Preventing Charging/Coating

There are a number of ways to reduce or even eliminate charging on insulators:

But sometimes you will have to apply a conductive coat...

The key point for Electron Backscatter Diffraction (EBSD) coating is to keep the coat very thin, typically in the range of 2-5nm, if it is too thick, the signal to noise ratio will decrease significantly and result in very poor EBSPs. If the coating is too thin, there won’t be sufficient conductive material to dissipate the charge. Ideally the coat should be carbon either sputtered or evaporated onto the sample, but it is possible to use other coating materials such as gold or tungsten. In cases where the coat is a little too thick, it may be possible to obtain good EBSPS by increasing the accelerating voltage to penetrate through the coating.

Typical effects observed when samples are charging:

Secondary electron image of an uncoated Zirconia sample. Charging is causing instability and huge variations in the signal.
Orientation contrast image (FSD) from an uncoated Zirconia sample. Charging is not visible in the signal levels but can lead to distortions in the image.Orientation contrast image (FSD) from an uncoated Zirconia sample. Charging is not visible in the signal levels but can lead to distortions in the image.
Electron image from uncoated Zirconia sample. To the left is shown the secondary electron image and to the right the orientation contrast image based on the FSD. Charging effects are clearly visible in the SE image and less so in the FSD image.