Article
Materials Science, Multidisciplinary
Francesco Delodovici, Paolo Barone, Silvia Picozzi
Summary: In this research, the finite-size effects on the structural properties and polarization of rhombohedral phase of HfO2 under biaxial compressive strain are analyzed. The presence of surface charges is shown to greatly reduce the polarization compared to its bulk value, attributed to coupling between compressive strain and phase-transition order parameter, as well as changes in ferroelectric distortion. Additionally, two alternative explanations for this phenomenon are presented.
Article
Physics, Applied
Wenbin Ouyang, Fanhao Jia, Chang Liu, Xuli Cheng, Yaping Meng, Ruiling Gao, Silvia Picozzi, Wei Ren
Summary: In this study, the relative stability and ferroelectricity of the R3 and R3m phases of HfO2 were compared, revealing a phase transition from R3 to R3m under biaxial compressive strain. The direction and magnitude of polarization in both phases can be tuned by strain. Through symmetry mode analysis, the improper nature of ferroelectricity is elucidated.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Multidisciplinary
Li-Yang Ma, Shi Liu
Summary: In this study, the influence of oxygen vacancies on the performance of HfO2-based devices was systematically investigated using a first-principles-based variable-cell nudged elastic band technique. It was found that positively charged oxygen vacancies can promote the transition from nonpolar phases to polar phases kinetically, facilitated by a transient high-energy tetragonal phase and charge-carrier-inert ferroelectricity. The intricate coupling between the kinetics of structural polymorphism and the charge state of the oxygen vacancy has important implications for the origin of ferroelectricity and various exotic effects in HfO2-based thin films.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Veniero Lenzi, Jose P. B. Silva, Bretislav Smid, Vladimir Matolin, Cosmin M. Istrate, Corneliu Ghica, Judith L. MacManus-Driscoll, Luis Marques
Summary: In this study, it is found that oxygen vacancies in rhombohedral ZrO2 thin films not only stabilize the phase, but also contribute to the ferroelectric polarization. Experimental investigation, coupled with density functional theory calculations, reveals the importance of oxygen vacancies for stabilizing rhombohedral ZrO2 thin films with superior ferroelectric properties.
ENERGY & ENVIRONMENTAL MATERIALS
(2023)
Article
Polymer Science
Peng Lin, Xueyan Liu, Shisong Ren, Jian Xu, Yi Li, Mingliang Li
Summary: This research aims to determine the optimal film thickness range for high-content polymer-modified asphalt mixtures. Insufficient film thickness negatively affects performance, while excessive thickness reduces mixture stiffness. The optimal film thickness range falls within 12.9 to 14.9 μm, ensuring the best balance between performance and aging durability.
Article
Energy & Fuels
Yee H. Robin Chang, Tiem L. Yoon, Keat H. Yeoh, Thong L. Lim
Summary: The study explores the optimization of thermoelectric performances of stable Cm-SnSSe and P3m1-SnSeS phases, which exhibit low thermal conductivity and satisfactory thermoelectric performances beyond 400 K. Hole doping at 10(20) cm(-3) concentration leads to improved ZT values and broad temperature plateau, showing potential for industrial waste heat management.
INTERNATIONAL JOURNAL OF ENERGY RESEARCH
(2021)
Article
Chemistry, Multidisciplinary
Woomin Park, Seungbeom Park, Yeongjun Mun, Dongchan Lee, Kwang-Suk Jang
Summary: A thickness-controlled fabrication method for obtaining flexible, free-standing Ag2Se films with nanostructured raw materials was proposed in this study. By introducing the post-annealing process, flexible, free-standing Ag2Se films can be obtained. The flexibility and thermoelectric performance of the films were systematically investigated, and it was found that films with thicknesses of 110 μm or less exhibited excellent flexible properties.
JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
(2023)
Article
Materials Science, Multidisciplinary
Hei Man Yau, Xinxin Chen, Chi Man Wong, Deyang Chen, Jiyan Dai
Summary: By using X-ray diffraction and Transmission Electron Microscope, researchers revealed the epitaxial growth of Al-doped HfO2 thin films on differently oriented SrTiO3 substrates, showing various phase structures and ferroelectric properties. The film grown on (111) SrTiO3 substrate exhibited the largest electromechanical effect, indicating the orientation control of phase transitions and ferroelectricity in Al-doped HfO2 thin films.
MATERIALS CHARACTERIZATION
(2021)
Article
Chemistry, Physical
Tae Gun Kim, Hyunung Yu, Seung Mi Lee, Gyea Young Kwak, Jiyoung Shin, Kyung Joong Kim
Summary: In this study, the effect of surface contamination on thickness measurement of HfO2 films by MEIS and XPS was compared. It was found that the offset value variation due to surface carbon layer was negligibly small in MEIS (0.020 nm) but large in XPS (0.131 nm). MEIS was concluded to be a reliable ZOM for calibrating offset values in thickness measurement of ultra-thin oxide films with minimal effect of surface contamination.
APPLIED SURFACE SCIENCE
(2021)
Review
Nanoscience & Nanotechnology
Uwe Schroeder, Min Hyuk Park, Thomas Mikolajick, Cheol Seong Hwang
Summary: This Review summarizes the properties and origin of ferroelectricity in HfO2-based materials, discusses the thermodynamic and kinetic factors influencing the formation of the ferroelectric phase, and evaluates their potential applications. Through concerted efforts, academia and industry have improved our understanding of the material properties and root causes of the unexpected formation of the ferroelectric phase, paving the way for inducing the polar phase even in bulk materials.
NATURE REVIEWS MATERIALS
(2022)
Article
Construction & Building Technology
Zedi Zhang, Jialei Wang, Jinyan Shi, Kaidong Han, Jia Xiao
Summary: This study investigates the impacts of mix proportion parameters on the dynamic stability of mortar. The results show that increasing the fineness of ground limestone and the aggregate to binder ratio can improve the dynamic stability. The velocity of a single sand and the paste film thickness were found to play a role in understanding the variation of dynamic stability.
CONSTRUCTION AND BUILDING MATERIALS
(2022)
Article
Materials Science, Ceramics
Zhezhe Deng, Yongshuai Xie, Wei Liu, Jianhong Dong, Ying Peng, Ze Zhu, Luyi Zhu, Guanghui Zhang, Xinqiang Wang, Dong Xu
Summary: This paper investigates the synthesis of high strength HfO2 nanofibers using self-synthesis polyacetylcatonahafnium (PAHf) with electrospinning method. The HfO2 fibers with Y2O3 as stabilizer exhibit good flexibility, high strength and thermal stability.
CERAMICS INTERNATIONAL
(2022)
Article
Chemistry, Multidisciplinary
Guoqiang Xi, Zhao Pan, Yue-Wen Fang, Jie Tu, Hangren Li, Qianqian Yang, Chen Liu, Huajie Luo, Jiaqi Ding, Shuai Xu, Shiqing Deng, Qingxiao Wang, Dongxing Zheng, Youwen Long, Kuijuan Jin, Xixiang Zhang, Jianjun Tian, Linxing Zhang
Summary: A method of anion-induced polarization rotation with chemical strain is proposed to improve the ferroelectricity of BiFeO3 thin films. The sulfurization of the films leads to a substantial enhancement in room-temperature ferroelectric polarization, increasing the remnant polarization by 170% from 58 to 100.7 μC cm(-2).
MATERIALS HORIZONS
(2023)
Article
Chemistry, Physical
Xinjie Wang, Yi-Chi Wang, Biaolin Peng, Jianyu Deng, Ya Yang, Wenhong Sun, Zhonglin Wang
Summary: This paper investigates the influence of thickness on the performance of ferroelectric thin films and reveals that thicker films enhance spontaneous polarization but decrease dielectric permittivity, coercivity field, residual polarization, efficiency, and energy density, and gradually transition the positive electrocaloric effect into a negative regime. These changes can be attributed to the variation of in-plane tensile stresses with thickness, resulting in an increase in the tetragonal phase and a decrease in the rhombohedral phase structure.
Article
Materials Science, Ceramics
Yue Peng, Zhe Wang, Wenwu Xiao, Yu Ma, Fenning Liu, Xinran Deng, Xiao Yu, Yan Liu, Genquan Han, Yue Hao
Summary: This study investigated the polarization switching speed of HfO2-ZrO2 (HZO) ferroelectric films with different thicknesses using TaN/HZO/TaN capacitors. The inhomogeneous field mechanism (IFM) model was employed to characterize the switching dynamics, revealing different characteristic time constants for HZO samples of varying thicknesses. The results provide insights into the local field distribution in capacitors with different HZO thicknesses and offer implications for the design and optimization of HZO films for advanced nanonode applications.
CERAMICS INTERNATIONAL
(2022)
Article
Chemistry, Multidisciplinary
Kitae Eom, Hanjong Paik, Jinsol Seo, Neil Campbell, Evgeny Y. Tsymbal, Sang Ho Oh, Mark S. Rzchowski, Darrell G. Schlom, Chang-Beom Eom
Summary: This study reports the formation of 2-dimensional electron gases (2DEGs) with high mobility at room temperature at the LaScO3/BaSnO3 interface. By reducing the dislocation density and obtaining an atomically flat surface through specific treatment methods, an order of magnitude higher mobility at room temperature than previously achieved is achieved. This work opens up new possibilities for exploring the exciting physics of stannate-based 2DEGs at temperatures relevant to applications in oxide nanoelectronics.
Article
Chemistry, Multidisciplinary
Kai Huang, Ding-Fu Shao, Evgeny Y. Tsymbal
Summary: In this study, we demonstrate the electrical control of DMI and magnetic skyrmions in a Fe3GeTe2 monolayer through the ferroelectric polarization of an adjacent 2D vdW ferroelectric In2Se3. The results show that the magnitude and sign of DMI can be controlled by ferroelectric polarization reversal, leading to the creation and annihilation of skyrmions.
Article
Physics, Multidisciplinary
Jianting Dong, Xinlu Li, Gautam Gurung, Meng Zhu, Peina Zhang, Fanxing Zheng, Evgeny Y. Tsymbal, Jia Zhang
Summary: Antiferromagnetic spintronics is a subfield of spintronics that takes advantage of antiferromagnets producing no stray fields and exhibiting ultrafast magnetization dynamics. This study demonstrates the potential of utilizing noncollinear antiferromagnetic metals to achieve high tunneling magnetoresistance (TMR) effect, which can be used to detect the Néel vector and produce multiple nonvolatile resistance states.
PHYSICAL REVIEW LETTERS
(2022)
Article
Nanoscience & Nanotechnology
S. Ryu, H. Zhou, T. R. Paudel, N. Campbell, J. Podkaminer, C. W. Bark, T. Hernandez, D. D. Fong, Y. Zhang, L. Xie, X. Q. Pan, E. Y. Tsymbal, M. S. Rzchowski, C. B. Eom
Summary: Atomic flat (111) interfaces between insulating perovskite oxides provide a landscape for new electronic phenomena, such as graphene-like coordination between interfacial metallic ion layer pairs leading to topologically protected states. In this study, epitaxial heterostructures of (111)-oriented LaAlO3/SrTiO3 (LAO/STO) were investigated, and it was found that the LAO overlayer eliminates the structural reconstruction of the STO (111) surface through an electronic reconstruction, determining the properties of the resulting two-dimensional conducting gas.
Article
Engineering, Electrical & Electronic
Arnab Bose, Nathaniel J. Schreiber, Rakshit Jain, Ding-Fu Shao, Hari P. Nair, Jiaxin Sun, Xiyue S. Zhang, David A. Muller, Evgeny Y. Tsymbal, Darrell G. Schlom, Daniel C. Ralph
Summary: Symmetry plays a central role in determining the polarization of spin currents induced by electric fields. In this study, an out-of-plane damping-like torque is shown to be generated in RuO2/permalloy devices when the Neel vector of the collinear antiferromagnet RuO2 is canted relative to the sample plane. By measuring characteristic changes in the electric-field-induced torque vector, it is found that RuO2 generates a spin current with a well-defined tilted spin orientation parallel to the Neel vector. This antiferromagnetic spin Hall effect has distinct symmetries from other mechanisms of spin-current generation reported in antiferromagnetic and ferromagnetic materials.
NATURE ELECTRONICS
(2022)
Article
Nanoscience & Nanotechnology
Alexey Lipatov, Pradeep Chaudhary, Zhao Guan, Haidong Lu, Gang Li, Olivier Cregut, Kokou Dodzi Dorkenoo, Roger Proksch, Salia Cherifi-Hertel, Ding-Fu Shao, Evgeny Y. Tsymbal, Jorge Iniguez, Alexander Sinitskii, Alexei Gruverman
Summary: Recent theoretical predictions have suggested that two-dimensional van der Waals materials may exhibit ferroelectric properties, opening up exciting possibilities for scalable low-power electronic devices. Experimental evidence of polarization response has been observed in narrow-band semiconductors and semimetals known as transition metal chalcogenides (TMCs), with molybdenum disulfide (MoS2) being one of the most promising 2D electronic materials. However, despite theoretical predictions, no ferroelectricity has been experimentally detected in MoS2, although its emergence could enhance its potential for electronics applications.
NPJ 2D MATERIALS AND APPLICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Zhijun Ma, Qi Zhang, Lingling Tao, Yihao Wang, Daniel Sando, Jinling Zhou, Yizhong Guo, Michael Lord, Peng Zhou, Yongqi Ruan, Zhiwei Wang, Alex Hamilton, Alexei Gruverman, Evgeny Y. Tsymbal, Tianjin Zhang, Nagarajan Valanoor
Summary: Resonant tunneling and negative differential resistance behaviors modulated by ferroelectricity have been demonstrated in perovskite-oxide quantum well structures, paving the way for ferroelectric-based quantum-tunneling devices in future oxide electronics.
ADVANCED MATERIALS
(2022)
Article
Chemistry, Physical
Yu Yun, Pratyush Buragohain, Ming Li, Zahra Ahmadi, Yizhi Zhang, Xin Li, Haohan Wang, Jing Li, Ping Lu, Lingling Tao, Haiyan Wang, Jeffrey E. Shield, Evgeny Y. Tsymbal, Alexei Gruverman, Xiaoshan Xu
Summary: Ferroelectricity can be achieved in epitaxial HfO2 films with high structural order, indicating that it is an intrinsic property of HfO2-based materials. This discovery has significant implications for optimizing the performance of HfO2-based materials in device applications.
Article
Multidisciplinary Sciences
Shuai Hu, Ding-Fu Shao, Huanglin Yang, Chang Pan, Zhenxiao Fu, Meng Tang, Yumeng Yang, Weijia Fan, Shiming Zhou, Evgeny Y. Tsymbal, Xuepeng Qiu
Summary: Deterministic and field-free switching is demonstrated in a Ni/Co multilayer by exploiting the magnetic spin Hall effect in adjacent Mn3Sn, which is essential for low-power spintronics.
NATURE COMMUNICATIONS
(2022)
Article
Multidisciplinary Sciences
Zhongran Liu, Han Wang, Ming Li, Lingling Tao, Tula R. Paudel, Hongyang Yu, Yuxuan Wang, Siyuan Hong, Meng Zhang, Zhaohui Ren, Yanwu Xie, Evgeny Y. Tsymbal, Jingsheng Chen, Ze Zhang, He Tian
Summary: Domain-wall nanoelectronics is a new paradigm for non-volatile memory and logic technologies, where domain walls serve as an active element. Charged domain walls in ferroelectric structures have unique electronic and transport properties, which are useful for various nanoelectronics applications. In this study, a strategy for controllable creation and manipulation of charged domain walls in BiFeO3 ferroelectric films is reported, and their functionality as a memristor a few unit cells thick is demonstrated.
Article
Chemistry, Physical
Zifang Liu, Pengfei Hou, Lizhong Sun, Evgeny Y. Tsymbal, Jie Jiang, Qiong Yang
Summary: In this work, a two-dimensional van der Waals heterostructure composed of an alpha-In2Se3 ferroelectric and a hexagonal IV-VI semiconductor is designed, and an in-plane ferroelectric tunnel junction based on these heterostructures is proposed. First-principles calculations show that the electronic band structure of the designed heterostructures can be switched between insulating and metallic states by ferroelectric polarization. It is demonstrated that the in-plane ferroelectric tunnel junction exhibits two distinct transport regimes, tunneling and metallic, for OFF and ON states, respectively, resulting in a giant tunneling electroresistance effect with the OFF/ON resistance ratio exceeding 1 x 10(4). The results provide a promising approach for high-density ferroelectric memory based on 2D ferroelectric/semiconductor heterostructures.
NPJ COMPUTATIONAL MATERIALS
(2023)
Article
Chemistry, Physical
D. C. Mahendra, Ding-Fu Shao, Vincent D. -H. Hou, Arturas Vailionis, P. Quarterman, Ali Habiboglu, M. B. Venuti, Fen Xue, Yen-Lin Huang, Chien-Min Lee, Masashi Miura, Brian Kirby, Chong Bi, Xiang Li, Yong Deng, Shy-Jay Lin, Wilman Tsai, Serena Eley, Wei-Gang Wang, Julie A. Borchers, Evgeny Y. Tsymbal, Shan X. Wang
Summary: By utilizing unconventional spins generated in a MnPd3 thin film grown on an oxidized silicon substrate, the authors observed both conventional spin-orbit torques and unconventional out-of-plane and in-plane anti-damping-like torques in MnPd3/CoFeB heterostructures, enabling complete field-free switching of perpendicular cobalt. These unconventional torques are attributed to the low symmetry of the (114)-oriented MnPd3 films. The results provide a path towards practical spin channels in ultrafast magnetic memory and logic devices.
Article
Physics, Multidisciplinary
Haoying Sun, Jiahui Gu, Yongqiang Li, Tula R. Paudel, Di Liu, Jierong Wang, Yipeng Zang, Chengyi Gu, Jiangfeng Yang, Wenjie Sun, Zhengbin Gu, Evgeny Y. Tsymbal, Junming Liu, Houbing Huang, Di Wu, Yuefeng Nie
Summary: By applying uniaxial strain, we achieved pure in-plane polarized ferroelectricity in ultrathin SrTiO3 membranes, which allows for the investigation of ferroelectric size effects without the interference of the depolarization field. Our study reveals that the stability of ferroelectricity is influenced by the thickness-dependent dipole-dipole interactions within the transverse Ising model.
PHYSICAL REVIEW LETTERS
(2023)
Article
Multidisciplinary Sciences
Shu Shi, Haolong Xi, Tengfei Cao, Weinan Lin, Zhongran Liu, Jiangzhen Niu, Da Lan, Chenghang Zhou, Jing Cao, Hanxin Su, Tieyang Zhao, Ping Yang, Yao Zhu, Xiaobing Yan, Evgeny Y. Tsymbal, He Tian, Jingsheng Chen
Summary: The authors demonstrate the stabilization of the metastable orthorhombic phase in Hf0.5 Zr0.5O2 films through interface engineering and hole doping.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Ding-Fu Shao, Shu-Hui Zhang, Rui-Chun Xiao, Zi-An Wang, W. J. Lu, Y. P. Sun, Evgeny Y. Tsymbal
Summary: In this study, we demonstrate the realization of a spin-neutral tunneling anomalous Hall effect (TAHE) in an antiferromagnetic (AFM) tunnel junction driven by spin-neutral currents. We show that the symmetry mismatch between the AFM electrode and the nonmagnetic barrier with strong spin-orbit coupling (SOC) results in spin-dependent momentum filtering, generating transverse Hall currents in each electrode. This finding opens up new possibilities for research in magnetoelectronics and spintronics.
