Sampling Depth Controlled by Accelerating Voltage in a Low Voltage SEM

Abstract A fundamental new pathway to a basic understanding of nanostructured composite thin films has been recently afforded by advances in both high brightness field emission electron source and electron optics in the SEM. The key advantages of controlling the incident electron beam at low energies (< 5 keV) for surface imaging has been largely focused on goals such as the reduction of sample charging and minimization of macroscopic radiation damage. In this paper, we present a new opportunity to obtain sampling depth information by controlling the incident electron beam energy. One of the major factors which determines the contrast seen in SEM images is the interaction of the incident electron beam with the solid. As a result of this interaction, the secondary electron yield is proportional to the stopping power of the electron as described by the Bethe penetration depth,where dE/dl is the stopping power of incident electron with energy Einc and Emin is some suitable lower energy limit for the interaction.