Ferroelectricity in $\mathrm{HfO_2}$ from a chemical perspective
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arXiv
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| Autori principali: | , , , , , , , , , |
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| Natura: | Preprint |
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2022
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| author | Yuan, Jun-Hui Mao, Ge-Qi Xue, Kan-Hao Bai, Na Wang, Chengxu Cheng, Yan Lyu, Hangbing Sun, Huajun Wang, Xingsheng Miao, Xiangshui |
| author_facet | Yuan, Jun-Hui Mao, Ge-Qi Xue, Kan-Hao Bai, Na Wang, Chengxu Cheng, Yan Lyu, Hangbing Sun, Huajun Wang, Xingsheng Miao, Xiangshui |
| contents | 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2201_00210 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Ferroelectricity in $\mathrm{HfO_2}$ from a chemical perspective Yuan, Jun-Hui Mao, Ge-Qi Xue, Kan-Hao Bai, Na Wang, Chengxu Cheng, Yan Lyu, Hangbing Sun, Huajun Wang, Xingsheng Miao, Xiangshui Materials Science 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. |
| title | Ferroelectricity in $\mathrm{HfO_2}$ from a chemical perspective |
| topic | Materials Science |
| url | https://arxiv.org/abs/2201.00210 |