Showing papers on "Electron backscatter diffraction published in 1982"
TL;DR: In this paper, multiple electron scattering between weak beams has been used as the basis for a simple method to determine the absolute polarity of some non-centrosymmetric crystals.
Abstract: Multiple electron scattering between weak beams has been used as the basis for a simple method to determine the absolute polarity of some non-centrosymmetric crystals. For crystals with the sphalerite structure many orientations have been found in which small departures from centrosymmetry produce large effects on the convergent-beam diffraction patterns (microdiffraction). The effects are reasonably independent of thickness and so can be analyzed qualitatively without the use of computers.
193 citations
TL;DR: The crystal structure of gypsum, CASO4.2H20, has been refined to R w −0.023 and R -0.036 for 610 neutron diffraction intensities collected at room temperature (294 K) for a unit cell with a = 5.679 (5), b = 15.202 (14), c 6.522 (6) A, fl 118.2 A a, d c = 2.3 g cm -3.
Abstract: The crystal structure of gypsum, CASO4.2H20, has been refined to R w -0.023 and R -0.036 for 610 neutron diffraction intensities collected at room temperature (294 K) for a unit cell with a = 5.679 (5), b = 15.202 (14), c 6.522 (6) A, fl 118.43 (4) °, and space group I2/a, Z = 4, V = 495.2 A a, d c = 2.3 g cm -3. The refinement was based on a model with anisotropic thermal motion for all atoms, and an isotropic secondary-extinction coefficient. The O H bonds of the water molecule are 0.942(3) and 0.959 (3)A and hence significantly different. The difference, 0.017 (4)A,, is in accordance with spectroscopic stretching-frequency differences for the two O H bonds. The water molecule donates two hydrogen bonds of 1.856 (2) and 1.941 (2) A to sulfate O atoms. The shortest hydrogen bond is not linear, the O H . . . O angle being 170.9 (2) °, whereas the other bond has an angle of 177.2 (2) °. H H is 1.533 (3) A and H O H 107.5 (2) °. The sulfate ion is definitely not a regular tetrahedron. The S O distances are equal [1.474 (1) and 1.471 (1)A], but the O S O angles are not [111.1(1), 111.0(1), 111.1(1) and 106.3 (1)°], leading to differences in the O O tetrahedral edges [2.429 (1), 2.432 (2), 2.426 (2) and 2.357 (1)A]. The shortest edge is shared between the sulfate tetrahedron and the square-bipyramidal CaO s group.
158 citations
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TL;DR: The results obtained from the use of the two techniques are in acceptable agreement and indicate that the interlayer spacings in the Cu(110) surface exhibit a damped, oscillatory deviation from the bulk value, in qualitative agreement with the predictions of Landman, Hill, and Mostoller as mentioned in this paper.
Abstract: Complementary studies of the Cu(110) surface have been carried out by means of low-energy electron diffraction and high-energy ion scattering. The results obtained from the use of the two techniques are in acceptable agreement and indicate that the interlayer spacings in the Cu(110) surface exhibit a damped, oscillatory deviation from the bulk value, in qualitative agreement with the predictions of Landman, Hill, and Mostoller.
96 citations
TL;DR: In this paper, the authors used CBED to determine Burgers vectors of straight dislocations and loops in silicon from observations of splitting of HOLZ lines within the forward scattered beam Bragg disk, and from splitting of Kikuchi lines associated with HOLZ Bragg reflections.
Abstract: Convergent-beam electron diffraction (CBED) patterns contain diffracted beams from higher-order Laue zones (HOLZ), in addition to the more often observed diffracted beams from the zeroth-order reciprocal lattice zone (ZOLZ) that contains the origin of the reciprocal lattice. Since HOLZ diffraction vectors have non-zero components along the incident electron beam direction, they can detect components of static real-lattice displacement fields that lie along the incident electron beam direction, an event not possible for diffracted beams normal to the incident electron beam direction (i.e. ZOLZ diffracted beams). This effect is used in the present work to determine Burgers vectors of straight dislocations and loops in silicon from observations of splitting of HOLZ lines within the forward scattered beam Bragg disk, and from splitting of Kikuchi lines associated with HOLZ Bragg reflections. The method was also applied with limited success to dislocations in aluminum; here splitting was more difficult to observe because of the rather strong diffuse background in the CBED patterns. Calculations of HOLZ line splitting due to the presence of a dislocation in the irradiated crystal volume were in good qualitative agreement with the experimental observations. Effects on CBED patterns to be expected from some partial dislocations are discussed. This CBED method can be very useful for the determination of non-ZOLZ fault vector components in an atomic resolution structure-imaging microscope. These instruments usually have specimen tilt ranges limited to about 10°; thus conventional Burgers-vector analysis is not generally possible. Finally, the present CBED results show clearly that the projection approximation generally used to interpret structure fringe images is not strictly valid. the changes in fringe images or weak-beam images from HOLZ excitations remain to be evaluated.
82 citations
TL;DR: In this paper, the crystal structures of the defect pyrochlores TaWO 5.5, HTaWO 6, DTa WO 6, H 2 Ta 2 O 6, D 0.4 H 1.6 Ta WO 2.6, and H 2 T O 6 · H 2 O, have been investigated by neutron powder diffraction.
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TL;DR: In this article, the reliability of linear polymer structures determined by using electron diffraction data is investigated, and the results of n-beam dynamical calculations and kinematic calculations which take account of crystal bending are compared with experimental structure factors for five published structures.
Abstract: The reliability of linear polymer structures determined by using electron diffraction data is investigated. The results of n-beam dynamical calculations and kinematic calculations which take account of crystal bending are compared with experimental structure factors for five published structures. In specific cases, both dynamical scattering and crystal bending effects are found to be important. Finally, guidelines are given for obtaining electron diffraction data which are optimal for structure solution.
TL;DR: In this paper, the resolution improvement and/or phase correction method devised for X-ray crystallography has been developed within the weak-scattering approximation for electron crystallography, where the information of electron micrography and electron diffraction can be effectively combined.
Abstract: The resolution improvement and/or phase correction method devised for X-ray crystallography has been developed within the weak-scattering approximation for electron crystallography. Here the information of electron micrography and electron diffraction can be effectively combined. The usefulness of this method to improve the resolution and to improve the image quality has been demonstrated by test calculations. This method will be effective for radiation-sensitive materials, because it can work with only one micrograph and the diffraction data.
TL;DR: In this article, a microprobe reflection high energy electron diffraction (RHEED) apparatus including an electron gun with a probe size of 0.1 µm operated under ultrahigh vacuum, has been constructed.
Abstract: A micro-probe reflection high-energy electron diffraction (RHEED) apparatus including an electron gun with a probe size of 0.1 µm operated under ultrahigh vacuum, has been constructed. This makes it possible to obtain bright, sharp diffraction patterns from micro-areas of clean surfaces, and to take RHEED-microscope images of crystal surfaces. Using this apparatus, a technique for determining the crystallographic orientations of surface micro-areas within an accuracy of ±1° has been developed. This is done by analyzing Kikuchi patterns emitted at low angles, and spatial distributions having various crystallographic orientations are obtained by taking RHEED-microscope images. From the results of applying this technique to polycrystal-Silicon surfaces, it is found that it is very useful in determining the crystallographic orientations of surface micro-areas.
TL;DR: In this article, the authors found five orientational relationships and several degrees of texturing between α-Zr(0001) and its oxide, and extended the earlier study of the relationship.
TL;DR: In this paper, Ag M 4 N 4,5 N 4.5 Auger electron diffraction and Ag 3D X-ray photoelectron diffraction from Ag(110) surface have been measured and interpreted kinematically.
Abstract: Ag M 4 N 4,5 N 4,5 Auger electron diffraction and Ag 3d X-ray photoelectron diffraction from Ag(110) surface have been measured and interpreted kinematically. There is very good agreement between the experiment and the interpretation showing the applicability of the kinematical interpretation.
TL;DR: In this paper, an X-ray single crystal analysis of MnSO4·5H2O showed that the manganese atoms are octahedrally coordinated by oxygen atoms, four belonging to water molecules and two to sulphate groups.
Abstract: Abstract X-ray single crystal analysis of MnSO4·5H2O shows that the manganese atoms are octahedrally coordinated by oxygen atoms, four of which belong to water molecules and two to sulphate groups. A model derived from the crystal structure was fitted to the X-ray scattering intensities from aqueous MnSO4. Good agreement with experimental data is achieved using a model in which Mn(H2O)6-z(OSO3)z+2-2z interacts with about ten water molecules and each sulphate ion with about seven water molecules.
TL;DR: It has been shown by gas phase electron diffraction analysis that the conformation of the 1,3-propanediol molecule is determined by an intramolecular hydrogen bond as mentioned in this paper.
TL;DR: A superlattice was found to arise as a result of ordering of the Bi and Ba atoms in the structure of the BaO system as mentioned in this paper, which can be regarded as microdomains within the parent crystal matrix.
TL;DR: In this paper, a new structure refinement of p-C6H4(CN)2 was performed by means of neutron-diffraction-measurements at room temperature, and the results were compared with former X-ray analyses by Rij and Britton, and Drück and Littke.
Abstract: A new structure refinement of p-C6H4(CN)2 was performed by means of neutron-diffraction-measurements at room temperature. The results are compared with former X-ray analyses by Rij and Britton, and Drück and Littke. The agreement of the parameters of the non-hydrogen atoms is found to be satisfactory.
TL;DR: In this article, an X-ray diffraction experiment on a 2.98 molar ZnSO4 aqueous solution has been interpreted in terms of coordination models and the best agreement between model and experimental structure functions was reached when the Zn2+ ion is hydrated in octahedral form, with twelve water molecules in a second hydration shell, bonded by shortened H-bonds to the first hydration shells.
Abstract: An X-ray diffraction experiment on a 2.98 molar ZnSO4 aqueous solution has been interpreted in terms of coordination models. The best agreement between model and experimental structure functions was reached when the Zn2+ ion is hydrated in octahedral form, with twelve water molecules in a second hydration shell, bonded by shortened H-bonds to the first hydration shell. The sulfate group is loosely coordinated by 8.2 water molecules. Besides the dominating Zn(H2O)2+6 complexes, about 40% [Zn(H2O)5SO4] inner complexes were found to be consistent with the X-ray data. Alternative models of cationic hydration are critically examined and for the sulfate group the independent atom approximation is compared with a spherical molecular description.
TL;DR: In this article, a microprobe reflection high-energy electron diffraction (micro-probe RHEED) technique has been used to observe the epitaxial growth of Al at room temperature on a polycrystal-Si (poly-Si) surface.
Abstract: A micro-probe reflection high-energy electron diffraction (micro-probe RHEED) technique has been used to observe the epitaxial growth of Al at room temperature on a polycrystal-Si (poly-Si) surface. A new beam-scanning method has also been developed to remove the image-shortening effect caused by a small glancing angle of incidence. From the Auger electron intensities, diffraction patterns and RHEED microscope images of an Al-deposited poly-Si surface, it is found that an Al film several atomic layers thick with the Al lattice constant grows epitaxially on the poly-Si surface with almost uniform sticking probability. The results show that the micro-probe RHEED technique is useful in studying the crystal growth of materials deposited on crystal surfaces, especially on polycrystal surfaces.
Journal Article•
TL;DR: In this paper, electron diffraction and imaging in the transmission electron microscope were used to study the structure of boundaries with misorientations from 4·7° to 38·5°, and a strong tendency for these boundaries to facet in a periodic fashion was observed.
Abstract: Samples of high-purity, secondary recrystallized Fe–3%Si sheet which contained [110] tilt boundaries with a wide range of angular misorientation have been prepared by a series of rolling and annealing steps. Electron diffraction and imaging in the transmission electron microscope were used to study the structure of boundaries with misorientations from 4·7° to 38·5°. The boundaries investigated were either parallel to or slightly inclined to the electron beam. A strong tendency for these boundaries to facet in a periodic fashion was observed, and electron diffraction effects from both the facets and from periodic arrays of grain boundary dislocations were found. In most samples the facets occurred along a direction which bisected the angle between the [110] directions of the two crystals comprising the boundary. This direction is shown to contain a high density of 0-lattice points. The occurrence and spacing of the grain boundary dislocations are considered in terms of 0-lattice concepts. It is su...