论文标题
HFO $ _2 $的阶段竞争与第一原理相关的电场
Phase Competition in HfO$_2$ with Applied Electric Field from First Principles
论文作者
论文摘要
在这项工作中，第一原理密度功能理论的计算的结果用于构建HFO $ _2 $的能量景观及其Y和ZR取代的衍生物，这是对称型晶格模式振幅的函数。这些复杂的能源景观具有多个局部最小值，对应于四方，oiii（$ pca2_1 $）和OIV（$ PMN2_1 $）阶段。我们发现，非极性四方相和铁电OIII相之间的能屏障可以通过Y和ZR取代降低。在hf $ _ {0.5} $ zr $ _ {0.5} $ o $ _2 $带有订购的阳离子安排的情况下，ZR替换使OIV相位不稳定，并且它成为四方到OIII相位转换的中间状态。使用这些能量景观，我们解释了针对具有各种野外方向选择的电场循环计算的结构变换和磁滞回路。还讨论了这些结果对解释实验观察的含义，例如唤醒和分裂效应。这些结果和分析加深了我们对基于HFO $ _2 $的电影中铁电和野外循环行为的起源的理解，并允许我们提出改善其功能性能的策略。
In this work, the results of first-principles density-functional-theory calculations are used to construct the energy landscapes of HfO$_2$ and its Y and Zr substituted derivatives as a function of symmetry-adapted lattice-mode amplitudes. These complex energy landscapes possess multiple local minima, corresponding to the tetragonal, oIII ($Pca2_1$), and oIV ($Pmn2_1$) phases. We find that the energy barrier between the non-polar tetragonal phase and the ferroelectric oIII phase can be lowered by Y and Zr substitution. In Hf$_{0.5}$Zr$_{0.5}$O$_2$ with an ordered cation arrangement, Zr substitution makes the oIV phase unstable, and it become an intermediate state in the tetragonal to oIII phase transition. Using these energy landscapes, we interpret the structural transformations and hysteresis loops computed for electric-field cycles with various choices of field direction. The implications of these results for interpreting experimental observations, such as the wake-up and split-up effects, are also discussed. These results and analysis deepen our understanding of the origin of ferroelectricity and field cycling behaviors in HfO$_2$-based films, and allow us to propose strategies for improving their functional properties.
