Scanning Microscopy


The serious use of cathodoluminescence (CL) in petrography began about 30 years ago with the electron microprobe analyzer. Investigators soon began to use simpler instruments mounted directly on optical microscopes - cathodoluminescence microscope attachments (CMAs).

A major advantage of the CMA, compared to a scanning electron microscope (SEM) or electron microprobe analyzer (EMPA), is the capability to switch quickly between CL observations and high quality conventional optical microscope observations. Beam currents available in the CMA are higher than in the SEM or EMPA and one sees an instantaneous real time true color display of the CL pattern.

CMAs are based on either cold cathode or hot cathode electron guns. Typical operation is at 0-30 keV, 0-1 mA, and a focused beam. Modern cold cathode systems include regulation of current and voltage in the discharge. Conductive coatings on samples are not required with cold cathode guns.

Recent developments include accessories for energy dispersive spectroscopy (EDS), cooled stage operation, and improvements in systems for spectral analysis of CL emission.

CMAs are finding wide application in the earth sciences and also in the study of ceramics, glasses, synthetic crystals, archaeological specimens, and other areas.

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