Crystal Thickness Research Articles

A new technical solution to the problem of increasing the resolution of X-ray diffraction methods

A new technical solution to the problem of increasing the resolution of X-ray diffraction methods has been proposed and implemented, based on linearly enlarging the X-ray topographic patterns. For implementation of the suggested method, a novel device has been developed, created and tested that makes it possible to scan synchronously the slit for transmitting separate parts of the X-ray diffraction pattern and the X-ray film with a predetermined speed ratio. The possibility of significantly increasing the resolution of X-ray diffraction patterns with the suggested new scanning method has been experimentally proven. It was shown that if individual parts of the diffracted beam are passed successively through a narrow slit, which is synchronously scanned along with the X-ray detecting film, we obtain an enlargement in topographic patterns. A proposed scheme for enlarging the image in parts and a description and the operating principle of the scanning device are also presented. The relationship between the ratio of the speeds of the slit and the X-ray film movement and the parameters of the scanning device and the sample (slit width, total thickness of thin crystals, thickness of a thick crystal etc.) was revealed. The speeds of the reciprocating motion of the slit and the X-ray film were calculated. It has been experimentally proven that the scanning process does not introduce new information into the interference pattern but only enlarges it, since these patterns in sectional topograms differ only in size in the scattering plane.

Templating effect of monoglycerides in controlling the spatial distribution of solid fat crystals within double emulsions.

The spatial distribution of fat crystals significantly impacts the stability and digestion properties of emulsions. This study investigated the templating effect of monoglycerides in controlling the spatial distribution of solid fat crystallization within double emulsions. Double emulsions were formulated with glyceryl monostearate (GMS), glyceryl monolaurate (GML), glyceryl monooleate (GMO), beeswax (BW), glyceryl distearate (GDS), and glyceryl tristearate (GTS) in the oil phase. Monoglycerides influenced the spatial distribution pattern of BW crystals, while minimally affecting GDS and GTS. Cooling at 4°C increased interfacial crystallization without altering distribution patterns. Monoglycerides raised the onset and peak crystallization temperatures and enthalpy in BW emulsions, with GMS showing the most significant effects. Adding GMS slowed nucleation rates and extended induction times, promoting interface crystallization. The templating effect also reduced crystal lamellar thickness, facilitating the transition from β-crystalline to β' crystalline in BW. These findings provide insights into selecting crystallizing emulsifiers and enhancing double emulsion stability.

Increasing flatness of surface bands of multilayer rhombohedral graphite with crystal thickness

Increasing flatness of surface bands of multilayer rhombohedral graphite with crystal thickness

Effect Cu and La on the Solidification Structure and Magnetic Properties of Fe-6.5wt.%Si Alloy under Arc Melting

This study investigates the influence of Cu and La additions on the solidification structure and phase formation behavior of Fe-6.5wt%Si high silicon steel. The alloy's phase composition and structure were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The magnetic performance was measured using a high and low-temperature vibration magnetometer. The results revealed that the microstructure of the Fe-6.5wt.%Si alloy ingot, treated with Cu and La inhibitors, is segmented into three layers. From the bottom to the top, the phase morphology is fine crystals, columnar crystals, and isoaxial crystals. Adding Cu and La inhibitors significantly refined the Fe-6.5wt.%Si alloy; adding 0.05% Cu transformed thick columnar crystals into slender branches, while 0.03% La led to a uniform refinement of grains. Cu addition maintained the alloy saturation magnetization strength but increased coercivity. La addition decreased the alloy's saturation magnetization and increased coercivity.

Optimization of LYSO crystals and SiPM parameters for the CMS MIP timing detector

For the High-Luminosity (HL-LHC) phase, the upgrade of the Compact Muon Solenoid (CMS) experiment at CERN will include a novel MIP Timing Detector (MTD).The central part of MTD, the barrel timing layer (BTL), is designed to provide a measurement of the time of arrival of charged particles with a precision of 30 ps at the beginning of HL-LHC, progressively degrading to 60 ps while operating in an extremely harsh radiation environment for over a decade.In this paper we present a comparative analysis of the time resolution of BTL module prototypes made of LYSO:Ce crystal bars read out by silicon photo-multipliers (SiPMs).The timing performance measured in beam test campaigns is presented for prototypes with different construction and operation parameters, such as different SiPM cell sizes (15, 20, 25 and 30 μm), SiPM manufacturers and crystal bar thicknesses. The evolution of time resolution as a function of the irradiation level has been studied using non-irradiated SiPMs as well as SiPMs exposed up to 2 × 1014 neq/cm2 fluence.The key parameters defining the module time resolution such as SiPM characteristics (gain, photon detection efficiency, radiation induced dark count rate) and crystal properties (light output and dimensions) are discussed.These results have informed the final choice of the MTD barrel sensor configuration and offer a unique starting point for the design of future large-area scintillator-based timing detectors in either low or high radiation environments.

Polycondensation, cyclization and disproportionation of solid Poly(L-lactide) trifluoroethyl esters and the simultaneous formation of extended chain crystals and extended ring crystals

Two poly(L-lactide)s (PLAs) with a degree of polymerization (DP) of 20 or 100 were prepared by trifluoroethanol-initiated ring-opening polymerization (ROP) catalyzed by tin(II) 2-ethyl hexanoate (SnOct2). These PLAs were annealed at 140 °C or at 160 °C in the presence of SnOct2, and the changes in topology and molecular weight distribution (MWD) were monitored by matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectrometry and gel permeation chromatography (GPC). For the PLA with a DP 20, the main reaction was polycondensation combined with higher dispersities. In the case of the DP 100, PLA polycondensation was combined with disproportionation and the formation of a new MWD maximum around m/z 3500. In addition, extensive cyclization occurred, and the resulting cyclic PLAs crystallized separately from the linear chains in the form of extended ring crystals. These results also suggest that both extended chain and extended ring crystals posses the same crystal thickness as a result of thermodynamically controlled transesterification in the solid state.

Materials beyond monolayers: The magnetic quasi-1D semiconductor CrSBr

The all-surface nature of atomically thin van der Waals materials can present challenges for practical applications. Fortunately, new layered materials are on the horizon that preserve their useful properties even when thicker than a monolayer. Here, we summarize our interest in one of these emergent materials, the magnetic semiconductor CrSBr. We describe monolayer properties exhibited by this material in its bulk form, discussing how the quasi-1D electronic structure of CrSBr allows mono- or bilayer physics to be displayed even in thick crystals. Long-range magnetic order offers additional tuning with the coupled lattice, spin, orbit, and charge degrees of freedom enabling magneto-correlated phenomena. We discuss the stability of CrSBr in air and show atomic scale structural manipulation through electron beam-driven transformations. We conclude that the stability and structural amenability of CrSBr provide opportunities for imagining devices that use bulk crystals yet exploit unique magnetic and quantum confinement effects.Graphical abstract

Preparation of sunflower wax-based oleofoams and its application in inflatable reduced-fat mayonnaise

The present work aimed to prepare inflatable reduced-fat mayonnaise by using sunflower wax-based oleofoams (SWOF) as an oil phase. The effects of SW concentrations on the microstructure and the physical properties of oleofoams were investigated. Then the stable oleofoam formulations were chosen to prepare inflatable mayonnaise, and the functionality related to the physical (textural properties and thermal stability) and sensory attributes (appearance, color, and viscosity) of inflatable reduced-fat mayonnaise was compared with commercial low-fat mayonnaise (CLFM) & full-fat mayonnaise (CFFM). The microstructure study of SWOF indicated the presence of clearly visible SW crystals at the air-oil boundary and inside the continuous phase. This suggests that the stability of SWOF was accomplished through both Pickering and network crystallization. The SWOF exhibited a multi-layered sandwich structure, and the crystal layer thickness increased in oleofoams as the SW concentration rose. The oleofoams containing exceeded 6 wt% SW had better foamability and stability, a more elastic network, and a clear surface texture. Inflatable mayonnaise prepared by 10SWOF had comparable brightness, mouthfeel, and texture to CLFM, but sensitized to temperature. In general, the whipped mayonnaise prepared in this investigation had an acceptable appearance and textural properties and was suitable for foods that do not require heating.

Optimizing single crystal diamond mosaic growth: A study on seed thickness variation and pre-growth treatment

The limitations on the size of single-crystal diamond applications still need to be addressed for practical use. This study systematically investigates the impact of variations in seed crystal thickness and pre-growth treatments on step bonding, defect formation, and stress distribution in the mosaic growth of single-crystal diamond films. The findings suggest that variations in seed crystal thickness within 50 μm result in a smooth mosaic junction and high crystal quality, while a 100 μm variation results in noticeable defects and stress concentrations, hindering adequate bonding. Pre-growth treatment improves crystal quality by reducing polycrystalline formations and stress concentrations. Optical microscopy and Raman mapping confirm that pre-growth treated mosaic regions exhibit smooth steps and seamless bonding, with FWHM values between 3 and 5 cm−1, consistent with the quality of non-mosaic growth regions.

Intensive γ -ray light sources based on oriented single crystals

The feasibility of gamma-ray light sources based on the channeling phenomenon of ultrarelativistic electrons and positrons in oriented single crystals is demonstrated using rigorous numerical modeling. Case studies are presented for 10 GeV and sub-GeV e−/e+ beams incident on 10−1−100 mm thick diamond and silicon crystals. It is shown that for moderate values of the beam average current (≲10 μA), the average photon flux in the energy range of 100–102 MeV emitted within the 101–103 μrad cone and 1% bandwidth can be on the level of 1010 photon/s for electrons and 1010–1012 photon/s for positrons. These values are higher than the fluxes available at modern laser-Compton gamma-ray light sources. Published by the American Physical Society 2024

InAs Terahertz Metalens Emitter for Focused Terahertz Beam Generation

Metasurfaces have opened doors to combining multiple photonic functionalities in a single compact device. In particular, the ability to generate short terahertz (THz) pulses with precise wavefront engineering in a single THz metasurface redefined the role metasurfaces can play in THz systems. Here, an InAs metalens emitter which generates and focuses a THz pulse beam is demonstrated using a 130 nm thick InAs metasurface designed as a binary‐phase Fresnel zone plate. The THz beam is focused to a spot of ≈430 μm at 1 THz with a short focal length of 5 mm and large numerical aperture of 0.5. Nanoscale InAs Mie resonators comprising the metasurface enable THz generation with an amplitude as high as 20 times compared to plasmonic THz emitters and several times compared to a 1 mm thick ZnTe crystal. This InAs metasurface emitter provides a new paradigm for designing THz imaging, spectroscopy, and communication systems, where THz beam generation and shaping are performed with a single device without compromising the generation efficiency, while eliminating losses and avoiding limitations of phase matching of conventional nonlinear optics approaches.

Exploring the mechanisms of benzanilide crystal growth and morphology: Crystal surface structure, solvent diffusion and solvent-interface interactions

Flaky crystals are fragile, rendering them unsuitable for various applications including use, processing, storage and transportation. This work investigates the growth and morphology regulation mechanisms of flaky crystals using benzanilide as a model material. Initially, block-like crystals are prepared by solvent screening and cooling crystallization with its morphology greatly improved. Subsequently, growth kinetics of (111), (1–10) and (020) faces are established with crystal growth experiments. The crystal growth of (001) face is also determined to follow a two-dimensional nucleation model with the microscopic surface analysis using atomic force microscopy. The changes of the surface integration resistance and the growth step height are regarded as kinetic mechanisms of the growth behavior and crystal morphology modulation by solvent and supersaturation. Finally, the molecular mechanism of the modulation of the solvent in crystal morphology is revealed base on crystal surface structure analysis and molecular dynamics simulations. The weak solvent-interface polar interactions facilitate the incorporation of benzanilide molecules into the weak polarity (001) face, leading to the surface roughening and increased crystal thickness when employing strongly polar solvents such as acetonitrile. Unlike the former, the relatively weak hydrogen bonding interactions between solvents and strong polarity (020) face, and the higher diffusion ability of molecules promote the rapid growth and disappearance of (020) face in ethanol and acetonitrile with strong hydrogen bond formation ability. This study can contribute to a deeper understanding of the solvent effect on crystal morphology and provide guidance for optimizing crystallization conditions to obtain shape-tailored crystal products.

Enhancing interfacial heat conduction in diamond-reinforced copper composites with boron carbide interlayers for thermal management

In this work, we have synthesized a copper/boron carbide/diamond composite structure via magnetron sputtering. Surface roughness of the diamond layers was characterized using atomic force microscopy (AFM), and interfacial thermal conductance (ITC) between copper and diamond was experimentally measured by the Time-domain Thmoreflectance (TDTR) technique. Molecular dynamics (MD) simulations were conducted to investigate the influence of the <010> crystal plane thickness of boron carbide and interface roughness on the ITC. The results indicate a significant increase in ITC with the incorporation of a <010>-oriented boron carbide interlayer. The ITC initially rose and then fell as the boron carbide layer thickness increased, reaching a maximum of 286.52 MW m−2 K−1 for a three-layer (approximately 2 nm) interlayer, which is 14.1 times higher than that of the unmodified interface. Additionally, by creating a three-dimensional sinusoidal rough interface, we observed that increasing interface roughness can further enhance heat transfer efficiency up to a certain threshold, beyond which a saturation in phonon heat conduction is anticipated. The simulation outcomes are in good agreement with the experimental data, confirming the reliability of our findings.

Terahertz phase imaging of large-aperture liquid crystal modulator with ITO interdigitated electrode

Abstract We have fabricated and characterized a large-aperture electrooptic phase modulation device operating in the terahertz (THz) frequency range. The device consists of a 1.6 mm thick nematic liquid crystal placed between glass plates with a novel interdigitated electrode design. Using THz time-domain spectroscopy (THz-TDS) coupled with raster scanning imaging, we evaluated phase modulation across a 25 mm diameter LC device and mapped the spatial uniformity of phase shift. Our results confirm the functionality of the LC cell as a controllable quarter-wave plate at 0.26 THz and half-wave plate at 0.52 THz. This work contributes to the development of large-aperture and transmissive LC devices as low-cost phase plates for THz waves and paves the way for future applications in THz modulators.

Bonacinaite, Sc(AsO4) ⋅ 2H2O, the first scandium arsenate

Abstract. The new mineral bonacinaite (IMA2018-056), Sc(AsO4) ⚫ 2H2O, was found on the dumps of the Varenche Mine (Saint-Barthélemy, Nus, Aosta Valley, Italy), an old manganese mine, where it occurs as a low-temperature hydrothermal mineral associated mainly with quartz, granular braunite, undefined manganese oxides, arseniopleite, manganberzeliite and thortveitite. Bonacinaite forms colourless (with faint to distinct violet tints), pseudohexagonal, thick tabular crystals, up to 0.25 mm in size, sometimes with annular internal zones showing violet tinges, or as small, faintly violet lath-shaped crystals. The crystals are transparent and brittle, with vitreous lustre. The calculated density of an almost pure bonacinaite crystal is 2.82 g cm−3. Optically, bonacinaite is biaxial negative, α=1.598(4), β=1.618(3), and γ=1.638(3) (measured with a Na light source, 589 nm); 2V (measured) is large, and 2V (calculated) = −88.9°. The empirical formula, based on six O atoms per formula unit is (Sc0.90Mn3+0.08Fe3+0.01Pb0.01)Σ1.00[(As0.95P0.06)Σ1.01O4] ⚫ 2H2O. Bonacinaite has monoclinic symmetry, with space group P21/n and unit-cell parameters (single-crystal data / powder diffraction data) a=5.533(1)/5.521(1), b=10.409(2)/10.336(3), c=9.036(2)/9.059(4) Å, β=91.94(3)/91.97(4), V=520.1(2)/516.7(3) Å3 and Z=4. The crystal structure was refined from single-crystal intensity data obtained from a distinctly Al- and P-bearing crystal to R1(F) = 3.7 % for 1178 reflections. Bonacinaite is isotypic with the other members of the metavariscite group: kolbeckite, metavariscite and phosphosiderite.

(Invited) Amplified Spontaneous Emission Dynamics of a Lead Halide Perovskite Crystal as Revealed by Femtosecond Transient Absorption Microscopy

Organic-inorganic lead halide perovskite materials (e.g. CH3NH3PbX3, CsPbX3, X=Cl, Br, I) have various attractive properties not only for solar cells but also for LED and nanoscale lasers because of their wavelength tunability and low lasing threshold. Such an efficient lasing is indispensable for their applications, and the essential needs are miniaturization and low threshold. While this material was reported in 2009 for use in solar cells, it is also expected to be used in light-emitting and laser devices due to its easy tunability of emission wavelength and low-cost fabrication. However, the low-threshold lasing mechanism of lead halide perovskites has not been established due to various theories on the interaction state between light and carriers generated in the cavity at the initial stage and the carrier-carrier interaction state, which has greatly hindered progress in improving performance. In the present study, we have measured transient absorption spectra of a single CH₃NH₃PbBr₃ microcrystal using a femtosecond transient absorption microscopy to reveal the initial carrier process that induces nonlinear luminescence[1].CH3NH3PbBr3 crystals were prepared by a previously reported method. Aqueous lead(II) acetate solution (100 mg/mL) was dropped onto a glass slide and dried at 60°C for 30 min to obtain a film of lead acetate. Microcrystals of CH3NH3PbBr3 were then obtained by immersing the film in methylammonium bromide solution (5 mg/mL) with isopropanol as a solvent for 20 hours at room temperature in air.For transient absorption measurements, a regeneratively amplified femtosecond pulse (Spectra-Physics, Solstice, 795 nm, 1 kHz) was split in two; the second harmonic of one beam was used as the excitation light, and the white light generated with the other beam by introducing it into an optical parametric amplifier (Light Conversion, TOPAS) and focusing the obtained signal light (1.3 mm) into a CaF2 plate was used as the probe light.Fig. 1(a) shows the transient absorption spectra of lead halide perovskite excited at the intensities over the lasing threshold. The spectral signals that were not observed before the time origin (-1 ps) were significantly observed with modulated spectral shape after the time origin (≥0 fs). The spectral bleaching around 540 nm indicates carrier generation by the excitation light, and the relaxation of the bleaching indicates the recombination of electrons and holes. Furthermore, at around 557 nm, a bleaching signal appeared as shown in Fig. 1(b), that was not represented in the transient absorption spectrum excited at the intensity below the lasing threshold. This signal is suggested to be due to amplified stimulated emission. Spectral modulation is often observed as interference of light propagating in thin-film systems. The thickness of the perovskite crystals is around 200-300 nm, which is suitable to observe the optical interference. However, generally, this interference tends to become lower in frequency as one observes longer wavelengths, which is essentially different from the modulation observed here. The spectra modulation appeared immediately after the carrier was generated, and the modulation continued for up to 1ns. These results suggest that the modulation is caused by the electric field effect of the generated carriers on the electron spectrum. Franz-Keldysh’s theory is often used for spectral modulation in the presence of an electric field. In reflectance transient absorption spectroscopy, the electric field modulated spectrum has been explained in the GaInP2 system by Franz-Keldysh’s theory in systems where charges are generated on the semiconductor surfaces[2]. These results indicate the spectral modulation occurred from the charges separated on the surface of the crystal. We will discuss the mechanism of amplified spontaneous emission and low threshold lasing dynamics at the conference site. Funding: This study was partly supported by KAKENHI (Grant Number JP22H04755, JP19K05190) and JST FOREST (JPMJFR213G).

KCl acts as a flux to assist the growth of sub-millimeter-scale metallic 2D non-layered molybdenum dioxide

AbstractTwo-dimensional (2D) metal oxides (2DMOs), such as MoO2, have made impressive strides in recent years, and their applicability in a number of fields such as electronic devices, optoelectronic devices and lasers has been demonstrated. However, 2DMOs present challenges in their synthesis using conventional methods due to their non-van der Waals nature. We report that KCl acts as a flux to prepare large-area 2DMOs with sub-millimeter scale. We systematically investigate the effects of temperature, homogeneous time and cooling rate on the products in the flux method, demonstrating that in this reaction a saturated homogenous solution is obtained upon the melting of the salt and precursor. Afterward, the cooling rate was adjusted to regulate the thickness of the target crystals, leading to the precipitation of 2D non-layered material from the supersaturated solution; by applying this method, the highly crystalline non-layered 2D MoO2 flakes with so far the largest lateral size of up to sub-millimeter scale (~ 464 μm) were yielded. Electrical studies have revealed that the 2D MoO2 features metallic properties, with an excellent sheet resistance as low as 99 Ω·square−1 at room temperature, and exhibits a property of charge density wave in the measurement of resistivity as a function of temperature. Graphical abstract TOC (Table of Content)

A comparative study of crystal geometry, material, and reconstruction algorithms on MicroPET scanner performance

Small-animal PET, also known as microPET, has been developed to enhance image quality by improving spatial resolution and sensitivity due to its smaller ring and crystal size. However, the reduction of crystal size and the presence of gaps between cuboidal crystals could reduce sensitivity. MicroPET with tapered arrays has been developed to simultaneously improve sensitivity and spatial resolution. This study compared the performance of 14 × 14 and 28 × 28 array microPETs using LSO and CZT crystal materials. The impact of crystal design and reconstruction algorithms on image quality and performance parameters was investigated, using GATE Monte Carlo simulation toolkit. The findings showed that sensitivity increased with crystal thickness, particularly in LSO. The 14 × 14 arrays consistently exhibited higher sensitivity, while the 28 × 28 arrays had superior spatial resolution. NECR values increased with crystal thickness, with LSO outperforming CZT. Scatter and random fractions were low. Different reconstruction algorithms had negligible effects on FWHM and CNR but influenced SNR, with the COSEM algorithm achieving significantly reduced noise. The small size of crystals and tapered arrays contributed to improved sensitivity and spatial resolution. However, there was a trade-off between sensitivity and spatial resolution. LSO crystals showed better performance, but the choice between array sizes depended on specific imaging requirements. This study provides insights into optimizing microPET design for enhanced imaging capabilities.

In Situ Visual Observation of Surface Energy-Controlled Heterogeneous Nucleation of Metal Nanocrystals.

Electrochemical growth of metal nanocrystals is pivotal for material synthesis, processing, and resource recovery. Understanding the heterogeneous interface between electrolyte and electrode is crucial for nanocrystal nucleation, but the influence of this interaction is still poorly understood. This study employs advanced in situ measurements to investigate the heterogeneous nucleation of metals on solid surfaces. By observing the copper nanocrystal electrodeposition, an interphase interaction-induced nucleation mechanism highly dependent on substrate surface energy is uncovered. It shows that a high-energy (HE) electrode tended to form a polycrystalline structure, while a low-energy (LE) electrode induced a monocrystalline structure. Raman and electrochemical characterizations confirmed that HE interface enhances the interphase interaction, reducing the nucleation barrier for the sturdy nanostructures. This leads to a 30.92-52.21% reduction in the crystal layer thickness and a 19.18-31.78% increase in the charge transfer capability, promoting the formation of a uniform and compact film. The structural compactness of the early nucleated crystals enhances the deposit stability for long-duration electrodeposition. This research not only inspires comprehension of physicochemical processes correlated with heterogeneous nucleation, but also paves a new avenue for high-quality synthesis and efficient recovery of metallic nanomaterials.

The impact of template effect at different temperatures on homocrystallization-to-stereocomplexation transformation in Poly(L-lactide)/Poly(d-lactide) racemic blends

Stereocomplexation, formed between enantiomeric poly(L-lactide) (PLLA) and poly(d-lactide) (PDLA), is 50 °C higher than the melting point of PLLA (or PDLA) homocrystallites (HCs). In a certain temperature range, stereocomplexation can induce homocrystallization-to-stereocomplexation (HC-to-SC) transformation through template effect. In this work, a series of temperature programs designed through differential scanning calorimetry (DSC) were used to study the impact of template effect at different temperatures (TH-S) on HC-to-SC transformation in PLLA/PDLA racemic blends. It was found that HCs can be efficiently converted to stereocomplex crystallites (SCs) through template effect when TH-S was 210 °C. When TH-S was 220 °C, SCs with large lamellar crystal thickness were obtained, which had a higher melting point, about 10 °C higher than the conventional SCs. At a TH-S of 230 °C, the melt-crystallization peaks of HCs and SCs were clearly observed during the DSC cooling process because PLLA/PDLA helical pairs were still retained in the PLLA/PDLA melt. The results demonstrated that the residual PLLA/PDLA helical pairs can accelerate remarkably the crystallization rate of SCs and generated new SCs due to template effect, and the new SCs significantly accelerated the crystallization rate of HCs resulted from the heterogeneous nucleation effect. Non-isothermal crystallization behavior of PLLA/PDLA racemic blends at different cooling rates was also studied. The results indicate that the lower cooling rate promotes SCs formation more strongly than the promotion effect on HCs.