Investigation of reflection anisotropy induced by micropipe defects on the surface of a 4H-SiC single crystal using scanning anisotropy microscopy

Optical reflection anisotropy microscopy mappings of micropipe defects on the surface of a 4H-SiC single crystal are studied by the scanning anisotropy microscopy(SAM)system.The reflection anisotropy(RA)image with a'butterfly pattern'is obtained around the micropipes by SAM.The RA image of the edge dislocations is theoretically simulated based on dislocation theory and the photoelastic principle.By comparing with the Raman spectrum,it is verified that the micropipes consist of edge dislocations.The different patterns of the RA images are due to the different orientations of the Burgers vectors.Besides,the strain distribution of the micropipes is also deduced.One can identify the dislocation type,the direction of the Burgers vector and the optical anisotropy from the RA image by using SAM.Therefore,SAM is an ideal tool to measure the optical anisotropy induced by the strain field around a defect.

Branch-Chain-Rich Diisopropyl Ether with Steric Hindrance Facilitates Stable Cycling of Lithium Batteries at-20℃

Li metal batteries(LMBs)offer signifi-cant potential as high energy density alternatives;nev-ertheless,their performance is hindered by the slow desolvation process of electrolytes,particularly at low temperatures(LT),leading to low coulombic efficiency and limited cycle stability.Thus,it is essential to opti-mize the solvation structure thereby achieving a rapid desolvation process in LMBs at LT.Herein,we introduce branch chain-rich diisopropyl ether(DIPE)into a 2.5 M Li bis(fluorosulfonyl)imide dipropyl ether(DPE)elec-trolyte as a co-solvent for high-performance LMBs at-20℃.The incorporation of DIPE not only enhances the disorder within the electrolyte,but also induces a steric hindrance effect form DIPE’s branch chain,excluding other solvent molecules from Li+solvation sheath.Both of these factors contribute to the weak interactions between Li^(+)and solvent molecules,effectively reducing the desolvation energy of the electrolyte.Consequently,Li(50μm)||LFP(mass loading~10 mg cm^(-2))cells in DPE/DIPE based electrolyte demonstrate stable performance over 650 cycles at-20℃,delivering 87.2 mAh g^(-1),and over 255 cycles at 25℃ with 124.8 mAh g^(-1).DIPE broadens the electrolyte design from molecular structure considera-tions,offering a promising avenue for highly stable LMBs at LT.

Simple substituents make big differences in photophysical performances of 2,1,3-benzothiadizole-conjugated spiropyrans

Developing multifunctional spiropyran dyes is of particular importance in diverse applications.In the present study,we synthesized two 2,1,3-benzothiadiazole-conjugated spiropyrans(BT-SP-NO2and BTSP-NMe2)with distinct substituents.These donor-acceptor-structured spiropyrans exhibited typical twisted intramolecular charge transfer features and strong emissions in low-polarity solvents with fluorescence quantum yields(QYs)of up to 90.7%.Like traditional spiropyrans,the electron-acceptor-substituted BT-SP-NO2exhibited excellent photochromic behavior under multiple alternating UV—Vis irradiation,while the electron-donor-substituted BT-SP-NMe2was an acidochromic dye.In addition,the substituent groups distinctly affected the packing modes of these spiropyrans in the solid state.BTSP-NMe2showed a much stronger solid-state emission(QY of 59.0%)than BT-SP-NO2.Moreover,these two dyes were utilized as biocompatible probes for the specific light-up imaging of lipid droplets.

Angular and planar transport properties of antiferromagnetic V_(5)S_(8)

Systemically angular and planar transport investigations are performed in layered antiferromagnetic(AF)V_(5)S_(8).In this AF system,obvious anomalous Hall effect(AHE)is observed with a large Hall angle of 0.1 compared to that in ferromagnetic(FM)system.It can persist to the temperatures above AF transition and exhibit strong angular field dependence.The phase diagram reveals various magnetic states by rotating the applied field.By analyzing the anisotropic transport behavior,magnon contributions are revealed and exhibit obvious angular dependence with a spin-flop vanishing line.The observed prominent planar Hall effect and anisotropic magnetoresisitivity exhibit two-fold systematical angular dependent oscillations.These behaviors are attributed to the scattering from spin–orbital coupling instead of nontrivial topological origin.Our results reveal anisotropic interactions of magnetism and electron in V5S8,suggesting potential opportunities for the AF spintronic sensor and devices.

Comparison of Different Crucible Materials for the Growth of AlN Crystals

Choice of crucible material is a key issue during the growth of AIN crystal. The stabilities at high temperature and life-spans of boron nitride （BN） crucible, tantalum （Ta） crucible and tungsten （W） crucible were compared. Tantalum crucible behaved worse at high temperature and life-span was shortened as compared with the other two crucible materials. It was very crisp and easy to crack. In contrast, self-seeded AIN crystals with different morphologies could be obtained at different high temperatures using BN crucible. The boron nitride crucible was stable below 2200 ℃, above which it would decompose. Thus it was unsuitable for the bulky AIN crystal growth. Tungsten crucible could endure the temperatures higher than 2200℃. Unfortunately we could only get AIN polycrystallines using tungsten crucible. After 50- 100 hours＇ run, the crucible was destroyed completely due to the multiple deep cracks. XRD results of destroyed tungsten crucible indicated that the main phases are tungsten carbide and tungsten nitride.

Synthesis of High Purity SiC Powder for High-resistivity SiC Single Crystals Growth

High purity silicon carbide （SIC） powder was synthesized in-situ by chemical reaction between silicon and carbon powder. In order to ensure that the impurity concentration of the resulting SiC powder is suitable for high-resistivity SiC single crystal growth, the preparation technology of SiC powder is different from that of SiC ceramic. The influence of the shape and size of carbon particles on the morphology and phase composition of the obtained SiC powder were discussed. The phase composition and morphology of the products were investigated by X-ray diffraction, Raman microspectroscopy and scanning electron microscopy. The results show that the composition of resulting SiC by in-situ synthesis from Si/C mixture strongly depends on the nature of the carbon source, which corresponds to the particle size and shape, as well as the preparation temperature. In the experimental conditions, flake graphite is more suitable for the synthesis of SiC powder than activated carbon because of its relatively smaller particle size and flake shape, which make the conversion more complete. The major phase composition of the full conversion products is β-SiC, with traces of α-SiC. Glow discharge mass spectroscopy measurements indicated that SiC powder synthesized with this chemical reaction method can meet the purity demand for the growth of high-resistivity SiC single crystals.

Picosecond Stimulated Raman Scattering of SrWO4 Crystal

Stimulated Raman scattering （SRS） of picosecond pulses is investigated in a new crystal SrWO4. The second harmonic generation of a mode-locked Nd：YAG laser system is used as the pump source. In an external singlepass configuration, the SRS thresholds for the first to the fourth Stokes lines are measured. For the first Stokes line, the steady-state gain coefficient of the SrWO4 crystal is calculated to be 15.96cm//GW. In our experiment, as many as five Stokes lines （559.23 nm, 589.61 nm, 623.49 nm, 661.50 nm, 704.44 nm） and three anti-Stokes lines （506.97nm, 484.34 nm, 463.65nm） are observed, and the total conversion efficiency is as high as 62%.

Femtosecond laser direct writing of flexibly configured waveguide geometries in optical crystals:fabrication and application

Optical waveguides are far more than mere connecting elements in integrated optical systems and circuits.Benefiting from their high optical confinement and miniaturized footprints,waveguide structures established based on crystalline materials,particularly,are opening exciting possibilities and opportunities in photonic chips by facilitating their on-chip integration with different functionalities and highly compact photonic circuits.Femtosecond-laser-direct writing(FsLDW),as a true three-dimensional(3D)micromachining and microfabrication technology,allows rapid prototyping of on-demand waveguide geometries inside transparent materials via localized material modification.The success of FsLDW lies not only in its unsurpassed aptitude for realizing 3D devices but also in its remarkable material-independence that enables cross-platform solutions.This review emphasizes FsLDW fabrication of waveguide structures with 3D layouts in dielectric crystals.Their functionalities as passive and active photonic devices are also demonstrated and discussed.

Laser Synthesis and Microfabrication of Micro/ Nanostructured Materials Toward Energy Conversion and Storage

Nanomaterials are known to exhibit a number of interesting physical and chemical properties for various applications,including energy conversion and storage,nanoscale electronics,sensors and actuators,photonics devices and even for biomedical purposes.In the past decade,laser as a synthetic technique and laser as a microfabrication technique facilitated nanomaterial preparation and nanostructure construction,including the laser processing-induced carbon and non-carbon nanomaterials,hierarchical structure construction,patterning,heteroatom doping,sputtering etching,and so on.The laser-induced nanomaterials and nanostructures have extended broad applications in electronic devices,such as light–thermal conversion,batteries,supercapacitors,sensor devices,actuators and electrocatalytic electrodes.Here,the recent developments in the laser synthesis of carbon-based and non-carbon-based nanomaterials are comprehensively summarized.An extensive overview on laser-enabled electronic devices for various applications is depicted.With the rapid progress made in the research on nanomaterial preparation through laser synthesis and laser microfabrication technologies,laser synthesis and microfabrication toward energy conversion and storage will undergo fast development.

Synthesis, Crystal Structure, and Topology Analysis of One Novel Interpenetrated 2D Cobalt Coordination Polymer, {[Co(HTCB)(4,4'-btb)]·H_2O}_n

One novel cobalt coordination polymer, {[Co（HTCB）（4,4＇btb）]＇HzO}n （1, H3TCB = 1,3,5-tris（4-carboxyphenyl）benzene, 4,4＇-btb = 4,4＇-bis（1,2,4-triazol-3-yl）biphenyl）, has been synthesized and characterized by elemental analysis, IR, powder X-ray diffraction （PXRD）, and thermogravimetric （TG） analyses. X-ray diffraction analysis reveals that complex 1 is a 2D 2-fold interpenetrated {44,62}-sql [Co（HTCB）（4,4＇-btb）] sheet based on the 1D [Co（HTCB）]n chains and 1D [Co（4,4＇-btb）]n chains. The crystal of 1 crystallizes in triclinic, space group P1 with a = 9.529（12）, b = 13.914（16）, c = 14.906（17） A, V= 1903（4） A3, Z = 2, C45H34N6CoO71 Mr= 829.71, Dc = 1.448 g/cm3, F（000） = 858 andμ（MoKa） = 0.514 mm-1. The final R = 0.0655 and wR = 0.1136 for 6603 observed reflections with 1 〉 2a（/） and R = 0.1136 and wR = 0.1747 for all data.

Crystal growth, spectroscopic characteristics, and Judd–Ofelt analysis of Dy:Lu_2O_3 for yellow laser

Dy：Lu2O3 was grown by the float-zone （Fz） method. According to the absorption spectrum, the Judd-Ofelt （JO） parameters Ω2, Ω4, and Ω6 were calculated to be 4.86 × 10-20 cm2, 2.02 × 10-20 cm2, and 1.76 ×10-20 cm2, respectively. The emission cross-section at 574 nm corresponding to the 4F9/2 →6H13/2 transition was calculated to be 0.53 ×10 20 cm2. The yellow （4F9/2 →6H13/2 transition） to blue （4F9/2 →6H15/2 transition） intensity ratio ranges up to 12.9. The fluorescence lifetime of the 4F9/2 energy level was measured to be 112.1 μs. These results reveal that Dy：Lu2O3 is a promising material for use in yellow lasers.

Characteristics of 355 nm Laser Damage in KDP and DKDP Crystals

We present the characteristics of bulk damage induced by the third harmonic of Nd：YAG laser irradiation in KDP and DKDP crystals. Bulk damage occurs as a few or a series of pinpoints consisting of a core and the deforming zone. The results of a 1-on-1 test reveal that the pinpoint size increases with incvreasing fluence, and the pinpoint density increases exponentially with increasing fluence. The results of an s-on-1 test indicate that the pinpoint density increases gradually with laser pulse number, but the size does not grow. These results are consistent with a model in which nanoabsorbers are assumed to exist in the crystal and the initiation of damage is determined by heating them to the critical temperature.

Growth Characteristics and Mechanism of Surface and Bulk Damage in KDP and DKDP Crystals

By testing the number increase and size growth of surface and bulk laser induced damage in KDP and DKDP crystals, we observe different growth characteristics of surface and bulk damage under multiple 355nm laser irradiations. The size of the surface damage grows exponentially, but that of the bulk damage does not grow. In contrast, the bulk damage number increases, but that of surface damage does not increase significantly. We attribute the differences to the different formation of the damage initiators and the different damage testing volumes.

Growth and Characteristic of YbAl_3(BO_3)_4 Crystal

YbAl3(BO3)4 crystal of good optical quality was grown by the flux method. The structure of YbAl3(BO3)4 crystal was determined by single-crystal X-ray diffraction. The experiment shows that YbAl3(BO3)4 belongs to the double bo-rates with a trigonal structure. The space group is R32 and its unit cell constants were measured to be a = 0.92965 nm, c=0.72129 nm, V = 0.53673 nm3, Z=3. The transmittance spectra were measured. The cut-off of YbAl3(BO3)4 crystal is 216 nm, and there are two absorption peaks located at 940 and 975 nm from 190 nm to 2600 nm. The thermal properties of YbAl3(BO3)4 crystal were studied for the first time. The average thermal expansion coefficients were determined to be 2×10-6/℃, 9.5×10-6/℃along a- and c- direction. The specific heat of YbAl3(BO3)4 crystal was measured to be 0.6695 J·(g·℃) -1 at room temperature . All results indicate that the YbAl3(BO3)4 crystal is an excellent stoichioimet-ric laser material.

Influence of SiO_3^(2-)Impurity on the Optical Properties of KDP Crystal

In this paper,potassium dihydrogen phosphate（KDP） crystals were grown in the presence of a series of silicate（SiO32-） impurity concentrations via conventional temperature cooling and rapid growth methods,respectively.It revealed that the SiO32-impurity could lead to the decrease of transmittance at the region of ultraviolet band for pyramidal sectors and slightly increased the transmittance for prismatic sectors.SiO32-could enter into the crystal lattice and create lattice defects,which consequently increased the density of light scatter.The decrease of laser damage threshold was attributed to the lattice defects and the redundant electrons brought by the replacement of SiO32-at the PO43-position.

Oscillating Frequency Response of a Langasite Crystal Microbalance in Liquid Phase

The frequency responses of a langasite crystal microbalance （LCM） in liquid phase were investigated. It was shown that the LCM possessed much stronger oscillating ability in liquid phase than that of the commonly used quartz crystal microbalance （QCM）. The frequency shifts of the LCM to the changes in mass loading, as well as viscosity and density of the liquid were measured. The LCM was applied to monitor the adsorption process of an ionic liquid film to ethanol vapor.

Effect of Strontium Ion on the Growth and Second-Harmonic Generation Properties of GdCa_(4)O(BO_(3))_(3) Crystal

Large sized and optical quality GdCa_(4)O(BO_(3))_(3)(GdCOB)crystal with calcium partially substituted by strontium(Sr)ions was grown for the first time.The x-ray powder diffraction shows that the Sr ion has an effect on the cell parameters of the GdCOB crystal Second-harmonic generation(SHG)experiments were performed on the Sr:GdCOB and GdCOB crystals along the spatial phase-matching direction.The results show that the cw green laser output power is 1.04 W when the laser diode pump power is 10 W in the Nd:YVO_(4)/Sr:GdCOB intracavity laser.Considering the slope efficiency of Nd:YVO_(4) and the fundamental laser in cavity,the intracavity SHG conversion efficiency of the GdCOB crystal is 21%while it is 24%for the Sr:GdCOB crystal,the SHG conversion efficiency is improved by 14%.The effect of the Sr ions on the nonlinearity of the GdCOB crystal is also discussed by using the anion group theory.

Synthesis,Crystal Structure,and Magnetic Property of One 3D Nickel Coordination Polymer Based on 2-Hydroxy-5-(3',5'-terephthalic acid)Pyridine and 1,4-Bis(1-imdazoly)benzene

One novel nickel coordination polymer, {[Ni（OTP）（bib）1.5（H2O）]·2H2O}n（1, H2 OTP = 2-hydroxy-5-（3＇,5＇-terephthalic acid） pyridine, bib = 1,4-bis（1-imdazoly）benzene）, has been synthesized and characterized by elemental analysis（EA）, IR, powder X-ray diffraction（PXRD）, and thermogravimetric（TG） analyses. The crystal of 1 crystallizes in monoclinic, space group P21/n with a = 12.2860（5）, b = 13.8246（6）, c = 19.0140（8） A, β = 104.3870（1）°, V = 3128.2（2） A3, Z = 4, C32H28N7 Ni O8, Mr = 697.32, Dc = 1.481 g/cm^3, F（000） = 1444 and μ（Mo Kα） = 0.684 mm-1. The final R = 0.0704 and w R = 0.1764 for 5485 observed reflections with I 2σ（I） and R = 0.1087 and wR = 0.2010 for all data. Topology analysis reveals that complex 1 is a 3D 2-fold interpenetrated {4^4·6^6}-nov net based on the 1D [Ni（OTP）]n chain and the 2D [Ni2（bib）3]n sql sheet. And the variable-temperature magnetic susceptibility measurements exhibit weak antiferromagnetic coupling interaction.

Thermal and Mechanical Properties of a Complex Nonlinear Optical Material:Cadmium Mercury Thiocyanate Crystal

Institute of Crystal Materials and State Key Laboratory of Crystal Materials,Shandong University,Ji'nan 250100(Received 18 March 2000)The data of the thermal expansion and specific heat of cadmium mercury thiocyanate crystal have been obtained.The specific heat is 0.7588J/g℃at room temperature.The thermal expansion occurs in the direction parallel to the c-axis,and the thermal contraction occurs in the direction parallel to the a-axis.The thermal expansion is the same as the thermal contraction at 353 K.The relationship between thermal properties and crystal structure is discussed.

Synthesis and Crystal Structure of E-4,4’-Bis(N,N-di-n-butylamino)stilbene

The title compound E-4,4＇-bis（N,N-di-n-butylamino）stilbene （abbreviated to BDBAS） was synthesized by a simple and effective solvent-free wittig reaction with a higher yield.Its crystal structure was determined by a four-circle diffractometer. The crystal data： C30H46N2, Mr =434.69, monoclinic, space group P21/n, a = 9.7805（13）, b = 14.3249（16）, c = 10.0243（16） ,A°, a =90.00, β = 98.639（11）, γ = 90.00°, V = 1388.5（3） ,A°^3, Z = 2, Dc = 1.040 g/cm^3, F（000） = 480,μ（MoKa） = 0.059 mm^-1, the final R = 0.0778 and wR = 0.2064. The results reveal that the molecule is a completely reverse 7r-conjugate system.