Precision In X-Ray Data Computed By Monte Carlo Calculations

1999 ◽  
Vol 5 (S2) ◽  
pp. 86-87
Author(s):  
Eric Lifshin ◽  
Amy Linsebigler ◽  
Raynald Gauvin
Keyword(s):  
Electron Beam ◽  
Repeated Measurements ◽  
X Ray ◽  
Intensity Measurements ◽  
Beam Incidence ◽  
Excitation Volume ◽  
Counting Statistics ◽  
Normal Electron ◽  
Analytical Expressions ◽  
Single Set

The analytical expressions used in ZAF and ϕ(ρz) calculations give single values for the composition of each element for a single set of intensity measurements from samples and standards. Confidence intervals in composition are established by looking at the variability of repeated measurements. They are usually attributed to x-ray counting statistics or experimental reproducibility factors such as sample repositioning. Uncertainty in the equations themselves or the parameters that go into them are rarely considered. The derivations of ZAF and ϕ(ρz) equations are primarily based on the case where flat single-phase regions, relative to the x-ray excitation volume, are examined using normal electron beam incidence. Use of these equations has been extended to non-normal electron beam incidence as well as the quantitative analysis of layered structures, but usually with less theoretical justification. Finally, special experimental cases including porous structures, rough surfaces, vertical interfaces and small particles are very difficult or impossible to model by the single application of a set of analytical equations to convert measured x-ray intensities to elemental composition.

Bulk Composition from Electron Beam Excited X-RAY Analysis?

1992 ◽  
Vol 50 (2) ◽  
pp. 1662-1663
Author(s):  
Charles R. Herrington ◽  
Joseph D. Geller
Keyword(s):  
Electron Beam ◽  
Inductively Coupled Plasma ◽  
Bulk Composition ◽  
Optical Emission ◽  
X Rays ◽  
Bulk Analysis ◽  
X Ray ◽  
Inductively Coupled ◽  
Electron Beam Excitation ◽  
Excitation Volume

Bulk analysis is often accomplished using techniques such as classical wet chemistry, atomic absorption, x-ray fluorescence, inductively coupled plasma, combustion procedures, and optical emission spectroscopy. To use "ZAF" or other programs (which are for electron beam excited x-ray spectra) to convert "k" or intensity ratios to concentration it is required that the electron beam excitation volume be homogeneous. The correction programs calculate atomic number, absorption, and fluorescence factors from the detected x-ray intensity fractions assuming the x-rays are coming from this homogeneous volume. If the specimen is not homogeneous within the excitation volume the program will miscalculate the factors. Often used (but incorrectly applied) methods for analyzing large areas on bulk materials are defocusing of the electron beam and rastering a focussed beam over areas to cover the phases present. The purpose of this study is to demonstrate the dangers of improperly applying these corrections and to demonstrate the alternate technique of using phase area analysis combined with the chemistry and density of each phase to arrive at bulk composition.

Non-Destructive Chemical-State Analysis of Thin Films and Surface Layers (1-1000 nm) by Low-Energy Electron-Induced X-ray Spectroscopy (LEEIXS)

1989 ◽  
Vol 33 ◽  
pp. 247-259 ◽  
Author(s):  
Angeli K. Gyani ◽  
Phillip McClusky ◽  
David S. Urch ◽  
M. Charbonnicr ◽  
F. Gaillard ◽  
...  
Keyword(s):  
Electron Beam ◽  
Sample Surface ◽  
Peak Position ◽  
Chemical State ◽  
Electron Gun ◽  
X Rays ◽  
X Ray ◽  
Zinc Oxide Films ◽  
Normal Electron ◽  
Nitride Layers

AbstractThe penetration depth of 1-12 keV electrons in most materials is less than one micron and the characteristic soft x-rays that are produced can be used to identify the elements present in the surface. Varying the energy of the incident electron beam enables the depth of analysis to be controlled.Soft x-rays often exhibit large 'chemical effects' (changes in peak profile and peak position) which can he correlated with chemical changes. A study of such effects for each element present in the sample surface, as a function of electron-beam energy, can in some cases, permit changes in the chemical state (valency - coordination number-spin state etc.) to be determined as a function of depth.Such analyses can be carried out either in a conventional x-ray spectrometer in which the x-ray tube has been replaced by a gas-discharge source, or in a spectrometer in which the sample is bombarded with electrons from a normal electron gun. In this paper these techniques are outlined and some applications reviewed:- the analysis of oxide layers on aluminium and steel, the analysis of aluminium-nitride layers produced by MOCVD on gallium arsenide, the analysis of silica fiims (with added boron and phosphorus oxides) on silicon and the analysis of zinc-oxide films on glass.

Aspects of microanalysis in a transmission electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 510-511
Author(s):  
R. Sinclair ◽  
B.E. Jacobson
Keyword(s):  
Grain Size ◽  
Electron Beam ◽  
Electron Microscope ◽  
Chemical Analysis ◽  
Transmission Electron Microscope ◽  
Vapor Deposition ◽  
Critical Currents ◽  
X Ray ◽  
Fine Grain ◽  
Transmission Electron

INTRODUCTIONThe prospect of performing chemical analysis of thin specimens at any desired level of resolution is particularly appealing to the materials scientist. Commercial TEM-based systems are now available which virtually provide this capability. The purpose of this contribution is to illustrate its application to problems which would have been intractable until recently, pointing out some current limitations.X-RAY ANALYSISIn an attempt to fabricate superconducting materials with high critical currents and temperature, thin Nb3Sn films have been prepared by electron beam vapor deposition [1]. Fine-grain size material is desirable which may be achieved by codeposition with small amounts of Al2O3 . Figure 1 shows the STEM microstructure, with large (∽ 200 Å dia) voids present at the grain boundaries. Higher quality TEM micrographs (e.g. fig. 2) reveal the presence of small voids within the grains which are absent in pure Nb3Sn prepared under identical conditions. The X-ray spectrum from large (∽ lμ dia) or small (∽100 Ǻ dia) areas within the grains indicates only small amounts of A1 (fig.3).

Thickness and composition determinations from T.E.M. specimens using both x-ray and backscattered electron data

1984 ◽  
Vol 42 ◽  
pp. 576-577
Author(s):  
M.D. Ball ◽  
H. Lagace ◽  
M.C. Thornton
Keyword(s):  
Electron Microscope ◽  
Atomic Number ◽  
Transmission Electron Microscope ◽  
Convenient Method ◽  
Flow Chart ◽  
X Ray ◽  
Intensity Measurements ◽  
Transmission Electron ◽  
Electron Intensity ◽  
Backscattered Electron

The backscattered electron coefficient η for transmission electron microscope specimens depends on both the atomic number Z and the thickness t. Hence for specimens of known atomic number, the thickness can be determined from backscattered electron coefficient measurements. This work describes a simple and convenient method of estimating the thickness and the corrected composition of areas of uncertain atomic number by combining x-ray microanalysis and backscattered electron intensity measurements.The method is best described in terms of the flow chart shown In Figure 1. Having selected a feature of interest, x-ray microanalysis data is recorded and used to estimate the composition. At this stage thickness corrections for absorption and fluorescence are not performed.

X-ray micro tomography in the scanning electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 106-107 ◽  
Author(s):  
W. Brünger
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Target Surface ◽  
The Body ◽  
X Rays ◽  
Cross Sectional ◽  
X Ray ◽  
Micro Tomography ◽  
Scanning Electron

Reconstructive tomography is a new technique in diagnostic radiology for imaging cross-sectional planes of the human body /1/. A collimated beam of X-rays is scanned through a thin slice of the body and the transmitted intensity is recorded by a detector giving a linear shadow graph or projection (see fig. 1). Many of these projections at different angles are used to reconstruct the body-layer, usually with the aid of a computer. The picture element size of present tomographic scanners is approximately 1.1 mm2.Micro tomography can be realized using the very fine X-ray source generated by the focused electron beam of a scanning electron microscope (see fig. 2). The translation of the X-ray source is done by a line scan of the electron beam on a polished target surface /2/. Projections at different angles are produced by rotating the object.During the registration of a single scan the electron beam is deflected in one direction only, while both deflections are operating in the display tube.

Searching for the causes why some of the paintings by Mihaly Munkacsy are darkening

1990 ◽  
Vol 48 (2) ◽  
pp. 204-205
Author(s):  
Imre Pozsgai ◽  
Klara Erdöhalmi-Torok
Keyword(s):  
Electron Beam ◽  
Cross Section ◽  
Polyester Resin ◽  
National Gallery ◽  
X Ray ◽  
Art Historians ◽  
Made In ◽  
Grinding And Polishing

The paintings by the great Hungarian master Mihaly Munkacsy (1844-1900) made in an 8-9 years period of his activity are deteriorating. The most conspicuous sign of the deterioration is an intensive darkening. We have made an attempt by electron beam microanalysis to clarify the causes of the darkening. The importance of a study like this is increased by the fact that a similar darkening can be observed on the paintings by Munkacsy’s contemporaries e.g Courbet and Makart. A thick brown mass the so called bitumen used by Munkacsy for grounding and also as a paint is believed by the art historians to cause the darkening.For this study, paint specimens were taken from the following paintings: “Studio”, “Farewell” and the “Portrait of the Master’s Wife”, all of them are the property of the Hungarian National Gallery. The paint samples were embedded in a polyester resin “Poly-Pol PS-230” and after grinding and polishing their cross section was used for x-ray mapping.

Practical Importance of Spatial Resolution and Analytical Sensitivity in AEM X-ray Microanalysis

1990 ◽  
Vol 48 (2) ◽  
pp. 432-433
Author(s):  
J. Zhang ◽  
D.B. Williams ◽  
J.I. Goldstein
Keyword(s):  
Spatial Resolution ◽  
Practical Importance ◽  
Beam Current ◽  
Specimen Thickness ◽  
Analytical Sensitivity ◽  
Related Factors ◽  
X Ray ◽  
Probe Size ◽  
Excitation Volume ◽  
Two Parameters

Analytical sensitivity and spatial resolution are important and closely related factors in x-ray microanalysis using the AEM. Analytical sensitivity is the ability to distinguish, for a given element under given conditions, between two concentrations that are nearly equal. The analytical sensitivity is directly related to the number of x-ray counts collected and, therefore, to the probe current, specimen thickness and counting time. The spatial resolution in AEM analysis is determined by the probe size and beam broadening in the specimen. A finer probe and a thinner specimen give a higher spatial resolution. However, the resulting lower beam current and smaller X-ray excitation volume degrade analytical sensitivity. A compromise must be made between high spatial resolution and an acceptable analytical sensitivity. In this paper, we show the necessity of evaluating these two parameters in order to determine the low temperature Fe-Ni phase diagram.A Phillips EM400T AEM with an EDAX/TN2000 EDS/MCA system and a VG HB501 FEG STEM with a LINK AN10 EDS/MCA system were used.

Electron Beam-Induced Mass Loss in Freeze-Dried Tissue and Protein Samples

1985 ◽  
Vol 43 ◽  
pp. 470-471
Author(s):  
M.E. Cantino ◽  
M.K. Goddard ◽  
L.E. Wilkinson ◽  
D.E. Johnson
Keyword(s):  
Electron Beam ◽  
Salivary Gland ◽  
Mass Loss ◽  
Counting Rate ◽  
Dose Dependence ◽  
X Ray ◽  
Large Samples ◽  
Freeze Dried ◽  
Muscle Homogenate ◽  
Large Muscle

Quantification in biological x-ray microanalysis depends on accurate evaluation of mass loss. Although several studies have addressed the problem of electron beam induced mass loss from organic samples (eg., 1,2). uncertainty persists as to the dose dependence, the extent of loss, the elemental constituents affected, and the variation in loss for different materials and tissues. in the work described here, we used x-ray counting rate changes to measure mass loss in albumin (used as a quantification standard), salivary gland, and muscle.In order to measure mass loss at low doses (10-4 coul/cm2 ) large samples were needed. While freeze-dried salivary gland sections of the required dimensions were available, muscle sections of this size were difficult to obtain. To simulate large muscle sections, frog or rat muscle homogenate was injected between formvar films which were then stretched over slot grids and freeze-dried. Albumin samples were prepared by a similar procedure. using a solution of bovine serum albumin in water. Samples were irradiated in the STEM mode of a JEOL 100C.

Layered and ion implantation specimens as possible reference materials for the electron-probe microanalysis

1992 ◽  
Vol 50 (2) ◽  
pp. 1652-1653
Author(s):  
G. Remond ◽  
R.H. Packwood ◽  
C. Gilles ◽  
S. Chryssoulis
Keyword(s):  
Ion Implantation ◽  
Reference Materials ◽  
Analytical Techniques ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
X Ray ◽  
Spatially Resolved ◽  
Analytical Expressions ◽  
Original Approach ◽  
Depth Concentration

Merits and limitations of layered and ion implanted specimens as possible reference materials to calibrate spatially resolved analytical techniques are discussed and illustrated for the case of gold analysis in minerals by means of x-ray spectrometry with the EPMA. To overcome the random heterogeneities of minerals, thin film deposition and ion implantation may offer an original approach to the manufacture of controlled concentration/ distribution reference materials for quantification of trace elements with the same matrix as the unknown.In order to evaluate the accuracy of data obtained by EPMA we have compared measured and calculated x-ray intensities for homogeneous and heterogeneous specimens. Au Lα and Au Mα x-ray intensities were recorded at various electron beam energies, and hence at various sampling depths, for gold coated and gold implanted specimens. X-ray intensity calculations are based on the use of analytical expressions for both the depth ionization Φ (ρz) and the depth concentration C (ρz) distributions respectively.

Development of x-ray beam profile monitor based on in-house grown crystal and application in electron beam imaging

2020 ◽  
Author(s):  
Mohit Tyagi ◽  
P. S. Sarkar ◽  
R. S. Sengar ◽  
Ashwani Kumar ◽  
Jagannath ◽  
...  
Keyword(s):  
Electron Beam ◽  
Grown Crystal ◽  
Beam Profile ◽  
X Ray ◽  
Beam Profile Monitor
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