Electron-Optical Techniques

Abstract

Bombardment by electrons results in various phenomena of which the following are most useful for the study of feldspars: (1.) Emission of X-rays whose wavelength and intensity permit chemical analysis of major elements in very small areas of thin foils in an electron microscope (Lorimer 1987 MM 51 49-60). See Chapter 13 for technique of electron probe microanalysis which allows chemical analysis of major and minor elements within surface areas a few micrometers across. (2.) Emission of light (cathodoluminescence) whose wavelength and intensity permit rapid evaluation of chemical zoning and crystallization conditions involving certain trace elements and physical defects. See Section 12.2. (3.) Transmission and diffraction of electrons: the techniques of transmission electron diffraction and microscopy (TEM) permit observation of the texture and atomic arrangements right down to domains a few unit cells across; this is the main topic of this chapter. (4.) Emission of secondary electrons from the surface: the technique of scanning electron microscopy (SEM) allows determination of the topography of the surface. Back-scattered electrons can furnish high-resolution atomic- number contrast and crystallographic-orientation contrast. (5.) Other techniques make use of absorbed electrons, inelastically scattered electrons, Auger electrons etc.