Article

1998 ◽  
Vol 76 (8) ◽  
pp. 621-643 ◽  
Author(s):  
D T Jiang ◽  
E D Crozier
Keyword(s):  
Critical Angle ◽  
Incident Angle ◽  
Anomalous Scattering ◽  
Multilayer Systems ◽  
Total Electron ◽  
X Ray ◽  
Cu Film ◽  
Scattering Effects ◽  
Glancing Angle ◽  
Reflectivity Data

The techniques for glancing-angle XAFS of ultrathin multilayer systems have been analyzed, with an emphasis on the conditions of detection modes under which distortion-free fine structure data are obtainable. The XANES of a multilayer system obtained in the total reflection geometry can be distorted because of anomalous dispersion effects in the sample layer and in adjacent media. The former plays a negligible role in ultrathin film cases. The latter, caused by the interference of the evanescent waves from the interfaces involved, cannot always be ignored. The distortion depends on the glancing angle, the composition of the layered structure (mainly the thickness of the layer of interest and the material of other layers), the energy from the absorption edge, and the detection modes adopted. Calculated results of these effects are presented and analytical expressions are provided in closed form. Experimental XANES data of a buried 8 monolayer (ML) Cu film, representing the thin limit, and 37 ML Ni, representing the medium thickness are used to illustrate the theory. In the thin limit, filtered fluorescence XANES data are independent of angle and are not distorted. However, total electron-yield and reflectivity data do depend on angle and are significantly distorted near the critical angle. The thickness dependence of the EXAFS measured at glancing angles is also analyzed. It is shown that both the distortions in EXAFS amplitude and phase caused by the anomalous scattering effects are strongly dependent on the sample film thickness, but when the sample thickness is in the range of 10 atomic layers the distortions are practically negligible for all X-ray incident angles. Experimental data for 8 ML bct Cu grown on Ag(001) substrate indicate that the phase and amplitude of the data have no detectable dependence on the X-ray incident angle through the critical-angle region, in agreement with the calculated results. PACS Nos. 61.10Ht, 87.64 Fb, 68.00, 68.35-p, and 68.55-a

A Total reflection X-Ray Spectrograph for Fluorescent Analysis of Light Elements

1968 ◽  
Vol 12 ◽  
pp. 496-505 ◽  
Author(s):  
R. D. Davies ◽  
H. K. Herglotz
Keyword(s):  
Critical Angle ◽  
Incident Angle ◽  
Incident Beam ◽  
Wavelength Dependence ◽  
Light Elements ◽  
X Ray ◽  
Beam Incident ◽  
Open Window ◽  
Angle Of Reflection ◽  
Initial Results

AbstractA novel x-ray spectrograph for the analysis of light elements has been developed based on previous computations and confirming experiments by one of as (H. K. Herglotz). The major components of the instrument are an efficient fluorescent source, a totally reflecting mirror, and an open window photomultiplier. Identification of wavelengths in the range 15 < λ < 80 Å is achieved by the wavelength dependence of the critical angle of reflection of an x-ray beam incident on a suitably chosen low absorption reflector. As the incident angle is increased through the critical angle for a particular wavelength, the reflected beam intensity is sharply reduced; hence, a periodic vibration of the incident beam through a small angular range about the critical angle furnishes a strong a.c. reflected signal characteristic of one narrow wavelength band only.Initial results promise a simple, easy-to-operate instrument for the routine analysis of elements boron to fluorine.

scholarly journals Structural characterization using the multiple scattering effects in grazing-incidence small-angle X-ray scattering

2008 ◽  
Vol 41 (1) ◽  
pp. 134-142 ◽  
Author(s):  
Byeongdu Lee ◽  
Chieh-Tsung Lo ◽  
P. Thiyagarajan ◽  
Dong R. Lee ◽  
Zhongwei Niu ◽  
...  
Keyword(s):  
Multiple Scattering ◽  
Small Angle ◽  
Incident Angle ◽  
Average Distance ◽  
Grazing Incidence ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Effects ◽  
Multiple Scattering Effects ◽  
Ray Scattering

The multiple scattering effects present in grazing-incidence small-angle X-ray scattering (GISAXS) data and interference between them are addressed theoretically as well as experimentally with measurement of a series of patterns at different incident angles, referred to as `incident-angle-resolved GISAXS' (IAR-GISAXS). X-ray reflectivity (XR), GISAXS and IAR-GISAXS of virus particles on Si-substrate supported-polystyrene films have been measured and all the data have been analyzed with appropriate formalisms. It was found that under certain conditions it is possible to extract the correct structural features of the materials from the GISAXS/IAR-GISAXS data using the kinematic SAXS formalisms, without the need to use the distorted-wave Born approximation. Furthermore, the Kiessig fringes in GISAXS enable the measurement of the average distance between the particle and the substrate, similar to the measurement of film thickness using the fringes in the XR data. It is believed that the methods developed here will expand the application of GISAXS as they enable the application of model-independent and kinematic SAXS theories to nanostructured two-dimensional ordered films.

The Phase of Scattering Profiles & X-Ray/Neutron Reflectivity

1994 ◽  
Vol 376 ◽  
Author(s):  
P.S. Pershan
Keyword(s):  
Critical Angle ◽  
Scattering Amplitude ◽  
Surface Scattering ◽  
Neutron Reflectivity ◽  
Phase Problem ◽  
X Ray Diffraction ◽  
Phase Information ◽  
X Ray ◽  
Reflectivity Data ◽  
Amplitude Density

ABSTRACTThe phase problem that troubles x-ray diffraction is also a problem for x-ray and neutron reflectivity; however, there are a range of small angles just beyond the critical angle for which the reflectivity contains information on the phase of the surface scattering amplitude. In principle this phase information can be used to determine the asymmetry of the normal gradient of the scattering amplitude density. We discuss here practical conditions under which this symmetry can, or cannot, be extracted from reflectivity data.

Observation of the strain field near the Si(111) 7 × 7 surface with a new X-ray diffraction technique

1998 ◽  
Vol 5 (3) ◽  
pp. 964-966 ◽  
Author(s):  
Takashi Emoto ◽  
Koichi Akimoto ◽  
Ayahiko Ichimiya
Keyword(s):  
Strain Field ◽  
Critical Angle ◽  
Total Reflection ◽  
Surface Structures ◽  
Native Oxide ◽  
Oxide Surface ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Glancing Angle

A new X-ray diffraction technique has been developed in order to measure the strain field near a solid surface under ultrahigh vacuum (UHV) conditions. The X-ray optics use an extremely asymmetric Bragg-case bulk reflection. The glancing angle of the X-rays can be set near the critical angle of total reflection by tuning the X-ray energy. Using this technique, rocking curves for Si surfaces with different surface structures, i.e. a native oxide surface, a slightly oxide surface and an Si(111) 7 × 7 surface, were measured. It was found that the widths of the rocking curves depend on the surface structures. This technique is efficient in distinguishing the strain field corresponding to each surface structure.

Preferred Orientation of Cu2O Nano-/Micro-Protrusions Grown by Ar Ion Irradiation

2010 ◽  
Vol 638-642 ◽  
pp. 1784-1789 ◽  
Author(s):  
Shogo Oda ◽  
Hiroyuki Tanaka ◽  
Shunichiro Tanaka
Keyword(s):  
Electron Backscatter Diffraction ◽  
Ion Irradiation ◽  
Incident Angle ◽  
Growth Direction ◽  
Preferred Orientation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Glancing Angle ◽  
Backscatter Diffraction ◽  
Growth Technology

We have developed a bottom-up growth technology for nanostructures from a Cu surface by Ar ion irradiation. Cu2O conical nano-/micro-protrusions have been nucleated and grown from the surface of a preoxidized Cu plate by Ar ion irradiation in low vacuum. In this study, the growth direction or preferred orientation of the protrusions was analysed using glancing angle X-ray diffraction (GAXRD) analysis and an X-ray diffraction pole figure (XRD-PF) measurement. The GAXRD patterns showed that the main phase of the product obtained by Ar irradiation was Cu2O, shown as the highest peak of Cu2O (111), and CuO was additionally formed. The intensity ratio of Cu2O (110) to Cu2O (111) increased as the X-ray incident angle decreased from 10.0 to 0.5 deg, which indicated that the basal plane of the protrusions including the substrate was (110). Additionally, the XRD-PF {011}<001> 3-D plots showed the <110> preferred orientation of the product. These results explain that the growth direction or preferred orientation of the Cu2O protrusions is mainly <110>. The growth direction of the protrusions was separated and confirmed as <110> by checking the electron backscatter diffraction pattern (EBSP) of each protrusion.

Anomalous Wide-Angle X-ray Scattering Apparatus on the GILDA Beamline at the ESRF

1998 ◽  
Vol 5 (5) ◽  
pp. 1258-1262 ◽  
Author(s):  
C. Meneghini ◽  
A. Balerna ◽  
F. Boscherini ◽  
S. Pascarelli ◽  
S. Mobilio
Keyword(s):  
High Efficiency ◽  
Detection System ◽  
Anomalous Scattering ◽  
Wide Angle ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Effects ◽  
Experimental Apparatus ◽  
Beam Stability ◽  
Ray Scattering

The experimental apparatus for anomalous wide-angle X-ray scattering (AWAXS) on the GILDA beamline at the ESRF is described. The main features are the high beam stability and reproducibility which allow anomalous scattering effects to be resolved also on dilute elements, the large spectral range which allows AWAXS experiments at the K edges of heavy elements, and the use of a high-efficiency detection system. The apparatus has been tested in extreme conditions by performing AWAXS experiments at the Eu K edge in Eu-doped Sr metaphosphate glasses.

Anomalous grazing-incidence small-angle X-ray scattering of Ga2O3-based nanoparticles

2018 ◽  
Vol 51 (2) ◽  
pp. 436-445 ◽  
Author(s):  
Christine Revenant
Keyword(s):  
Absorption Edge ◽  
Small Angle ◽  
Incident Angle ◽  
Grazing Incidence ◽  
Core Shell ◽  
Dense Layer ◽  
Anomalous Scattering ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Grazing-incidence small-angle X-ray scattering (GISAXS) performed at several X-ray energies in the vicinity of the absorption edge of a considered element is called anomalous GISAXS (AGISAXS). This emerging technique takes advantage of the variation of the scattering factor near an absorption edge, allowing the morphology of multi-component nanomaterials to be unraveled. The selected model system for AGISAXS simulations is mainly an In2O3layer containing Ga2O3-based nanoparticles. The transmission coefficients at the different X-ray energies near the GaKedge are identical at one specific incident angle (near the critical angle). Hence, it could be relevant to perform AGISAXS at this incident angle in order to cancel the transmission modification as the X-ray energy changes. For buried nanoparticles, grazing-incidence effects are negligible with respect to the anomalous element-specific contribution provided that the experiments are performed at energies a few electronvolts below the absorption edge. Interestingly, AGISAXS has a clearly different intensity behaviorversusX-ray energy for an embedded monodisperse spherical particle, a hole and a core–shell particle. Hence, AGISAXS can be used to unambiguously distinguish such embedded particles. Moreover, even for a dense layer of core–shell nanoparticles on a substrate, anomalous effects are much larger than grazing effects as the X-ray energy changes. Finally, it is shown that experimental anomalous scattering can be significant and can be satisfactorily simulated.

Determination of the Anomalous Scattering Factors in the Soft-X-ray Range using Diffraction from a Multilayer

1998 ◽  
Vol 31 (5) ◽  
pp. 700-707 ◽  
Author(s):  
L. Sève ◽  
J. M. Tonnerre ◽  
D. Raoux
Keyword(s):  
Fluorescence Yield ◽  
Bragg Diffraction ◽  
Anomalous Scattering ◽  
Total Electron Yield ◽  
Total Electron ◽  
X Ray ◽  
Scattering Factor ◽  
X Ray Absorption ◽  
Kronig Relation

Bragg diffraction from an Ag/Ni multilayer was used to determine independently both the real and imaginary parts of the anomalous scattering factor (ASF) around the NiLIIIandLIIedges in the soft-X-ray range. Huge resonant variations were observed with f'' reaching 55\,r_o and f' decreasing to −63 r_o at the NiLIIIedge. The independent measurements of f' and f'' are tested for coherency using the Kramers–Kronig relation. The f'' values are also compared with those derived from X-ray absorption methods such as total electron yield and fluorescence yield measurements.

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