cathodoluminescence • 1 min reading time

Sample preparation for cathodoluminescence imaging

Sample preparation techniques

Cathodoluminescence is a specific form of luminescence caused by ‘free’ electrons (or simply electron propagating through space).

Cathodoluminescence can be generated in the material when an electron beam interacts with it. The technique has proven to be a probeless and contactless inspection with a broad spectral range. 

But what are the necessary preparation steps that are needed to perform cathodoluminescence imaging? The sample preparation procedure is not difficult. Here are the steps that you would need to take.

  1. First thing that needs to be checked is whether the sample is high vacuum compatible. 

  2. Then you need to understand whether the sample is conducting.

  3. If the sample is not conducting then it is recommended to either coat it with carbon or metal, such as gold or platinum. Another solution would be using an ESEM imaging mode (a high-pressure mode), which is available in some SEMs, to counteract the charging. 

The most common preparation technique for naturally grown materials is thin sectioning (20 to 30 microns). This method is commonly used to prepare geological samples. Another way to prepare natural samples is to embed it in resin (and image a so-called plug). 

Man-made materials, on the other hand, such as silicon wafer, are normally flat and conducting already, so no additional preparation is needed in most of the cases. 

However, for all the materials polishing can be very helpful to flatten the sample. 

Additionally to the previously mentioned materials, it is possible to look at the materials in the powder form. For that, the powder can be put on a carbon tape to keep it in one position and also coat it with carbon or metal if needed. 

It is important to note that these steps are needed also to prepare the sample for general SEM imaging, so cathodoluminescence imaging does not add work to sample preparation.