Analysis of epitaxial laterally overgrown silicon structures by high resolution x‐ray rocking curve imaging

Spatially resolved rocking curve imaging has been used to analyze laterally overgrown silicon layers grown by liquid phase epitaxy. We were able to study both the overgrown layer as well as the strain fluctuations of the Si substrate underneath by means of a tabletop x‐ray topographic setup. The strain‐field analysis reveals relative changes of the lattice parameter up to 3.5×10^‐6 in the silicon substrate underneath the overgrown layer in particular regions and a down bending of both wings of the epitaxial overgrown layers. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐ray Rotation‐Tilt‐Method — First Results of a new X‐ray Diffraction Technique

That from us as X‐ray Rotation‐Tilt Technique (XRT Method) designated procedure principle represents a world innovation and overcomes essential disadvantages of comparable diffraction techniques known up to now. Starting from the origin and the informational content of the XRT interferences a realization of a special equipment and selected examples of some first applications are presented.     

Synthesis and X‐ray powder diffraction studies of semiconducting alloys in the system AgCd2‐xZnxGaS4

X‐ray powder technique was used in the investigation of AgCd₂GaS_4–'AgZn₂GaS₄' section to determine the region of AgCd₂GaS₄‐based solubility. It was established that the solid solution forms up to 75 mol.% 'AgZn₂GaS₄'. The refinement of AgCd_0.5Zn_1.5GaS₄ structure was performed. This alloy crystallizes in orthorhombic structure (space group Pmn2₁ ) with unit cell parameters a =0.78772(2), b =0.67221(2), c =0.64019(2) nm, V =0.33899(3) nm³. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Observation of individual dislocations in 6H and 4H SiC by means of back‐reflection methods of X‐ray diffraction topography

SiC crystals of high structural perfection were investigated with several methods of X‐ray diffraction topography in Bragg‐case geometry. The methods included section and projection synchrotron white beam topography and monochromatic beam topography. The investigated 6H and 4H samples contained in large regions dislocations of density not exceeding 10³ cm^‐2. Most of them cannot be interpreted as hollow core dislocations (micro‐ or nano‐pipes). The concentration of the latter was lower than 10² cm^‐2. The present investigation confirmed the possibility of revealing dislocations with all used methods. The quality of presently obtained Bragg‐case multi‐crystal and section images of dislocation enabled analysis based on comparison with numerically simulated images. The analysis confirmed the domination of screw‐type dislocations in the investigated crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐ray powder diffraction structural characterization of Ba1‐xEuxTiO3 ternary oxides

The single‐phase Ba_1‐xEu_xTiO₃ (0.1≤x≤0.4) samples have been synthesized by solid state reaction under high pressure and ‐temperature. X‐ray powder diffraction data was determined by MS Modeling using Reflex Powder Indexing technique. The Ba_1‐xEu_xTiO₃ series exhibited an interesting orthorhombic‐tetragonal‐cubic structural transformation as Eu composition increases, the distinct change of the X‐ray diffraction peak profile in the vicinity of 45.5º is characteristic of structural transformation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Observation of the δ to ε Zr‐hydride transition by in‐situ synchrotron X‐ray diffraction

We investigate the formation and dissolution of hydrides in commercially pure zirconium powder in‐situ using high‐energy synchrotron X‐ray radiation. Experimental results showed a continuous phase transition between the δ and ε zirconium hydride phases with indication of a second order phase transformation.     

Crystal structure refinement of the ternary compound Cu2SnTe3 by X‐ray powder diffraction

The ternary compound Cu₂SnTe₃ crystallizes in the Imm2 (Nº 44) space group, Z = 2, with a = 12.833(4) Å, b = 4.274(1) Å, c = 6.043(1) Å, V = 331.5(1) ų. Its structure was refined from X‐ray powder diffraction data using the Rietveld method. The refinement of 25 instrumental and structural variables led to R_p = 10.2%, R_wp = 11.8%, R_exp = 7.7%, R_B = 10.6%, S = 1.6 and χ² = 2.6, for 5501 step intensities and 163 independent reflections. This compound is isostructural with Cu₂GeSe₃, and consists of a three‐dimensional arrangement of slightly distorted CuTe₄ and SnTe₄ tetrahedra connected by common corners. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐ray powder diffraction study of the semiconducting alloy Cu2Cd0.5Mn0.5GeSe4

The structure of the semiconducting alloy Cu₂Cd_0.5Mn_0.5GeSe₄ was refined from an X‐ray powder diffraction pattern using the Rietveld method. The present alloy crystallizes in the wurtz‐stannite structure, space group Pmn2₁ (N^o 31), and unit cell parameters values of a = 8.0253(2) Å, b = 6.8591(2) Å, c = 6.5734(2) Å and V = 361.84(2) ų. The structure exhibits a three‐dimensional arrangement of slightly distorted CuSe₄, Cd(Mn)Se₄ and GeSe₄ tetrahedras connected by corners. © 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Thermal behavior of biogenic apatite crystals in bone: An X‐ray diffraction study

The thermal behavior of the bovine bone mineral and synthetic stoichiometric hydroxyapatite was investigated by X‐ray diffraction. The bone samples in solid (planar oriented pieces) and in powder form were examined to elucidate how the microstructural and textural properties of bone mineral are modified under heating. As could be expected, the thermal behavior of the bone mineral depends not only on the structural distortions, but also on the crystal habit, texture and ordering of biocrystals in tissue. The temperature growth of biogenic apatite crystals, unlike synthetic hydroxyapatite, is seen to be nonmonotonic and multi‐staged. At 600 to 700°C the biomineral crystallites grow rapidly due to disappearance of the mosaic structure as the lattice imperfections are annealed. After heating between 700°C and 900°C the bone mineral appears to be composed of roughly equidimensional ≥200 nm crystals. The further growth of the crystals in the range from 900 to 1300°C occurs by the mass transport mechanism, supporting the idea that the bone mineral is not a discrete aggregation of crystals, but rather a continuous mineral phase with direct crystal‐crystal bonding. Estimates are presented to show the important role of the surface mass transport mechanism in the growth of apatite crystals. The material obtained by heating a cortical bone fragment between 900°C and 1300°C turns out to be composed of two crystal types: crystals oriented along the bone axis (major morphology) and those of differing shape and orientation (minor morphology). The heating‐induced variations in the longitudinal and transverse dimensions of differing‐morphology crystals are found to be coherent. Small amounts of CaO, MgO and other crystalline phases are seen to be formed in the bone mineral under heating. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Divergent beam hard X‐ray diffraction used for the simultaneous imaging of radiographic and crystallographic information

A transmission method and experimental set‐up were developed for the nondestructive characterisation of the quality of bulk single crystals/ large coarsely crystalline polycrystals or components. The method works by combination of X‐ray projection microscopy (X‐ray shadow microscopy) with bremsstrahlung interferences from divergent beam hard X‐rays, in order to form simultaneously enlarged radiographic images and crystallographic information in one measurement. The method and equipment are patent registered. In the paper some of the first results are presented. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐ray diffraction and magnetization studies of BiFeO3 multiferroic compounds substituted by Sm3+, Gd3+, Ca2+

The multiferroic compounds Bi_0.9Sm_0.1FeO₃, Bi_0.9Gd_0.1FeO₃, Bi_0.9Ca_0.1FeO₃, Bi_0.9Sm_0.05Ca_0.05FeO₃, and Bi_0.9Gd_0.05Ca_0.05FeO₃ were prepared by the conventional ceramic method and were characterized by X‐ray diffraction, vibrating sample magnetometry, and differential scanning calorimetry. The compounds were found to have the rhombohedral perovskite‐like structure, accompanied by a small residual Bi₂Fe₄O₉ impurity phase. Magnetic hysteresis loops with enhanced remnant magnetization and coercive field were obtained for the Gd‐containing compounds. The improvement of magnetic behavior of the Gd‐containing compounds is thought to arise mainly from the partial suppression of the spiral spin structure and the stronger interaction between magnetic ions. The magnetic transition temperatures of the compounds were found to be in the range 300‐310 °C. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐ray Reflectivity from Sinusoidal Surface Relief Gratings

The sinusoidal shape of light‐induced surface relief gratings of polymers can be probed by x‐ray scattering techniques. A particular approach of kinematic x‐ray scattering theory is developed to interpret experimental scattering curves. The simulations demonstrate the particular sensitivity of x‐ray reflectivity for very small grating amplitudes. At angles of incidence close to the critical angle of total external reflection a grating amplitude h < 2 nm already provides measurable grating peaks. In general the grating amplitude h can be measured from the envelope function over the grating peak maxima. The capability of the approach is demonstrated by simulation of the reflection curve recorded from a polymer sample with non uniform grating height.     

X‐ray Diffraction Topography at a Synchrotron Radiation Source Applied to the Study of Bonded Silicon on Insulator Material

New possibilities of X‐ray diffraction topography offered by the modern synchrotron radiation sources for the investigation of wafer‐bonded material are demonstrated. They allowed detecting defects and long‐range strain fields at and close to the bonding interface. A quantitative estimation of the deformation of the region near to the bonding interface was possible e.g. by investigating focussing distances and dominant spatial frequencies of contrast patterns (often in the order of 200 μm). In typical wafer bonded material the maximum bonding‐induced inclination of the lattice planes was in the order of 10 arcsec and the approximate amplitude of the deformation in the order of 1.5 nm. The sensitivity of the presented methods to characterize the influence of various process parameters was demonstrated.     

X‐ray structural phase analysis of CdTe semiconductor annealed in air

X‐ray structural phase analysis of CdTe semiconductor, thermally annealed in air at temperature range 373‐773 K and annealing time 24 hrs, is investigated applying Rietveld method. The results showed that at low temperatures < 523 K, oxygen diffuses into the (1/21/21/2) interstitial sites of the CdTe lattice and its relative occupancy increases with the annealing temperature. For higher temperatures ≥ 523 K, the thermally grown oxide CdTeO₃ phase is developed on expense of CdTe phase. The percentage phase abundance of each phase is determined at each temperature applying a standardless method. The rate of oxidation with temperature is found to be non‐linear.     

Automatic detection and high resolution fine structure analysis of conic X‐ray diffraction lines

The presented method demonstrates a first step in the development of a high resolution “Residual stress microscope” and facilitates through the implementation of largely automated procedures a fast detection of diffraction lines in the form of conic sections. It has been implemented for, but is not exclusively used for the Kossel technique and the “X‐ray Rotation‐Tilt Method” (XRT). The resulting multifaceted evaluable data base of many X‐ray diffraction radiographies can be used not only for the systematic analysis of anomalies in diffraction lines (reflection fine structure), but also for direct calculation and output of precision residual stress tensors. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Grazing Incidence In‐plane Diffraction Measurement of In‐plane Mosaic with Microfocus X‐ray Tubes

The in‐plane mosaic structure of Au/Fe and GaN‐based epitaxial layers has been determined directly by laboratory‐based grazing incidence in‐plane x‐ray diffraction in which Bragg reflections normal to the plane of the wafer are probed. High intensity and acceptable signal‐to‐noise can be obtained with no modifications to commercially available equipment. Excellent agreement is obtained between measurements of the same Au/Fe multilayer samples at the European Synchrotron Radiation Facility in Grenoble and with the laboratory system employing a focused x‐ray beam from a microfocus generator. The technique is particularly important for the GaN‐based systems as it uniquely provides a measure of the so‐called twist mosaic independent of the out‐of plane (tilt) mosaic.     

Quantitative Determination of Crystalline Na5P3O10 –I (Form‐I) in Commercial Tripolyphosphate using X‐ray Diffraction Patterns

An x‐ray diffraction method (XRD) for quantitative determination of the crystalline Na₅P₃O₁₀‐I (Form‐I) in a mixture of Form‐I/Form‐II was applied for commercial pentasodium tripolyphosphate analysis. The XRD pattern of the Form‐I shows the unique non‐overlapping 2θ peak at a position of ≈ 21.8 deg. and also at ≈ 29.0 deg. (Cu radiation). The area (integral of the intensity) under the peaks is proportional to the amount of the Form‐I in the mixture covering the range up to 100 wt.%. That enables one to obtain a calibration line and to determine the amount of Form‐I in the mixture of Form‐I/Form‐II and also in commercial pentasodium tripolyphosphate. Commercial samples with high Form‐I concentration, in case they are contaminated with sodium pyrophosphate (Na₄P₂O₇), should be diluted with Form‐II to bring the concentration of the Form‐I below 50 wt.% in the analysed sample.     

Single‐crystal sapphire microstructure for high‐resolution synchrotron X‐ray monochromators

We report on the growth and characterization of sapphire single crystals for X‐ray optics applications. Structural defects were studied by means of laboratory double‐crystal X‐ray diffractometry and white‐beam synchrotron‐radiation topography. The investigations confirmed that the main defect types are dislocations. The best quality crystal was grown using the Kyropoulos technique. Therein the dislocation density was 10²–10³ cm⁻² and a small area with approximately 2*2 mm² did not show dislocation contrast in many reflections. This crystal has suitable quality for application as a backscattering monochromator. A clear correlation between growth rate and dislocation density is observed, though growth rate is not the only parameter impacting the quality.     

Growth imperfections in oriented grown KDP crystals by X‐ray topographic analysis

Potassium dihydrogen phosphate (KDP) crystals were restrained to grow in two dimensions only, using a specially designed platform. This enables us to grow the blanks of frequency conversion elements that satisfy type‐II phase matching direction out of a type‐II phase‐matched seed crystal. Synchrotron radiation topography was used to study the growth mechanism of these profiling grown KDP crystals. It is found that both dislocation growth mechanism and layer growth mechanism were involved in the growing process. Inclusions, growth striations and dislocations were the main defects that influenced the crystalline quality of these crystals. High‐resolution X‐ray diffraction was employed to study the lattice integrality of the crystal.     

Crystal structure refinement of CuxAg1‐xInTe2 bulk material determined from X‐ray powder diffraction data using the Rietveld method

The influence of the Cu‐content in the quaternary compounds Cu_xAg_1‐xInTe₂ (0 ≤ x ≤1) on the structural properties of the bulk material was discussed. Bulk ingot materials of Cu_xAg_1‐xInTe₂ solid solutions (x = 0.0, 0.25, 0.50, 0.75 and 1.0) have been synthesized by fusion of the constituent elements in the stoichiometric ratios in vacuum‐sealed silica tubes. The materials compositions were confirmed by using energy dispersive analysis of X‐rays (EDAX). X‐ray powder diffraction measurements were performed for all the prepared samples at 300 K in step scanning mode. The analysis of X‐ray data has indicated that the crystal structure of the prepared materials with different compositions is single‐phase polycrystalline materials corresponding to the tetragonal chalcopyrite structure with space group I 2d. The crystal structural parameters were refined by Rietveld method using the Full Prof program. The refined lattice constants (a and c), anion positional parameter, u, and the determined bond distances and angles were found to vary with composition, x, attaining zero tetragonal distortion at x ≈ 0.75, which corresponds to an ideal tetragonal unit cell. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)