Quantitative Electron Probe Microanalysis of Nonconducting Specimens: Science or Art?

2004 ◽  
Vol 10 (6) ◽  
pp. 733-738 ◽  
Author(s):  
Guillaume F. Bastin ◽  
Hans J.M. Heijligers
Keyword(s):  
Electrical Conductivity ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Light Element ◽  
X Ray ◽  
Surface Charging ◽  
Quantitative Electron Probe Microanalysis ◽  
Quantitative Analyses ◽  
Intensity Ratios ◽  
Effect Of Surface

The influence of a lack of sufficient electrical conductivity on the results of quantitative electron probe microanalysis has been investigated on a number of oxides. The effect of surface charging and the way it alters the emitted X-ray signals has been studied. It is shown that the presence of conducting coatings, such as carbon or copper, will affect the interelement X-ray intensity ratios, whatever the thickness of the coating may be. Although the effects for heavier elements may be acceptable, they cannot be ignored for a light element such as oxygen, where strong variations with coating thickness were observed. Quantitative analyses of oxygen, on uncoated well-conducting oxide specimens, using uncoated well-conducting hematite (Fe2O3) as a standard yielded excellent results in the range between 4 and 40 kV with the φ(ρz) software used. As soon as coated nonconducting specimens were examined, using the same hematite standard, coated under exactly the same conditions, widely scattering and noncoherent results were obtained. These discrepancies can only be attributed to a lack of conductivity.

Measurement and parameterization of ϕ(ρz) curves for quantitative electron probe microanalysis

1990 ◽  
Vol 48 (2) ◽  
pp. 190-191
Author(s):  
J. D. Brown
Keyword(s):  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Absorption Coefficients ◽  
Computing Power ◽  
X Ray ◽  
Practical Applications ◽  
Absorption Correction ◽  
Exponential Decrease ◽  
Quantitative Electron Probe Microanalysis ◽  
Z Curve

The goal of correction methods for quantitative electron probe microanalysis is to convert k-ratios for any type of specimen, any x-ray line and all electron beam energies into accurate concentrations. Early attempts to approach this goal were hindered by sparse data on electron interactions with solids, limited knowledge of x-ray parameters such as mass absorption coefficients and limited computing power which made necessary mathematical simplifications in practical applications.In developing the early models for quantitative analysis, the argument was made that the absorption correction was insensitive to the shape of the ϕ(ρz) curve. For that reason, a number of very crude models which ranged from constant x-ray generation as a function of depth(l) to an exponential decrease from the surface(2) were used. In fact, these models worked quite well for the restricted conditions for which they were designed but of course lack accuracy when applied to more general situations. ϕ(ρz) measurements

EPMA of submicron coatings containing ultralight elements

1992 ◽  
Vol 50 (2) ◽  
pp. 1628-1629
Author(s):  
Peter Willich
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Analytical Sensitivity ◽  
X Ray ◽  
Quantitative Electron Probe Microanalysis ◽  
X Ray Absorption ◽  
Primary Electrons ◽  
Critical Excitation

Materials containing ultralight elements (B, C, N, O) in combination with a metal are of considerable interest in thin film technology. Quantitative electron probe microanalysis of the coatings should be independent of the substrate and has to be carried out under the condition that the ultimate depth of x-ray emission (Rx) is within the provided film thickness of 0.2-0.8 μm. Rx, for an element (critical excitation energy Ec) in a specified matrix is controlled by the energy (E0) of the primary electrons. EPMA of high atomic number elements (Ec = 2-7 keV), under the condition of Rx < 1 μm, frequently requires operation at a low overvoltage of E0/Ec < 2. Consequendy, tne x-ray intensities are very low and the analytical sensitivity is drastically reduced. For the ultralight elements the strong effects oft x-ray absorption always lead to a shallow depth of x-ray emission, even at a high overvoltage.

Low-Voltage Electron-Probe Microanalysis of Fe–Si Compounds Using Soft X-Rays

2013 ◽  
Vol 19 (6) ◽  
pp. 1698-1708 ◽  
Author(s):  
Phillip Gopon ◽  
John Fournelle ◽  
Peter E. Sobol ◽  
Xavier Llovet
Keyword(s):  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Low Voltage ◽  
Mass Attenuation Coefficient ◽  
X Rays ◽  
X Ray ◽  
Voltage Electron ◽  
Increased Sensitivity ◽  
Quantitative Analyses ◽  
Areas Of Interest

AbstractConventional electron-probe microanalysis has an X-ray analytical spatial resolution on the order of 1–4 μm width/depth. Many of the naturally occurring Fe–Si compounds analyzed in this study are smaller than 1 μm in size, requiring the use of lower accelerating potentials and nonstandard X-ray lines for analysis. Problems with the use of low-energy X-ray lines (soft X-rays) of iron for quantitative analyses are discussed and a review is given of the alternative X-ray lines that may be used for iron at or below 5 keV (i.e., accelerating voltage that allows analysis of areas of interest <1 μm). Problems include increased sensitivity to surface effects for soft X-rays, peak shifts (induced by chemical bonding, differential self-absorption, and/or buildup of carbon contamination), uncertainties in the mass attenuation coefficient for X-ray lines near absorption edges, and issues with spectral resolution and count rates from the available Bragg diffractors. In addition to the results from the traditionally used Fe Lα line, alternative approaches, utilizing Fe Lβ, and Fe Ll-η lines, are discussed.

Development of a Spectral Database for Testing Quantitative Electron Probe Microanalysis of Rough, Bulk Samples

2000 ◽  
Vol 6 (S2) ◽  
pp. 928-929
Author(s):  
Dale E. Newbury
Keyword(s):  
Surface Roughness ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Flat Surface ◽  
X Ray ◽  
Quantitative Electron Probe Microanalysis ◽  
Counting Statistics ◽  
Spectral Database ◽  
Geometric Effects ◽  
The Ideal

The vast majority of applications of electron probe x-ray microanalysis takes place on specimens which deviate significantly from the ideal configuration. Classic quantitative x-ray microanalysis makes the tacit assumption that the only reason the unknown differs in emitted x-ray intensity from standards is that there is a difference in composition between them. While this seems trivial, it forces the analyst to eliminate a major non-compositional source of possible intensity differences, namely the geometric effects associated with surface roughness. An important early paper by Yakowitz demonstrated that deviations from an ideal flat surface due to surface topography could seriously degrade the accuracy of analysis. Yakowitz interrupted the grinding and polishing procedure on pure elements and alloys at various stages and measured the variance in the x-ray intensity as the probe was scanned across the surface as compared to the predicted distribution based on counting statistics.

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