Anomalous Small Angle X-Ray Scattering Studies of Metal-Germanium Alloys

1990 ◽  
Vol 187 ◽  
Author(s):  
Marybeth Rice ◽  
Soichi Wakatsuki ◽  
Arthur Bienenstock
Keyword(s):  
Small Angle ◽  
Density Fluctuations ◽  
Nanometer Scale ◽  
X Ray ◽  
Composition Modulation ◽  
X Ray Scattering ◽  
Metal Atoms ◽  
Electron Density Fluctuations ◽  
Scale Composition ◽  
Ray Scattering

AbstractThe tunability of synchrotron radiation was used to perform anomalous small angle x-ray scattering (ASAXS) experiments on amorphous metal-germanium (a-Mx Ge1−x) alloys with the aim of detecting and characterizing compohitioK modulation and phase separation. Small angle x-ray scattering is sensitive to electron density fluctuations on a scale of tens to thousands of Angstroms. The combination of SAXS with the anomalous dispersion effect allows one to distinguish composition modulation from density fluctuations arising from voids and defects. Data gathered from a-FexGe1−x and a-WxGe1−x samples in the low metal concentration regime show nanometer scale composition modulation. In these samples the density of Ge atoms is uniform throughout the sample. The small angle x-ray scattering arises from fluctuations in the density of metal atoms.

On the nanostructure of radiation-amorphized zircon and pyrochlores: a small-angle x-ray scattering study

2005 ◽  
Vol 220 (8) ◽  
Author(s):  
Susana Ríos ◽  
Christopher M. Martin ◽  
Karl R. Whittle
Keyword(s):  
Small Angle ◽  
Annealing Temperature ◽  
Characteristic Length ◽  
Structural Features ◽  
Density Fluctuations ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Electron Density Fluctuations ◽  
Ray Scattering

AbstractNanoscale structural features of amorphous zircon and pyrochlore produced by self-irradiation induced amorphization have been characterized by small-angle X-ray scattering (SAXS). Electron density fluctuations were observed in the untreated samples and studied as a function of annealing temperature (up to 1300 °C). In untreated zircon, density fluctuations were found to have a characteristic length-scale of approximately 1 nanometer diameter. A clear scattering maximum develops at ∼3 nm

Small-angle x-ray scattering characterization of self-irradiated zircon

2003 ◽  
Vol 792 ◽  
Author(s):  
Susana Ríos ◽  
Ekhard K. H. Salje
Keyword(s):  
Small Angle ◽  
Small Variation ◽  
Density Fluctuations ◽  
Strong Increase ◽  
X Ray ◽  
Amorphous Content ◽  
X Ray Scattering ◽  
Zircon Structure ◽  
Electron Density Fluctuations ◽  
Ray Scattering

ABSTRACTSmall-angle x-ray scattering (SAXS) measurements were performed on two natural zircons: one with an amorphous content close to 85 %, and the second one x-ray amorphous. Electron density fluctuations were observed in the untreated samples, and studied as a function of various heat-treatments. In the starting material, density fluctuations were found to have a characteristic length-scale of approximately 1 nanometer diameter. Below 800 °C, the SAXS contribution (Q<10 nm-1) showed only a small variation as a function of temperature. Above 800 °C, a strong increase in intensity is observed, accompanied by the precipitation of 2–3 nm zirconia domains. At high enough temperatures, >1000 °C, when the amorphous phase recrystallizes into the starting zircon structure, characteristics of surface-scattering are observed, associated to large zircon regions.

Small-Angle X-Ray Scattering Studies of Glow-Discharge-Produced a-SiGe:H Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
Scott J. Jones ◽  
Yan Chen ◽  
D. L. Williamson ◽  
G.D. Mooney
Keyword(s):  
Glow Discharge ◽  
Small Angle ◽  
Film Plane ◽  
Density Fluctuations ◽  
Size Distributions ◽  
General Increase ◽  
X Ray ◽  
X Ray Scattering ◽  
Electron Density Fluctuations ◽  
Ray Scattering

ABSTRACTElectron density fluctuations associated with microstructural features on a scale from about 1 to 25 nm in glow-discharge-deposited a-Si1-xGex:H films were studied by the technique of small-angle x-ray scattering (SAXS). Films prepared in four different deposition systems (in different laboratories) have been characterized and a general increase in the SAXS signal with increasing x is observed. Density deficiencies determined from film flotation measurements lead to the correlation of the increased scattering intensities with increases in the volume fractions of micro voids. Modeling of the data yields void size distributions that demonstrate significantly more of the larger voids (2 to 6 nm) than found at x=0 (around 1 nm). For the alloys with x>0.4, the scattering at the smallest angles was observed to decrease substantially upon tilting of the sample relative to the x-ray beam. This result contrasts with the small or no changes in SAXS upon tilting device-quality x=0 films. This anisotropie scattering associated with the tilting experiments has been modeled with distributions of ellipsoidal microvoids that are preferentially oriented with their major axes normal to the film plane. This latter result is consistent with a columnar-like microstructure. However, one film with x=0.37 shows no evidence for such microstructure.

scholarly journals The inertia-equivalent ellipsoid: a link between atomic structure and low-resolution models of small globular proteins determined by small-angle X-ray scattering

1992 ◽  
Vol 25 (2) ◽  
pp. 181-191 ◽  
Author(s):  
J. J. Müller ◽  
H. Schrauber
Keyword(s):  
Small Angle ◽  
Computer Experiment ◽  
Density Fluctuations ◽  
Molecular Surface ◽  
Triaxial Ellipsoid ◽  
Correction Factors ◽  
Low Resolution ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Low-resolution three-parameter models of the shape of a biopolymer in solution can be determined by a new indirect method from small-angle X-ray scattering without contrast-variation experiments. The basic low-resolution model employed is a triaxial ellipsoid – the inertia-equivalent ellipsoid (IEE). The IEE is related to the tensor of inertia of a body and the eigenvalues and eigenvectors of this tensor can be calculated directly from the atomic coordinates and from the homogeneous solvent-excluded body of a molecule. The IEE defines a mean molecular surface (like the sea level on earth) which models the molecular shape adequately if the IEE volume is not more than 30% larger than the dry volume of the molecule. Approximately 10 to 15% of the solvent-excluded volume is outside the ellipsoid; the radii of gyration of the IEE and of the homogeneous molecular body are identical. The largest diameter of the IEE is about 5 to 15% (~0.2–0.8 nm) smaller than the maximum dimension of globular molecules with molecular masses smaller than 65000 daltons. From the scattering curve of a molecule in solution the IEE can be determined by a calibration procedure. 29 proteins of known crystal structure have been used as a random sample. Systematic differences between the axes of the IEE, calculated directly from the structure, and the axes of the scattering-equivalent ellipsoids of revolution, estimated from the scattering curve of the molecule in solution, are used to derive correction factors for the axial dimensions. Distortions of model dimensions of 20 to 40% (up to 1 nm), caused by misinterpretation of scattering contributions from electron density fluctuations within the molecule, are reduced to a quarter by applying these correction factors to the axes of the scattering-equivalent ellipsoids of revolution. In a computer experiment the axes of the inertia-equivalent ellipsoids have been determined for a further nine proteins with the same accuracy. The automated estimation of the IEE from the scattering curve of a molecule in solution is realized by the Fortran77 program AUTOIEE.

Characterising density fluctuations in liquid yttria aluminates with small angle x-ray scattering

2009 ◽  
Author(s):  
G. Neville Greaves ◽  
Martin C. Wilding ◽  
Quang Vu Van ◽  
Odile Majérus ◽  
Louis Hennet ◽  
...  
Keyword(s):  
Small Angle ◽  
Density Fluctuations ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Correlation of Small-Angle X-Ray Scattering and Solar Cell Performance of a-SiGe:H Alloys

1993 ◽  
Vol 297 ◽  
Author(s):  
S.J. Jones ◽  
Y. Chen ◽  
D.L. Williamson ◽  
X. Xu ◽  
J. Yang ◽  
...  
Keyword(s):  
Solar Cell ◽  
Small Angle ◽  
Film Surface ◽  
Nanometer Scale ◽  
Low Density ◽  
Solar Cell Performance ◽  
X Ray ◽  
X Ray Scattering ◽  
Cell Structures ◽  
Ray Scattering

Small-angle x-ray scattering (SAXS) measurements were made on a-SiGe:H alloys to study microstructure on the nanometer scale as a function of Ge content, and the results were compared with representative single-junction solar cell properties. Samples consisting of only the i-layer were used for SAXS. Above a Ge content of 20 %, a significant increase in SAXS was seen. From measurements made with the samples tilted relative to the incident x-ray beam, the increase in scattering is attributed to the appearance of elongated low density regions in the film, modeled as ellipsoidal microvoids, which are preferentially oriented perpendicular to the film surface and may be related to columnar-like microstructure. Flotation density measurements support the presence of low density regions. Initial and light-degraded measurements on corresponding solar cell structures do not show a correlation between SAXS and initial cell properties; there is, however, some evidence that the light-induced degradation is higher for cells with larger amounts of SAXS-detected microstructure and this needs further investigation.

Small-angle X-ray scattering study on correlation length and density fluctuations in a supercritical CO2–water mixture

2002 ◽  
Vol 198 (2) ◽  
pp. 251-256 ◽  
Author(s):  
Jianling Zhang ◽  
Juncheng Liu ◽  
Liang Gao ◽  
Xiaogang Zhang ◽  
Zhenshan Hou ◽  
...  
Keyword(s):  
Correlation Length ◽  
Small Angle ◽  
Supercritical Co2 ◽  
Density Fluctuations ◽  
Water Mixture ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Ray Scattering

Small angle x-ray scattering of a supercritical electrolyte solution: The effect of density fluctuations on the hydration of ions

2005 ◽  
Vol 122 (19) ◽  
pp. 194505 ◽  
Author(s):  
Denis Testemale ◽  
Marie Vanessa Coulet ◽  
Jean Louis Hazemann ◽  
Jean Paul Simon ◽  
Françoise Bley ◽  
...  
Keyword(s):  
Electrolyte Solution ◽  
Small Angle ◽  
Density Fluctuations ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals Density fluctuations in oxide glasses investigated by small-angle X-ray scattering

2007 ◽  
Vol 40 (s1) ◽  
pp. s512-s516 ◽  
Author(s):  
Claire Levelut ◽  
Rozenn Le Parc ◽  
Annelise Faivre ◽  
Ralf Brüning ◽  
Bernard Champagnon ◽  
...  
Keyword(s):  
Small Angle ◽  
Density Fluctuations ◽  
Oxide Glasses ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering
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