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Deposition Pressure Dependent Electric Properties of (Hf, Zr)O2 Thin Films Made by RF Sputtering Deposition Method
摘要： To study the applications for ferroelectric non-volatile memory and ferroelectric memristor, etc., deposition pressure dependent electric the properties of (Hf, Zr)O2 thin films by RF sputtering deposition method were investigated. The bottom electrode was TiN thin film to produce stress effect on the formation of orthorhombic phase and top electrode was Pt thin film by DC sputtering deposition. Deposition pressure was varied along with the same other deposition conditions, for example, sputtering power, target to substrate distance, post-annealing temperature, annealing gas, annealing time, etc. The structural and electric properties of the above thin films were investigated. As a result, it is confirmed that the electric properties of the (Hf, Zr)O2 thin films depend on the deposition pressure which affects structural properties of the thin films, such as, structural phase, ratio of the constituents, etc.
关键词： (Hf,Zr)O2,Sputtering,Deposition pressure,Ferroelectric
更新于2025-09-23 15:23:52
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Enhanced Second Harmonic Generation from Ferroelectric HfO <sub/>2</sub> -Based Hybrid Metasurfaces
摘要： Integrated nonlinear metasurfaces leading to high-efficiency optical second harmonic generation (SHG) are highly desirable for optical sensing, imaging, and quantum photonic systems. Compared to traditional metal-only metasurfaces, their hybrid counterparts, where a non-centrosymmetric nonlinear photonic material is incorporated in the near field of a metasurface, they can significantly boost SHG efficiency. However, it is difficult to integrate such devices on-chip due to material incompatibilities, thickness scaling challenges and the narrow band gaps of nonlinear optical materials. Here, we demonstrate significantly enhanced SHG in on-chip integrated metasurfaces by using nanometer thin films of ferroelectric Y:HfO2. This material has the merit of CMOS compatibility, ultra-violet transparency up to 250 nm and significant scalability down to sub 10 nm when deposited on silicon. We observe a twenty times magnitude enhancement of the SHG intensity from the hybrid metasurface compared to a bare ferroelectric HfO2 thin film. Moreover, a 3-fold SHG enhancement is observed from the hybrid metasurface compared to a control structure using non-ferroelectric HfO2, demonstrating a major contribution to the SHG signal from ferroelectric Y:HfO2. The effective second-order nonlinear optical coefficient χ(2) of Y:HfO2 is determined to be 6.0 ± 0.5 pm/V, which is comparable to other complex nonlinear photonic oxide materials. Our work provides a general pathway to build an efficient on-chip nanophotonic nonlinear light source for SHG using ferroelectric HfO2 thin films.
关键词： second harmonic generation (SHG),nonlinear photonics,metasurface,plasmonics,ferroelectric Y:HfO2
更新于2025-09-23 15:23:52
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Electrode Dependence of Local Electrical Properties of Chemical-Solution-Deposition-Derived BiFeO <sub/>3</sub> Thin Films
摘要： The nanoscale electrical properties of chemical solution deposition(CSD)-derived BiFeO3 grown on pulsed laser ablated La0.67Sr0.33MnO3//SrTiO3 (001) thin film heterostructures are investigated using a host of scanning probe microscopy techniques, including electrostatic force microscopy(EFM), scanning Kelvin probe microscopy(SKPM), piezoresponse force microscopy (PFM), and conductive AFM(CAFM). EFM and SKPM confirm the p-type nature of the CSD derived BFO thin films as well as charge accumulation at the film surface after electrical bias. For BiFeO3 films of a fixed thickness (~35 nm), the local current-voltage (I-V) behavior obtained by CAFM is strongly dependent on the La0.67Sr0.33MnO3 bottom electrode thickness. BiFeO3 films on a 20 nm thick La0.67Sr0.33MnO3 demonstrate the typical switchable diode behavior governed by polarization orientation. However, when the thickness of La0.67Sr0.33MnO3 is reduced to less than 5 nm, the BiFeO3 films show only forward diode behaviors regardless of polarization orientation, when the applied bias is up to ±4 V. Higher sweep bias (i.e. ±8V) breaks down the diode, following which the BiFeO3 film shows strong resistive switching. The interface band structure for the ultra-thin LSMO case, which is very sensitive to accumulation/depletion of carriers at the BFO-LSMO interface, is suggested as the trigger for this resistive switching.
关键词： chemical solution deposition,ferroelectric,electrical properties,ultrathin lanthanum strontium manganite,p-type bismuth ferrite thin films
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Influence of Composition and Preparation on Crystalline Phases and Morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) Relaxor-Ferroelectric Terpolymer
摘要： The influence of chemical composition and crystallisation conditions on the ferroelectric and paraelectric phases and the resulting morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer films with 55.4/37.2/7.3 mol% or with 62.2/29.4/8.4 mol% of VDF/TrFE/CFE was studied. Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) with 75/25 mol% VDF/TrFE was employed as reference material. Fourier-Transform Infrared Spectroscopy (FTIR) was used to determine the fractions of the relevant terpolymer phases, and X-Ray Diffraction (XRD) was employed to assess the crystalline morphology. The FTIR results show an increase of the fraction of paraelectric phases after annealing. On the other hand, XRD results indicate a more stable paraelectric phase in the terpolymer with higher CFE content.
关键词： P(VDF-TrFE-CFE) terpolymer,Curie transition,relaxor-ferroelectric polymer,ferroelectric and paraelectric phases
更新于2025-09-23 15:22:29
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Ferroelectric Origin and Distortion Modes in Doped BiFeO <sub>3</sub> by Crystallography Approach
摘要： There are conflicts about the ferroelectric origin and the relationship of two distortion modes, namely, the ferroelectric (FE) mode and antiferrodistortive (AFD) mode. Here the two distortion modes and enhanced ferroelectric properties (Pr=89.5 μC cm-2) are observed in BiFeO3 thin films doped with small radius Mg2+ (A-site) deposited on (111) Pt/Ti/SiO2/Si substrates by a sol-gel method, the relationship of the two distortion modes turns from cooperative to competitive as the FE mode strengthens. A new explanation of ferroelectric origin and distortion modes in doped BiFeO3 by the Defect Dipoles Driven Distortions Theory (abbreviate DDD) from crystallography is reported. Meanwhile, the crystal structure regulation mechanism of doped BiFeO3 thin films with substantially enhanced ferroelectric properties is also put forward. The distances of the positive and negative charge center in [FeO6] octahedrons evidently increase by Mg2+ doping compared with that in the Bi0.9Sm0.1Fe0.95Mn0.05O3 (BSFMO). The change of distances is contributed to the law of the atomic migration from the move of oxygen vacancies and the attraction of defect dipoles. A positive effect on ferroelectric properties of the appropriate increase in oxygen vacancies is explored, which is explained by "the probability of possible position that oxygen vacancies occurred" and "the relationship between the leakage current and the overlapping oxygen positions". The potential structure and more suitable doping ions are successfully predicted by the crystal structure regulation mechanism. In addition, it brings a new direction for the search of other structure regulation ions so as to realize the perfect ferroelectric properties for practical application, which will become an important beginning of ferroelectric materials design.
关键词： ferroelectric properties,structural distortions,crystallography,ferroelectric origin,defect dipoles
更新于2025-09-23 15:22:29
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The Growth Window of Ferroelectric Epitaxial Hf <sub/>0.5</sub> Zr <sub/>0.5</sub> O <sub/>2</sub> Thin Films
摘要： The metastable orthorhombic phase of hafnia is generally obtained in polycrystalline films, whereas in epitaxial films its formation has been much less investigated. We have grown Hf0.5Zr0.5O2 films by pulsed laser deposition and the growth window (temperature and oxygen pressure during deposition, and film thickness) for epitaxial stabilization of the ferroelectric phase is mapped. The remnant ferroelectric polarization, up to around 24 μC/cm2, depends on the amount of orthorhombic phase and strain, and increases with temperature and pressure for fixed film thickness. Leakage current decreases by increasing thickness and temperature, and particularly by reducing oxygen pressure. The coercive electric field (EC) depends on thickness (t) according the EC - t-2/3 scaling, which is observed by the first time in ferroelectric hafnia, and the scaling extends to thickness below 5 nm. The proven ability to tailor functional properties of high quality epitaxial ferroelectric Hf0.5Zr0.5O2 films paves the way towards progress in understanding their ferroelectric properties and prototyping devices.
关键词： Growth parameters,Pulsed laser deposition,Ferroelectric HfO2,Ferroelectric oxides,Epitaxial stabilization,Oxide thin films
更新于2025-09-23 15:22:29
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Efficient separation of photo-generated charges in a ferroelectric molecular wire: nonadiabatic dynamics study on 3,5-dicyano-1,7-dimethylopyrrolo[3,2-f]indole trimer
摘要： In this work we propose and verify computationally a novel idea of spontaneous separation of charges photo-generated in a highly polar molecular 'wire'. The nuclear and electronic structure of the investigated system, so as the evolution of charge carriers, are characterized at the semi-empirical OM2/MRCI level of theory. Results point to the conclusion that 90% of optically prepared excitons break into charge carriers (holes and electrons) localized on the opposite monomeric units of the trimer on the time scale of 30 fs. Our findings can be helpful in design of photoactive and conducting components for molecular photovoltaic applications.
关键词： ferroelectric polymers,nonadiabatic molecular dynamics,molecular photovoltaics,photo-generated charge separation,molecular wire
更新于2025-09-23 15:22:29
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Lead-free Ag <sub/> 1-3 <i>x</i> </sub> La <sub/><i>x</i> </sub> NbO <sub/>3</sub> Antiferroelectric Ceramics with High Energy Storage Density and Efficiency
摘要： Environmentally benign lead-free bulk ceramics with high recoverable energy density (Wrec) are very attractive in advanced pulsed power capacitors. In this work, composition engineering was adopted by La3+ modification to improve the energy storage performance of Ag1-3xLaxNbO3 ceramics. It was found the antiferroelectric (AFE) phase was stabilized after La3+ substitution, as a result of the reduced tolerance factor t. Significant improvement of Wrec and energy storage efficiency (η) were achieved with value of 3.12 J/cm3 and 0.63 for x=0.02 at an electric field of 230 kV/cm, more than 1.5 times the value of pure AgNbO3 (Wrec=1.9 J/cm3, η=0.40). The excellent energy storage properties are resulted from the increased antiferroelectric-ferroelectric phase transition electric field (EF), ferroelectric-antiferroelectric phase transition electric field (EA) and breakdown electric field (Eb). The enhanced Eb was ascribed to the decreased grain size and increased electrical resistivity upon La3+ modification. The feature makes Ag1-3xLaxNbO3 a potential candidate for energy storage applications.
关键词： energy storage,ferroelectricity/ferroelectric materials,lead-free ceramics,dielectric materials/properties
更新于2025-09-23 15:22:29
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Nanoconfinement-Induced Giant Electrocaloric Effect in Ferroelectric Polymer Nanowire Array Integrated with Aluminum Oxide Membrane to Exhibit Record Cooling Power Density
摘要： The electrocaloric effect (ECE) offers a unique mechanism to realize environmentally friendly and highly efficient solid-state cooling that completely differs from the conventional vapor-compression refrigeration. Here a new class of hybrid films composed of ferroelectric polymer nanowire array and anodic aluminum oxide (AAO) membrane is reported, which displays pronounced ECE driven by relatively low electric fields. Under confinement and orientation of AAO channels on the crystallization of the polymer, the polymer nanowire array shows substantially enhanced ECE that is about three times that of the corresponding thin films. Simultaneously, the integrated AAO membrane forms thermally conducting channels for the polymer nanowires, enabling the efficient transfer of cooling energy and operation of the EC materials under high frequencies, which are unattainable based on the currently available EC structures. Consequently, the integrated polymer nanowire–AAO hybrid film exhibits the state-of-the-art cooling power density, outperforming the current ferroelectric polymers, ceramics, and composites. This work opens a new route for the development of scalable, high-performance EC materials for next-generation refrigeration.
关键词： electrocaloric effect,nanoconfinement,cooling power density,heat transfer,ferroelectric polymer
更新于2025-09-23 15:22:29
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Significance of Micro and Nano PZT Particles on Dielectric and Piezoelectric Properties of PZT-PVDF Composites
摘要： PZT-PVDF composites were prepared using different particle size of PZT and a hot press apparatus has been used for making samples. The structural and compositional analysis of the composite sample was done by using Scanning Electron Microscope (SEM) and Energy Dispersive Analysis of X-rays (EDAX) respectively. The grain size of the ball milled PZT powder was analyzed using powder X-Ray Diffraction (XRD). The samples were poled at a fixed temperature for about an hour under different poling fields. The dielectric constant (εr) and the piezoelectric properties like piezoelectric strain coefficient (d33) and voltage coefficient (g33) of composite have been analyzed.
关键词： composite,ferroelectric materials,dielectric constant,strain coefficient,voltage coefficient,particle size,lead zirconate titanate
更新于2025-09-23 15:22:29