Cathodoluminescence (CL) microanalysis provides high-sensitivity spectra and high-resolution images associated with impurity and structural defects at the nanoscale and from luminescent materials including minerals, semiconductor, and dielectric/insulating materials. Cathodoluminescence is the non-incandescent emission of light (photons) emitted from materials excited by an electron beam. CL photons (UV-VIS-NIR) are produced as a result of electronic transitions between the conduction and valence band and may also involve electronic transitions associated with defect levels within the band gap. Microscopic defects such as imperfections and impurities influence the optical, electrical, and mechanical properties of scientifically and technologically important materials. CL microanalysis is therefore a useful microanalytical technique for characterizing these properties with high sensitivity and spatial resolution. CL image resolution can range from sub-10 nm to microns, dependent on experimental arrangement (STEM-CL, SEM-CL, optical CL microscopy), electron beam parameters, specimen configuration, carrier diffusion, etc. The sensitivity of CL microanalysis is dependent on the specimen and, in the absence of self-absorption and competitive recombination centers, can be several magnitudes more sensitive than X-ray microanalysis. In particular, quantitative CL microanalysis of trace impurity concentrations while challenging has recently been shown to be possible for a range of minerals.

The environmental scanning electron microscope (ESEM) is not typically used for quantitative analysis by energy dispersive x-ray spectrometry (EDS) because the electron beam is scattered by the chamber gas forming a broad tail or skirt rather than a focused spot. Scattered electrons can contribute x-rays from areas not directly under the beam, which compromises the spectrum for quantitative analysis. For specimens compatible with high vacuum, quantitative EDS analysis in a conventional electron microscope is preferred. However, the ESEM has found its niche in providing a vehicle for investigating those specimens that for any of a variety of reasons are not suitable for high vacuum electron microscopy and microanalysis. For these specimens, it is important that we find the most accurate way to perform EDS analysis in the low vacuum environment.

Research has focused on reducing, accounting for, predicting, or measuring the electron scattering on a simplified system. Instrumental tricks to reduce the scattering of the primary electron beam have been reported in the past.

The scattering of primary beam electrons has several implications for energy dispersive X-ray analysis on the environmental scanning electron microscope (ESEM). One of the most basic problems is determining the spatial distribution and fraction of primary beam electrons scattered under typical high pressure analysis conditions A method for studying the scattering of the primary electron beam in the ESEM has been demonstrated. The method involves the use of self-assembled alkanethiol monolayers (SAM) which are sensitive to damage by primary beam electrons. After irradiation, the electron damaged molecules can be exchanged out of the monolayer by immersion in a second alkanethiol solution. The spatial distribution of this second marker compound can then be imaged directly by static secondary ion mass spectrometry (SSIMS). Alternatively, only a single fluorinated thiol is used and the decrease in fluorine secondary ion signal is used to map the electron damage.