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Shi S, Cao T, Xi H, Niu J, Jing X, Su H, Yu X, Yang P, Wu Y, Yan X, Tian H, Tsymbal EY, Chen J. Stabilizing the Ferroelectric Phase of Hf_{0.5}Zr_{0.5}O_{2} Thin Films by Charge Transfer. PHYSICAL REVIEW LETTERS 2024; 133:036202. [PMID: 39094151 DOI: 10.1103/physrevlett.133.036202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 04/08/2024] [Accepted: 06/06/2024] [Indexed: 08/04/2024]
Abstract
Ferroelectric hafnia-based thin films have attracted significant interest due to their compatibility with complementary metal-oxide-semiconductor technology (CMOS). Achieving and stabilizing the metastable ferroelectric phase in these films is crucial for their application in ferroelectric devices. Recent research efforts have concentrated on the stabilization of the ferroelectric phase in hafnia-based films and delving into the mechanisms responsible for this stability. In this study, we experimentally demonstrate that stabilization of the ferroelectric phase in Hf_{0.5}Zr_{0.5}O_{2} (HZO) can be controlled by the interfacial charge transfer and the associated hole doping of HZO. Using the meticulously engineered charge transfer between an La_{1-x}Sr_{x}MnO_{3} buffer layer with variable Sr concentration x and an HZO film, we find the optimal x=0.33 that provides the required hole doping of HZO to most efficiently stabilize its ferroelectric phase. Our theoretical modeling reveals that the competition of the hole distribution between the threefold and fourfold coordinated oxygen sites in HZO controls the enhancement or reduction of the ferroelectric phase. Our findings offer a novel strategy to stabilize the ferroelectric phase of hafnia-based films and provide new insights into the development of ferroelectric devices compatible with CMOS.
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Affiliation(s)
| | | | - Haolong Xi
- School of Materials and Energy, Electron Microscopy Centre of Lanzhou University and Key Laboratory of Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, China
- Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | | | | | | | | | | | | | | | - He Tian
- Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
- School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, China
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Choi H, Cho YH, Kim SH, Yang K, Park MH. Hafnia-Based Ferroelectric Memory: Device Physics Strongly Correlated with Materials Chemistry. J Phys Chem Lett 2024; 15:983-997. [PMID: 38252652 DOI: 10.1021/acs.jpclett.3c03363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Hafnia-based ferroelectrics and their semiconductor applications are reviewed, focusing on next-generation dynamic random-access-memory (DRAM) and Flash. The challenges of achieving high endurance and high write/read speed and the optimal material properties to achieve them are discussed. In DRAM applications, the trade-off between remanent polarization (Pr), endurance, and operation speed is highlighted, focusing on reducing the critical material property Ec (coercive field). Novel phase formation and interfacial redox chemistry are reviewed as potential game-changers for ferroelectric memories. Regarding Flash operation, the need for an ideal Pr and Ec ratio is emphasized, as excessive Pr can lead to charge trapping, resulting in fatigue and pass disturbance in the NAND array. Achieving the right balance of Pr and Ec for ferroelectric NAND with hafnia-based ferroelectrics remains challenging. This Perspective also recognizes technical advancements in FeFET technology, offering potential solutions for improved performance and casting a positive outlook on the future of ferroelectric memory technology.
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Affiliation(s)
- Hyojun Choi
- Department of Materials Science and Engineering & Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Yong Hyeon Cho
- Department of Materials Science and Engineering & Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Se Hyun Kim
- Department of Materials Science and Engineering & Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Kun Yang
- Department of Materials Science and Engineering & Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Min Hyuk Park
- Department of Materials Science and Engineering & Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
- Research Institute of Advanced Materials, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
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Wu Y, Zhang Y, Jiang J, Jiang L, Tang M, Zhou Y, Liao M, Yang Q, Tsymbal EY. Unconventional Polarization-Switching Mechanism in (Hf, Zr)O_{2} Ferroelectrics and Its Implications. PHYSICAL REVIEW LETTERS 2023; 131:226802. [PMID: 38101373 DOI: 10.1103/physrevlett.131.226802] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 02/07/2023] [Accepted: 10/25/2023] [Indexed: 12/17/2023]
Abstract
HfO_{2}-based ferroelectric thin films are promising for their application in ferroelectric devices. Predicting the ultimate magnitude of polarization and understanding its switching mechanism are critical to realize the optimal performance of these devices. Here, a generalized solid-state variable cell nudged elastic band method is employed to predict the switching pathway associated with domain-wall motion in (Hf,Zr)O_{2} ferroelectrics. It is found that the polarization reversal pathway, where threefold coordinated O atoms pass across the nominal unit-cell boundaries defined by the Hf/Zr atomic planes, is energetically more favorable than the conventional pathway where the O atoms do not pass through these planes. This finding implies that the polarization orientation in the orthorhombic Pca2_{1} phase of HfO_{2} and its derivatives is opposite to that normally assumed, predicts the spontaneous polarization magnitude of about 70 μC/cm^{2} that is nearly 50% larger than the commonly accepted value, signifies a positive intrinsic longitudinal piezoelectric coefficient, and suggests growth of ferroelectric domains, in response to an applied electric field, structurally reversed to those usually anticipated. These results provide important insights into the understanding of ferroelectricity in HfO_{2}-based ferroelectrics.
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Affiliation(s)
- Yao Wu
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Yuke Zhang
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Jie Jiang
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Limei Jiang
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Minghua Tang
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Yichun Zhou
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Min Liao
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Qiong Yang
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
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Park JY, Choe DH, Lee DH, Yu GT, Yang K, Kim SH, Park GH, Nam SG, Lee HJ, Jo S, Kuh BJ, Ha D, Kim Y, Heo J, Park MH. Revival of Ferroelectric Memories Based on Emerging Fluorite-Structured Ferroelectrics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2204904. [PMID: 35952355 DOI: 10.1002/adma.202204904] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 07/25/2022] [Indexed: 06/15/2023]
Abstract
Over the last few decades, the research on ferroelectric memories has been limited due to their dimensional scalability and incompatibility with complementary metal-oxide-semiconductor (CMOS) technology. The discovery of ferroelectricity in fluorite-structured oxides revived interest in the research on ferroelectric memories, by inducing nanoscale nonvolatility in state-of-the-art gate insulators by minute doping and thermal treatment. The potential of this approach has been demonstrated by the fabrication of sub-30 nm electronic devices. Nonetheless, to realize practical applications, various technical limitations, such as insufficient reliability including endurance, retention, and imprint, as well as large device-to-device-variation, require urgent solutions. Furthermore, such limitations should be considered based on targeting devices as well as applications. Various types of ferroelectric memories including ferroelectric random-access-memory, ferroelectric field-effect-transistor, and ferroelectric tunnel junction should be considered for classical nonvolatile memories as well as emerging neuromorphic computing and processing-in-memory. Therefore, from the viewpoint of materials science, this review covers the recent research focusing on ferroelectric memories from the history of conventional approaches to future prospects.
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Affiliation(s)
- Ju Yong Park
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Duk-Hyun Choe
- Beyond Silicon Lab, Samsung Advanced Institute of Technology (SAIT), Suwon, 16678, Republic of Korea
| | - Dong Hyun Lee
- Department of Materials Science and Engineering and Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Seoul, 08826, Republic of Korea
| | - Geun Taek Yu
- School of Materials Science and Engineering, Pusan National University, Busan, 46241, Republic of Korea
| | - Kun Yang
- Department of Materials Science and Engineering and Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Seoul, 08826, Republic of Korea
| | - Se Hyun Kim
- Department of Materials Science and Engineering and Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Seoul, 08826, Republic of Korea
| | - Geun Hyeong Park
- Department of Materials Science and Engineering and Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Seoul, 08826, Republic of Korea
| | - Seung-Geol Nam
- Beyond Silicon Lab, Samsung Advanced Institute of Technology (SAIT), Suwon, 16678, Republic of Korea
| | - Hyun Jae Lee
- Beyond Silicon Lab, Samsung Advanced Institute of Technology (SAIT), Suwon, 16678, Republic of Korea
| | - Sanghyun Jo
- Beyond Silicon Lab, Samsung Advanced Institute of Technology (SAIT), Suwon, 16678, Republic of Korea
| | - Bong Jin Kuh
- Semiconductor Research and Development Center, Samsung Electronics, Hwaseong, 18448, Republic of Korea
| | - Daewon Ha
- Semiconductor Research and Development Center, Samsung Electronics, Hwaseong, 18448, Republic of Korea
| | - Yongsung Kim
- Beyond Silicon Lab, Samsung Advanced Institute of Technology (SAIT), Suwon, 16678, Republic of Korea
| | - Jinseong Heo
- Beyond Silicon Lab, Samsung Advanced Institute of Technology (SAIT), Suwon, 16678, Republic of Korea
| | - Min Hyuk Park
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
- Department of Materials Science and Engineering and Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Seoul, 08826, Republic of Korea
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5
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Park JY, Lee DH, Park GH, Lee J, Lee Y, Park MH. A perspective on the physical scaling down of hafnia-based ferroelectrics. NANOTECHNOLOGY 2023; 34:202001. [PMID: 36745914 DOI: 10.1088/1361-6528/acb945] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 02/05/2023] [Indexed: 06/18/2023]
Abstract
HfO2-based ferroelectric thin films have attracted significant interest for semiconductor device applications due to their compatibility with complementary metal oxide semiconductor (CMOS) technology. One of the benefits of HfO2-based ferroelectric thin films is their ability to be scaled to thicknesses as low as 10 nm while retaining their ferroelectric properties; a feat that has been difficult to accomplish with conventional perovskite-based ferroelectrics using CMOS-compatible processes. However, reducing the thickness limit of HfO2-based ferroelectric thin films below the sub 5 nm thickness regime while preserving their ferroelectric property remains a formidable challenge. This is because both the structural factors of HfO2, including polymorphism and orientation, and the electrical factors of HfO2-based devices, such as the depolarization field, are known to be highly dependent on the HfO2thickness. Accordingly, when the thickness of HfO2drops below 5 nm, these factors will become even more crucial. In this regard, the size effect of HfO2-based ferroelectric thin films is thoroughly discussed in the present review. The impact of thickness on the ferroelectric property of HfO2-based thin films and the electrical performance of HfO2-based ferroelectric semiconductor devices, such as ferroelectric random-access-memory, ferroelectric field-effect-transistor, and ferroelectric tunnel junction, is extensively discussed from the perspective of fundamental theory and experimental results. Finally, recent developments and reports on achieving ferroelectric HfO2at sub-5 nm thickness regime and their applications are discussed.
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Affiliation(s)
- Ju Yong Park
- Department of Materials Science and Engineering & Inter-university Semiconductor Research Center, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Dong Hyun Lee
- Department of Materials Science and Engineering & Inter-university Semiconductor Research Center, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Geun Hyeong Park
- Department of Materials Science and Engineering & Inter-university Semiconductor Research Center, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Jaewook Lee
- Department of Materials Science and Engineering & Inter-university Semiconductor Research Center, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Younghwan Lee
- Research Institute of Advanced Materials, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Min Hyuk Park
- Department of Materials Science and Engineering & Inter-university Semiconductor Research Center, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
- Research Institute of Advanced Materials, College of Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
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6
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Shao Y, Yang W, Wang Y, Deng Y, Liao N, Zhu B, Lin X, Jiang L, Jiang J, Yang Q, Zhong X. Synergistic effect of Si concentration and distribution on ferroelectric properties optimization of Si:HfO 2ferroelectric thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:415401. [PMID: 35901791 DOI: 10.1088/1361-648x/ac8513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 07/28/2022] [Indexed: 06/15/2023]
Abstract
In this paper, a phase-field model of Si-doped hafnium oxide-based ferroelectric thin films is established. And then, the synergistic effect of Si concentration and distribution on ferroelectric properties optimization of Si:HfO2ferroelectric thin films is studied with the proposed model. It is found that no matter how Si dopant is distributed in the film, the volume fraction of the ferroelectric phase in the film increases first and then decreases with the increase of Si concentration. However, compared with the uniform distribution, the layered distribution is more likely to great improve ferrelectric properties. When Si dopant is uniformly distributed in the film, the highest remanent polarization value that the film can obtain via Si concentration modulation is 38.7μC cm-2, and the corresponding Si concentration is 3.8 cat%, which is consistent with the experimental results. When Si dopant is layered in the film, and the concentration difference between the Si-rich and Si-poor layers is 7.6%, in the Si concentration range of 3.6 cat%-3.8 cat%, the residual polarization of the film reaches 46.4-46.8μC cm-2, which is 20% higher than that when Si dopant are evenly distributed in the film. The above results show that selecting the Si layered distribution mode and controlling the concentration difference between Si-rich and Si-poor layers in an appropriate range can greatly improve the films' ferroelectric properties and broaden the Si concentration optimization range of the ferroelectric properties of the films. The result provides further theoretical guidance on using Si doping to adjust the ferroelectric properties of hafnium oxide-based films.
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Affiliation(s)
- Yanping Shao
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Wanting Yang
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Yuanyao Wang
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Yuhui Deng
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Ningtao Liao
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Bingyan Zhu
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Xin Lin
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Limei Jiang
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Jie Jiang
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Qiong Yang
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Xiangli Zhong
- Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan 411105, People's Republic of China
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
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7
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Du X, Sun H, Wang H, Li J, Yin Y, Li X. High-Speed Switching and Giant Electroresistance in an Epitaxial Hf 0.5Zr 0.5O 2-Based Ferroelectric Tunnel Junction Memristor. ACS APPLIED MATERIALS & INTERFACES 2022; 14:1355-1361. [PMID: 34958206 DOI: 10.1021/acsami.1c18165] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
HfO2-based ferroelectric materials are good candidates for constructing next-generation nonvolatile memories and high-performance electronic synapses and have attracted extensive attention from both academia and industry. Here, a Hf0.5Zr0.5O2-based ferroelectric tunnel junction (FTJ) memristor is successfully fabricated by epitaxially growing a Hf0.5Zr0.5O2 film on a 0.7 wt % Nb-doped SrTiO3 (001) substrate with a buffer layer of La2/3Sr1/3MnO3 (∼1 u.c.). The FTJ shows a high switching speed of 20 ns, a giant electroresistance ratio of ∼834, and multiple states (eight states or three bits) with good retention >104 s. As a solid synaptic device, tunable synapse functions have also been obtained, including long-term potentiation, long-term depression, and spike-timing-dependent plasticity. These results highlight the promising applications of Hf0.5Zr0.5O2-based FTJ in ultrafast-speed and high-density nonvolatile memories and artificial synapses.
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Affiliation(s)
- Xinzhe Du
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, and CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, University of Science and Technology of China, Hefei 230026, China
| | - Haoyang Sun
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, and CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, University of Science and Technology of China, Hefei 230026, China
| | - He Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, and CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, University of Science and Technology of China, Hefei 230026, China
| | - Jiachen Li
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, and CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, University of Science and Technology of China, Hefei 230026, China
| | - Yuewei Yin
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, and CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xiaoguang Li
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, and CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, University of Science and Technology of China, Hefei 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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8
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Yuan ZL, Sun Y, Wang D, Chen KQ, Tang LM. A review of ultra-thin ferroelectric films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:403003. [PMID: 34261050 DOI: 10.1088/1361-648x/ac145c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 07/14/2021] [Indexed: 06/13/2023]
Abstract
Ultrathin ferroelectrics are of great technological interest for high-density electronics, particularly non-volatile memories and field-effect transistors. With the rapid development of micro-electronics technology, there is an urgent requirement for higher density electronic devices, which need ultra-thin ferroelectric materials films. However, as ferroelectric films have becomes thinner and thinner, electrical spontaneous polarization signals have been found in a few atomic layers or even monolayer structures. The mechanisms of detection and formation of these signals are not well understood and various controversial interpretations have emerged. In this review, we summarized the recent research progress in the ultra-thin film ferroelectric material, such as HfO2, CuInP2S6, In2Se3, MoTe2and BaTiO3. Various key aspects of ferroelectric materials are discussed, including crystal structure, ferroelectric mechanism, characterization, fabrication methods, applications, and future outlooks. We hope this review will offer ideas for further improvement of ferroelectric properties of ultra-thin films and promotes practical applications.
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Affiliation(s)
- Zi-Lin Yuan
- Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Yu Sun
- Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Dan Wang
- College of Science, Central South University of Forestry and Technology, Changsha 410004, People's Republic of China
- Hunan Province Key Laboratory of Materials Surface & Interface Science and Technology, College of Material Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, People's Republic of China
| | - Ke-Qiu Chen
- Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Li-Ming Tang
- Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
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9
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Ferroelectricity in Si-Doped Hafnia: Probing Challenges in Absence of Screening Charges. NANOMATERIALS 2020; 10:nano10081576. [PMID: 32796703 PMCID: PMC7466465 DOI: 10.3390/nano10081576] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 08/05/2020] [Accepted: 08/07/2020] [Indexed: 11/28/2022]
Abstract
The ability to develop ferroelectric materials using binary oxides is critical to enable novel low-power, high-density non-volatile memory and fast switching logic. The discovery of ferroelectricity in hafnia-based thin films, has focused the hopes of the community on this class of materials to overcome the existing problems of perovskite-based integrated ferroelectrics. However, both the control of ferroelectricity in doped-HfO2 and the direct characterization at the nanoscale of ferroelectric phenomena, are increasingly difficult to achieve. The main limitations are imposed by the inherent intertwining of ferroelectric and dielectric properties, the role of strain, interfaces and electric field-mediated phase, and polarization changes. In this work, using Si-doped HfO2 as a material system, we performed a correlative study with four scanning probe techniques for the local sensing of intrinsic ferroelectricity on the oxide surface. Putting each technique in perspective, we demonstrated that different origins of spatially resolved contrast can be obtained, thus highlighting possible crosstalk not originated by a genuine ferroelectric response. By leveraging the strength of each method, we showed how intrinsic processes in ultrathin dielectrics, i.e., electronic leakage, existence and generation of energy states, charge trapping (de-trapping) phenomena, and electrochemical effects, can influence the sensed response. We then proceeded to initiate hysteresis loops by means of tip-induced spectroscopic cycling (i.e., “wake-up”), thus observing the onset of oxide degradation processes associated with this step. Finally, direct piezoelectric effects were studied using the high pressure resulting from the probe’s confinement, noticing the absence of a net time-invariant piezo-generated charge. Our results are critical in providing a general framework of interpretation for multiple nanoscale processes impacting ferroelectricity in doped-hafnia and strategies for sensing it.
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10
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Yang L, Peng Y, Yang Y, Liu J, Huang H, Yu B, Zhao J, Lu Y, Huang Z, Li Z, Lombardi JR. A Novel Ultra-Sensitive Semiconductor SERS Substrate Boosted by the Coupled Resonance Effect. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2019; 6:1900310. [PMID: 31380169 PMCID: PMC6662085 DOI: 10.1002/advs.201900310] [Citation(s) in RCA: 104] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Revised: 03/28/2019] [Indexed: 05/21/2023]
Abstract
Recent achievements in semiconductor surface-enhanced Raman scattering (SERS) substrates have greatly expanded the application of SERS technique in various fields. However, exploring novel ultra-sensitive semiconductor SERS materials is a high-priority task. Here, a new semiconductor SERS-active substrate, Ta2O5, is developed and an important strategy, the "coupled resonance" effect, is presented, to optimize the SERS performance of semiconductor materials by energy band engineering. The optimized Mo-doped Ta2O5 substrate exhibits a remarkable SERS sensitivity with an enhancement factor of 2.2 × 107 and a very low detection limit of 9 × 10-9 m for methyl violet (MV) molecules, demonstrating one of the highest sensitivities among those reported for semiconductor SERS substrates. This remarkable enhancement can be attributed to the synergistic resonance enhancement of three components under 532 nm laser excitation: i) MV molecular resonance, ii) photoinduced charge transfer resonance between MV molecules and Ta2O5 nanorods, and iii) electromagnetic enhancement around the "gap" and "tip" of anisotropic Ta2O5 nanorods. Furthermore, it is discovered that the concomitant photoinduced degradation of the probed molecules in the time-scale of SERS detection is a non-negligible factor that limits the SERS performance of semiconductors with photocatalytic activity.
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Affiliation(s)
- Lili Yang
- State Key Laboratory of High Performance Ceramics and Superfine MicrostructuresShanghai Institute of CeramicsChinese Academy of Sciences1295 Dingxi RoadShanghai200050P. R. China
- University of Chinese Academy of SciencesNo.19(A) Yuquan RoadBeijing100049P. R. China
- Center of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of SciencesBeijing100049P. R. China
| | - Yusi Peng
- State Key Laboratory of High Performance Ceramics and Superfine MicrostructuresShanghai Institute of CeramicsChinese Academy of Sciences1295 Dingxi RoadShanghai200050P. R. China
- University of Chinese Academy of SciencesNo.19(A) Yuquan RoadBeijing100049P. R. China
- Center of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of SciencesBeijing100049P. R. China
| | - Yong Yang
- State Key Laboratory of High Performance Ceramics and Superfine MicrostructuresShanghai Institute of CeramicsChinese Academy of Sciences1295 Dingxi RoadShanghai200050P. R. China
- University of Chinese Academy of SciencesNo.19(A) Yuquan RoadBeijing100049P. R. China
- Center of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of SciencesBeijing100049P. R. China
| | - Jianjun Liu
- State Key Laboratory of High Performance Ceramics and Superfine MicrostructuresShanghai Institute of CeramicsChinese Academy of Sciences1295 Dingxi RoadShanghai200050P. R. China
| | - Haoliang Huang
- National Synchrotron Radiation LaboratoryUniversity of Science and Technology of ChinaHefei230026P. R. China
| | - Bohan Yu
- University of Chinese Academy of SciencesNo.19(A) Yuquan RoadBeijing100049P. R. China
- Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing100190P. R. China
| | - Jimin Zhao
- University of Chinese Academy of SciencesNo.19(A) Yuquan RoadBeijing100049P. R. China
- Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing100190P. R. China
| | - Yalin Lu
- National Synchrotron Radiation LaboratoryUniversity of Science and Technology of ChinaHefei230026P. R. China
| | - Zhengren Huang
- State Key Laboratory of High Performance Ceramics and Superfine MicrostructuresShanghai Institute of CeramicsChinese Academy of Sciences1295 Dingxi RoadShanghai200050P. R. China
| | - Zhiyuan Li
- South China University of TechnologyGuangzhou510640GuangdongP. R. China
| | - John R. Lombardi
- Department of ChemistryThe City College of New York160 Convent AvenueNew YorkNY10031USA
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