ABSTRACT
This is intended as a brief introduction to some of the common tech-niques used in materials characterization. It is designed for people who are novices in this field but are interested in using the tech-niques in their research. Some examples of application techniques to phosphors examination as well as some references are listed below in the end of each paragraph. Extensive and authoritative discus-sions can be found in the numerous books and journal articles on this subject. 3.1 Morphology Analysis with Scanning Electron
MicroscopyThe scanning electron microscope (SEM) is a microscope that uses electrons instead of light to form an image. In SEM an electron beam is scanned across a sample’s surface. The electrons interact with the atoms that make up the sample producing signals that contain information about the sample’s surface topography, composition and other properties. The scanning electron microscope was first constructed by von Ardenne in 1938 when he added scan coils to a transmission electron microscope. The real first scanning electron microscope to employ secondary electron detection was developed by Zworykin and his team in 1942. In our days the scanning electron
microscope has many advantages over traditional microscopes. The SEM has a large depth of field, which allows more of a specimen to be in focus at one time. The SEM also has much higher resolution, so closely spaced specimens can be magnified at much higher levels. All of these advantages, as well as the actual strikingly clear images, make the scanning electron microscope one of the most useful in-struments in research today. With SEM we can investigate:
Topography • The surface features of an object or “how it looks,” its texture; detectable features limited to a few nanometers Morphology • The shape, size, and arrangement of the particles making up the object that are lying on the surface of the sample or have been exposed by grinding or chemical etching; detectable features limited to a few nanometers Composition • The elements and compounds the sample is composed of and their relative ratios, in areas ~1 μm in diameter Crystallographic Information• The arrangement of atoms in the specimen and their degree of order; only useful on single-crystal particles >20 μm
3.1.1 Electron Beam Interaction with Solid Matter When an electron beam is bombarding a solid surface secondary electrons, back-scattered electrons, Auger electrons, cathodolumi-nescence, and characteristic X-rays are produced (Fig. 3.1).These main signals provide the greatest amount of information in SEM, but it is rare that a single machine would have detectors for all possible signals. We consider briefly all possible information from different siganals and everybody decides himself what is more important for his investigations.
