Elastic electron-specimen interactions

Electron-Specimen Interactions 29.2.3.3.1. Elastic and Inelastic Scattering... 

The phenomena of beam broadening as a function of specimen thickness are illustrated in Fig. 4.20 each figure represents 200 electron trajectories in silicon calculated by Monte Carlo simulations [4.91, 4.95-4.97] for 100-keV primary energy, where an infinitesimally small electron probe is assumed to enter the surface. In massive Si the electrons suffer a large number of elastic and inelastic interactions during their paths through the material, until they are finally completely stopped. The resulting penetration depth of the electrons is approximately 50 pm and in the... 

When a solid is bombarded with high energy electrons the interaction produces secondary electrons (elastic), back-scattered electrons (inelastic), low loss electrons. Auger electrons, photo electrons, electron diffraction, characteristic x-rays, x-ray continuum, light, hole electron pairs and specimen current. These interactions are used to identify the specimen and elements of the specimen and can also be used to physically characterize particulate systems. 

Kikuchi lines result from inelastic scattering of electrons in specimens. Generally, an electron scatters elastically when it interacts with an atomic nucleus. The mass of a nucleus is much larger than that of an electron. Thus, their interaction is similar to a ball hitting wall where the ball bounces without energy loss. However, when the electron interacts with an electron in an atomic shell, energy will transfer between the two electrons during collision, which is referred... 

Backscattered (high-energy) electrons are elastically scattered beam electrons. The electrcms are deflected back out of the specimen interaction volume. 

By considering only elastic scattering events, the interaction of the specimen with the electron beam can be described through a complex transmission function (object wave-function) 0(f) which represents the ratio between the outgoing and the incoming electron wave-functions f = (x, y) is a two-dimensional vector lying on a plane perpendicular to the optic axis z which is parallel, and in the same direction, to the electron beam. In the standard phase object approximation ... 

When a beam of charged particles passes through a thin specimen, the beam transmitted in the forward direction includes some particles that scattered elastically off atomic nuclei or lost energy due to interaction with electrons (inelastically scattered) as well as those particles that were left unscattered. An image formed with this forward-transmitted beam is referred to as a bright field image. 

Since the specimen is thin compared to the mean free path of the incident electrons, most will not interact at all with the constituent atoms of the sample but will simply pass undeflected through the material. However, provided the sample is crystalline, some fraction of the incident electrons will be scattered from crystal planes within the material by Bragg diffraction, and give rise to characteristic spots or rings in an electron diffraction pattern. These diffracted electrons lose little or none of their incident energy in such Bragg scattering events and are said to be elastically scattered. 

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