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Deposition of orientation-controlled thick (K,Na)NbO<sub>3</sub> films on metal substrates by repeated hydrothermal deposition technique
摘要： (K,Na)NbO3 thick films were grown at 240°C on Ni-based metal substrates by repeated hydrothermal method. The metal substrates were covered with two types of buffer layers; SrRuO3/LaNiO3 and SrRuO3. Film thickness monotonically increased with increasing number of deposition cycles. The 27 μm-thick film was obtained on the metal substrate with SrRuO3/LaNiO3 by four cycles. The obtained films tended to show {100}c orientation and their degree of orientation increased with increasing number of deposition cycles. Films deposited on SrRuO3/LaNiO3-covered metal substrates showed more highly {100}c orientation compared with those on SrRuO3-covered metal substrates. Remnant polarization and coercive field measured at 5 kHz were 12 μC/cm2 and 70 kV/cm, while their effective values of piezoelectric coefficient (d33) was 35–40 pm/V for both films. These properties remained unchanged irrespective of a number of deposition cycles despite the orientation change of films. These results show that repeated hydrothermal deposition technique is one of the effective ways to prepare thick (K,Na)NbO3 films on metal substrates.
关键词： Metal substrate,Lead-free (K,Na)NbO3 film,Orientation control,Ferroelectric and piezoelectric properties,Hydrothermal,synthesize
更新于2025-09-12 10:27:22
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Proceedings of Meetings on Acoustics [Acoustical Society of America 172nd Meeting of the Acoustical Society of America - Honolulu, Hawaii (28 November – 2 December 2016)] - Distribution of point defects in phononic periodically poled lithium niobate
摘要： The concentration of point defects is investigated along the neighboring domains in a ZX-cut periodically poled lithium niobate (PPLN) plate. PPLN is a ferroelectric phononic crystal (FPC) in which the inversion of polarization occurs across the interdomain wall. The spectra of photoluminescence (PL) are recorded along the domain structure parallel to the x-axis, at room temperature. The PL spectra reveal a nonuniform distribution of defects along the PPLN. The striking result is that some defects have narrow extrema in PL-intensity right in the interdomain wall location. The spread in PL intensity from the average is higher in PPLN when compared to single crystal lithium niobate. Engineering application of these findings may be new non-destructive characterization method of ferroelectric phononic crystals.
关键词： photoluminescence,phononic periodically poled lithium niobate,point defects,ferroelectric phononic crystals
更新于2025-09-12 10:27:22
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The composition and poling-dependent photovoltaic studies in ferroelectric (Bi1?xSrx)(Fe1?xTix)O3 thin films
摘要： The polycrystalline (Bi1?xSrx)(Fe1?xTix)O3 (x = 0.0, 0.05, 0.10, and 0.20) thin films were grown on Pt(111)/TiO2/SiO2/ Si(100) substrates using chemical solution deposition technique. X-ray diffraction pattern revealed that pure BiFeO3 film is crystallized in rhombohedrally distorted crystal structure. However, the patterns for doped samples displayed a mixed-phase (rhombohedral + tetragonal) structure. The Raman studies revealed the emergence of B mode related to the tetragonal phase along with the modes corresponding to the rhombohedral phase in doped systems. The photovoltaic studies displayed a large photovoltaic response for the parent compound with an open-circuit voltage of 0.47 V. However, it showed a decrease in the photovoltaic response with an increase in composition x. The composition-dependent photovoltaic response could be correlated to the evolution of tetragonal phase fractions and the polarization. Additionally, the poling-dependent photovoltaic studies revealed the dominant role played by the polarization in comparison with the interface Schottky effect. This work gives an improved understanding of the ferroelectric photovoltaic mechanism and, therefore, may offer guidelines to design and optimize photovoltaic materials.
关键词： ferroelectric,photovoltaic,chemical solution deposition,polarization,thin films
更新于2025-09-12 10:27:22
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Ferroelectric PZT thin films for photovoltaic application
摘要： The ferroelectric photovoltaic response characteristics of Lead Zirconate Titanate (PZT) thin film in metal-ferroelectric-metal (MFM) configuration is studied under 33 mode upon exposure to UV radiations. PZT thin films of 180 nm are prepared on inter-digital electrodes patterned silicon substrate (with silicon dioxide as insulating layer) using chemical solution deposition (CSD) technique followed by rapid thermal annealing. PZT thin films are found to be in single phase and possess high electrical polarization (50μC/cm2). Significant increase in photocurrent and large value of open circuit voltage (1.0 V) is observed for the prepared ferroelectric photovoltaic film under UV illumination.
关键词： Lead zirconium titanate,Chemical deposition,Polarization,Ferroelectric,Photovoltaics
更新于2025-09-12 10:27:22
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Dielectric and electro-optic properties of two biphenylyl benzoate-based ferroelectric mesogens with tilted hexagonal phases
摘要： Two partially fluorinated ferroelectric liquid crystals (2F3R, 3F3R) with biphenylyl benzoate core have been investigated by frequency domain dielectric spectroscopy and electro-optic method. Both the compounds exhibit SmC* phase over a wide range of temperature along with tilted hexatic phase SmF* and soft crystal phases SmJ* (in 2F3R) and SmG* (in 3F3R) and one coexistence phase of (SmF*+SmC*). Both BOO phason and tilt phason relaxations are observed in SmF* phase and cooperative relaxation behaviour is also observed in crystal-like smectic phases. Goldstone mode relaxation is observed in SmC* phase and Maxwell Wagner mode is observed in all the phases. In 2F3R soft mode is detected in both SmC* and SmA* phases but not in 3F3R which melts directly to isotropic phase from SmC* phase. Compounds possess moderate values of spontaneous polarisation and exhibit quite sharp electrical response especially in 2F3R. Rotational viscosities, pitch and elastic constant are also measured. Effect of chain length and fluorination on various physical parameters has been discussed.
关键词： soft mode,tilted hexagonal phase,BOO and tilt phason mode,spontaneous polarisation,Ferroelectric liquid crystal,response time
更新于2025-09-12 10:27:22
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Reflection Spectra of Composite Photonic Crystals Based on Anodic Alumina Filled with Ferroelectric Sodium Nitrite
摘要： Re?ection spectra of a composite one-dimensional photonic crystal (PC) based on porous anodic alumina ?lled with ferroelectric sodium nitrite have been recorded in the wavelength range of 400 to 1200 nm. Signi?cant spectral shifts of the ?rst and second stopbands are revealed for the composite PC. The stopband spectral half-width is found to decrease by a factor of four to ?ve. The possibility of applying composite alumina-based photonic crystals as selective narrowband mirrors is discussed.
关键词： reflection spectra,ferroelectric sodium nitrite,photonic crystals,anodic alumina,stopbands
更新于2025-09-12 10:27:22
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In-situ stress modulated ferroelectric photovoltaic effect in cluster-assembled TbFe <sub/>2</sub> /Bi <sub/>5</sub> Ti <sub/>3</sub> FeO <sub/>15</sub> heterostructural films
摘要： TbFe2/Bi5Ti3FeO15 heterostructural ?lms were prepared by inserting cluster-assembled TbFe2 microdiscs into a Bi5Ti3FeO15 matrix using low energy cluster beam deposition combined with sol-gel methods. The phase structure, ferroelectric properties, bandgap, photovoltaic spectral response, and performances of the ferroelectric photovoltaic effect were modulated by the in situ stress driven by magnetostriction of TbFe2 clusters under external magnetic ?elds. The short-circuit current, open-circuit voltage, and power conversation ef?cient increase with the in situ stress, reaching 0.026 mA/cm2, 9.5 V, and 5.88 (cid:2) 10(cid:3)2%, respectively, under a maximum in-stress of 0.075 GPa. So the high open-circuit voltage above bandgap is attributed to the distinct bandgap shifting and the effective separation of photogenerated electron-hole pairs derived from the in situ stress induced large built-in ?eld. The in situ stress dominated symmetry breaking contributes to the improvement of the power conversation coef?cient. The in situ dynamic internal stress provides a high ef?cient approach to modulate and improve ferroelectric photovoltaic effects.
关键词： magnetostriction,in situ stress,ferroelectric photovoltaic effect,bandgap shifting,TbFe2/Bi5Ti3FeO15 heterostructural films
更新于2025-09-12 10:27:22
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Second harmonic microscopy of poled x-cut thin film lithium niobate: Understanding the contrast mechanism
摘要： Thin film lithium niobate has been of great interest recently, and an understanding of periodically poled thin films is crucial for both fundamental physics and device developments. Second-harmonic (SH) microscopy allows for the noninvasive visualization and analysis of ferroelectric domain structures and walls. While the technique is well understood in bulk lithium niobate, SH microscopy in thin films is largely influenced by interfacial reflections and resonant enhancements, which depend on film thicknesses and substrate materials. We present a comprehensive analysis of SH microscopy in x-cut lithium niobate thin films, based on a full three-dimensional focus calculation and accounting for interface reflections. We show that the dominant signal in backreflection originates from a copropagating phase-matched process observed through reflections, rather than direct detection of the counterpropagating signal as in bulk samples. We simulate the SH signatures of domain structures by a simple model of the domain wall as an extensionless transition from a ?χ(2) to a +χ(2) region. This allows us to explain the main observation of domain structures in the thin-film geometry, and, in particular, we show that the SH signal from thin poled films allows to unambiguously distinguish areas, which are completely or only partly inverted in depth.
关键词： lithium niobate,thin films,ferroelectric domain structures,Second-harmonic microscopy,nonlinear optics
更新于2025-09-12 10:27:22
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The Perfect Solar Cell
摘要： Within a few years only, methylammonium lead iodide (MAPbI3), and later more advanced organic metal halide perovskites, have performed an unprecedented rally towards highest power conversion efficiencies. A team of six scientists at Karlsruhe Institute of technology (KIt) has found evidence for ferroelectric domains in MAPbI3 thin-films. For their research, the team was awarded the Erwin-Schr?dinger-Prize of the helmholtz Association and the helmholtz Foundation.
关键词： Perovskite solar cells,Ferroelectric domains,MAPbI3,Photovoltaics,Energy conversion
更新于2025-09-12 10:27:22
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Ferroelectric barium titanate derivatives containing Mo and Mg for transparent photovoltaic applications
摘要： Using first-principles methods, we investigate the electronic properties of the [Ba(Mo1/2,Mg1/2)O3]x-[BaTiO3]1?x solid solution derived from barium titanate as a potential candidate to be used in photovoltaic devices. Focusing on the bandgap and its origin, we study the effect of different possible Mo and Mg contents, arrangements, and phases of [Ba(Mo1/2,Mg1/2)O3]x-[BaTiO3]1?x. We find that [Ba(Mo1/2,Mg1/2)O3]0.25-[BaTiO3]0.75 is a viable candidate for use in transparent photovoltaics due to its energy bandgap of 2.6 eV in the rhombohedral phase. In all cases, [Ba(Mo1/2,Mg1/2)O3]x-[BaTiO3]1?x materials exhibit spontaneous polarization that allows the exploitation of the bulk photovoltaic effect and in principle may allow high power conversion efficiency exceeding the Shockley-Queisser limit for these materials.
关键词： ferroelectric,photovoltaic,transparent,bandgap,barium titanate
更新于2025-09-11 14:15:04