carlo simulation for the variation in the energy barrier of the polarization flipping confirmed the increase of characteristic switching speed.
关于氧缺陷的研究将增进我们对那些决定整体材料性能的因素的理解。各种研究已经考察了氧缺陷与HfO薄膜中从非极性相到极性相的相变之间的关系。然而，关于氧缺陷对铁电相本身开关动力学的影响的报道很少。在此，我们报道了氧缺陷诱导的掺硅HfO薄膜铁电开关性能的增强。通过控制退火条件，我们控制了铁电正交HfO相中氧缺陷的浓度。与低温（600°C）退火相比，HfO薄膜的快速高温（800°C）退火加速了特征开关速度。扫描透射电子显微镜和电子能量损失谱（EELS）表明，热退火增加了氧缺陷，第一性原理计算表明随着氧缺陷增加，极化翻转的能垒降低。极化翻转能垒变化的蒙特卡罗模拟证实了特征开关速度的增加。
