Grain Surface Relaxation Effects in Powder Diffraction

2004 ◽  
pp. 413-454 ◽  
Author(s):  
M. Leoni ◽  
P. Scardi
Keyword(s):  
Powder Diffraction ◽  
Surface Relaxation ◽  
Relaxation Effects ◽  
Grain Surface

Grain Surface Relaxation and Grain Interaction in Powder Diffraction

2004 ◽  
Vol 443-444 ◽  
pp. 1-10 ◽  
Author(s):  
Matteo Leoni
Keyword(s):  
Powder Diffraction ◽  
Surface Relaxation ◽  
X Ray Diffraction ◽  
Polycrystalline Thin Film ◽  
Average Cell ◽  
Surfaces And Interfaces ◽  
Grain Interaction ◽  
Single Grain ◽  
Grain Surface

The role of grain surfaces and interfaces in nanocrystalline materials is investigated by X-ray diffraction (XRD). Two apparently distinct aspects show the importance of the interaction of a single grain with the environment in which it is placed: the role of grain-grain interaction in determining the residual stress in a polycrystalline thin film and the surface effects in single powder grains on the macroscopic average cell parameter determined by powder diffraction. A brief theoretical introduction of the phenomena and their possible modelling is presented together with a discussion of practical examples.

Surface relaxation effects on the properties of porous silicon

2002 ◽  
Vol 91 (5) ◽  
pp. 3085-3089 ◽  
Author(s):  
E. Vázquez ◽  
J. Tagüeña-Martı́nez ◽  
L. E. Sansores ◽  
C. Wang
Keyword(s):  
Porous Silicon ◽  
Surface Relaxation ◽  
Relaxation Effects

Influence of surface relaxation on the contrast of threading edge dislocations in synchrotron X-ray topographs under the condition of g · b = 0 and g · b × l = 0

2021 ◽  
Vol 54 (2) ◽  
Author(s):  
Hongyu Peng ◽  
Tuerxun Ailihumaer ◽  
Fumihiro Fujie ◽  
Zeyu Chen ◽  
Balaji Raghothamachar ◽  
...  
Keyword(s):  
Ray Tracing ◽  
Depth Profiling ◽  
Simulation Method ◽  
Surface Relaxation ◽  
X Ray ◽  
Relaxation Effects ◽  
Orientation Contrast ◽  
Relaxation Depth ◽  
Edge Dislocations ◽  
Ray Tracing Simulation

Residual contrast of threading edge dislocations is observed in synchrotron back-reflection X-ray topographs of 4H-SiC epitaxial wafers recorded using basal plane reflections where both g · b = 0 and g · b × l = 0. The ray-tracing simulation method based on the orientation contrast formation mechanism is applied to simulate images of such dislocations by applying surface relaxation effects. The simulated contrast features match the observed features on X-ray topographs, clearly demonstrating that the contrast is dominated by surface relaxation. Depth profiling indicates that the surface relaxation primarily takes place within a depth of 5 µm below the surface.

Influence of Surface Relaxation and Multi-Dislocation Strain Field Interactions on X-ray Topographic Images of Dislocations in Semiconductor Materials

1992 ◽  
Vol 262 ◽  
Author(s):  
Jun Wu ◽  
Thomas Fannin ◽  
Michael Dudley ◽  
Vijay Shastry ◽  
Peter Anderson
Keyword(s):  
Local Stress ◽  
Surface Relaxation ◽  
Contour Analysis ◽  
Displacement Fields ◽  
X Ray ◽  
Relaxation Effects ◽  
Slip Bands ◽  
Sensitive Function ◽  
Local Slip ◽  
Surface Intersections

ABSTRACTAnalysis of the white beam synchrotron x-ray topographic contrast behavior of screw dislocations comprising slip bands in silicon, observed under low absorption conditions, is presented. For both individual and groups of dislocations, observed “Direct Image” contrast at the surface intersections of dislocation lines, on reflections for which g·b=0, could be accounted for using equi-misorientation contour analysis using displacement fields which take surface relaxation effects into account. This contrast is shown to be a sensitive function of the local stress environment. In addition, diffuse area contrast observed within and in the vicinity of slip bands on such reflections is also observed to be very sensitive to long range strain fields associated with adjacent slip bands and other defects in the local slip band environment.

Determination of Strain Distributions in Aluminum Thin Films as a Function of Temperature by the use of Synchrotron Grazing Incidence X-Ray Scattering

1991 ◽  
Vol 239 ◽  
Author(s):  
Ramnath Venkatraman ◽  
Paul R. Besser ◽  
Sean Brennan ◽  
John C. Bravman
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Grazing Incidence ◽  
Surface Relaxation ◽  
Line Broadening ◽  
X Ray ◽  
Relaxation Effects ◽  
X Ray Scattering ◽  
Ray Scattering

ABSTRACTWe have measured elastic strain distributions with depth as a function of temperature in Al thin films of various thicknesses on oxidized silicon using synchrotron grazing incidence X-ray scattering (GIXS). Disregarding minor surface relaxation effects that depend on the film thickness, it is shown that there are no gross strain gradients in these films in the range of temperatures (between room temperature and 400°C) considered. We also observe X-ray line broadening effects, suggesting an accumulation of dislocations on cooling the films, and their annealing out as the films are reheated.

Influence of Surface Relaxation on X-Ray Topographic Imaging of Interfacial Dislocations in Heterosystems.

1990 ◽  
Vol 209 ◽  
Author(s):  
Gong-Da Yao ◽  
Jun Wu ◽  
Michael Dudley ◽  
Vijay Shastry ◽  
Peter Anderson
Keyword(s):  
Surface Relaxation ◽  
X Ray ◽  
Relaxation Effects ◽  
Single Crystal Films ◽  
Crystal Films ◽  
Interfacial Dislocations ◽  
Depth Sensitivity ◽  
Edge Dislocations ◽  
Topographic Imaging ◽  
Laue Geometry

ABSTRACTThe influence of surface relaxation on the imaging of dislocations in thin single crystal films, using white beam synchrotron radiation topography in grazing Bragg-Laue geometry, has been assessed. The predicted visibility of dislocation images on grazing Bragg- Laue topographs, for the particular case of interfacial edge dislocations in a GaAs/Si heterostructure, is shown to be strongly influenced. Agreement between predicted and observed visibility could only be obtained by incorporating the surface relaxation effects, which thus strongly influence the depth sensitivity of the technique, i.e. the ability to pinpoint the depth of a dislocation. Dislocation image widths are also influenced by these effects.

Powder diffraction in studies of nanocrystal surfaces: chemisorption on Pt

2014 ◽  
Vol 47 (6) ◽  
pp. 2069-2077 ◽  
Author(s):  
Zbigniew Kaszkur ◽  
Piotr Rzeszotarski ◽  
Wojciech Juszczyk
Keyword(s):  
Surface Science ◽  
Surface Reconstruction ◽  
Powder Diffraction ◽  
Relaxation Effect ◽  
Peak Shift ◽  
Physicochemical Process ◽  
Diffraction Peak ◽  
Surface Relaxation ◽  
Structure Evolution ◽  
Crystallographic Structure

Atoms at the surface of nanocrystals contribute appreciably to the X-ray diffraction pattern. Phenomena like chemisorption, affecting the displacement of surface atoms with respect to their positions in the perfect crystallographic structure, cause diffraction peak shifts and intensity changes. These effects are easily measurable for small nanocrystals up to 10 nm size. This article reports diffraction effects of chemisorption of adsorbing gases H2, O2, CO and NO for a series ofin situpowder diffraction experiments on nanocrystalline Pt supported on silica. On the basis of previous diffraction observation of Pt surface reconstruction during hydrogen desorption, it was possible to quantify this effectversuscrystallite size and rationalize the observed diffraction peak shift for the other adsorbing species. This enabled the surface reconstruction to be distinguished from the surface relaxation effect, the latter depending monotonically on the adsorption energy. Even if no phase transition occurs, monitoring of a peak's position, intensity, width and gas composition (viamass spectrometry) during a carefully designed physicochemical process (including surface chemical reaction) enables insight into and understanding of the surface structure evolution (e.g.amorphization, relaxation, reconstruction or changes in the overall morphology). The proposed technique can be used as a surface science tool, allowing studies of nanocrystals under high pressure.

scholarly journals Carbon and Neon Ion Bombardment Induced Smoothing and Surface Relaxation of Titania Nanotubes

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2458
Author(s):  
Astrid Kupferer ◽  
Michael Mensing ◽  
Jan Lehnert ◽  
Stephan Mändl ◽  
Stefan Mayr
Keyword(s):  
Mass Density ◽  
Particle Surface ◽  
Surface Characteristics ◽  
Ion Bombardment ◽  
Surface Relaxation ◽  
Nanotube Arrays ◽  
Relaxation Effects ◽  
Titania Nanotube Arrays ◽  
Titania Nanotube ◽  
Neon Ion

Titania nanotube arrays with their enormous surface area are the subject of much attention in diverse fields of research. In the present work, we show that not only 60 keV and 150 keV ion bombardment of amorphous titania nanotube arrays yields defect creation within the tube walls, but it also changes the surface morphology: the surface relaxes and smoothens in accordance with a curvature-driven surface material’s transport mechanism, which is mediated by radiation-induced viscous flow or radiation-enhanced surface diffusion, while the nanotubes act as additional sinks for the particle surface currents. These effects occur independently of the ion species: both carbon and neon ion bombardments result in comparable surface relaxation responses initiated by an ion energy of 60 keV at a fluence of 1 × 1016 ions/cm2. Using atomic force microscopy and contact angle measurements, we thoroughly study the relaxation effects on the surface topography and surface free energy, respectively. Moreover, surface relaxation is accompanied by further amorphization in surface-near regions and a reduction in the mass density, as demonstrated by Raman spectroscopy and X-ray reflectivity. Since ion bombardment can be performed on global and local scales, it constitutes a versatile tool to achieve well-defined and tunable topographies and distinct surface characteristics. Hence, different types of nanotube arrays can be modified for various applications.

Surface relaxation effect on diffraction contrast at Ni4W composite particles

1990 ◽  
Vol 48 (4) ◽  
pp. 500-501
Author(s):  
H. Zhao ◽  
G.C. Weatherly ◽  
K.T. Aust
Keyword(s):  
Thin Foil ◽  
Relaxation Effect ◽  
Displacement Function ◽  
Low Energy ◽  
Surface Relaxation ◽  
Matrix Interface ◽  
Beam Direction ◽  
Strain Fields ◽  
Diffraction Contrast ◽  
Relaxation Effects

In TEM studies, difficulties may arise in understanding the image contrast of a defect if surface relaxation effects are not considered. It is desirable to calculate the displacement function which includes the effect from both the defect itself and surface relaxation in a thin foil whenever possible. A TEM study of the Ni4W phase in a Ni-37%wtW alloy has revealed the multivariant domain (MVD) structures of the Ni4W bet phase as the low energy configuration. Ni4W plates were composed of laths of perpendicular twins aligned along the <110>m direction with perpendicular twin boundaries (PTBs) parallel to the {110}m plane of the (Ni) fee matrix. At the MVD/matrix interface, anomalous diffraction contrast was observed under various two beam conditions when the sample was viewed along the <011>m direction with the MVD/matrix interface parallel to the beam direction. A typical example is shown in Fig. 1. This phenomenon can be attributed to a surface relaxation effect which is related to the alternating shear strain fields resulting from the formation of the MVDs.

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