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Article overview
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Ferroelectricity in $mathrm{HfO_2}$ from a chemical perspective | | Jun-Hui Yuan
; Ge-Qi Mao
; Kan-Hao Xue
; Na Bai
; Chengxu Wang
; Yan Cheng
; Hangbing Lyu
; Huajun Sun
; Xingsheng Wang
; Xiangshui Miao
; | | Date: |
1 Jan 2022 | | Abstract: | 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. | | Source: | arXiv, 2201.00210 | | Services: | Forum | Review | PDF | Favorites | |
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