34 results on '"Ren, Wei"'
Search Results
2. Spectral tweezers: Single sample spectroscopy using optoelectronic tweezers.
- Author
-
Zaman, Mohammad Asif, Wu, Mo, Ren, Wei, Jensen, Michael A., Davis, Ronald W., and Hesselink, Lambertus
- Subjects
SPECTROMETRY ,OPTICAL tweezers - Abstract
A scheme that combines optoelectronic tweezers (OET) with spectroscopic analysis is presented. Referred to as spectral tweezers, the approach uses a single focused light beam that acts both as the trapping beam for OET and the probe beam for spectroscopy. Having simultaneous manipulation and spectral characterization ability, the method is used to isolate single micro-samples from clusters and perform spectral measurements. Experimental results show that a characteristic spectral signature can be obtained for a given sample. The proposed approach can be easily integrated into the optical setups used for conventional OETs with only a few additional optical components, making it a convenient tool for bio-analytical applications. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. Structural stability and polarization analysis of rhombohedral phases of HfO2.
- Author
-
Ouyang, Wenbin, Jia, Fanhao, Liu, Chang, Cheng, Xuli, Meng, Yaping, Gao, Ruiling, Picozzi, Silvia, and Ren, Wei
- Subjects
STRUCTURAL stability ,FERROELECTRIC thin films ,PHASE transitions ,FERROELECTRICITY ,HAFNIUM oxide - Abstract
Since the experimental observation of a rhombohedral phase of hafnium oxide, there remains controversy over whether this phase belongs to the R3 or R3m space group. Moreover, the origin of polarization in these two rhombohedral phases has not been comparatively elucidated. Here, we present a theoretical study comparing the relative stability and ferroelectricity of the R3 and R3m phases of HfO
2 , representing two potential forms of heavily Zr-doped ferroelectric thin films of hafnia found recently. We comprehensively investigate their structural stability and polarization response under in-plane compressive strain. A phase transition from R3 to R3m is discovered under biaxial compressive strain. The direction and magnitude of polarization in both phases can be tuned by strain. Through symmetry mode analysis, we elucidate the improper nature of ferroelectricity. These findings may advance understanding of ferroelectricity in hafnia thin films. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
4. Nonvolatile multiferroic coupling in van der Waals heterostructure.
- Author
-
Li, Yongchang, Hu, Tao, Guo, Pan, and Ren, Wei
- Subjects
MAGNETOELECTRIC effect ,MAGNETIC moments ,NONVOLATILE memory ,MAGNETISM ,FERROELECTRICITY - Abstract
Nonvolatile multiferroic coupling that can be controlled by electric fields has a wide range of future electronic multistate applications. Through first-principles calculations, we have revealed such magnetoelectric effect in van der Waals heterostructure systems consisting of CuCrP
2 Se6 and VS2 . The distinct magnetic moments for Se atoms on the upper and lower surfaces of the CuCrP2 Se6 substrate lead to different interlayer magnetic coupling configurations. Meanwhile, by varying the number of substrate layers, we can manipulate the direction of V's magnetic moment during ferroelectric reversal. This intricate interplay of ferroelectricity, magnetism, and ferrovalley enables the creation of electric switchable states. These findings provide ideas for nonvolatile memories controlled directly through electric fields. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
5. Local displacive correlation in the tetragonal relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-0.15PbTiO3.
- Author
-
Wang, Zhen, Zhuang, Jian, Li, Fei, Ren, Wei, Ye, Zuo-Guang, and Zhang, Nan
- Subjects
RELAXOR ferroelectrics ,MONTE Carlo method ,DISTRIBUTION (Probability theory) ,BARIUM titanate ,ATOMIC models ,LOW temperatures - Abstract
Over the past decades, lead-based relaxor ferroelectrics have served as the model systems to unravel the relationship between electromechanical properties and local structure. Here, by employing pair distribution function analysis and the reverse Monte Carlo method, we investigate the local structural features and their temperature dependence in relaxor ferroelectric Pb(Zn
1/3 Nb2/3 )O3 -xPbTiO3 with x = 0.15 (PZN-15PT), which has a tetragonal average structure, but displays frequency dependence at low temperatures. The refined atomic model suggests that ordered polar nanoregions (PNRs) originate from the strong atomic displacive correlation, and their polar directions are the same as the crystallographic symmetry axis. The dipoles in the disordered matrix have weak correlations and can be averaged into a global tetragonal symmetry. These findings establish a detailed picture of the local structure of lead-based relaxor ferroelectrics and provide a deeper insight into the nature of PNRs. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
6. A peculiar topological Hall effect in noncentrosymmetric ternary carbide GdCoC2.
- Author
-
Xu, Yang, Ren, Wei, Ma, Shengcan, Chen, Changcai, Fang, Chunsheng, Luo, Xiaohua, and Mo, Zhaojun
- Subjects
- *
HALL effect , *MAGNETORESISTANCE , *CURIE temperature , *PHASE transitions , *MAGNETIC transitions , *MAGNETIC fields , *CHIRALITY of nuclear particles - Abstract
A peculiar topological Hall effect (THE) is reported in a noncentrosymmetric ternary carbide GdCoC2. The GdCoC2 reveals a magnetic ordering transition from paramagnetic to ferromagnetic state at the Curie temperature TC = 15.6 K, followed by a commensurate-incommensurate phase transition at Tt = 14.1 K. Below Tt, the competition between an external magnetic field and magnetic interactions, including the Dzyaloshinskii–Moriya interaction, would give rise to characteristic spin textures with non-zero scalar spin chirality χ ijk , or even topologically protected spin configurations like skyrmions, for which the exotic spin-charge coupled phenomena are induced. Besides a large negative magnetoresistance (MR) up to ∼−52% at 14 K, a remarkably sharp topological Hall signal is observed with almost no anomalous Hall resistivity below 10 K. The topological Hall resistivity ( ρ xy T ) of GdCoC2 reaches a maximum value of ∼0.23 μΩ cm at 3 K under μ0H = 0.6 T. The mechanism underlying the exceptional THE with relatively large ρ xy T value in GdCoC2 is discussed in detail. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
7. Ferroelectric and negative piezoelectric properties in oxyhydroxide monolayers γ-XOOH (X = Al, Ga, and In).
- Author
-
Cheng, Xuli, Xu, Shaowen, Liu, Chao, Cui, Yaning, Ouyang, Wenbin, Jia, Fanhao, Wu, Wei, and Ren, Wei
- Subjects
PIEZOELECTRICITY ,MULTIFERROIC materials ,DATA warehousing ,MONOMOLECULAR films ,BARIUM titanate ,FERROELECTRICITY ,FERROELASTICITY ,LEAD titanate ,SOLAR neutrinos - Abstract
Two-dimensional (2D) multiferroic materials with coexisting ferroelasticity (FA) and ferroelectricity (FE) have potential applications in high-density data storage and sonar detectors. Here, based on first-principles calculations, we predict a series of stable 2D FA-FE multiferroic structures, namely, γ-XOOH (X = Al, Ga, and In) monolayers. By analyzing the lattice symmetry and orientation distribution of hydroxyls, we find that XOOH monolayers possess both in-plane ferroelastic and ferroelectric polarization, as well as antiferroelectric ordering caused by the anti-parallel alignment of hydroxyls. Interestingly, the perpendicular reorientation of in-plane FE polarization accompanies 90° ferroelastic switching. Moreover, they show an unusual negative transverse piezoelectric effect originated from the clamped-ion term. The multiferroic properties of the XOOH monolayers provide an excellent platform to study electroelastic effects. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
8. A peculiar topological Hall effect in noncentrosymmetric ternary carbide GdCoC2.
- Author
-
Xu, Yang, Ren, Wei, Ma, Shengcan, Chen, Changcai, Fang, Chunsheng, Luo, Xiaohua, and Mo, Zhaojun
- Subjects
HALL effect ,MAGNETORESISTANCE ,CURIE temperature ,PHASE transitions ,MAGNETIC transitions ,MAGNETIC fields ,CHIRALITY of nuclear particles - Abstract
A peculiar topological Hall effect (THE) is reported in a noncentrosymmetric ternary carbide GdCoC
2 . The GdCoC2 reveals a magnetic ordering transition from paramagnetic to ferromagnetic state at the Curie temperature TC = 15.6 K, followed by a commensurate-incommensurate phase transition at Tt = 14.1 K. Below Tt , the competition between an external magnetic field and magnetic interactions, including the Dzyaloshinskii–Moriya interaction, would give rise to characteristic spin textures with non-zero scalar spin chirality χ ijk , or even topologically protected spin configurations like skyrmions, for which the exotic spin-charge coupled phenomena are induced. Besides a large negative magnetoresistance (MR) up to ∼−52% at 14 K, a remarkably sharp topological Hall signal is observed with almost no anomalous Hall resistivity below 10 K. The topological Hall resistivity ( ρ xy T ) of GdCoC2 reaches a maximum value of ∼0.23 μΩ cm at 3 K under μ0 H = 0.6 T. The mechanism underlying the exceptional THE with relatively large ρ xy T value in GdCoC2 is discussed in detail. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
9. Mid-infrared swept cavity-enhanced photoacoustic spectroscopy using a quartz tuning fork.
- Author
-
Nie, Qinxue, Wang, Zhen, Borri, Simone, Natale, Paolo De, and Ren, Wei
- Subjects
PHOTOACOUSTIC spectroscopy ,TUNING forks ,PHOTOACOUSTIC effect ,QUANTUM cascade lasers ,MOLECULAR spectroscopy ,OPTICAL resonators - Abstract
We report the development of swept cavity-enhanced photoacoustic spectroscopy using a quartz tuning fork for ultra-sensitive and high-resolution molecular spectroscopy. By using a quantum cascade laser (QCL) as the mid-infrared light source, a dual-feedback Pound–Drever–Hall locking method is proposed to lock the QCL frequency to a continuously swept optical cavity. By placing an off-beam quartz-enhanced photoacoustic spectroscopy module in a 48-mm Fabry–Pérot cavity, we are able to achieve ultra-sensitive gas detection based on the doubly resonant photoacoustic effect. As a proof-of-concept, we use a distributed feedback QCL to exploit the CO line at 2190.02 cm
−1 , where the cavity-locked QCL is scanned over a spectral range of 10 GHz with a spectral resolution of ∼3 MHz. With the incident laser power of 7.3 mW, the optical cavity (finesse 1931) builds up the intracavity power beyond 3 W. Our photoacoustic spectrometer achieves the minimum detection limit of 375 part-per-trillion (ppt) at the averaging time of 150 s and the normalized noise equivalent absorption coefficient of 1.27 × 10−9 Wcm−1 Hz−1/2 . [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
10. Resolution improvement of optoelectronic tweezers using patterned electrodes.
- Author
-
Zaman, Mohammad Asif, Wu, Mo, Ren, Wei, Jensen, Michael A., Davis, Ronald W., and Hesselink, Lambertus
- Subjects
ELECTROMAGNETIC fields ,ELECTRODES ,ELECTRIC fields ,OPTICAL resolution ,NUMERICAL analysis - Abstract
An optoelectronic tweezer (OET) device is presented that exhibits improved trapping resolution for a given optical spot size. The scheme utilizes a pair of patterned physical electrodes to produce an asymmetric electric field gradient. This, in turn, generates an azimuthal force component in addition to the conventional radial gradient force. Stable force equilibrium is achieved along a pair of antipodal points around the optical beam. Unlike conventional OETs where trapping can occur at any point around the beam perimeter, the proposed scheme improves the resolution by limiting trapping to two points. The working principle is analyzed by performing numerical analysis of the electromagnetic fields and corresponding forces. Experimental results are presented that show the trapping and manipulation of micro-particles using the proposed device. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
11. Pressure induced isostructural phase transition with volume expansion in DyFeO3 orthoferrite.
- Author
-
Tao, Jiaqi, Zheng, Xu, Xu, Jianing, Dong, Hongliang, Chen, Bin, Ren, Wei, Cao, Shixun, and Gao, Tian
- Subjects
PHASE transitions ,SYMMETRY groups ,PEROVSKITE ,RAMAN spectroscopy ,CELL size - Abstract
The orthorhombic O and O′ structure phases of ABO
3 -type perovskites possess the same symmetry and quite different physical properties. In this work, a pressure induced isostructural O′–O phase transition with volume expansion and less distortion in DyFeO3 orthoferrite was experimentally observed and studied by high-pressure x-ray diffraction and Raman spectroscopy measurements. Up to 35.2 GPa, DyFeO3 crystallizes in an orthorhombic Pbnm symmetry structure. With no change in the symmetry group, distinct O′-phase and O-phase were verified below 13.1 GPa and above 15.1 GPa, respectively. Meanwhile, the lattice becomes less distorted and metrically pseudo-cubic on the high-pressure side. The cell volume expands by a step in the intermediate pressure window accompanied by a decrease in spontaneous strain. It is suggested that FeO6 octahedra are more compressible than DyO12 sites under pressure. This work claimed the physical mechanism underlying phonon dynamics and variation of local structure symmetry of DyFeO3 , which can be considered as the basic view for RFeO3 perovskites. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
12. Topological visualization of the plasmonic resonance of a nano C-aperture.
- Author
-
Zaman, Mohammad Asif, Ren, Wei, Wu, Mo, Padhy, Punnag, and Hesselink, Lambertus
- Subjects
- *
PLASMONICS , *VECTOR topology , *RESONANCE , *VECTOR fields , *METALLIC surfaces - Abstract
The plasmonic response of a nano C-aperture is analyzed using the Vector Field Topology (VFT) visualization technique. The electrical currents that are induced on the metal surfaces when the C-aperture is excited by light is calculated for various wavelengths. The topology of this two-dimensional current density vector is analyzed using VFT. The plasmonic resonance condition is found to coincide with a distinct shift in the topology which leads to increased current circulation. A physical explanation of the phenomenon is discussed. Numerical results are presented to justify the claims. The analyses suggest that VFT can be a powerful tool for studying the physical mechanics of nano-photonic structures. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
13. Volume-matched piezoelectric LaN/REN superlattices from first-principles.
- Author
-
Yang, Xiaoqing, Su, Tianhao, Hu, Minglang, Li, Yongchang, Gao, Heng, Jia, Fanhao, Fang, Le, Chen, Yangyang, Zhou, Bin, Su, Haijun, Bellaiche, L., and Ren, Wei
- Subjects
SUPERLATTICES ,MAGNETIC materials ,PIEZOELECTRIC devices ,ELASTIC constants ,RARE earth metals ,LEAD titanate ,NITRIDES ,BARIUM titanate - Abstract
LaN/rare earth nitride (REN) superlattices, having magnetic REN as one of the parent components, are constructed and studied by first-principles calculations. In particular, they are found to be mechanically and dynamically stable with (anti-)ferromagnetic and ferroelectric orderings. We reveal that the volume matching condition is applicable to these superlattices, which results in the elastic constant C
33 softening and, when combined with a small c/a value, induces a huge piezoelectric response near the unstrained state. We also show that in-plane biaxial strain can precisely control the nature (indirect or direct) and value of the electronic bandgap. Moreover, the unpaired magnetically active 4f-electrons reduce the c-direction off-centric distortion of the wurtzite structure, making possible the switching of the ferroelectric polarization. This work, therefore, reveals that the volume matching condition also applies to magnetic materials and provides guidance for the design of multiferroic rare-earth nitride superlattices in piezoelectric devices. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
14. Lead free 0.9Na1/2Bi1/2TiO3–0.1BaZr0.2Ti0.8O3 thin film with large piezoelectric electrostrain.
- Author
-
Yang, Hao, Zhao, Jinyan, Ren, Wei, Ye, Zuo-Guang, Vinayakumar, K. B., Dias, Rosana A., Pinto, Rui M. R., Zhuang, Jian, and Zhang, Nan
- Subjects
BISMUTH ,LEAD zirconate titanate films ,PIEZOELECTRIC thin films ,PIEZOELECTRIC devices ,THIN films ,SPIN coating ,DIELECTRIC loss ,FERROELECTRICITY - Abstract
A sodium bismuth titanate-based thin film is widely investigated lead-free piezoelectrics with potential applications for modern micro-devices such as PiezoMEMS. In this work, a 0.9Na
1/2 Bi1/2 TiO3 –0.1BaZr0.2 Ti0.8 O3 thin film was deposited on a Pt/Ti/SiO2 /Si (001) substrate by the sol–gel spin coating method. The deposited piezoelectric film shows low dielectric loss and high remnant polarization. The measured ferroelectricity loop showed a coercive field of 110 kV/cm and a saturation polarization of 46.83 μC/cm2 . The piezoelectric response of this thin film does not decrease from room temperature to around 100 °C. The fabricated piezoelectric device with bottom and top electrodes showed a large macro-scale strain value of ∼4% under the DC (30 V) and AC voltages (f = 800 kHz, Vpp = 10 V). [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
15. Infrared photodetector based on 2D monoclinic gold phosphide nanosheets yielded from one-step chemical vapor transport deposition.
- Author
-
Zhang, Yushuang, Chen, Jie, Chen, Cheng, Xu, Tengfei, Gao, Heng, Dong, Zhuo, Zhang, Yan, Li, Chang, Yu, Qiang, Yu, Wenzhi, Miao, Jinshui, Wang, Peng, Ren, Wei, Pan, Anlian, and Zhang, Kai
- Subjects
CHEMICAL vapor deposition ,NANOSTRUCTURED materials ,PHOTODETECTORS ,CHARGE carrier mobility ,GOLD nanoparticles - Abstract
Infrared detection by binary phosphides is of great interest due to their high carrier mobility, excellent stability, and high absorbance coefficient, as they have a wide range of applications in civil and military fields. As the only metastable phase in gold phosphide, Au
2 P3 has attracted great attention in fundamental research and optoelectronic applications. Here, we synthesized high-quality and environmentally stable Au2 P3 nanosheets through a modified facile one-step mineralization-assisted chemical vapor transport method. Through systematic infrared photoluminescence characterizations, it is found that the as-synthesized Au2 P3 nanosheets display an impressive mid-infrared luminescence band centered at about 6.64 μm (0.187 eV) at room temperature. Furthermore, Au2 P3 -based self-powered photodetectors display outstanding infrared detection performance with D* = 2.9 × 1010 Jones at 1550 nm and D* = 1.9 × 108 Jones at 2611 nm, respectively. Our results suggest that the synthesized Au2 P3 nanosheets could be promising candidates for future chip-based infrared nanophotonic and optoelectronic circuitry. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
16. In-plane magnetization and electronic structures in BiFeO3/graphene superlattice.
- Author
-
Chen, Chen, Zeng, Junjie, Ren, Yafei, Fang, Le, Wu, Yabei, Zhang, Peihong, Hu, Tao, Wang, Jian, Qiao, Zhenhua, and Ren, Wei
- Subjects
ELECTRONIC structure ,MAGNETIZATION ,MAGNETIC moments ,CHARGE exchange ,MECHANICAL properties of condensed matter - Abstract
We predict the presence of gapped electronic structures in an artificial superlattice of graphene embedded in (111)-oriented BiFeO
3 layers based on first-principles calculations. Due to the electron transfer and the proximity effect at the BiFeO3 /graphene interface, we find that magnetic moments of Fe atoms near a graphene layer were slightly less than that of bulk Fe atoms. Regarding the ferromagnetic moment orientation of Fe atoms in perovskite BiFeO3 , we reveal that the in-plane magnetization gives the ground state. The bandgap depends on the magnetization direction and the separation between the graphene layer and the perovskite BiFeO3 slab, which might be adjusted by applying external uniaxial stress in an experiment. Our results provide a route for designing hybrid 2D materials with emerging properties that are not available in single materials alone. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
17. Ferroic properties and piezoelectric response of Mg2XN3 (X = V, Cr).
- Author
-
Hu, Minglang, Yang, Xiaoqing, Su, Tianhao, Ma, Xiaonan, and Ren, Wei
- Subjects
WIDE gap semiconductors ,PIEZOELECTRIC materials ,RAW materials ,COMPUTER storage devices ,PIEZOELECTRICITY ,PIEZOELECTRIC thin films - Abstract
Nitrides are of increasing interest since they are usually wide-bandgap semiconductors and the available environmental raw materials are abundant. Using first-principles predictions, we reveal that Mg
2 XN3 (X = V, Cr) compounds show remarkably large ferroelectric polarization and piezoelectric response. Quantitative theoretical analysis further indicates the asymmetric orbital hybridization to be the origin of the ferroelectricity. Since Cr has one more 3d electron than V, it is found that Mg2 CrN3 is multiferroic with a ferromagnetic ground state. We further show that the epitaxial strain can regulate the piezoelectricity, and thus, both Mg2 CrN3 and Mg2 VN3 exhibit a larger piezoelectric response than the reported nitride piezoelectric materials under appropriate tensile epitaxial strain. Our findings provide guidance for potential applications of nitride materials in spintronics, sensors, and memory devices. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
18. Molecular beam epitaxy growth and strain-induced bandgap of monolayer 1T′-WTe2 on SrTiO3(001).
- Author
-
Li, Huifang, Chen, Aixi, Wang, Li, Ren, Wei, Lu, Shuai, Yang, Bingjie, Jiang, Ye-Ping, and Li, Fang-Sen
- Subjects
TUNNELING spectroscopy ,BAND gaps ,FERMI level ,CHARGE transfer ,MOLECULAR beam epitaxy ,MONOMOLECULAR films - Abstract
A monolayer 1T′-WTe
2 film is grown on SrTiO3 (001) with in-plane tensile strain. A height of ∼0.7 nm, obvious charge transfer, and incommensurate charge fluctuations in 1T′-WTe2 suggest strong coupling to the STO substrate. Scanning tunneling spectroscopy on the surface reveals that a large energy gap opens at the Fermi level with nearly zero conductance. The opened energy gap decreases with the increase in the WTe2 island size. The lack of the metallic edge state on monolayer 1T′-WTe2 /SrTiO3 (001) indicates the absence of the quantum spin Hall (QSH) state. Our study here demonstrates that the energy gap of monolayer 1T′-WTe2 can be tuned by lattice strain and illustrates the importance of interface coupling to realize the metallic edge state and QSH in monolayer 1T′-WTe2 . [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
19. Significantly enhanced electrical properties in CaBi2Nb2O9-based high-temperature piezoelectric ceramics.
- Author
-
Long, Changbai, Wang, Bo, Ren, Wei, Zheng, Kun, Fan, Huiqing, Wang, Dawei, and Liu, Laijun
- Subjects
PIEZOELECTRIC materials ,CURIE temperature ,PIEZOELECTRIC ceramics ,PIEZOELECTRICITY ,MAGNETS ,HIGH temperatures ,BISMUTH ,CERAMICS - Abstract
A synergetic effect of Li/Nd at the A site and W/Mn at the B site co-substitution on electrical properties of calcium bismuth niobate (CaBi
2 Nb2 O9 , CBNO)-based ceramics is proposed in this paper. CBNO primarily shows mixed p-type and ionic conduction due to a trace of oxygen vacancies (VO •• ). Both bulk resistivity (ρb ) and activity energy (Ea ) for conduction are dramatically increased by the co-substitution in Ca0.92 (Li1/2 Nd1/2 )0.08 Bi2 Nb2− x (W3/4 Mn1/4 )x O9 [CBNO-LN-x(WM), x = 0–0.02]. Consequently, the modified compositions almost show an intrinsic conducting mechanism due to a significant suppression of the VO •• concentration. Furthermore, the synergetic effect of Li/Nd at the A site and W/Mn at the B site greatly improves the piezoelectricity coefficient (d33 ), which is up to ∼21.1 pC/N in the optimized composition [CBNO-LN-10(WM)]. This combined with a high Curie temperature (TC = ∼946 °C) and high resistivity indicates that CBNO-LN-10(WM) is a good promising material in high-temperature piezoelectric applications. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
20. Velocity-amplified monostable dual-charged electret dome energy harvester using low-speed finger tapping.
- Author
-
Feng, Yue, Zhou, Zilong, Fu, Dongxiao, and Ren, Wei
- Subjects
HAMILTON'S equations ,KINETIC energy ,ENERGY harvesting ,POWER density - Abstract
Power generation from linear finger-tapping-based electrostatic energy harvesting (FTEEH) devices is hindered by the slow capacitance variation under low-speed finger-tapping (FT) motion. Herein, a velocity amplification mechanism is proposed, which exploits the snap-through behavior of a dual-charged electret monostable dome structure and thus greatly enhances the power generation of FTEEH devices from slow FT motion. The kinetic energy and velocity amplification during the buckling event were effectively predicted for various specimens using the modified Föppl–von Kármán equations and Hamilton's principle. A high degree of dynamic velocity amplification was demonstrated both theoretically and experimentally and quantified with respect to the velocity gain and power gain. Specifically, the velocity of the capacitance variation of the designed FTEEH device, driven by a slow FT motion at 2.7 cm/s, was substantially increased to 18.5 cm/s, affording a high velocity gain of 6.9 and a correspondingly large power gain of 6.8. The proposed velocity-amplified nonlinear FTEEH device was compared with recently developed linear FTEEH devices that do not utilize this velocity amplification mechanism and found to yield a large pulse width of 90.0 ms (full width) and a high volumetric power density of 1015.7 μW/cm
3 . [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
21. Substrate-modulated ferromagnetism of two-dimensional Fe3GeTe2.
- Author
-
Zhang, Luman, Song, Luyao, Dai, Hongwei, Yuan, Jun-Hui, Wang, Mingshan, Huang, Xinyu, Qiao, Lei, Cheng, Hui, Wang, Xia, Ren, Wei, Miao, Xiangshui, Ye, Lei, Xue, Kan-Hao, and Han, Jun-Bo
- Subjects
MAGNETIC circular dichroism ,FERROMAGNETISM - Abstract
We systematically investigated the modulation effects of substrates on the ferromagnetism properties of Fe
3 GeTe2 experimentally and theoretically. The polar refractive magnetic circular dichroism results demonstrate that the ferromagnetism could be modulated significantly by selecting different substrates. We explain this phenomenon using the first-principles calculation, revealing that it was induced by the lattice distortion and charge redistribution between the interfaces. Our work is useful to understand the fundamental mechanism of tunable ferromagnetism and paves the way for exploring interface physics and practical spintronic applications of two-dimensional ferromagnetic van der Waals crystals. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
22. Magnetic and electronic properties of Cr2Ge2Te6 monolayer by strain and electric-field engineering.
- Author
-
Wang, Kangying, Hu, Tao, Jia, Fanhao, Zhao, Guodong, Liu, Yuyu, Solovyev, Igor V., Pyatakov, Alexander P., Zvezdin, Anatoly K., and Ren, Wei
- Subjects
MONOMOLECULAR films ,SEMICONDUCTORS ,PHONON dispersion relations ,FERROMAGNETIC materials ,BAND gaps - Abstract
A two-dimensional ferromagnetic semiconductor Cr
2 Ge2 Te6 (CGT) was recently found to possess extraordinary characteristics and has great potential in the emerging field of spintronics. Using first-principles calculations, we examined the stabilities of this layered system by studying the cleavage energies and phonon dispersion. The ferromagnetic ground state has an in-plane spin polarization and bandgaps of about 0.26 eV by Perdew-Burke-Ernzerhof-van der Waals and 0.91 eV by the Heyd-Scuseria-Ernzerhof functional. Furthermore, we employed strain engineering and an external electric field to control the electronic and magnetic properties. In addition, we studied the magnetic anisotropy energy as well as its modulation under the electric field. We predict the CGT monolayer to be the easy plane ferromagnet, and the perpendicular electric field could affect the ferromagnetic stability along different directions. Our obtained results provide guidance for the potential applications of monolayer CGT for magnetic nanodevices, spintronic, and straintronic applications. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
23. Electronic transport of organic-inorganic hybrid perovskites from first-principles and machine learning.
- Author
-
Li, Limeng, You, Yang, Hu, Shunbo, Shi, Yada, Zhao, Guodong, Chen, Chen, Wang, Yin, Stroppa, Alessandro, and Ren, Wei
- Subjects
PEROVSKITE ,DENSITY functional theory ,MACHINE learning ,METHYLAMMONIUM ,GREEN'S functions - Abstract
Using the data-mining machine learning technique and the non-equilibrium Green's function method in combination with density functional theory, we studied the electronic transport properties of the organic-inorganic hybrid perovskite MAPbI
3 . The band structures of MAPbI3 from first-principles show that the ferroelectric and antiferroelectric dipole configurations have very little influence on the energy bandgap. Furthermore, we investigated the tunnel junctions made of MAPbI3 and 48 different metal electrodes, with the same fixed lattice constant as MAPbI3 . With the increase in the number of perovskite unit cells, the electron transmission coefficients are found to decrease exponentially in general. For data mining studies, several different methods are employed to develop models for predicting electron transport properties. In particular, the gradient boosting regression tree model was tested and found to be the most effective tool among all these algorithms for fast prediction of the electron transmission coefficients and performance ranking of all studied metal electrodes. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
24. Local structures and temperature-driven polarization rotation in Zr-rich PbZr1-<italic>x</italic>Ti<italic>x</italic>O3.
- Author
-
Wang, Zhen, Zhang, Nan, Yokota, Hiroko, Glazer, A. M., Yoneda, Yasuhiro, Ren, Wei, and Ye, Zuo-Guang
- Subjects
PIEZOELECTRICITY ,POLARIZATION (Nuclear physics) ,SYNCHROTRONS ,MONTE Carlo method ,DISTRIBUTION (Probability theory) - Abstract
PbZr
1- Tix Ox 3 , which has abundant structural variations in the corresponding physical properties, has been used in a large variety of applications. To understand the effect of the structure on its high-performance piezoelectric properties, its local and average structures are studied. Total scattering data have been obtained from high-energy synchrotron powder diffraction experiments at 20 K and 300 K. Using the reverse Monte Carlo method, information on cation displacements has been extracted from X-ray Pair Distribution Function data. This suggests that the local disorder of the B cations is mainly driven by thermal motion, while the local disorder of Pb is most likely caused by more complex factors, such as displacive disorder. Both rhombohedral and monoclinic local polarizations are observed in Zr-rich PZT, whose directions depend on temperature. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
25. Domain structure and in-plane switching in a highly strained Bi0.9Sm0.1FeO3 film.
- Author
-
Chen, Weigang, Ren, Wei, You, Lu, Yang, Yurong, Chen, Zuhuang, Qi, Yajun, Zou, Xi, Wang, Junling, Sritharan, Thirumany, Yang, Ping, Bellaiche, L., and Chen, Lang
- Subjects
- *
THIN films , *IRON oxides , *HYSTERESIS loop , *POLARIZATION (Electricity) , *MICROSCOPY - Abstract
We report the domain structure and ferroelectric properties of a 32 nm-thick Bi0.9Sm0.1FeO3 film epitaxially grown on a LaAlO3 (LAO) substrate. This film exhibits a monoclinic Mc phase, with its monoclinic distortion and anisotropy of in-plane (IP) lattice parameters being both smaller than those of pure BiFeO3 (BFO) grown on LaAlO3. Polarization hysteresis loops measured using a quasi-planar capacitor show an in-plane polarization up to 30 μC/cm2. Piezoresponse force microcopy demonstrates that a 180° in-plane polarization switching accompanied by a 90° domain wall rotation takes place after electric poling. First-principles calculations suggest the differences between highly strained Sm-substituted and pure BiFeO3. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
26. Low temperature epitaxial growth of Ge quantum dot on Si(100)-(2×1) by femtosecond laser excitation.
- Author
-
Er, Ali Oguz, Ren, Wei, and Elsayed-Ali, Hani E.
- Subjects
- *
LOW temperatures , *EPITAXY , *GERMANIUM , *QUANTUM dots , *FEMTOSECOND lasers , *PULSED laser deposition , *ATOMIC force microscopy , *ELECTRON diffraction - Abstract
Low temperature epitaxy of Ge quantum dots on Si(100)-(2×1) by femtosecond pulsed laser deposition under femtosecond laser excitation was investigated. Reflection high-energy electron diffraction and atomic force microscopy were used to analyze the growth mode and morphology. Epitaxial growth was achieved at ∼70 °C by using femtosecond laser excitation of the substrate. A purely electronic mechanism of enhanced surface diffusion of the Ge adatoms is proposed. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
27. Gated armchair nanotube and metallic field effect.
- Author
-
Ren, Wei, Cho, T. H., Leung, T. C., and Chan, C. T.
- Subjects
- *
CARBON nanotubes , *ELECTRIC fields , *ELECTRIC potential , *DENSITY functionals , *TRANSISTORS - Abstract
We propose a useful metallic field effect element based on the electric field control of armchair single-wall carbon nanotube. The electron conduction channels are enhanced by imposing a transverse gate voltage. Multiple Dirac points have been revealed theoretically by our density functional and tight binding calculations. Our electron transport results show that the performance of such unique transistors depends mainly on the diameter of nanotube exploited. The critical field strength required decreases rapidly with the tube diameter. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
28. Structural stability and polarization analysis of rhombohedral phases of HfO2.
- Author
-
Ouyang, Wenbin, Jia, Fanhao, Liu, Chang, Cheng, Xuli, Meng, Yaping, Gao, Ruiling, Picozzi, Silvia, and Ren, Wei
- Subjects
- *
STRUCTURAL stability , *FERROELECTRIC thin films , *PHASE transitions , *FERROELECTRICITY , *HAFNIUM oxide - Abstract
Since the experimental observation of a rhombohedral phase of hafnium oxide, there remains controversy over whether this phase belongs to the R3 or R3m space group. Moreover, the origin of polarization in these two rhombohedral phases has not been comparatively elucidated. Here, we present a theoretical study comparing the relative stability and ferroelectricity of the R3 and R3m phases of HfO2, representing two potential forms of heavily Zr-doped ferroelectric thin films of hafnia found recently. We comprehensively investigate their structural stability and polarization response under in-plane compressive strain. A phase transition from R3 to R3m is discovered under biaxial compressive strain. The direction and magnitude of polarization in both phases can be tuned by strain. Through symmetry mode analysis, we elucidate the improper nature of ferroelectricity. These findings may advance understanding of ferroelectricity in hafnia thin films. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
29. Local displacive correlation in the tetragonal relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-0.15PbTiO3.
- Author
-
Wang, Zhen, Zhuang, Jian, Li, Fei, Ren, Wei, Ye, Zuo-Guang, and Zhang, Nan
- Subjects
- *
RELAXOR ferroelectrics , *MONTE Carlo method , *DISTRIBUTION (Probability theory) , *BARIUM titanate , *ATOMIC models , *LOW temperatures - Abstract
Over the past decades, lead-based relaxor ferroelectrics have served as the model systems to unravel the relationship between electromechanical properties and local structure. Here, by employing pair distribution function analysis and the reverse Monte Carlo method, we investigate the local structural features and their temperature dependence in relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-xPbTiO3 with x = 0.15 (PZN-15PT), which has a tetragonal average structure, but displays frequency dependence at low temperatures. The refined atomic model suggests that ordered polar nanoregions (PNRs) originate from the strong atomic displacive correlation, and their polar directions are the same as the crystallographic symmetry axis. The dipoles in the disordered matrix have weak correlations and can be averaged into a global tetragonal symmetry. These findings establish a detailed picture of the local structure of lead-based relaxor ferroelectrics and provide a deeper insight into the nature of PNRs. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
30. Nonlinear optical properties of lanthanum doped lead titanate thin film using Z-scan technique.
- Author
-
Zhao, Qingchun, Liu, Yun, Shi, Wensheng, Ren, Wei, Zhang, Liangying, and Yao, Xi
- Subjects
LANTHANUM ,LEAD ,NONLINEAR optics - Abstract
Lanthanum doped lead titanate (PLT) thin films with good surface morphology and perovskite structure were fabricated by the metalo-organic decomposition process. Their nonlinear optical property was investigated by Z-scan technique. PLT30 thin films on the quartz substrate display strong nonlinear optical effects. A nonlinear refractive index as high as 3.0×10-7 esu was obtained for the thin film. All the results show that PLT ferroelectric thin films are promising materials for nonlinear optics. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]
- Published
- 1996
- Full Text
- View/download PDF
31. Large rotating field entropy change in ErFeO3 single crystal with angular distribution contribution.
- Author
-
Huang, Ruoxiang, Cao, Shixun, Ren, Wei, Zhan, Sheng, Kang, Baojuan, and Zhang, Jincang
- Subjects
SINGLE crystals ,ANGULAR distribution (Nuclear physics) ,MAGNETIC anisotropy ,MAGNETIC cooling ,MAGNETIZATION - Abstract
We report the rotating field entropy of ErFeO3 single-crystal in a temperature range of 3-40 K. The giant magnetic entropy change, ΔSM = -20.7 J/(kg K), and the refrigerant capacity, RC = 273.5 J/kg, are observed near T=6 K. The anisotropic constants at 6 K, K1 = 1.24× 103 J/kg, K2 = 0.74 × 103 J/kg, in the bc plane are obtained. By considering the magnetocrystalline anisotropy and Fermi-Dirac angular distribution along the orientation of spontaneous magnetization, the experimental results can be well simulated. Our present work demonstrates that ErFeO3 crystal may find practical use for low temperature anisotropic magnetic refrigeration. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
32. Manipulation of the crystal structure defects: An alternative route to the reduction in lattice thermal conductivity and improvement in thermoelectric performance of CuGaTe2.
- Author
-
Wu, Wenchang, Li, Yapeng, Du, Zhengliang, Meng, Qingsen, Sun, Zheng, Ren, Wei, and Cui, Jiaolin
- Subjects
CRYSTAL structure ,THERMOELECTRICITY ,THERMAL conductivity measurement ,SEEBECK coefficient ,ANTISITE defects ,ENERGY bands - Abstract
Here, we present the manipulation of the crystal structure defects: an alternative route to reduce the lattice thermal conductivity (κL) on an atomic scale and improve the thermoelectric performance of CuGaTe2. This semiconductor with defects, represented by anion position displacement (u) and tetragonal deformation (η), generally gives low κL values when u and η distinctly deviate from 0.25 and 1 in the ideal zinc-blende structure, respectively. However, this semiconductor will show high Seebeck coefficients and low electrical conductivities when u and η are close to 0.25 and 1, respectively, due to the electrical inactivity caused by an attractive interaction between donor-acceptor defect pairs (GaCu2+ + 2VCu-). [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
33. Conduction mechanisms for off-state leakage current of Schottky barrier thin-film transistors.
- Author
-
Yeh, Kuan-Lin, Lin, Horng-Chih, Huang, Rou-Gu, Tsai, Ren-Wei, and Huang, Tiao-Yuan
- Subjects
THIN film transistors ,FIELD emission - Abstract
Conduction mechanisms for the off-state leakage in Schottky barrier thin-film transistor were explored. It was found that the field-emission process dominates the leakage conduction of the device with the conventional structure as the field strength in the drain junction becomes high, and results in the strong gate-induced drain leakage (GIDL) like phenomenon. In contrast, for the device with a field-induced-drain structure, the high-field region is pulled away from the silicided drain. As a result, the field-emission conduction is eliminated, so the GIDL-like leakage current is effectively suppressed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]
- Published
- 2001
- Full Text
- View/download PDF
34. Local structures and temperature-driven polarization rotation in Zr-rich PbZr1-<italic>x</italic>Ti<italic>x</italic>O3.
- Author
-
Wang, Zhen, Zhang, Nan, Yokota, Hiroko, Glazer, A. M., Yoneda, Yasuhiro, Ren, Wei, and Ye, Zuo-Guang
- Subjects
- *
PIEZOELECTRICITY , *POLARIZATION (Nuclear physics) , *SYNCHROTRONS , *MONTE Carlo method , *DISTRIBUTION (Probability theory) - Abstract
PbZr1-
x Tix O3, which has abundant structural variations in the corresponding physical properties, has been used in a large variety of applications. To understand the effect of the structure on its high-performance piezoelectric properties, its local and average structures are studied. Total scattering data have been obtained from high-energy synchrotron powder diffraction experiments at 20 K and 300 K. Using the reverse Monte Carlo method, information on cation displacements has been extracted from X-ray Pair Distribution Function data. This suggests that the local disorder of the B cations is mainly driven by thermal motion, while the local disorder of Pb is most likely caused by more complex factors, such as displacive disorder. Both rhombohedral and monoclinic local polarizations are observed in Zr-rich PZT, whose directions depend on temperature. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.