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.

The Detection of Transmitted Energy Loss Electrons for Elemental Analysis

1975 ◽  
Vol 33 ◽  
pp. 236-237
Author(s):  
D. E. Johnson ◽  
M. Isaacson
Keyword(s):  
Energy Loss ◽  
Elemental Analysis ◽  
Detection Efficiency ◽  
Collection Efficiency ◽  
Incident Beam ◽  
Light Elements ◽  
Beam Direction ◽  
X Ray ◽  
Transmitted Energy

Elemental analysis by means of energy loss electrons transmitted through thin specimens has the potential of being a very useful technique for the microanalysis of light elements (e.g. 1-5). The advantages of the energy loss technique over x-ray detection have been discussed in detail in ref. 1. They are basically, the lack of dependence of the detection efficiency on the fluorescent yield (which decreases rapidly with decreasing Z) and the possibility of increased collection efficiency of the energy loss electrons (which are concentrated at relatively small angles with respect to the incident beam direction).

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

scholarly journals Total reflection X-ray fluorescence

2019 ◽  
Vol 4 (7) ◽  
Author(s):  
Martina Schmeling
Keyword(s):  
Thin Layer ◽  
Trace Analysis ◽  
Critical Angle ◽  
Incident Angle ◽  
Biological Tissues ◽  
Total Reflection ◽  
Angle Of Incidence ◽  
X Ray ◽  
Flat Substrate ◽  
Layer Analysis

Abstract Total reflection X-ray fluorescence (TXRF) spectrometry is a non-destructive and surface sensitive multi-element analytical method based on energy dispersive X-ray fluorescence spectrometry with detection limits in the lower picogram range. It utilizes the total reflection of the primary X-ray beam at or below the critical angle of incidence. At this angle, the fluorescence intensity is substantially enhanced for samples present as small granular residue or as thin homogenous layer deposited at the surface of a thick substrate. Generally, two types of application exist: micro- and trace-analysis as well as surface and thin-layer analysis. For micro- and trace-analysis, a small amount of the solid or liquid sample is deposited on an optically flat substrate, typically quartz or polycarbonate. The dried residue is analyzed at a fixed angle setting slightly below the critical angle. Quantification is carried out by means of internal standardization. For surface and thin-layer analysis, the surface of an optically flat substrate is scanned. Variations of the incident angle of the primary X-ray beam provide information about the type and sometimes also the amount of material present at or slightly below the surface of the substrate. Major fields of application are environmental samples, biological tissues, objects of cultural heritage, semiconductors and thin-layered materials and films.

Arsenic segregation in polysilicon

1983 ◽  
Vol 41 ◽  
pp. 154-155 ◽  
Author(s):  
P.E. Batson ◽  
C.R.M. Grovenor ◽  
D.A. Smith ◽  
C. Wong
Keyword(s):  
Incident Beam ◽  
Silicon Wafers ◽  
Chemical Polishing ◽  
Bright Field Image ◽  
Beam Size ◽  
Stem Analysis ◽  
Bright Field ◽  
Twin Boundaries ◽  
X Ray ◽  
Line Scan

In this work As doped polysilicon was deposited onto (100) silicon wafers by APCVD at 660°C from a silane-arsine mixture, followed by a ten minute anneal at 1000°C, and in one case a further ten minute anneal at 700°C. Specimens for TEM and STEM analysis were prepared by chemical polishing. The microstructure, which is unchanged by the final 700°C anneal,is shown in Figure 1. It consists of numerous randomly oriented grains many of which contain twins.X-ray analysis was carried out in a VG HB5 STEM. As K α x-ray counts were collected from STEM scans across grain and twin boundaries, Figures 2-4. The incident beam size was about 1.5nm in diameter, and each of the 20 channels in the plots was sampled from a 1.6nm length of the approximately 30nm line scan across the boundary. The bright field image profile along the scanned line was monitored during the analysis to allow correlation between the image and the x-ray signal.

Optimizing conditions for x-ray microchemical analysis in analytical electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 548-549 ◽  
Author(s):  
N. J. Zaluzec
Keyword(s):  
Solid Angle ◽  
Analytical Electron Microscopy ◽  
Incident Beam ◽  
Thin Foil ◽  
Experimental Conditions ◽  
X Ray ◽  
Microchemical Analysis ◽  
Analytical Electron ◽  
Image Position ◽  
Incident Beam Energy

The ultimate sensitivity of microchemical analysis using x-ray emission rests in selecting those experimental conditions which will maximize the measured peak-to-background (P/B) ratio. This paper presents the results of calculations aimed at determining the influence of incident beam energy, detector/specimen geometry and specimen composition on the P/B ratio for ideally thin samples (i.e., the effects of scattering and absorption are considered negligible). As such it is assumed that the complications resulting from system peaks, bremsstrahlung fluorescence, electron tails and specimen contamination have been eliminated and that one needs only to consider the physics of the generation/emission process.The number of characteristic x-ray photons (Ip) emitted from a thin foil of thickness dt into the solid angle dΩ is given by the well-known equation

Voltage and Orientation Dependence of Characteristic X-Ray Production in Thin Crystals

1985 ◽  
Vol 43 ◽  
pp. 414-415
Author(s):  
G. Thomas ◽  
K. M. Krishnan ◽  
Y. Yokota ◽  
H. Hashimoto
Keyword(s):  
Standing Wave ◽  
Incident Beam ◽  
Orientation Dependence ◽  
Incident Plane Wave ◽  
Crystalline Materials ◽  
X Ray ◽  
Incident Plane ◽  
Crystal Unit Cell ◽  
Beam Orientation ◽  
Acceleration Voltage

For crystalline materials, an incident plane wave of electrons under conditions of strong dynamical scattering sets up a standing wave within the crystal. The intensity modulations of this standing wave within the crystal unit cell are a function of the incident beam orientation and the acceleration voltage. As the scattering events (such as inner shell excitations) that lead to characteristic x-ray production are highly localized, the x-ray intensities in turn, are strongly determined by the orientation and the acceleration voltage. For a given acceleration voltage or wavelength of the incident wave, it has been shown that this orientation dependence of the characteristic x-ray emission, termed the “Borrmann effect”, can also be used as a probe for determining specific site occupations of elemental additions in single crystals.

Multislice calculations of RHEED patterns from vicinal Si (001)

1993 ◽  
Vol 51 ◽  
pp. 1000-1001
Author(s):  
Scott Lordi
Keyword(s):  
Misorientation Angle ◽  
Incident Angle ◽  
Incident Beam ◽  
Experimental Results ◽  
Bragg Condition ◽  
Vicinal Surfaces ◽  
Kinematic Theory ◽  
Step Edges

Vicinal Si (001) surfaces are interesting because they are good substrates for the growth of III-V semiconductors. Spots in RHEED patterns from vicinal surfaces are split due to scattering from ordered step arrays and this splitting can be used to determine the misorientation angle, using kinematic arguments. Kinematic theory is generally regarded to be inadequate for the calculation of RHEED intensities; however, only a few dynamical RHEED simulations have been attempted for vicinal surfaces. The multislice formulation of Cowley and Moodie with a recently developed edge patching method was used to calculate RHEED patterns from vicinal Si (001) surfaces. The calculated patterns are qualitatively similar to published experimental results and the positions of the split spots quantitatively agree with kinematic calculations.RHEED patterns were calculated for unreconstructed (bulk terminated) Si (001) surfaces misoriented towards [110] ,with an energy of 15 keV, at an incident angle of 36.63 mrad ([004] bragg condition), and a beam azimuth of [110] (perpendicular to the step edges) and the incident beam pointed down the step staircase.

scholarly journals Possible Pitfalls in the Analysis of Minerals and Loose Materials by Portable XRF, and How to Overcome Them

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 33
Author(s):  
Valérie Laperche ◽  
Bruno Lemière
Keyword(s):  
Fluorescence Spectroscopy ◽  
Laboratory Data ◽  
Data Sets ◽  
Light Elements ◽  
Portable Xrf ◽  
X Ray ◽  
Protective Films ◽  
The Matrix ◽  
Valuable Complement ◽  
Physical Effects

Portable X-ray fluorescence spectroscopy is now widely used in almost any field of geoscience. Handheld XRF analysers are easy to use, and results are available in almost real time anywhere. However, the results do not always match laboratory analyses, and this may deter users. Rather than analytical issues, the bias often results from sample preparation differences. Instrument setup and analysis conditions need to be fully understood to avoid reporting erroneous results. The technique’s limitations must be kept in mind. We describe a number of issues and potential pitfalls observed from our experience and described in the literature. This includes the analytical mode and parameters; protective films; sample geometry and density, especially for light elements; analytical interferences between elements; physical effects of the matrix and sample condition, and more. Nevertheless, portable X-ray fluorescence spectroscopy (pXRF) results gathered with sufficient care by experienced users are both precise and reliable, if not fully accurate, and they can constitute robust data sets. Rather than being a substitute for laboratory analyses, pXRF measurements are a valuable complement to those. pXRF improves the quality and relevance of laboratory data sets.

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