Scanning Microscopy


The general principles of the low-temperature spectroscopic cathodoluminescence (LTSCL) technique in the scanning electron microscope (SEM) are outlined. CL microscopy and spectroscopy are now being extended in new directions. Analysis of the intrinsic CL from quantum well materials by LTSCL is proving valuable for microcharacterization and such work can be expected to expand rapidly. The main, early CL results in this exciting field are summarized here. In geology, CL microscopy, without spectroscopy, is widely used via electron-beam attachments to light microscopes and the addition of spectral analysis to these studies is overdue. Much CL from minerals and ceramics comes from trace amounts of rare earth or transition metal ions, so the nature of this important type of emission is briefly described. Results on ceramic materials illustrating the advances in the field and the distinctive nature of the rare earth and transition metal ion emission bands are reviewed. The fascinating high Tc superconducting ceramics emit CL and there are a number of papers reporting the emission spectra of these materials, but no theoretical interpretation of the information is yet available. A new factor in the situation is the commercial availability of complete LTSCL systems, removing one of the main obstacles to the adoption of the technique by more laboratories.

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