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.

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.

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

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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.

A review of β-Ga_2O_3 single crystal defects, their effects on device performance and their formation mechanism

As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislocations, voids, twin, and small defects. Their effects on device performance were discussed. Dislocations and their surrounding regions can act as paths for the leakage current of SBD in single crystals. However, not all voids lead to leakage current. There's no strong evidence yet to show small defects affect the electrical properties. Doping impurity was definitely irrelated to the leakage current. Finally, the formation mechanism of the defects was analyzed. Most small defects were induced by mechanical damages. The screw dislocation originated from a subgrain boundary. The edge dislocation lying on a plane slightly tilted towards the(102) plane, the(101) being the possible slip plane. The voids defects like hollow nanopipes, PNPs, NSGs and line-shaped grooves may be caused by the condensation of excess oxygen vacancies, penetration of tiny bubbles or local meltback. The nucleation of twin lamellae occurred at the initial stage of "shoulder part" during the crystal growth. These results are helpful in controlling the occurrence of crystal defects and improving the device performance.

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.

Characteristics of 355 nm Laser Damage in KDP and DKDP Crystals

我们在场体积损坏的特征由 Nd 的第三泛音导致了: 在 KDP 和 DKDP 晶体的钇铝柘榴石激光照耀。体积损坏作为由一个核心和使变形的地区组成的一些或一系列针尖发生。1-on-1 测试的结果表明针尖尺寸与 inevreasing fluence 增加，并且针尖密度与增加 fluence 指数地增加。s-on-1 测试的结果显示针尖密度与激光脉搏数字逐渐地增加，但是尺寸不成长。这些结果与 nanoabsorbers 在被假定在水晶存在的一个模型一致，损坏的开始被加热他们到批评温度决定。

Effect of S Substitution for P Point Defects in KDP Crystals： First-Principles Study

电子结构和硫在钾 dihydrogen 磷酸盐(KDP ) 代替的黄磷的几何分发被第一原则的计算调查。点缺点在精力差距下面变窄到大约 4.9 eV，相应于在修正以后的 355 nm 的二光子的吸收。这能在 KDP 晶体解释激光损坏抵抗的减少。而且，缺点扭曲水晶结构并且削弱契约，特别 O-H 契约，这些契约可以因此是第一个地点在激光照耀下面裂开。[从作者抽象]

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.

Researches on the Growth Habit and Optical Properties of Fe^(3+) Ion Doped KDP Crystal

During the process of KDP crystal growth, metal ions strongly affect the growth habit and optical properties of KDP single crystal. In this paper, KDP crystals were grown from an aqueous solution doped with different concentration of Fe^3＋ dopant by traditional temperaturereduction method and ＂point-seed＂ rapid growth method. Furthermore, we examined the light scatter and measured the transmission of these KDP crystals. It is found that the dopant of Fe^3＋ ion can improve the stability of the KDP growth solution when its concentration is less than 30 ppm. The effects of Fe^3＋ ion on the growth habit and optical properties of KDP crystal are also obvious.

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.

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 borates 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 stoichioimetric laser material.

Growth, Thermal and Optical Properties of Dy_xY_((1-x)Al_3(BO_3)_4 Crystal

Single crystal of dysprosium-doped yttrium aluminum tetraborate Dy:YAl 3(BO 3) 4(Dy:YAB) was grown by the flux method. The room-temperature absorption spectrum and low-temperature fluorescence spectrum of Dy 3+:YAl 3(BO 3) 4 crystal were measured. The yellow emission transitions ( 4F 9/2→ 6H 13/2)at 575 nm is more intense than other transitions. The specific heat and thermal expansion were measured. The specific heat is 0.93 J·g -1·℃ -1 at room temperature. The maximum of the thermal expansion occurs in the direction parallel to the c-axis and the minimum occurs in the direction parallel to the a-axis. The thermal expansion coefficient along c-axis is almost 6.5 times larger than that along a-axis.

Crystal Structure and Judd–Ofelt Analysis of Er^(3+) Doped LuAl_3(BO_3)_4 Crystal

Single crystal Er：LuAl3 （BO3） （Er：LuAB） is successfully grown using the top-seeded solution growth method wlth a K2Mo3O10 flux. The cell parameters of the grown crystal are estimated by an x-ray single crystal diffactometor and x-ray powder diffraction analysis. The result indicates that it still belongs to the space group R32. The obtained unit-cell parameters are a = 9.2793（19） a, c = 7.210（3） a, V = 537.65（27） a3, and Z = 3. The absorption spectrum is measured at room temperature. The spectroscopy properties axe investigated based on the Judd Ofelt （J-O） theory, and the effective J-O parameters were calculated to be Ω2 = 8.33 ×10^- 20, Ω4 = 3.83 ×10^-20, and Ω6 = 3.55 × 10^- 20. The emission spectra of Er：LuAB crystal at room temperature are also studied and the 4I11/2 →4I13/2 fluorescence around 3170nm is observed. The emission cross section calculated by the F-L formula is 8.6 × 10^-20 cm2. These results suggest that the Er：LuAB crystal may be a promising -3 μm laser material.

Synthesis, Crystal Structure and Nonlinear Optical Properties of Nickel(Ⅱ) Complex with Schiff-base Ligand

The nickel(Ⅱ) complex with the new ligand of S-benzyl-b-N-[10-ethyl- phenothiazine-3-methylene]dithiocarbazate(HL) crystallizes in the triclinic system, space group P?with a = 7.516(1), b = 11.322(1), c = 13.366(1) , a = 84.818(1), b = 81.688(1), g = 76.037(1), V = 1090.26(3) 3, Z = 1, Dc = 1.413 g/cm3, F(000) = 482, m(MoKa) = 0.774 mm-1 (l = 0.7103 ?, R = 0.0573 and wR = 0.1375 for 3357 observed reflections with I ≥ 2s(I). The HL has lost a proton from its tautomeric thiol form and acts as a single negatively charged bidentate ligand coordinating to the nickel ion via the mercapto sulfur and b-nitrogen atoms. The geometry around Ni(Ⅱ) is almost square-planar with two equivalent NiN and NiS bonds. The nonlinear absorption of HL and NiL2 solutions (in DMF) was measured by open-aperture Z-scan technique at the wavelength of 532 nm.

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.