There is discussion in the literature about coating vs. decoration. When a metal grain from such a source strikes the surface of a specimen creating islands of coating. Metals such as chromium, tantalum, and tungsten tend to stick where they land upon the surface of the specimen. Therefore, they are coatings. Grain size of the metal produced is also important.
Smaller grains provide better resolution.
This is because they obscure less specimen detail. Cr and W can produce grain sizes on the order of 1.5 nanometer. Thus, Cr and W coatings can generate higher resolution images. In the discussion of signal generation, it was stated that the amount of backscattered electrons increases with increasing atomic number. It was also stated that the BSE signal lacks high-resolution information.