Introduction to passive electron intensity modulation

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.

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Local thickness determination by Electron Energy Loss Spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100172450 ◽

1994 ◽

Vol 52 ◽

pp. 944-945

Author(s):

Suichu Luo ◽

John R. Dunlap ◽

Richard W. Williams ◽

David C. Joy

Keyword(s):

Energy Loss ◽

Analytical Electron Microscopy ◽

Mean Free Path ◽

Single Scattering ◽

Specimen Thickness ◽

Three Dimension ◽

Angular Correction ◽

Electron Intensity ◽

Image Position ◽

Inelastic Mean Free Path

In analytical electron microscopy, it is often important to know the local thickness of a sample. The conventional method used for measuring specimen thickness by EELS is:where t is the specimen thickness, λi is the total inelastic mean free path, IT is the total intensity in an EEL spectrum, and I0 is the zero loss peak intensity. This is rigorouslycorrect only if the electrons are collected over all scattering angles and all energy losses. However, in most experiments only a fraction of the scattered electrons are collected due to a limited collection semi-angle. To overcome this problem we present a method based on three-dimension Poisson statistics, which takes into account both the inelastic and elastic mixed angular correction.The three-dimension Poisson formula is given by:where I is the unscattered electron intensity; t is the sample thickness; λi and λe are the inelastic and elastic scattering mean free paths; Si (θ) and Se(θ) are normalized single inelastic and elastic angular scattering distributions respectively ; F(E) is the single scattering normalized energy loss distribution; D(E,θ) is the plural scattering distribution,

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Quantitative Electron Microscope with imaging plate

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100169778 ◽

1994 ◽

Vol 52 ◽

pp. 408-409

Author(s):

D. Shindo

Keyword(s):

Electron Microscope ◽

Dynamic Range ◽

Processing System ◽

Digital Data ◽

Imaging Plate ◽

Crystal Thickness ◽

X Ray Diffraction ◽

Resolution Electron ◽

Electron Intensity ◽

Diffraction Patterns

Imaging plate has good properties, i.e., a wide dynamic range and good linearity for the electron intensity. Thus the digital data (2048x1536 pixels, 4096 gray levels in log scale) obtained with the imaging plate can be used for quantification in electron microscopy. By using the image processing system (PIXsysTEM) combined with a main frame (ACOS3900), quantitative analysis of electron diffraction patterns and high-resolution electron microscope (HREM) images has been successfully carried out.In the analysis of HREM images observed with the imaging plate, quantitative comparison between observed intensity and calculated intensity can be carried out by taking into account the experimental parameters such as crystal thickness and defocus value. An example of HREM images of quenched Tl2Ba2Cu1Oy (Tc = 70K) observed with the imaging plate is shown in Figs. 1(b) - (d) comparing with a structure model proposed by x-ray diffraction study of Fig. 1 (a). The image was observed with a JEM-4000EX electron microscope (Cs =1.0 mm).

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