Precipitation in silicon wafers after high temperature preanneal studied by X-ray diffraction methods

We have investigated oxygen precipitation in Czochralski silicon wafers focusing on influence of nucleation temperature and high temperature pre-anneal during common three step treatment. Thick Si wafers were studied mainly by x-ray diffraction in Laue transmission geometry using Mo x-ray tube, but were also compared to reciprocal space maps obtained in Bragg reflection geometry. The analysis of measured diffraction scans in Laue geometry was performed by means of Takagi equations and statistical dynamical theory of diffraction. From the simulated Laue diffraction curves we find the size of the individual defect area and the fraction of strain area volume in the wafer. The results obtained from x-ray diffraction were compared to loss of interstitial oxygen according to infrared absorption spectroscopy and the size of SiO₂ precipitate core was estimated. These techniques are in agreement with transmission electron microscopy images.     

Microstructure of a composite with a quasicrystalline phase fraction obtained by directional solidification of Al61Cu27Fe12 alloy

The microstructure of a composite containing a quasicrystal phase, i.e. so-called crystal–quasicrystal (CQ) composite, was studied. The CQ composite was obtained by the Bridgman method via solidification of Al₆₁Cu₂₇Fe₁₂ alloy (numbers indicate at%). The process was conducted at a pull out rate of v = 0.07 mm/min. The average temperature gradient in the heating zone was 43 K/cm. The composite matrix consisted of cubic β phase Al(Fe, Cu), with reinforcement of λ-phase rod-shaped fibres surrounded by a quasicrystal icosahedral ψ phase, which also existed in the fibre core. The fibres were rhomboidal in cross-section. The composite was studied using X-ray and electron diffraction, light-optical and scanning electron microscopy (SEM), X-ray topography and Laue diffraction.     

Piezoelectric La3Ga5.3Ta0.5Al0.2O14 crystal: growth,crystal structure perfection,piezoelectric, and acoustic properties

A five-component crystal of lanthanum–gallium silicate group La₃Ga_5.3Ta_0.5Al_0.2O₁₄ (LGTA) was grown by the Czochralski method. The LGTA crystal possesses unique thermal properties and substitution of Al for Ga in the unit cell leads to a substantial increase of electrical resistance at high temperatures. The unit cell parameters of LGTA were determined by powder diffraction. X-ray topography was used to study the crystal structure perfection: the growth banding normal to the growth axis were visualized. The independent piezoelectric constants d ₁₁ and d ₁₄ were measured by X-ray diffraction in the Bragg and Laue geometries. Excitation and propagation of surface acoustic waves were studied by the double-crystal X-ray diffraction at the BESSY II synchrotron radiation source. The analysis of the diffraction spectra of acoustically modulated crystals permitted the determination of the velocity of acoustic wave propagation and the power flow angles in different acoustic cuts of the LGTA crystal.     

基于多层膜技术的硬X射线Laue透镜衍射效率的理论研究

采用耦合波理论分析了X射线在多层膜Laue透镜中的传播,选择Cu的Kα线作X射线光源,计算了多层膜Laue透镜的衍射效率.材料为WSi2/Si,最外层宽度为10 nm,深度为8 500 nm的多层膜Laue透镜,倾斜情况下外层区域局部光栅的衍射效率可达59%,理论上证明了多层膜Laue透镜是实现X射线聚焦的有效手段.     

大尺寸LnBa2Cu3O7-δ单晶的生长及其超导电性

本文报道大尺寸LnBa₂Cu₃O_7-δ(Ln=Y,Eu,Gd,Dy,Ho,Er,Tm,Yb,Lu)单晶生长及其超导电性,并讨论了(001)自然晶面的X射线多级衍射、劳厄相、旋进相等单晶鉴定法。 关键词：     

Anomalous transmission and Pendellösungen in electronically allowed nuclear laue diffraction of Mössbauer radiation

Nuclear resonant dynamical diffraction in transmission geometry was studied in case of an electronically allowed reflection. Mössbauer diffraction spectra were measured for both the Laue reflected and the Laue forward transmitted beam with high angular resolution. Pronounced energy Pendellösung beats were observed in the LR-beam. Complementary beats were indentified in the LT-beam, where also a strong suppression of nuclear resonance absorption and variations in the anomalous electronic absorption were revealed.     

SrTiO3(110) thin films grown directly on different oriented silicon substrates

We have grown (110)-oriented SrTiO₃ (STO) thin films on silicon without any buffer layer, by means of pulsed laser deposition technique. The crystal structures of the grown films were examined by X-ray diffraction analysis including θ–2θ scan and rocking curve as well as Laue diffraction methods. STO films with single (110) out-of-plane orientation were formed on all (100), (110) and (111)-oriented Si substrates. The in-plane alignments for the epitaxial STO films grown directly on Si (100) were found as STO[001]//Si[001] and STO[11̄0]//Si[010]. The results should be of interest for better understanding of the growth of perovskite oxide thin films on silicon wafers. PACS 77.55.+f; 68.55.JK; 81.15Fg     

Development of laser deposited multilayer zone plate structures for soft X-ray radiation

As a novel approach, the combination of pulsed laser deposition and focused ion beam was applied to fabricate different types of multilayer zone plate structures for soft X-ray applications. For this purpose, high quality non-periodic ZrO₂/Ti multilayers were deposited by pulsed laser deposition on planar Si substrates and on rotating steel wires with layer thicknesses according to the Fresnel zone plate law. Linear focusing optics were fabricated by cutting slices out of the multilayers by focused ion beam and placing them directly over pinholes within Si₃N₄ substrates. Additionally, it was shown that laser deposition of depth-graded multilayers on a wire is also a promising way for building up multilayer zone plates with point focus. First experiments using a table-top X-ray source based on a laser-induced plasma show that the determined focal length and spatial resolution of the fabricated multilayer Laue lens corresponds to the designed optic.     

Floating zone growth and magnetic and specific heat properties of La0.67Ca0.33Mn1-xFexO3（x=0.00,0.04）single crystals

Single crystals of La_0.67Ca_0.33MnO₃ and La_0.67Ca_0.33Mn_0.96Fe_0.04O₃ were obtained by floating zone method. Laue diffraction pattern and rocking curve of the single crystals show that their quality is good. The magnetic behaviours of these compounds have been studied. Fe doping significantly depresses the magnetic contribution to the total specific heat C_P, but slightly influences the lattice contribution at temperatures above 50K. The peak of C_P shifts towards high temperatures with increasing magnetic field. Both single crystals exhibit the first-order magnetic transition around the Curie temperature.     

Convergent beam electron diffraction study of Pb2CoWO6 at 100 K

A study by convergent beam electron diffraction has been performed in order to clarify the symmetry of the phase III of Pb₂CoWO₆. Microdiffractions with higher-order Laue zone on monodomain areas have confirmed the cell proposed in our preceding study. In addition, an ‘axial’ glide plane (c) has been found normal to the b axis. In the conditions of observation, the convergent beam electron diffraction patterns lead to an apparent point group mmm. No breakdown of a mirror symmetry could be found. The discrepancy between this result and the existence of a spontaneous polarisation is discussed.     

Structural phase transitions in (CH3)3NHCdCl3

The structure of (CH₃)₃NHCdCl₃ has been determined by single crystal X-ray diffraction at 174K. Phase changes around 342, 374, and 415 K have been detected by DTA and have been correlated with the dynamics of the organic groups via NMR measurements. No change of Laue symmetry has been observed between 170 and 400 K.     

Modified laser ablation process for nanostructured thermoelectric nanomaterial fabrication

A modified pulsed laser deposition process was used to enhance the nanostructure generation inside Bi₂Te₃ nanocrystals. In this process, an additional femotosecond laser beam was used to add an energy shock on the ablated flume, which can result in rich nanostructures embedded inside Bi₂Te₃ nanocrystals. A large Si wafer was used to ‘freeze’ such nanostructures and to effectively collect such nanostructured nanocrystals for further processing. The generated nanocrystals were studied by X-ray diffraction and scanning transmission electron microscopy, and the results prove the existence of such embedded nanostructures. Such nanocrystals were also characterized electrically and thermally for the conductivity measurements.     

On the Theory of X-Ray Diffractional Laue Focusing on Two Bent Crystals

The Laue focusing of a spherical x-ray wave onto dynamical diffraction by a double-bent crystal system is studied. The geometrical equations of two-dimensional Laue focusing and the intensity distribution formula are derived. A high sensitivity of the two-dimensional Laue focusing to the crystal thickness and bending radii difference is revealed. It is shown that this sensitivity can be used to control the crystal thickness with accuracy up to 100 and bending radii up to 10^-2 m. The focusing process of the spherical wave inside crystals as well as in vacuum is investigated. The possibility of using the two-crystal Laue system as a lens for x-ray microscopy is studied. The spectral characteristics of a twice-diffracted wave are discussed. The spectral resolution is demonstrated to be 10⁶.     

Tm:Y2SiO5晶体的生长和光谱性质研究

采用中频感应提拉法生长了高质量的Tm:Y₂SiO₅(Tm:YSO)晶体,测定了晶体的晶格常数和分凝系数.运用劳厄照相法确定了单斜晶系Tm:YSO晶体的三个偏振轴〈010〉,D₁和D₂,在室温下测量了三个偏振轴方向的吸收光谱、荧光光谱和荧光寿命,计算了晶体吸收峰的吸收线宽和吸收截面.研究发现,相对于其他两个偏振轴方向,D₁方向在790nm处出现较强的吸收峰, 关键词： 2SiO₅')" href="#">Tm:Y₂SiO₅ 单斜晶系 吸收光谱 荧光光谱     

Self-diffraction at a dynamic photonic crystal formed in a colloidal solution of quantum dots

Self-diffraction at a one-dimensional dynamic photonic crystal formed in the colloidal solution of CdSe/ZnS quantum dots has been discovered. This self-diffraction appears simultaneously with self-diffraction at induced transparency channels at the resonant excitation of the main electron–hole (excitonic) transition of quantum dots by two laser beams with a Gaussian intensity distribution over the cross section. It is shown that a nonlinear change in the absorption of colloidal quantum dots results in the formation of a transparency channel and an induced amplitude diffraction grating, and a significant nonlinear change in the refractive index (Δn ≈ 10^?3) in the absorbing medium is responsible for the formation of the dynamic photonic crystal. Self-diffracted laser beams are revealed propagating not only in directions corresponding to self-diffraction at the induced diffraction grating but also in directions satisfying the Laue condition.     

Microstructure of laser melted Al18B4O33w/2024Al composite

The microstructure of a laser treated Al₁₈B₄O₃₃w/2024Al composite has been investigated using transmission electron microscope (TEM), low-angle (glancing angle) X-ray diffraction (XRD) techniques. Various surface microstructures were observed in the laser treated composite. The Al₁₈B₄O₃₃ whisker on the surface of the composite was decomposed during laser surface melting, various decomposition products were studied in the laser treated composite. Eutectic phases and the precipitation in the matrix of the composite with laser-treated were observed. The main phases detected in the molten zone were aluminum and decomposition products Al₂O₃. The effect of laser treatment on the hardness of the composite was also examined. A surface hardness of 400 Hv was noted.     

Submicron focusing of XUV radiation from a laser plasma source using a multilayer Laue lens

The focusing properties of a one-dimensional multilayer Laue lens (MLL) were investigated using monochromatic soft X-ray radiation from a table-top, laser-produced plasma source. The MLL was fabricated by a focused ion beam (FIB) structuring of pulsed laser deposited ZrO₂/Ti multilayers. This novel method offers the potential to overcome limitations encountered in electron lithographic processes. Utilizing this multilayer Laue lens, a line focus of XUV radiation from a laser-induced plasma in a nitrogen gas puff target could be generated. The evaluated focal length is close to the designed value of 220 μm for the measurement wavelength of 2.88 nm. Divergence angle and beam waist diameter are measured by a moving knife edge and a far-field experiment, determining all relevant second-order moments based beam parameters. The waist diameter has been found to be approximately 370 nm (FWHM).     

Study of the influence of higher—order Laue zones on the exit wavefunction

Based on an analytical expression of electron dynamical diffraction derived recently,the exit wavefunctions of nonperiodic samples have been calculated.The results have shown that the amplitude and phase obtained by the analytical expression were in good agreement with those obtained using the multi-slice method.Besides,the influence of the higher-order Laue zone on the wavefunction for different sample thickness was studied in detail and the results showed that the exit wavefunction is dominated by the zero-order Laue zone.When the sample is very thin,the influence of the higher-order Laue zone should be considered.     

Light scattering at dielectric metasurfaces

“Photonic graphene” structures—submicron two-dimensional dielectric structures with a honeycomb lattice— are fabricated by laser lithography. The transition from the regime of light scattering by a metasurface to that of Laue diffraction at a two-dimensional photonic structure in the optical range is studied experimentally and theoretically. The optical diffraction patterns make it possible to determine the number of unit cells in a finite microstructured sample with the naked eye.     

High efficiency UV solid state lasers based on Ce:LiCaAlF6 crystals

We report the spectroscopy and laser results of cerium-doped colquiriite LiCaAlF₆ (LiCAF) single crystals. High quality samples have been grown using the Czochralski technique and characterized by means of X-ray Laue diffractometry, absorption and emission spectra. Moreover, we measured the lifetime and deduced the emission cross-sections of the laser transition. Using this crystal we realized two lasers devices: a high-efficiency laser emitting at 289 nm with a repetition rate (RR) of up to 2 kHz and a widely tunable laser (from 280 nm to 317 nm) with an RR of up to 4.3 kHz. The high quality of the crystal made it possible to obtain the highest slope efficiency (49%) ever reported to our knowledge for a Ce:LiCAF laser. PACS 42.55.Rz; 78.55.Hx; 81.10.Fq