Theory and application of electron channelling contrast imaging under controlled diffraction conditions

First, Monte Carlo modelling of electron-solid interactions is briefly reviewed regarding its historical development, followed by quantification in microbeam analysis with various types of signals generated by electron penetration in solids. Second, typical models stimulated by these improvements are explained by demonstrating some of the Monte Carlo calculations which are, the authors believe, still of practical interest and use. Then, a typical calculation procedure for Monte Carlo simulation is described in detail from the standpoint of a physicist who does his or her own programming. Third, up-to-date Monte Carlo calculations as applied to modern surface analysis, high-resolution scanning electron microscopy, Auger electron microscopy and X-ray photoelectron spectroscopy are also presented.

https://robots.iopscience.iop.org/article/10.1088/0034-4885/55/4/002/pdf

Monte Carlo modelling of electron-solid interactions

The parameters governing electron backscattering from thin films and from bulk solids are reviewed: Atomic scattering cross-section, atomic number, single/multiple scattering, film thickness, scattering angular distribution, angle of incidence, diffraction effects. Their influence on some important contrast mechanisms due to backscattered electrons in scanning electron microscopy (thickness contrast, Z/material contrast, tilting/topography contrast, crystal orientation contrast) is discussed. The most frequently used backscattering electron detection systems are briefly described.

Physical background of electron backscattering

A theory is developed to explain the magnetic domain contrast observed by scanning electron microscopy using the method reported recently [4, 5]. The theory is based on a model which assumes that the contrast is due to the Lorentz deflection of the incident electrons inside the specimen. Using this model, the dependence of the image contrast on various experimental parameters was calculated analytically. The model was confirmed by means of calculations carried out by computer simulation of electron trajectories (Monte Carlo techniques). The theory accounts satisfactorily for previous experimental results. A more detailed comparison of the theory with experimental results will be published in a subsequent paper.



Eine Theorie zur Erklarung des durch eine kurzlich beschriebene Methode [4, 5] im Rasterelektronenmikroskop beobachteten magnetischen Domanenkontrasts wurde entwickelt. Die Theorie ist auf ein Modell aufgebaut, in dem angenommen wird, das der Kontrast von der Lorentzablenkung der eingestrahlten Elektronen in der Probe stammt. Die Abhangigkeit des Bildkontrasts von verschiedenen experimentellen Parametern wurde nach dem Modell analytisch berechnet und die Ergebnisse mit den Rechnungen fur Computer-simulierte Elektronenbahnen verglichen. Die Theorie stimmt weitgehend mit den experimentelen Ergebnissen uberein; Einzelheiten werden in einer spateren Arbeit veroffentlicht.

A new method of observing magnetic domains by scanning electron microscopy I. Theory of the image contrast

This chapter provides an overview of the concepts of scanning electron microscopy () from a theoretical as well as practical operational perspective. The theory section begins with the basics of image formation followed by an explanation of the interaction of the electron beam with the sample. A description of the different types of electron guns is also included. The concepts involved with image formation from a rastered (or scanned) electron beam on a surface is explained along with the mechanisms of contrast generation from sample surface topography and sample composition. The different SEM detectors are also explained including a description of the practical application of detectors under various sample conditions. Numerous diagrams and figures in this chapter illustrate imaging geometries and possible SEM system configurations. Included in the chapter is an explanation of the various instrument operation parameters for different samples as well as a discussion of the effects of electron-beam accelerating voltages on sample imaging, contrast, and resolution.

Scanning Electron Microscopy

Experiments have been carried out to test the predictions of the theory of type II magnetic contrast, which is an effect enabling magnetic domains in materials including those with cubic anisotropy to be directly observed by scanning electron microscopy, previously presented in [1]. The experiments include measurements of the contrast as a function of the voltage and angle of incidence of the incident electron beam and of the angle of rotation of the specimen about its surface normal. The results are in good agreement with the theory and confirm beyond doubt that type II contrast arises from the alteration of incident electron trajectories within the solid by the internal magnetic induction. Domain images obtained by the use of type II contrast can be interpreted on the basis of this mechanism.



Experimente wurden durchgefuhrt, um die Vorhersagen der Theorie des magnetischen Kontrasts zweiter Art zu prufen, ein Effekt, der die direkte Beobachtung magnetischer Domanen in Materialien, einschlieslich solcher mit kubischer Anisotropie, im Abtast-Elektronenmikroskop gestattet, wie bereits in [1] berichtet wurde. Die Experimente schliesen Kontrastmessungen als Funktion der Spannung und des Einfallswinkels des einfallenden Elektronenstrahls sowie des Drehwinkels der Probe um seine Oberflachennormale ein. Die Ergebnisse befinden sich in guter Ubereinstimmung mit der Theorie und bestatigen unzweifelhaft, das der Kontrast zweiter Art von der Anderung der Trajektorien der einfallenden Elektronen innerhalb des Festkorpers durch innere magnetische Induktion herruhrt. Domanenbilder, die mit dem Kontrast zweiter Art erhalten werden, lassen sich auf der Grundlage dieses Mechanismus interpretieren.

A new method of observing magnetic domains by scanning electron microscopy. II. Experimental confirmation of the theory of image contrast

Contrast arising from the domain structure of ferromagnetic materials with cubic anisotropy has been observed in the scanning electron microscope. The contrast is due to differences in reflected and back-scattered electron yield from domains magnetized in different directions. A model which is capable of explaining the observed effects is proposed.

D. C. Joy

Papers

A new method of observing magnetic domains by scanning electron microscopy I. Theory of the image contrast

A new method of observing magnetic domains by scanning electron microscopy. II. Experimental confirmation of the theory of image contrast

Magnetic domain contrast from cubic materials in the scanning electron microscope

Scanning reflection electron micrographs of stacking faults in a Co‐4wt% Ti alloy