Artifacts conductive coatings

Etching is another preparation method that potentially enhances the information available by microscopy while at the same time providing opportunity to introduce many artifacts. Samples are etched and then generally used directly by AFM, or replicas made for TEM, or a conductive coating is applied to the etched surface for imaging by SEM. 

If the sample is an insulator there are still methods by which it can be studied in the instrument. The simplest approach is to coat it with a thin (10-nm) conducting film of carbon, gold, or some other metal. In following this approach, care must be taken to avoid artifacts and distortions that could be produced by nonuniform coatings or by agglomeration of the coating material. If an X-ray analysis is to be... 

All paint, gypsum, and natural stone samples were broken perpendicularly to the surface so as to produce rough surfaces. To avoid artifacts, most analyses were performed either on ultra-thin carbon-coated samples for the purpose of improving the conductivity or, if possible, on non-coated samples. Ultra-thin carbon-coated powder preparations were made from silicone-coated fillers. 

For optical microscopy of fracture surfaces usually little or no surface preparation is necessary. However, because plastics have poor electrical conductivity, for SEM examinations the sample surface generally needs to be coated with a conductive layer that prevents charging and heating. The energy carried into the sample can melt the polymer or vaporize low molecular contents locally and change the fracture surface irreversibly, making its interpretation impossible. On the other hand, to ensure artifact-free imaging, the applied layer itself must not have any visible structure and must be so thin that the structures on the surface are not hidden. 

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