If you were to examine surfaces in a typical SEM system using any number of surface analysis techniques, I think you'd be surprised at the results. You might expect to see all materials used to construct the vacuum chamber (e.g., plastic or stainless steel), but frequently the spectra will show mostly carbon, the most frequent culprit of SEM contamination. Carbon is adsorbed onto the walls of the vacuum chamber and builds up on the sample, thereby contaminating the SEM system and compromising image quality. By manufacturing and maintaining a clean SEM environment, this problem can be avoided, and you will increase the overall performance of your SEM system.