As developments in manufacturing methods allow fabrication of smaller and smaller devices, microscopic characterization by SEM has seen increasing demand. These samples have traditionally required pretreatment, by coating with a conductive film, before SEM examination.
Nonconductive samples are subject to a buildup of electrons on the examined surface.
Furthermore, samples that contain substantial water or other materials that volatilize in high vacuum also present challenges for SEM examination. These samples require controlled drying to allow the SEM chamber to reach high vacuum and to prevent deformation of the sample at the SEM vacuum. A micrograph of natural rubber with a coating of silicone lubricant. Often, sample pretreatment is only partially effective in preparing the samples for SEM examination. For example, wet samples change character when dried, thus appearing different in the SEM examination than in their native state.