Color contrast in scanning electron microscopy

A new procedure is developed for the investigation of luminescent solids in a scanning electron microscope operating in the cathode luminescence regime. The optical radiation produced when the electron beam interacts with the surface of the investigated substance is registered and used as a video signal to produce a color image corresponding to the emitted spectrum in the visible region. The use of color contrast greatly increases the information content over the hitherto used amplitude contrast in black and white. This process is effected in two ways. In the first, sequential photography is used with a single receiver with interchangeable light filters (blue, red, green), so that black and white color-separation photographs are produced. The color photograph of the investigated surface is then obtained by additive synthesis. In the second method, three receivers with filters are used, and the color image is produced by a three-channel amplification system directly on the screen of a color monitor. The second method offers considerable advantages over the first, permits observation of both static and dynamic processes, yields immediate information on the chemical and structural state of the surface, and permits direct photography on color film. With minerals as examples, it is shown that color cathode luminescence (CCL) permits observation of the zone character of the structure, grain boundaries, regions where certain elements are substituted for others, growth zones, etc. CCL makes it possible to analyze manufacturing-technology defects in color TV tubes and to reveal imperfections in heterojunctions and diode structures. When used in the analysis of soil objects, it is possible to obtain a qualitative picture of the distribution of microinclusion, as well as their partial identification.