Ferroelectric LiNbO3 Research Articles

Activation of Immobilized Glucose Oxidase Enzyme by Acoustic Wave Resonance Oscillation

Abstract Glucose oxidase enzyme was immobilized on ferroelectric LiNbO3 single crystals that were able to generate acoustic wave resonance oscillations by radio frequency electric power. The generation of the 3.6–14.7 MHz acoustic waves with lattice distortion vertical to the surface caused increases in the enzyme activity for glucose oxidation by decreasing the activation energy of reaction. A mechanism is proposed in which the acoustic waves enhance the interactions between the glucose substrate and the enzyme.

Electro-optical behaviour and dielectric dynamics of harvested ferroelectric LiNbO3 nanoparticle-doped ferroelectric liquid crystal nanocolloids

Nanocolloids comprising harvested ferroelectric LiNbO3 nanoparticles (≈25 nm) and ferroelectric liquid crystals were prepared and investigated. The impact of the amount of dispersed nanoparticles (0.01 wt%, 0.05 wt%, 0.10 wt%) on the electro-optical, dielectric and material parameters of the ferroelectric liquid crystals (FLCs) has been demonstrated. The dopant strongly influences the switching characteristics and has an effect on the saturation voltage of the FLC materials. Electro-optical measurements demonstrated that a relatively large (0.10 wt%) LiNbO3 dopant concentration decreases the response time and saturation voltage by approximately 40% and 25% respectively, compared with non-doped FLCs. The effect of LiNbO3 nanoparticle concentration on the material and dynamical parameters (i.e. spontaneous polarization, dielectric permittivity, dielectric absorption, dielectric strength, dc conductivity, and rotational viscosity) is presented. The observed behaviours are discussed in terms of capture of impurity ions on the surface of the harvested LiNbO3 nanoparticles. Ion capturing leads to enhancement of the localized electric field inside the smectic layers. The fast switching response and the low operational voltage of these FLC nanocolloids support their application in nanometric scale electronic devices.

Microstructure and memory characteristics of ferroelectric LiNbO3/ZnO composite thin films on Pt/TiO2/SiO2/Si substrates

Composite thin films consisting of ferroelectric LiNbO3 (LN) and ZnO semiconductor layers were grown on Pt/TiO2/SiO2/Si substrates and characterized. The films were single c-axis orientation and had well-defined interfaces without any evidence of interfacial interaction and diffusion. Due to the ferroelectric polarization of LN, counterclockwise capacitance–voltage memory windows were observed clearly. The memory window increased with applied voltage and no obvious charge injection happened. At ±8V, a large memory window of ∼3.3V was exhibited. The present results suggest that LN ferroelectric films combined with ZnO semiconductor would hold promise for high-performance nonvolatile memory devices.

Direct Probing of Charge Injection and Polarization‐Controlled Ionic Mobility on Ferroelectric LiNbO3 Surfaces

Mapping surface potential with time-resolved Kelvin probe force microscopy (tr-KPFM) in LiNbO3 periodically poled single crystals reveals activation of the surface ionic subsystem. Electric fields of certain strength induce injection of charge, formation of an active region in its vicinity and uneven distribution of screening charge on the opposite ferroelectric domains. Tr-KPFM technique allows investigating these phenomena in details.

First-principles investigation of graphene on the ferroelectric LiNbO3(001) surface

Recent experiments on graphene-ferroelectric field-effect transistors have introduced an excellent nonvolatility functionality. However, the mechanism of the antihysteresis behavior of graphene on some ferroelectric substrates is controversial. We carry out first-principles calculations to study the interface interaction between graphene and the ferroelectric LiNbO3(001) surface, and find that, when putting a bilayer graphene on a clean surface, the spontaneous polarization field can induce a gap of about 311 meV. If the clean surface is passivated with hydrogen, the electrons are trapped at the interface and nearly screen the polarization field. Our results reveal that the antihysteresis behavior originates from the charge trapping which occurs at the hydrogenated graphene-ferroelectric interface.

Electrical properties and local domain structure of LiNbO3 thin film grown by ion beam sputtering method

The nanocrystalline ferroelectric LiNbO3 films on (001) Si substrates with the random orientation of polycrystalline grains and the predominance of the grains with lateral orientation of the polar axis were grown using the ion beam sputtering method. The remanent polarization and the coercive field are 12 µC/cm2 and 29 kV/cm, respectively. The thermal annealing leads to the coarsening of the grains. The appearance of the “local texture,” which gives rise to the unipolarity of the heterostructures caused by the predominance of the one direction in the vertical component of the spontaneous polarization, is investigated.

Growth of highly near-c-axis oriented ferroelectric LiNbO3 thin films on Si with a ZnO buffer layer

Ferroelectric LiNbO3 thin film of high near-c-axis orientation was grown on Si by pulsed laser deposition using a thin ZnO buffer layer of high c-axis orientation. Both the LiNbO3 film and the ZnO layer consist of columnar grains with random in-plane twist relative to each other. The c axes of LiNbO3 grains tilt small angles with respect to the film growth direction and the deviation angles follow nearly Gaussian probability distribution within 5°. The out-of-plane tilt nucleation of LiNbO3 lattices on the waved surfaces of the ZnO layer leads to the near-c-axis oriented growth of the LiNbO3 film.

Vacancy-induced magnetism in ferroelectric LiNbO3 and LiTaO3

The possibilities of d0 magnetism induced by various defects in ferroelectric LiTaO3 and LiNbO3 are investigated by ab initio calculations. The stoichiometric LiTaO3 and LiNbO3 are nonmagnetic. The neutral Li, Nb and Ta vacancies could induce magnetism in LiNbO3 and LiTaO3, due to the spin-polarization of O 2p electrons. The neutral O vacancy could bring about the magnetic moment in LiNbO3, due to the spin-polarization of Nb s electron at the impurity band. For LiNbO3 and LiTaO3 with two neutral Li, Nb and Ta vacancies, ferromagnetic coupling are found to be energetically more favorable than antiferromagnetic coupling, except when two neutral Ta vacancies are 1st nearest-neighbored. For LiNbO3 with two neutral O vacancies, the antiferromagnetic coupling is preferred when two neutral O vacancies are 1st and 2nd nearest-neighbored, and the ferromagnetic coupling is energetically favorable when two neutral O vacancies are 3rd nearest-neighbored. It is possible to obtain the d0 LiNbO3 and LiTaO3 multiferroic materials through the introduction of appropriate intrinsic vacancies in them.

Linear and nonlinear optical response of LiNbO3 calculated from first principles

The dielectric function and second-harmonic generation spectrum of ferroelectric LiNbO(3) are calculated from first principles. The calculations are based on the electronic structure obtained within density functional theory. The use of the GW approach to account for quasiparticle effects and the subsequent solution of the Bethe-Salpeter equation lead to a dielectric function in excellent agreement with measured data. The second harmonic generation spectrum calculated within the independent (quasi) particle approximation predicts strong nonlinear coefficients for photon energies above about 1.5 eV. The comparison with measured data suggests that the inclusion of self-energy effects in the nonlinear response improves the agreement with experiment.

Multifunctional Protein-Enabled Patterning on Arrayed Ferroelectric Materials

This study demonstrates a biological route to programming well-defined protein-inorganic interfaces with an arrayed geometry via modular peptide tag technology. To illustrate this concept, we designed a model multifunctional fusion protein, which simultaneously displays a maltose-binding protein (MBP), a green fluorescence protein (GFPuv) and an inorganic-binding peptide (AgBP2C). The fused combinatorially selected AgBP2C tag controls and site-directs the multifunctional fusion protein to immobilize on silver nanoparticle arrays that are fabricated on specific domain surfaces of ferroelectric LiNbO(3) via photochemical deposition and in situ synthesis. Our combined peptide-assisted biological and ferroelectric lithography approach offers modular design and versatility in tailoring surface reactivity for fabrication of nanoscale devices in environmentally benign conditions.

Single-shot time-frequency imaging spectroscopy using an echelon mirror

We demonstrate single-shot time-frequency imaging spectroscopy with an echelon mirror for measuring ultrashort laser pulses as well as ultrafast responses of materials using the same optical setup. The echelon mirror produces a spatially encoded time delay for the probe pulse whereby both the probe and pump pulses are focused on samples with small spot size. Using the optical Kerr gate apparatus, we successfully mapped the time-frequency images of ultrashort laser pulses and subsequently evaluated the chirp characteristics with the phase-retrieval procedure on a single-shot basis. By simply replacing the Kerr medium with samples, we could also visualize the phonon-polariton oscillations in ferroelectric LiNbO3.

Synthesis and piezoelectric response of cubic and spherical LiNbO3 nanocrystals

Methods have been developed for the shape-selective synthesis of ferroelectric LiNbO3 nanoparticles. Decomposition of the single-source precursor, LiNb(O-Et)6, in the absence of surfactants, can reproducibly lead to either cube- or sphere-like nanoparticles. X-Ray diffraction shows that the LiNbO3 nanoparticles are rhombohedral (R3c). Sample properties were examined by piezoresponse force microscopy (PFM) and Raman where both sets of nanoparticles exhibit ferroelectricity. The longitudinal piezoelectric coefficients, d33, varied with shape where the largest value was exhibited in the nanocubes (17 pm V−1 for the cubes versus 12 pm V−1 for spheres).

Erratum: Correlated Thermal Motion in Ferroelectric LiNbO3 Studied Using Neutron Total Scattering and a Rietveld Analysis

Erratum: Correlated Thermal Motion in Ferroelectric LiNbO3 Studied Using Neutron Total Scattering and a Rietveld Analysis

Correlated Thermal Motion in Ferroelectric LiNbO3 Studied Using Neutron Total Scattering and a Rietveld Analysis

Correlated Thermal Motion in Ferroelectric LiNbO3 Studied Using Neutron Total Scattering and a Rietveld Analysis

Magnetic Properties in ${\rm Li}_{1-{\rm x}}{\rm A}_{\rm x}{\rm NbO}_{3}$ (${\rm A}={\rm Ca}$, Sr, and Ba) and ${\rm LiNbO}_{3-{\rm y}}{\rm M}_{\rm y}$ (${\rm M}={\rm F}$, Cl, and Br) From First-Principles Study

Based on first-principles study, the magnetic properties of the substitution for Li by A ( A=Ca, Sr, and Ba) and for O by M ( M=F, Cl, and Br) in LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> have been investigated. These substitutions in LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> could bring about the magnetic moments, which mainly arise from the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> orbital of Nb atoms surrounding the doping element. The magnetism induced by the substitutions in ferroelectric LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> provides one alternative route to fabricate the multiferroic materials.

Far-infrared dispersion of complex dielectric constant in the ferroelectric near-stoichiometric LiNbO 3:Fe

The dielectric properties of near-stoichiometric LiNbO 3:Fe single crystal have been investigated by using a terahertz time domain spectroscopy (THz–TDS) in a frequency range of 0.7–1.6 THz at room temperature. When coupled with an applied external optical field, an obvious photorefractive effect was observed, resulting in the modulation of the complex dielectric constant for near-SLN:Fe. The variation of refractive index |Δ n| has a linear relationship on scale with the applied light intensity accompanied with a steplike decrease. These findings were attributed to the internal space charge field of photorefraction and the light-induced domain reversal in the crystal.

Luminescence and second harmonic generation in Eu 3+/Eu 2+ embedded B 2O 3: LiNbO 3 non-linear glass–ceramics

Multifunctional europium doped Li 2O–Nb 2O 3–B 2O 2 glass has been prepared by melt-quench method. Through subsequent heat treatments glass has then been transformed into glass ceramics containing ferroelectric LiNbO 3 phase. The glass ceramics have shown enhanced Eu 3+ emission compared to parent glass when excited by 266 nm radiation. The emission measurements of glass ceramics have also shown the presence of Eu 2+ state along with Eu 3+ and Eu 2+ state was found to increase when glass was heated in inert atmosphere. Lifetime of the 5D 0 level of the Eu 3+ has been measured and a significant increase is found in case of glass ceramic prepared around glass transition temperature. Glass ceramics have also shown good second harmonic generation (SHG) with pulsed 1064 nm laser excitation.

Mechanical and thermal properties of Tb 2(MoO 4) 3 crystals

The mechanical and thermal properties of single crystal Tb 2(MoO 4) 3 have been systematically studied. The result of microhardness measurement indicates that the crystal belongs to the soft materials category. The thermodynamic parameters obtained from DTA analysis were used for determining the type of liquid–solid interface during crystal growth. Negative thermal expansion along the c-axis was observed, and this behavior was attributed to the bent Tb–O–Mo bonds. The specific heat of the crystal was measured to be 0.122 cal g −1 K −1 at 293.15 K. The thermal conductivity of Tb 2(MoO 4) 3 at room temperature was found to be smaller than that of representative ferroelectric LiNbO 3.

Polarization-specific adsorption of organic molecules on ferroelectric LiNbO3 surfaces

Polarization effect on adsorption of d-cysteine molecules on ferroelectric LiNbO3 surfaces is studied by a combination of infrared spectramicroscopy and spatially resolved x-ray absorption near edge spectroscopy. It is shown that even in the absence of any electronic excitation (optical or thermal), the adsorption is still polarization-specific with preferential d-cysteine deposition occurring on positive domains. This observation rules out molecular adsorption solely due to pyroelectric or photoinduced charge and suggests possible dipole-dipole interaction between polar d-cysteine molecules and ferroelectric polarization dipoles. The surface chemistry related to polarization-dependent variations in Li/Nb concentration is also implicated as a contributing factor in the domain-specific adsorption of d-cysteine.

Ultraviolet laser-induced photovoltaic effects in miscut ferroelectric LiNbO3 single crystals

This paper investigates the photovoltaic properties of miscut LiNbO3 single crystal with different thicknesses under irradiation of a 248 nm ultraviolet laser pulse with 20 ns duration without an applied bias. Nanosecond photovoltaic response is observed and faster rise time is obtained in thinner samples. In accord with the 248 nm laser duration, the full width at half maximum of the photovoltaic signals keeps a constant of ∼ 20 ns. With decrease of the crystal thickness, the photovoltaic sensitivity was improved rapidly at first and then decreased, and the maximum photovoltage occurred at 0.38 mm-thick single crystal. The present results demonstrate that decreasing the LiNbO3 single crystal thickness can obtain faster response time and improve the photovoltaic sensitivity.