2025-03-12 中国科学院（CAS）
Schematic diagram of the high-pressure charge transport experimental. (Image by PAN Xiaomei)
＜関連情報＞
- https://english.cas.cn/newsroom/research_news/phys/202503/t20250312_903732.shtml
- https://journals.aps.org/prb/abstract/10.1103/PhysRevB.111.115104
高圧下におけるHfO2の構造と電気的特性 Structural and electrical properties of HfO2 at high pressure
Xiaomei Pan, Erqiao Xue, Wen-Guang Li, Weijin Pan, Deyuan Yao, Xin Zhang, Yuewei Yin, Peng Cheng, Qi-Jun Liu et al.
Physical Review B Published: 4 March, 2025
DOI:https://doi.org/10.1103/PhysRevB.111.115104
Abstract
The structural and electrical properties of hafnium oxide (HfO2) have attracted significant interest due to its ferroelectric compatibility with existing silicon technologies and its scalability. Pressure has shown excellent capability in modulating the crystal structure of various materials. However, earlier works have presented conflicting results regarding the structural phase transitions in HfO2 under high pressure when different experimental methods are employed. For instance, Raman spectroscopy suggested a phase transition from the monoclinic to the orthorhombic phase at approximately 2.7–4.3 GPa, while X-ray diffraction observed no structural phase transition until 10 GPa. To clarify the crystal structure of HfO2 under high pressure, this study conducted high-pressure charge transport investigations on both pure HfO2 and 5% yttrium (Y)-doped HfO2 polycrystals. The results reveal abrupt changes in the charge transport of HfO2 at 3.5 ± 0.5 GPa and 15.2 ± 0.6 GPa, respectively. Combined analysis using high-pressure Raman spectroscopy and first-principles calculations indicates that these two transitions correspond to structural phase transitions from the monoclinic phase to the orthorhombic-I (OI) phase, and then to the orthorhombic-II (OII) phase. The doping of Y in HfO2 leads to a reduction in the phase transition pressure. Moreover, in situ ferroelectric hysteresis loop measurements under pressure suggest that the two high-pressure orthorhombic phases exhibit paraelectric properties. Our findings resolve the debate regarding pressure-induced structural phase transitions in the low-pressure region and provide deep insights into the relationship between the structure and charge transport properties of HfO2.
