scholarly journals Degradation of spatial resolution in thin-foil x-ray microchemical analysis due to plural scattering of electrons

1982 ◽  
Author(s):  
Mark Erickson Twigg
Keyword(s):  
Spatial Resolution ◽  
Thin Foil ◽  
X Ray ◽  
Microchemical Analysis

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

The spatial resolution of x-ray microanalysis in thin foils

1991 ◽  
Vol 49 ◽  
pp. 472-473
Author(s):  
D. B. Williams ◽  
J. R. Michael ◽  
J. I. Goldstein ◽  
A. D. Romig
Keyword(s):  
Spatial Resolution ◽  
Thin Foil ◽  
Beam Specimen ◽  
Beam Diameter ◽  
Worst Case ◽  
X Ray ◽  
Thin Foils ◽  
Elastic Scatter ◽  
Electron Beam Diameter ◽  
Beam Broadening

The spatial resolution of x-ray microanalysis in a thin foil is determined by the size of the beam-specimen interaction volume. This volume is a combination of the incident electron beam diameter (d) and the beam broadening (b) due to elastic scatter within the specimen. Definitions of spatial resolution have already been proposed on this basis but all present a worst case value for the resolution based on the dimensions of the beam emerging from the exit face of the foil.

Considerations of the Transmission of a Small Electron Probe Through a TEM Foil and Its Relation to Characteristic X-Ray Spatial Resolution

1981 ◽  
Vol 39 ◽  
pp. 282-283
Author(s):  
D. Imeson ◽  
J. B. Vander Sande
Keyword(s):  
Electron Beam ◽  
Spatial Resolution ◽  
Incident Beam ◽  
Thin Foil ◽  
Lateral Spreading ◽  
X Ray ◽  
Thin Foils ◽  
Transmission Electron ◽  
Composition Variation ◽  
Composition Determination

It is well established that when an electron beam is incident upon a thin foil in the form of a focused probe, as in STEM, multiple scattering events in the sample cause considerable lateral spreading of the electron beam. The volume of material excited by the electron beam is therefore much greater than that volume defined by simple projection of the incident beam through the sample. In the application of the techniques of quantitative X-ray analysis in STEM to regions of composition variation with small spatial extent this point becomes of crucial importance, being the main determinant of the ability to map such composition changes, or even to detect them. It is the view of the authors that there exists some confusion over the nature of the beam spreading phenomenon in thin foils of crystalline material and the concept of spatial resolution of composition determination by characteristic X-ray emission. We intend here to clarify these concepts by discussing the meaning and use of the term “beam broadening” in analytical transmission electron microscopy.

Sub-Micron Spatial Resolution Edx Microchemical Analysis Of Bulk Specimens In The Sem At Low Beam Voltages

1990 ◽  
Vol 48 (2) ◽  
pp. 234-235
Author(s):  
E D Boyes ◽  
D L Smith
Keyword(s):  
Spatial Resolution ◽  
Normal Incidence ◽  
Substantial Contribution ◽  
Beam Specimen ◽  
Plan View ◽  
X Ray ◽  
Interaction Volume ◽  
Beam Voltage ◽  
Microchemical Analysis ◽  
Probe Size

The spatial resolution of data in the SEM depends on the the original probe size of the instrument, the beam-specimen interaction volume and the signal escape range. The first two terms are strong functions of the beam voltage. The range [R] of the beam-specimen interaction for chemical microanalysis by x-ray spectroscopy [EDX] has a general dependence given by R ∝ E05/3. The data in Fig.1 were obtained in plan view with a beam at normal incidence using evaporated thin films of aluminum [Z=13] of various thicknesses on a silicon substrate of similar atomic number [Z=14]. The voltage at which the film and the substrate contribute equally to the [EDX] x-ray spectrum [Fig.2] can be measured with an accuracy of only a few volts. The experiment was designed to measure the depth of the interaction volume. In this geometry the data are independent of the probe size which makes a substantial contribution to the lateral resolution of analysis with a simple SEM operated at low voltages [E0 <5kV].

Improved sensitivity, accuracy and spatial resolution of light-element analysis in the SEM at low beam voltages

1992 ◽  
Vol 50 (2) ◽  
pp. 1630-1631
Author(s):  
E D Boyes ◽  
I R Hartmann ◽  
D L Smith ◽  
F W Gooding ◽  
L Hanna ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Light Element ◽  
Thin Foil ◽  
Bulk Sample ◽  
Element Analysis ◽  
Strong Function ◽  
Physical Separation ◽  
X Ray ◽  
Epma Analysis ◽  
Foil Specimen

We have found that at low beam voltages, and especially at or below 5kV, the sensitivity, accuracy and spatial resolution for light element EDX analysis of bulk specimens in the SEM are all improved, compared to the conventional 30kV, by more than a factor of 10x. The reduced range (R) of the electron beam into a bulk sample is a strong function of beam voltage (R ∝ E05/3). This translates directly into much better spatial resolution of analysis which can be well into the sub-micron range and often <0. 1μm, compared with the 1-10<m typical of conventional EPMA analysis at 30kV. The greatly reduced electron penetration, and therefore much shorter x-ray escape range, substantially reduces, and in many cases entirely eliminates absorption (A) and fluorescence (F) effects on the (ZAF) x-ray signal. The situation is similar to that with a detached thin foil specimen prepared for STEM/AEM by physical separation, where the A and F effects are also generally very small and quantitation is also simplified.

Spatial Resolution of Stem and EDS in an AL-GE Alloy

1982 ◽  
Vol 40 ◽  
pp. 490-491
Author(s):  
M. E. Twlgg ◽  
J. P. McCarthy ◽  
H. L. Fraser
Keyword(s):  
Spatial Resolution ◽  
Deleterious Effect ◽  
Aluminum Matrix ◽  
Concentration Profiles ◽  
X Ray ◽  
Accurate Knowledge ◽  
Microchemical Analysis ◽  
Apparent Concentration ◽  
Trajectory Simulations ◽  
Beam Broadening

As part of an effort to better understand beam broadening and its deleterious effect on the spatial resolution of x-ray microchemical analysis employing STEM and EDS, we have been studying apparent concentration profiles in the vicinity of germanium precipitates in an aluminum matrix. Because of the limited solubility of aluminum in germanium, we know that the precipitates are almost completely composed of Ge; accurate knowledge of the composition of such precipitates facilitates the modeling of the apparent concentration profiles via Monte Carlo trajectory simulations.

High-spatial-resolution x-ray microanalysis: Comparison of experiment and incoherent scattering calculations

1993 ◽  
Vol 51 ◽  
pp. 590-591
Author(s):  
J. R. Michael ◽  
A. D. Romig
Keyword(s):  
Electron Beam ◽  
Spatial Resolution ◽  
Thin Foil ◽  
Coherent Scattering ◽  
Incoherent Scattering ◽  
Spherical Particles ◽  
X Ray ◽  
Thin Foils ◽  
Oriented Parallel ◽  
Beam Broadening

There have been many experimental efforts to measure the spatial resolution for x-ray microanalysis in the analytical electron microscope (AEM). There have been three commonly utilized specimen geometries in these experiments: 1) segregant at a grain boundary, 2) interphase boundaries oriented parallel to the electron beam, and most recently 3) spherical particles embedded at various depths in thin foils. The results of many of these experiments have been analyzed with a number of models for the broadening of the electron beam as it traverses the thin foil. These models are typically based on incoherent electron scattering, typical of Monte Carlo simulations. A vast majority of the published spatial resolution data support the incoherent scattering models as the best simulation of spatial resolution for x-ray microanalysis in the AEM. Recent experimental work using embedded particles to measure beam broadening has been used to support the coherent scattering model of beam broadening.

Influence of X-Ray Induced Fluorescence on Energy Dispersive X-Ray Analysis of Thin Foils

1977 ◽  
Vol 35 ◽  
pp. 328-329
Author(s):  
E. A. Kenik ◽  
J. Bentley
Keyword(s):  
Thin Foil ◽  
Electron Excitation ◽  
Simple Approach ◽  
Foil Thickness ◽  
X Rays ◽  
X Ray ◽  
Hole Spectrum ◽  
Illumination System ◽  
Thin Foils ◽  
Intensity Ratios

Cliff and Lorimer (1) have proposed a simple approach to thin foil x-ray analy sis based on the ratio of x-ray peak intensities. However, there are several experimental pitfalls which must be recognized in obtaining the desired x-ray intensities. Undesirable x-ray induced fluorescence of the specimen can result from various mechanisms and leads to x-ray intensities not characteristic of electron excitation and further results in incorrect intensity ratios.In measuring the x-ray intensity ratio for NiAl as a function of foil thickness, Zaluzec and Fraser (2) found the ratio was not constant for thicknesses where absorption could be neglected. They demonstrated that this effect originated from x-ray induced fluorescence by blocking the beam with lead foil. The primary x-rays arise in the illumination system and result in varying intensity ratios and a finite x-ray spectrum even when the specimen is not intercepting the electron beam, an ‘in-hole’ spectrum. We have developed a second technique for detecting x-ray induced fluorescence based on the magnitude of the ‘in-hole’ spectrum with different filament emission currents and condenser apertures.

Spatial resolution of X-ray microanalysis in thin foils

1978 ◽  
Vol 36 (1) ◽  
pp. 544-545
Author(s):  
R. Hutchings ◽  
I.P. Jones ◽  
M.H. Loretto ◽  
R.E. Smallman
Keyword(s):  
Spatial Resolution ◽  
Electron Probe ◽  
Beam Divergence ◽  
Inelastic Interaction ◽  
Specimen Thickness ◽  
High Current ◽  
Beam Spreading ◽  
X Ray ◽  
Thin Foils ◽  
Complex Calculation

There is increasing interest in X-ray microanalysis of thin specimens and the present paper attempts to define some of the factors which govern the spatial resolution of this type of microanalysis. One of these factors is the spreading of the electron probe as it is transmitted through the specimen. There will always be some beam-spreading with small electron probes, because of the inevitable beam divergence associated with small, high current probes; a lower limit to the spatial resolution is thus 2αst where 2αs is the beam divergence and t the specimen thickness.In addition there will of course be beam spreading caused by elastic and inelastic interaction between the electron beam and the specimen. The angle through which electrons are scattered by the various scattering processes can vary from zero to 180° and it is clearly a very complex calculation to determine the effective size of the beam as it propagates through the specimen.

Precipitation in silicon: Microanalysis

1988 ◽  
Vol 46 ◽  
pp. 474-475
Author(s):  
R.W. Carpenter
Keyword(s):  
Transition Metals ◽  
Spatial Resolution ◽  
Thin Foil ◽  
Precipitation Reaction ◽  
High Current ◽  
Reaction Products ◽  
Carbon And Nitrogen ◽  
Dielectric Layers ◽  
Precipitation Processes ◽  
Areas Of Interest

Interest in precipitation processes in silicon appears to be centered on transition metals (for intrinsic and extrinsic gettering), and oxygen and carbon in thermally aged materials, and on oxygen, carbon, and nitrogen in ion implanted materials to form buried dielectric layers. A steadily increasing number of applications of microanalysis to these problems are appearing. but still far less than the number of imaging/diffraction investigations. Microanalysis applications appear to be paced by instrumentation development. The precipitation reaction products are small and the presence of carbon is often an important consideration. Small high current probes are important and cryogenic specimen holders are required for consistent suppression of contamination buildup on specimen areas of interest. Focussed probes useful for microanalysis should be in the range of 0.1 to 1nA, and estimates of spatial resolution to be expected for thin foil specimens can be made from the curves shown in Fig. 1.

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