Sputter coating prevents charging of the specimen, which would otherwise occur because of the accumulation of static electric fields. It also increases the amount of secondary electrons that can be detected from the surface of the specimen in the SEM and therefore increases the signal to noise ratio.

How does a sputter coater work?

Sputter coating is a physical vapor deposition process used to apply a very thin, functional coating on a substrate. The process starts by electrically charging a sputtering cathode which in turn forms a plasma causing material to be ejected from the target surface.

Why are samples gold coated in SEM?

Historically, the most frequently used sputter coating material has been gold because of its high conductivity and relatively small grain size, which makes it ideal for high-resolution imaging.