论文标题
从化学角度来
Ferroelectricity in $\mathrm{HfO_2}$ from a chemical perspective
论文作者
论文摘要
在薄膜中观察到的铁电性$ \ mathrm {hfo_2} $，与Si，Al等掺杂或$ \ Mathrm {Hf_ {0.5} Zr_ {0.5} Zr_ {0.5} o_2} $表格具有很大的技术意义。但是，软模式理论在解释这种铁电性的起源方面面临困难。在这项工作中，我们提出，$ \ mathrm {hfo_2/zro_2} $的7个阳离子配位数是这种铁电性的核心，这源于HF/ZR的适当离子radiic radiic radi radi fat o.与O.相比，与多种化合物相比$ \ mathrm {hfo_2} $和$ \ mathrm {zro_2} $很特别，因为它们接近7和8阳离子协调的边界，因此8配位四方中间阶段可以大大减少开关屏障。与$ \ Mathrm {HFO_2} $/$ \ Mathrm {Zro_2} $相比，还研究了其他7个协调候选人，包括$ \ mathrm {Sri_2} $，TAON，YSBR和YOF，详细分析了$ PCA2_1 $ PCA2_1 $ SEPARE。已经建立了基于离子半径比和协调数的首选开关路径规则。我们还显示了从$ \ mathrm {hfo_2} $中的单斜$ p2_1/c $ phase的可能路线，这与疲劳现象有关。
Ferroelectricity observed in thin film $\mathrm{HfO_2}$, either doped with Si, Al, etc. or in the $\mathrm{Hf_{0.5}Zr_{0.5}O_2}$ form, has gained great technical significance. However, the soft mode theory faces a difficulty in explaining the origin of such ferroelectricity. In this work, we propose that the 7 cation coordination number of $\mathrm{HfO_2/ZrO_2}$ lies at the heart of this ferroelectricity, which stems from the proper ionic radii of Hf/Zr compared with O. Among the numerous compounds with non-centrosymmetric nature, e.g., $mm2$ point group, $\mathrm{HfO_2}$ and $\mathrm{ZrO_2}$ are special in that they are close to the border of 7 and 8 cation coordination, such that the 8-coordination tetragonal intermediate phase could greatly reduce the switching barrier. Other 7-coordination candidates, including $\mathrm{SrI_2}$, TaON, YSBr and YOF are also studied in comparison to $\mathrm{HfO_2}$/$\mathrm{ZrO_2}$, and six switching paths are analyzed in detail for the $Pca2_1$ phase. A rule of preferred switching path in terms of ionic radii ratio and coordination number has been established. We also show the possible route from ferroelectric $Pca2_1$ phase to monoclinic $P2_1/c$ phase in $\mathrm{HfO_2}$, which is relevant to the fatigue phenomenon.
