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.