Intrinsic ferroelectricity in Y-doped HfO2 thin films

Yun, Yu; Buragohain, Pratyush; Li, Ming; Ahmadi, Zahra; Zhang, Yizhi; Li, Xin; Wang, Haohan; Li, Jing; Lu, Ping; Tao, Lingling; Wang, Haiyan; Shield, Jeffrey E.; Tsymbal, Evgeny Y.; Gruverman, Alexei; Xu, Xiaoshan

doi:10.1038/s41563-022-01282-6

Cited by 84 publications

(81 citation statements)

References 46 publications

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“…Under a poling field of 4.5 MV cm −1 , the extracted P r was 25.5 μC cm −2 and the E c value was about 3.0 MV cm −1 . The hysteresis loops showed a slightly rounded shape at the largest applied voltages, similarly as observed in other works, 17,[21][22][23] which might be attributed to the relatively high leakage. Fig.…”

Section: Resultssupporting

confidence: 86%

“…Among several criteria required for next-generation ferroelectric memory, the large polarization for achieving a high recording density and the high fatigue endurance for ensuring 10-year usage are critical ones to meet industrial standards. Though robust polarizations have been observed in both zirconia-based and hafniabased ferroelectrics, the co-existence of high polarization and good cycling endurance under high polarization stress has rarely been experimentally realized yet, 17,21,22 and this dilemma presents a tough challenge that remains to be tackled in order to expand and speed up their applications. In our efforts to develop cheap and simplified processes with fabrication-friendly materials (non-noble metals) for zirconiabased ferroelectrics to reach good endurances at high polarizations, herein, we report a thermal ALD process for zirconiabased thin films by applying W as a bottom electrode and implementing PDA as a thermal crystallization process.…”

Section: Introductionmentioning

confidence: 99%

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Hafnium-doped zirconia ferroelectric thin films with excellent endurance at high polarization

Cao

Zhang

2023

Nanoscale

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Section: Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Hafnium-doped zirconia ferroelectric thin films with excellent endurance at high polarization

Cao

Zhang

2023

Nanoscale

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“…Owing to the weak interlayer vdW-force in 2D-layered materials, structural control by interlayer twist/translation has successfully enabled the realization of the unexpected interlayer sliding ferroelectricity in Moiré superlattices and TMD heterostructures with artificially-tuned broken inversion symmetry via much more complex fabrication procedures 9 – 18 . On the other hand, doping, especially with rare-earth elements 19 , which can change the lattice structure (such as bond distance and angle, and atom position) of materials, e.g., via microstrain/structure constrain, has also been employed as an effective strategy to tune ferroelectric properties not only in traditional perovskite-based ferroelectrics 20 but also in newly-emerging HfO 2 -based ferroelectrics 21 , 22 , showing great potential for manipulating the fundamental properties of 2D vdW semiconductors.…”

Section: Introductionmentioning

confidence: 99%

Sliding ferroelectricity in van der Waals layered γ-InSe semiconductor

et al. 2023

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Two-dimensional (2D) van-der-Waals (vdW) layered ferroelectric semiconductors are highly desired for in-memory computing and ferroelectric photovoltaics or detectors. Beneficial from the weak interlayer vdW-force, controlling the structure by interlayer twist/translation or doping is an effective strategy to manipulate the fundamental properties of 2D-vdW semiconductors, which has contributed to the newly-emerging sliding ferroelectricity. Here, we report unconventional room-temperature ferroelectricity, both out-of-plane and in-plane, in vdW-layered γ-InSe semiconductor triggered by yttrium-doping (InSe:Y). We determine an effective piezoelectric constant of ∼7.5 pm/V for InSe:Y flakes with thickness of ∼50 nm, about one order of magnitude larger than earlier reports. We directly visualize the enhanced sliding switchable polarization originating from the fantastic microstructure modifications including the stacking-faults elimination and a subtle rhombohedral distortion due to the intralayer compression and continuous interlayer pre-sliding. Our investigations provide new freedom degrees of structure manipulation for intrinsic properties in 2D-vdW-layered semiconductors to expand ferroelectric candidates for next-generation nanoelectronics.

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“…Ferroelectrics based on hafnia, such as doped HfO 2 − and Hf 0.5 Zr 0.5 O 2 , − are quite unusual compared with conventional perovskite ferroelectrics. − First of all, though these oxides consist of mixed ionic-covalent bonding, it is unclear whether the covalence should play any role in the ferroelectricity. On the other hand, in perovskite oxide ferroelectrics, the existence of orbital hybridization and covalent bonding is important for the ferroelectric distortion .…”

Section: Introductionmentioning

confidence: 99%

Ferroelectricity in HfO₂ from a Coordination Number Perspective

et al. 2022

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Ferroelectricity observed in thin-film HfO 2 , either doped with Si, Al, and so forth or in the Hf 0.5 Zr 0.5 O 2 form, has gained great technical significance. While a trilinear coupling between phonon modes could explain its ferroelectric distortion, from a practical perspective, one may be concerned with a theory that is more straightforward to predict similar ferroelectric candidates through some apparent features of HfO 2 and ZrO 2 . In this work, we propose that the 7 cation coordination number of 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 a non-centrosymmetric nature, for example, the mm2 point group, HfO 2 and 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 SrI 2 , TaON, YSBr, and YOF, are also studied in comparison to HfO 2 /ZrO 2 , and six switching paths are analyzed in detail for the Pca2 1 phase. A rule of the preferred switching path in terms of the ionic radii ratio and coordination number has been established. We also show the possible route from the ferroelectric Pca2 1 phase to the monoclinic P2 1 /c phase in HfO 2 , which is relevant to the fatigue phenomenon.

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Intrinsic ferroelectricity in Y-doped HfO2 thin films

Cited by 84 publications

References 46 publications

Hafnium-doped zirconia ferroelectric thin films with excellent endurance at high polarization

Hafnium-doped zirconia ferroelectric thin films with excellent endurance at high polarization

Sliding ferroelectricity in van der Waals layered γ-InSe semiconductor

Ferroelectricity in HfO₂ from a Coordination Number Perspective

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Intrinsic ferroelectricity in Y-doped HfO2 thin films

Cited by 84 publications

References 46 publications

Hafnium-doped zirconia ferroelectric thin films with excellent endurance at high polarization

Hafnium-doped zirconia ferroelectric thin films with excellent endurance at high polarization

Sliding ferroelectricity in van der Waals layered γ-InSe semiconductor

Ferroelectricity in HfO2 from a Coordination Number Perspective

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Ferroelectricity in HfO₂ from a Coordination Number Perspective