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Electron Microscopy in Lung Research
Published in Joan Gil, Models of Lung Disease, 2020
In the SEM, the electrons are focused on the surface of the specimen and scanned across it. As they are deflected over the surface of the specimen, atoms near the point where the electrons enter the specimen are excited by the absorbed energy. As they decay back to ground state, they give off the absorbed energy by emitting secondary electrons, x-rays, or photons of light (cathodoluminescence) (Fig. 2). These secondary emissions all contain potential information about the specimen. In addition, some of the incident electrons are elastically scattered as a result of interactions with atomic nuclei in the specimen, and these electrons also contain information about the specimen. Ordinarily the secondary electrons are used to generate an image. The other types of emission are used for special applications, particularly analytical microscopy.
Patterned Sapphire and Chip Separation Technique in InGaN-Based LEDs
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
Figure 23.4a shows the cross-sectional transmission electron microscope (TEM) images under g = 0002 two-beam condition of the interface region between the CSPSS and a GaN layer grown on it, demonstrating that the ELOG-like mode on the CSPSS effectively suppresses the propagation of dislocation into the cone region, even though many dislocations were observed in the film grown on the basal plane of the sapphire. This reduction of dislocation was also confirmed by performing a cathodoluminescence (CL) measurement at room temperature as shown in Figures 23.4b and c. In bright regions, a radiative process dominates over a nonradiative process because of the lower density of structural defects. The dark spot density in the film grown on a CSS is roughly estimated to be about 7 × 108 cm−2. Apparently, the dark spot density in the film grown on a CSPSS was decreased to about 2 × 108 cm−2 in number.
Scintillation Detectors
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
The mechanisms by which various materials receive energy that is later emitted as visible light has given rise to a large number of names of phenomena, such as thermoluminescence (energy received due to thermal action and emitted differently than by black-body radiation); chemoluminescence (energy received through chemical reactions); or the common photoluminescence (energy received from visible or UV light). Radioluminescence or cathodoluminescence are phenomena whereby visible light is emitted following excitation by charged particles or only by electrons (cathodoluminescence). The overall term ‘scintillation’ roughly refers to the flashes of light that appear from a scintillator during de-excitation from a higher energy level and may thus to most readers be nearly identical to radioluminescence, a fluorescence or phosphorescence due to the absorbed energy from ionizing radiation. Scintillations are generally thought of as being the near prompt, fluorescent light, while the fraction of energy emitted as phosphorescence and delayed fluorescent light is at a minimum. Scintillation light may thus be treated as a subgroup of radioluminescence where timing of the emitted light is important. There may not be a complete consensus as to whether scintillation and radioluminescence cover the same physical phenomena, but this is out of the scope of this chapter. For a detailed description of the kinetics and mechanisms of scintillators please refer to [2] and [11].
Diagnostic Electron Microscopy of Retina
Published in Seminars in Ophthalmology, 2018
Rishikesh Kumar Gupta, Inderjeet Kaur, Tapas C. Nag, Jay Chhablani
Once the coherent beam of electrons interacts with the sample, some of the electrons reflect back (called backscattered electrons). Some electrons deliver their energy to the sample’s molecules and excite the outer surface electrons of the samples. These excited electrons get emitted, are known as the secondary electrons. Other types of electrons are X-rays, cathodoluminescence, and Auger electrons as shown in Figure 1. The specialized detector can detect all these different kinds of electrons, produce the images of the sample as illustrated in Figure 1, called SEM.29 SEM helps in the study of the surface properties of the sample. Apart from these, few electrons do not lose any energy while interacting with the sample due to elastic scattering, and few others lose the minimal amount of energy, called inelastic scattering. Also, very few electrons get transmitted without any scattering, called as unscattered electrons. These three types of transmitted electrons fall on the fluorescent screen and produce the quantitative images of the sample as shown in Figure 1, called TEM.28