A key benefit of the cathodoluminescence (CL) technique is the ability to capture optical emissions with spatial resolutions (potentially) down to 1 nm—far below the diffraction limit of conventional optical analysis techniques.
You can perform CL mapping in several different ways (acquisition modes) to understand better the spatial distribution of materials in your sample and their optical and electronic properties. To acquire this spatial information, a focused electron probe collects CL data (intensity or spectra) on a pixel-by-pixel basis as the electron beam is rastered across the surface of the specimen in a serial manner (X, Y).
There are several ways that the light emitted from a specimen can be analyzed to form a spatially resolved CL map:
- Unfiltered map – Measure the intensity integrated over all wavelengths (and angles and polarizations)
- Wavelength-filtered map – Measure the intensity over a (user-selected) wavelength range
- Color map – Determine the color based on sampling red, green and blue wavelengths
- Spectrum imaging – Capture the complete spectral information at each pixel
- Angle-resolved spectrum imaging – Obtain the emission pattern at each pixel
At first glance, a CL experiment may seem quite daunting because of the wealth of information generated by the technique. However, the actual workflow is relatively simple:
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Locate the region of interest within the sample.
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Set the desired SEM conditions.
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Ensure the alignment of the CL system to the SEM and sample is correct.
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Select the field of view (magnification) from which to collect a map.
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Optimize the map (optional).
In this section, we focus on capturing a map and optimizing the system to maximize the spatial resolution and signal-to-noise ratio.