Single Crystal Plates Research Articles

Optical Trapping-Induced New Polymorphism of β-Cyclodextrin in Unsaturated Solution

A new polymorph of β-cyclodextrin (β-CD) was produced by optical trapping with a 1064 nm continuous wave laser beam in D2O solution. Upon optical trapping of β-CD in unsaturated solutions, a single prism crystal or multiple plate crystals were formed at and near the laser focus. The resulting crystals differed in morphology and in the Raman spectrum. Furthermore, the solubility of the plate crystal in D2O was much lower than that of the prism crystal, implying that the former crystal is thermodynamically more stable than the latter. The single-crystal X-ray crystallographic analysis showed that the prism crystal has practically the same crystallographic parameters as the crystal reported for β-CD dodecahydrate and is thought to be the thermodynamically most stable phase. These results reveal that the plate crystal is a new polymorph characteristic of optical trapping. Crucially, this is the first success to produce a new polymorph via the laser-induced crystallization method. More interestingly, the generation probability of these two polymorphs turned out to be a critical function of the initial β-CD concentration, laser power, and laser polarization mode. In particular, the polymorphism could be entirely controlled by adjusting the initial concentration, which allowed us to obtain pure prism and plate crystals at high and low CD concentrations, respectively. The dynamics and mechanism of this unique optical trapping-induced polymorphism are discussed in terms of the pre-nucleation cluster size determined by the initial concentration, the trapping efficiency as a function of the cluster size and the laser power, and the molecular alignment in the pre-nucleation clusters steered by the laser polarization mode.

Effect of aspect ratio of piezoelectric constituents on the energy harvesting performance of magneto-mechano-electric generators

In this study, we investigate the effect of the aspect ratio (length (L)/width (W)) of piezoelectric constituents on the energy harvesting performance of cantilever-structured magneto-mechano-electric energy generators comprising magnetoelectric composites. 56 Pb(Mg1/3,Nb1/3)O3–10PbZrO3–34PbTiO3 (PMN-PZT) single crystal fiber bundled plates with different aspect ratios (L/W = 0.59, 0.78, 1, 1.25, and 1.6), a magnetostrictive Ni plate and NdFeB permanent magnet proof mass were used to fabricate the magneto-mechano-electric generator. The results of a finite element analysis showed that the output electric potential is strongly dependent on the aspect ratio of PMN-PZT single crystal fiber plates for dual potential-inducing mechanisms, i.e., the magnetic torque (flexural transverse) and magnetic magnetostrictive (in-plane longitudinal) vibrations. However, magnetostrictive vibrations rather than magnetic torque dominate the generated output energy. The experimental results show good agreement with the results of the finite element analysis. The magneto-mechano-electric harvester with a PMN-PZT single crystal fiber aspect ratio of 1.6 shows a ∼440% increment in the root mean square voltage and power and a ∼300% enhancement in the power density measured at a load resistance of 100 kΩ and a magnetic field of 10 Oe.

Influences of crack-face electric boundary conditions on stress intensity factors of ferroelectric single crystals

It is a challenge to determine the crack-tip stress intensity factors (SIFs) of ferroelectrics under large-scale domain switching. An I-integral method has been previously established for an impermeable crack. In order to investigate the influences of crack-face electric boundary conditions on domain switching and the SIFs, this paper develops the I-integral for permeable and conducting cracks to extract the crack-tip SIFs of ferroelectric materials. For all crack-face electric boundary conditions, the I-integral is independent of integration area size, even though the integration area contains domain walls. The phase field model based on the time-dependent Ginzburg-Landau theory combined with the I-integral method is employed to simulate a tensile test of a cracked PbTiO3 single-crystal plate through increasing the tensile stress step by step. The simulations show that the domain evolution process can be divided into three stages by two large-scale polarization reorientations (a local switching and a global switching) for all crack-face electric boundary conditions, including impermeable, permeable and conducting cases. In each stage, almost invariable domain pattern results in a nearly linear variation of the mode-I SIF. The mode-I SIF in the impermeable case is very close or even identical to that in the permeable case but significant larger than that in the conducting case. Except the local switching away from the crack, a local or global switching generally reduces the mode-I SIF obviously. Applied an increasing electric field, the domain evolution process contains two stages separated by a global switching causing a sudden increase of the mode-I SIF for the impermeable case and a sudden fall for the permeable and conducting cases.

Study of Lapping and Polishing Performance on Lithium Niobate Single Crystals.

Recently, the range of crystal materials used in industrial microelectronics has significantly increased. Lithium niobate single crystals are most often used in integrated optics, due to the high values of optical and electro-optical coefficients. An integral-optical circuit based on a lithium niobate single crystal is a key element in the production of local high-precision fiber-optic gyroscopic devices used in civil and military aviation and marine technologies. In the process of production of an integral-optical circuit, the most labor-intensive operations are mechanical processing, such as lapping and polishing. Technological problems that arise while performing these operations are due to the physical and mechanical properties of the material, as well as target surface finish. This work shows the possibility to achieve the required surface quality of lithium niobate single crystal plates by mechanization of lapping and polishing process in this article.

Giant Bulk Photostriction and Accurate Photomechanical Actuation in Hybrid Perovskites

AbstractIt is well known that a material may be strained by mechanical, thermal, electric, magnetic, and light stimuli, and this effect has been extensively utilized in industries. However, the observed photostrictive effect usually occurs in the very thin surface layer and the photostriction of most bulk materials has been too small to be applied in a device until now. Here, a giant bulk photostriction is achieved, evidenced by the measured linear strain ε ≈ 0.72–0.43% for MAPbI3 single crystal plates of 0.05–0.5 mm in thickness under the 532 nm illumination. More importantly, the MAPbI3 single crystals also exhibit accurate photomechanical actuation functionality and the actuator can precisely adjust the displacement from hundreds of pm to tens of μm or the angle of a hard mirror from ≈10−6 to 0.2 degree. The present work not only unveils the huge bulk photostriction in lead halide perovskite single crystals but also demonstrates a wireless photomechanical actuator which is much simpler and smaller than conventional piezoelectric actuators.

Study of the influence of treatment on the strength of undoped indium antimonide single-crystal plates

The method of plane-transverse bending was used to measure the strength of thin single-crystal plates of undoped InSb with a crystallographic orientation of (100). It was found that the strength of the plates (thickness ≤ 800 μm) depends on their processing. Using a full processing cycle (grinding and chemical polishing) allows to increase the strength of InSb plates by 2 times (from 3.0 to 6.4 kg/mm2). It is shown that the dependence of strength on processing for wafers with (100) orientation is similar to this dependence for wafers (111), while the strength of wafers (111) is 2 times higher. The contact profilometry method was used to measure the roughness of thin plates, which also passed successive processing steps. It was found that during a full cycle of processing, the roughness of InSb plates decreases (Ra from 0.6 to 0.04 μm), leading to a general smoothing of the surface roughness. The strength and roughness of the (100) InSb and GaAs wafers are compared. It was found that the strength of GaAs cut wafers is 2 times higher than the strength of InSb cut wafers and slightly increases after a full cycle of their processing. It was shown that the roughness of GaAs and InSb plates after a full cycle of surface treatment is significantly reduced: 10 times for InSb due to overall surface leveling and 3 times for GaAs (Rz from 2.4 to 0.8 μm) due to a decrease in the peak component. Conducting a full cycle of processing InSb plates can increase their strength by removing broken layers by sequential operations and reducing the risk of mechanical damage.

Optical grating and THz polarizer based on normal grade single crystal diamond fast fabricated by fs laser

In this paper, we have researched the fs laser induced the phase transition in the normal grade single crystal diamond plates. The results show that the optical properties and electric properties of the irradiated region closely relate to the degree of the phase transition. We have succeeded in fabricating the optical gratings on the surface and inside of the diamond plates even though only partial material in the irradiated region phase-transforms from single crystal phase to amorphous phase. The gratings can be used as terahertz polarizers likewise. The modulation depths are 53% at 1.6 THz and 40% at 2.52 THz, which can be further improved by optimizing the fabrication parameters and the fill factors of gratings. We have also fabricated the electric wire on the surface of the normal grade diamond plate.

Time Transient of Calcium and Phosphate Ion Adsorption by Rutile Crystal Facets in Hanks' Solution Characterized by XPS.

For the elucidation of the mechanism of calcium phosphate formation on commercially pure titanium (CP Ti) in the human body, rutile TiO2 single crystal plates with (001), (110), and (111) facets, namely, TiO2(001), TiO2(110), and TiO2(111), and polycrystalline plates (TiO2(poly)) were immersed in a simulated body fluid, Hanks' solution (Hanks), for 100-105 s, and the adsorption of calcium and phosphate ions was precisely characterized employing X-ray photoelectron spectroscopy (XPS). Previously published CP Ti data were used for comparison. Prior to immersion in Hanks, oxygen content was more than twice as high as that of titanium due to the existence of hydroxyl groups and water on the oxides. After immersion in Hanks, the composition and chemical state of the TiO2 substrates remained unchanged. Among the electrolytes contained in Hanks, only calcium and phosphate ions were adsorbed by and incorporated onto TiO2 surfaces. Adsorption of calcium ions onto rutile did not exhibit any systematic increase of calcium with immersion time except TiO2(poly). Adsorption of phosphate ions was initially constant, followed by an increase with the logarithm of immersion time. The adsorption rate of phosphate ions decreased in the following order: TiO2(001), TiO2(poly), TiO2(111), CP Ti, and TiO2(110). The coordination number and band gap of each crystal facet of rutile is important for the adsorption and incorporation of phosphate ions. Regular calcium phosphate formation on CP Ti is possibly enabled by the surface oxide film, which consists chiefly of amorphous TiO2. However, calcium phosphate formation kinetics on CP Ti differed from those on the TiO2 crystalline phase. These findings may further the understanding of CP Ti hard tissue compatibility.

Side-bounce beamlines using single-reflection diamond monochromators at Cornell High Energy Synchrotron Source

The design and implementation of new beamlines featuring side-bounce (single-reflection) diamond monochromators at Cornell High Energy Synchrotron Source (CHESS) are described. Undulator radiation is monochromated using aninterchangeable set of diamond crystal plates reflecting radiation in the horizontal (synchrotron) plane, where each crystal plate is set to one of the low-index Bragg reflections (111, 220, 311 and 400) in either Bragg or Laue reflection geometries. At the nominal Bragg angle of 18° these reflections deliver monochromated X-rays with photon energies of 9.7, 15.9, 18.65 and 22.5 keV, respectively. An X-ray mirror downstream of the diamond monochromator is used for rejection of higher radiation harmonics and for initial focusing of themonochromated beam. The characteristics of the X-ray beam entering the experimental station were measured experimentally and compared with the results of simulations. A reasonable agreement is demonstrated. It is shown thatthe use of selected high-dislocation-density `mosaic' diamond single-crystal plates produced using the chemical vapor deposition method yields a few-fold enhancement in the flux density of the monochromated beam in comparison with that delivered by perfect crystals under the same conditions. At present, the Functional Materials Beamline at CHESS, which is used for time-resolved in situ characterization of soft materials during processing, has been outfitted with the described setup.

Vibrational motion of a vortex lattice induced near the surface of a type-II superconductor by an external low-frequency ac magnetic field

The theoretical description and experimental study of a reversible vibrational vortex motion induced in a type-II superconductor by a weak low-frequency ac magnetic field are discussed. The case where the external magnetic field and vortex lines are parallel to the surface of the superconductor is considered. The equilibrium positions of vortices near a surface, the amplitude of their vibrations, and the contribution of this process to the dynamic permeability ${\ensuremath{\mu}}_{v}$ are calculated. In these calculations, the interactions of vortices with each other, with the surface, and with pinning centers are considered within the discrete vortex lattice model. The calculations in the London approximation are compared with the results obtained within a more accurate model, including the spatial variation of the order parameter in the vortex core by means of a variational function. It is shown that the structural parameters of the vortex lattice near the surface depend on the accuracy of the description of the intervortex interactions, but the contribution ${\ensuremath{\mu}}_{v}$ appears to be model independent. It is important that this conclusion is valid in the case of the exponential approximation for the interaction between vortex rows. In this approximation, the problem under consideration is analytically examined, and formulas describing the dependences of the parameters of the vortex lattice and the contribution ${\ensuremath{\mu}}_{v}$ on the external dc magnetic field and the characteristics of a superconductor are derived. The theoretical results are compared with experimental data for a $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$ high-${T}_{c}$ superconducting single-crystal plate. The magnetic field is parallel to the plate, i.e., to the crystallographic $ab$ plane. A strong anisotropy of the properties and shape of the crystal is considered when analyzing the experimental data. A procedure for the determination of the experimental dependence ${\ensuremath{\mu}}_{v}(H)$ is described. It is shown that the reversible vibrations of vortices occur near the planes of the single-crystal plate in the direction of the crystallographic $c$ axis, whereas vortices enter its lateral ends and leave them (along the structural layers) even at a small magnetic field amplitude of about 1 Oe. It is found that the developed theoretical description reproduces the experimental data ${\ensuremath{\mu}}_{v}(H)$ in the entire studied range of temperatures and magnetic fields under the assumptions that pinning is isotropic and the length of interaction of vortices with pinning centers is close to the coherence length.

Dynamic crystal plasticity modeling of single crystal tantalum and validation using Taylor cylinder impact tests

In this work, we extend a dislocation-density based constitutive theory for the dynamic thermomechanical behavior of crystals to body centered cubic (BCC) tantalum. Strain rate and temperature dependence of the slip resistance in the model is incorporated via an expression for the state-dependent instantaneous saturation dislocation density and a dynamic recovery fraction that affects the rate of generation of immobile dislocation density. Crystallographic slip along 111 on the {110} or {112} planes as well as their combination are examined. The Schmid stress serves as the driving force for dislocation motion and the twinning/anti-twinning sense of slip on {112} planes is accounted for by introduction of Peierls stress that depends upon this sense. The model parameters are calibrated using a two-stage Bayesian approach against experimentally generated uniaxial stress-strain compression curves at quasi-static and high strain rates over a range of temperatures. Velocity-time histories from single crystal flyer plate impact experiments were also used to parameterize this model. The calibrated model was applied to simulate previous Taylor cylinder impact experiments. Our results show that the model must include slip on {110} and {112} planes and also account for the twinning versus anti-twinning sense of slip on {112} planes, to appropriately represent the orientation dependence of the flow stress and match the deformed geometry of the single crystal Taylor cylinders.

Symmetry breaking in single-crystal SrTiO3 plates: EPR manifestations

Results of the electron paramagnetic resonance (EPR) studies of Fe3+ and Mn4+ impurity centers in high-quality single-crystal SrTiO3 plates with thickness are presented. Impurities served the paramagnetic probes of the crystal structure. Analysis of the collected data indicates that the symmetry of the crystal structure of thin (001) and (110) oriented strontium titanate plates above lowers in the bulk from the cubic to tetragonal. The structure of this high-temperature tetragonal state is different from that of the conventional low-temperature antiferrodistorsive phase and has not been reported for SrTiO3 before. It is shown that the effect does not originate from the residual stress; its magnitude and particular manifestations depend on plate orientation, surface quality and geometry of a sample. Peculiarities of the observed phenomenon are presented and the possible scenario of its realization is discussed.

Расчет эффективности удвоения частоты излучения субтерагерцового гиротрона за счет решеточной нелинейности в монокристаллической пластине InP

In this work, we calculated the efficiency of second harmonic generation for sub-THz gyrotron radiation in a single-crystal InP plate embedded in a conical metal waveguide. For the values of the losses at the doubled frequency (depending on the degree of purity of the InP crystal), the dimensions of the wafer are revealed that provide the optimal effective frequency conversion. Thus, the conversion factor f –>2f can reach 5 W/kW^2 when pumped at a frequency of 263 GHz and a loss of alpha_2f = 0.1 cm^-1. The possibility of a noticeable increase in the efficiency of frequency doubling with fine tuning of the phase matching due to the selection of the size of the submicron gap between the InP plate and the plates of the metal waveguide is shown. The results obtained can be used to solve applied problems in the field of dynamic nuclear polarization spectroscopy and nuclear magnetic resonance studies.

Релаксация поляризации при статическом прямом флексоэлектрическом эффекте в монокристалле SrTiO-=SUB=-3-=/SUB=-

The results of a study of the dielectric polarization induced by spherical bending of thin single-crystal SrTiO3 plates are presented, and the flexoelectric coefficients are estimated. The processes of relaxation of inhomogeneous deformation and induced polarization are investigated.

Absolute X-ray energy measurement using a high-accuracy angle encoder.

This paper presents an absolute X-ray photon energy measurement method that uses a Bond diffractometer. The proposed system enables the prompt and rapid in situ measurement of photon energies over a wide energy range. The diffractometer uses a reference silicon single-crystal plate and a highly accurate angle encoder called SelfA. The performance of the system is evaluated by repeatedly measuring the energy of the first excited state of the potassium-40 nuclide. The excitation energy is determined as 29829.39 (6) eV, and this is one order of magnitude more accurate than the previous measurement. The estimated uncertainty of the photon energy measurement was 0.7 p.p.m. as a standard deviation and the maximum observed deviation was 2 p.p.m.

Facet-selective charge separation in two-dimensional bismuth-based photocatalysts

In this review, we summarize recent advances in the facet design of bismuth-based single-crystal plates based on facet-dependent charge separation for photocatalytic reactions, and the manipulation of the spatial charge separation is highlighted.

Large Single Crystals of Two-Dimensional π-Conjugated Metal-Organic Frameworks via Biphasic Solution-Solid Growth.

Two-dimensional (2D) π-conjugated metal–organic frameworks (πMOFs) are a new class of designer electronic materials that are porous and tunable through the constituent organic molecules and choice of metal ions. Unlike typical MOFs, 2D πMOFs exhibit high conductivity mediated by delocalized π-electrons and have promising applications in a range of electrical devices as well as exotic physical properties. Here, we develop a growth method that generates single-crystal plates with lateral dimensions exceeding 10 μm, orders of magnitude bigger than previous methods. Synthesis of large single crystals eliminates a significant impediment to the fundamental characterization of the materials, allowing determination of the intrinsic conductivity and mobility along the 2D plane of πMOFs. A representative 2D πMOF, Ni-CAT-1, exhibits a conductivity of up to 2 S/cm, and Hall measurement reveals the origin of the high conductivity. Characterization of crystalline 2D πMOFs creates the foundation for developing electronic applications of this promising and highly diverse class of materials.

Epicycloid extinction-band assembly in Poly(decamethylene terephthalate) confined in thin films and crystallized at high temperatures

This work utilized an in-house synthesized aryl polyester, poly (decamethylene terephthalate) (PDT), to investigate the crystal assembly of unique camellia-flower-like extinction bands periodically assembled in spherulites formed at specific Tc's or driven by other kinetic factors. These extinction PDT bands at high Tc's (110–125 °C) and confined in thin films are packed by parallel flat plates of single-crystal-like dimensions in nanometer to micrometer scales (measuring 4 μm × 4 μm x 20 nm) self-assembled as terrace-like shingles that are bordered with an optically extinct boundary. The valley corresponds to where most amorphous ingredients accumulate and the growth precipitates suddenly from tip of ridge to near the substrate, resulting in an optical extinction border. All ridges (convex bands) are composed of discrete crystal plates aligned as roof-shingle stacks along the circumferential bands, and the crystals do not traverse across the bands. These lamellae on ridge bands are discrete and do not twist at all or rotate 360° angle continuously extending from nucleus to periphery. The circular-extinction bands of PDT of nanometer films (300–400 nm) are composed of parallel lamellae with the terrace alignment pointing along the circumferential direction; the epicycloid-extinction bands of thicker PDT specimens (2000–3000 nm) are assembled with single-crystal plates of lozenge shapes and aligned in growth-preferred directions to form petal-like tips.

Growth, spectroscopy and laser operation of monoclinic Nd:CsGd(MoO4)2 crystal with a layered structure

We report on the growth, structure, polarized spectroscopy and first laser operation of a double molybdate compound featuring a layered structure – the monoclinic Nd:CsGd(MoO4)2. Single-crystals of 3 at.% Nd:CsGd(MoO4)2 are grown from the flux using cesium trimolybdate (Cs2Mo3O10) as a solvent. They crystallize in the monoclinic system (sp. gr. P2/c) with lattice constants a = 9.5239(4) Å, b = 5.0752(5) Å, c = 8.0580(7) Å and β = 91.157(9)°. Nd:CsGd(MoO4)2 exhibits a perfect cleavage along the (100) plane. Polarized absorption and luminescence spectra of the Nd3+ dopant ion are measured. The maximum stimulated-emission cross-section is 29.0 × 10−20 cm2 at 1065.9 nm for light polarization E ||b. The luminescence lifetime is 145 μs. The transition probabilities are determined using the modified Judd-Ofelt theory yielding the intensity parameters Ω2 = 26.736, Ω4 = 12.736 and Ω6 = 17.771 [10−20 cm2] and α = 0.122 [10−4 cm]. Continuous-wave laser operation is achieved in cleaved single-crystal plates of Nd:CsGd(MoO4)2 yielding a maximum output power of 0.54 W at 1066 nm with a laser threshold of 70 mW, a slope efficiency η of 60.4% and a linearly polarized laser output (E ||b).

Электрополевой эффект в спектрах ЭПР центров Fe-=SUP=-3+-=/SUP=- и Mn-=SUP=-4+-=/SUP=- в тонких пластинках SrTiO-=SUB=-3-=/SUB=-

The results of the study of the electric field effect in the electron paramagnetic resonance spectra of the Fe3+ and Mn4+ impurity ions in thin oriented strontium titanate single-crystal plates are presented. The crystal structure of plates at T> 105 K turned out to be tetragonal, different from both the cubic and the antiferrodistortive tetragonal, inherent to SrTiO3 at T < 105 K. It is shown that for the studied centers, the electric field effect is quadratic in the applied electric field and has the same sign and order of magnitude, indicating the nonpolar origin of the observed high temperature tetragonal state. Analysis of the dependences of the axiality value on the applied field indicates that the electric field effect does not originate from the electrostriction and is due to the modification the wavefunction of the ground state of the impurity centers.