A new method to evaluate the quality of single crystal Cu by an X-ray diffraction butterfly pattern method

A new method for the evaluation of the quality of an Ohno continuous cast (OCC) Cu single crystal by X-ray diffraction (XRD) butterfly pattern was brought forward. Experimental results show that the growth direction of single crystal Cu is inclined from both sides of the single crystal Cu rod to the axis and is axially symmetric. The degree of deviation from the [100] orientation from the crystal axis is less than 5° with a casting speed 10–40 mm/min. The orientation of single crystal Cu does not have a fixed direction but is in a regular range. Moreover, the orientation of stray grains in the single crystal Cu is random from continuous casting.     

Transmission electron microscopy and X-ray diffraction studies of quantum wells

A series of In _x Ga_1?x As (x=0·47) quantum wells with InP barrier layers have been grown on InP substrates by metalorganic vapour phase epitaxy (MOVPE) at 625°C. The nominal well widths were defined during growth at (i) 25 Å, 39 Å, 78 Å and 150 Å for one sample and (ii) 78 Å for all 4 wells in another sample. The InP barrier widths have been kept constant at 150 Å. These layers have been characterized by X-ray diffraction (XRD) which from simulation gave the nominally 78 Å well width as 84 Å and the nominally 150 Å barrier width as 150·5 Å. Transmission electron microscopy (TEM) and high resolution TEM (HRTEM) have been carried out on etched and ion-milled samples for direct measurement of well and barrier widths. The well widths found from TEM are 25 Å, 40 Å, 75 Å and 150 Å. TEM micrographs revealed that, while the InP barrier layer is of good quality and the growth is confirmed to be epitaxial, dipoles are detected at the interface and the quantum well has some small disordered regions. These thickness measurements are in good agreement with earlier photoluminescence (PL) and secondary ion mass spectrometry (SIMS) studies.     

X-ray nanobeam diffraction imaging of materials

Unprecedented tools to image crystalline structure distributions in materials have been made possible by recent advances in X-ray sources, X-ray optics and X-ray methods. Nanobeams combined with diffraction have made it possible to image parameters that were traditionally only addressed as ensemble averages. This enables the study of highly heterogeneous materials such as microelectronic devices and opens a new field of material science on the mesoscale. Coherent nanobeams offer the opportunity to image nanomaterials in three dimensions with a resolution far smaller than the focused beam size. This has opened up new fields in X-ray diffraction in general and has become one of the main drivers for the enhancement of existing, and the construction of new, large scale scientific infrastructure projects around the world.     

Geometrical properties of the X-ray diffraction applied to Laue lenses

An analytical study of the geometrical properties of the X-ray diffraction applied to the case of Laue lenses is reported in this paper. The results of this investigation are analytical equations that describe the point in which a photon is diffracted as a function of the crystal position and of the X-ray source angular coordinates. In addition, the contributions to the lens Point Spread Function of each crystal is described, helping in understanding the optical properties of a Laue lens. The results obtained can be inserted in simulation and image deconvolution softwares for speeding up the calculations.     

High resolution X-ray diffraction studies of real structure of nearly perfect single crystals

Real structure together with composition and elemental purity of single crystals controls their properties. This paper reviews recent work carried out at the National Physical Laboratory on application of high resolution X-ray diffractometry, topography and diffuse X-ray scattering for direct observation and characterization of real structure of single crystals of silicon, gallium arsenide, diamond and LiNbO₃. A series of six multicrystal X-ray diffractometers have been designed, developed and fabricated indigenously. The most versatile of these systems is a five crystal X-ray diffractometer with state-of-the-art level resolution. These techniques and equipments have been applied in studying several interesting problems. Even in dislocation-free crystals of silicon, remarkable differences in the defect structure have been observed if the growth method was changed from float zone to Czochralski. Study of effect of externally applied electric fields and ion implantation on real structure of crystals has yielded interesting results. Images of ‘filaments’ which show nonhomogeneous distribution of electric current through semiconductors and insulators have been recorded for the first time in high resolution traverse topographs. Diffracted X-ray intensities could be modified by externally applied electric fields. It has been shown that implantation of BF ₂ ⁺ ions in silicon for producing shallow junctions does not produce homogeneous distribution of boron. The impurity is partially in clustered form. Biaxial stress introduced by thin depositions in substrate crystals are of considerable applied concern. The value and nature of stress have been determined in a number of systems. Typical results obtained on GaAs: multilayer metallizations are described. Also, degradation of perfection of substrates has been monitored. This work has shown that the stress is not homogeneously distributed and is quite anisotropic. A new high resolution X-ray diffraction technique has been developed for direct observation and study of forward diffracted X-ray beam and anomalous transmission of X-rays through ‘thin’ diamond crystals of varying degrees of perfection.     

X射线粉末衍射数据的校正

扼要介绍了X射线粉末衍射数据（峰位峰强和峰形）的校正方法和使用的标样。     

X-ray orientation microscopy using topo-tomography and multi-mode diffraction contrast tomography

Polycrystal orientation mapping techniques based on full-field acquisition schemes like X-ray Diffraction Contrast Tomography and certain other variants of 3D X-ray Diffraction or near-field High Energy Diffraction Microscopy enable time efficient mapping of 3D grain microstructures. The spatial resolution obtained with this class of monochromatic beam X-ray diffraction imaging approaches remains typically below the ultimate spatial resolution achievable with X-ray imaging detectors. Introducing a generalised reconstruction framework enabling the combination of acquisitions with different detector pixel size and sample tilt settings provide a pathway towards 3D orientation mapping with a spatial resolution approaching the one of state of the art X-ray imaging detector systems.     

Analysis of powder X-ray diffraction resolution using collimating and focusing polycapillary optics

Focusing X-ray optics can be used to increase the intensity onto small samples, greatly reducing data collection time. Typically, the beam convergence is restricted to avoid loss of resolution, since the focused beams broaden the resulting powder diffraction rings. However, with smooth Gaussian peaks, the resolution defined by the uncertainty in peak location can be much less than the peak width. Polycapillary X-ray optics were used to collimate and focus X-rays onto standard inorganic powder diffraction samples. Comparisons were made of system resolution and diffracted beam intensity with and without focusing and collimating optics using a standard small spot rotating anode system in point source geometry. The area detector and optics also allowed for the use of a low power 60 W source, without increasing either the collection time or the peak center error compared to the rotating anode no optic case. Resolution and intensity were in good agreement with those obtained from a simple geometrical model developed for the optics, which allows for system design and optimization for the desired sample characteristics. Foils and powders were used to model thin film samples while allowing both reflection and transmission measurements to more effectively verify theoretical modeling of beam parameters.     

XPS and X-ray diffraction studies of aluminum-doped zinc oxide transparent conducting films

Aluminum-doped zinc oxide transparent conducting films are prepared by spray pyrolysis at different dopant concentrations. These films are subsequently characterized by X-ray diffractometric and X-ray photoelectron spectroscopic (XPS) techniques. The results are compared with those obtained from pure zinc oxide films prepared under identical conditions. X-ray diffraction measurements show an increase in lattice parameters (c and a) for aluminum-doped films while their ratio remains the same. This study also indicates that within the XPS detection limit the films are chemically identical to pure zinc oxide. However, a difference in the core-electron line shape of the Zn 2p_3/2 photoelectron peaks is predicted. An asymmetry in Zn 2p_3/2 photoelectron peaks has been observed for aluminium-doped films. The asymmetry parameters evaluated from core-electron line-shape analysis yield a value of the order of 0.04±0.01. The value is found to lie between those obtained for pure zinc oxide and has been attributed to the presence of excess zinc in the films.     

X-ray diffraction study of epitaxial zinc and cadmium films prepared by hot-wall technique

Hot-wall technique greatly improves the quality of zinc and cadmium films deposited on glass substrate. At substrate temperature the growth of such films is well ordered, showing highly preferred orientation along c-axis. However, if the substrate temperature is increased beyond certain limit, we get polycrystalline growth of the films. This shows that the growth of zinc and cadmium films on glass substrate strongly depends on the substrate temperature.     

A high-energy X-ray diffraction, P and B solid-state NMR study of the structure of aged sodium borophosphate glasses

The structure of aged melt-quenched sodium borophosphate glasses of composition (P₂O₅)₄₀(B₂O₃)_x(Na₂O)_60−x (with x in the range 10–40) has been studied by high-energy X-ray diffraction (HEXRD), ³¹P and ¹¹B magic angle spinning (MAS) NMR. Similar to the fresh samples, both POP and POB linkages are found to be present in these glasses. All three techniques show that the cross-linking between borate and phosphate units increases with boron oxide content. Distinctively upon aging, the glass is found to hydrolyze causing the network to degrade. At the same time, crystalline phases are now also observed. XRD and DTA show that the samples have a higher tendency towards crystallization with increasing boron oxide content upon exposed to moisture. ³¹P and ¹¹B MAS NMR results are in agreement with these findings. TGA data show that samples with higher boron oxide content take up more moisture upon aging, suggesting that crystallization may be associated with glass hydrolysis. HEXRD results also suggest that sodium ions are preferentially associated with borate units with increasing boron oxide content.     

Microstructural changes in oxygen-irradiated zirconium-based alloy characterised by X-ray diffraction techniques

We have carried out irradiation with 116 MeV O⁵⁺ ions on Zr–1Sn–1Nb–0.1Fe (ZIRLO) alloy at different doses and the microstructural parameters of the irradiated samples have been characterised by X-ray Diffraction Line Profile Analysis (XRDLPA). The average volume-weighted and surface-weighted domain size, microstrain and dislocation density have been estimated as a function of dose. There was a drastic decrease in domain size from unirradiated sample to the sample at a dose of 1 × 10¹⁷ O⁵⁺/m², but these values saturated with increasing dose of irradiation. The values of microstrain were found to increase with dose. The dislocation density increased almost by an order of magnitude for the samples irradiated with 1 × 10¹⁸ O⁵⁺/m² and 5 × 10¹⁸ O⁵⁺/m² as compared to the unirradiated samples.     

High energy transmission micro-beam Laue synchrotron X-ray diffraction

Synchrotron-based micro-beam Laue diffraction is an experimental technique for the study of intra-granular lattice orientation and elastic strain in individual crystallites of polycrystalline engineering alloys. Traditionally the technique operates in reflection geometry with a polychromatic X-ray beam focused to a sub-micron spot and with photon energy ranging from approximately 5 to 30 keV. This allows the study of material in the near-surface region. In this paper the first feasibility study of extending this technique to a polychromatic beam with significantly higher photon energies from 50 to 300 keV is presented. At these energies, transmission through even thick samples can be achieved and it becomes possible to study deeply buried material volumes. The technique is demonstrated by recording an orientation map of a flat dogbone large-grained Ni sample. Comparison with an optical micrograph shows very good agreement, validating the feasibility of this approach.     

Synthesis,crystal structure and thermal analysis of a new stilbazolium salt crystal

A new organic crystal of 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium benzene sulfonate (DASBS) was synthesized and characterized for the first time. It is a derivative of 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) with the benzene sulfonate replacing p-toluenesulfonate. Single crystal XRD demonstrated that the crystal structure of DASBS·H₂O was triclinic. The thermal analysis of this new crystal was also conducted, and the melting point was obtained to be 232°C.     

Degradation assessment of welded joints by X-ray diffraction technique

Abstract

X-ray diffraction technique has been recognized as a useful tool for the assessment of material degradation extent after a long-time service. Framework 5 project “XPECTION” was dealing with this task with respect to high-temperature creep degradation of boiler tube steels. This paper summarizes partial results of an experimental programme concentrated on mechanical properties degradation of base metals of steel and Al-alloy test specimens of welded components as a result of fatigue loading.     

Measurement of residual stresses in CFRP laminates by X-ray diffraction method

The fabrication of CFRP laminates from prepregs involves curing at elevated temperatures. Residual stresses are set up due to the difference in thermal expansion coefficient between the matrix and the fibre. In this investigation, the X-ray diffraction method is used to measure the curing stresses in CFRP laminates by incorporating a very fine layer of aluminium particles during the lay up of the laminate. A calibration procedure is followed to correlate the strain in the crystalline particles, as measured by X-rays, with the composite strain and stress. Curing stresses measured by this technique are quite close to the value calculated from the differential coefficient of thermal expansion.     

Fast, micrometer scale characterization of group-III nitrides with laboratory X-ray diffraction

We have designed a convergent beam, concurrent detection X-ray diffractometer. The instrument was built by Bruker AXS and is equipped with a rotating anode generator, a Johannson monochromator crystal for beam focusing, and a Soller slit arrangement in combination with a knife edge in front of the sample which defines the illuminated area on the sample. Samples up to 12 in. can be mounted on the sample stage of a D8 Eulerian cradle. A large area detector enables rapid simultaneous detection of the diffracted intensity. The instruments allow for a fast evaluation of large samples at high lateral resolution. In favourable cases lateral resolution down to 1 μm is possible. Furthermore a grazing incidence diffractometer has been developed which allows for depth-dependent measurements at high intensity.     

A CCD area detector for X-ray diffraction under high pressure for rotating anode source

Details of a two-dimensional X-ray area detector developed using a charge coupled device, a image intensifier and a fibre optic taper are given. The detector system is especially optimized for angle dispersive X-ray diffraction set up using rotating anode generator as X-ray source. The performance of this detector was tested by successfully carrying out powder X-ray diffraction measurements on various materials such as intermetallics AuIn₂, AuGa₂, high Z material Pd and low Z scatterer adamantane (C₁₀H₁₆) at ambient conditions. Its utility for quick detection of phase transitions at high pressures with diamond anvil cell is demonstrated by reproducing the known pressure induced structural transitions in RbI, KI and a new structural phase transition in AuGa₂ above 10 GPa. Various softwares have also been developed to analyze data from this detector. Paper presented at the 5th IUMRS ICA98, October 1998, Bangalore     

A triple axis mode X-ray diffraction measurement on elastic strain distribution of lightly Cr-doped SI-GaAs for laser windows

The triple axis mode X-ray diffraction method is described, which has been used to measure the spatial variation in the lattice parameters of {1 0 0} lightly Cr-doped SI-GaAs laser windows. It has been found that a remarkable spatial variation of elastic strain exists in the window wafer. The results show that the thinner the wafer is, the smaller the stress spatial variation in the wafer. The elastic strain in the window wafer can be released by thermal annealing. The method can also be applicable to the precise lattice parameter measurements of the compound materials.     

A powder X-ray diffraction refinement of the BaNd2Ti3O10 structure

The structure parameters of BaNd₂Ti₃O₁₀ were refined based on Olsen’s model. This material has a monoclinic unit cell with space group P2₁/m. The unit cell parameters are: a=7.73030(14) Å, b=7.62578(14) Å, c=14.23174(31) Å, β=97.832(6)°. The structure can be considered as a layered perovskite-like structure, in which the perovskite block shows distortion. The various layers link in the order of (Ba_1/2O)-(Ba_1/2TiO₃)-(NdTiO₃)-(NdTiO₃).