Detailed Investigation of the Low-Energy Secondary Electron Yield (LE-SEY) of Clean Polycrystalline Cu and of Its Technical Counterpart

The detailed study of the secondary electron yield (SEY) of technical surfaces for very low electron landing energies (from 0 to 20 eV) is a very important parameter in many fields of research. Some of the devices used in all those fields of research base some of their essential functionalities on the number of electrons produced by a surface when hit by other electrons, namely, its SEY and, in most cases, its very-low-energy behavior SEY (LE-SEY). Despite such interest, the very low electron landing energy part of an SEY curve has been rarely addressed due to the intrinsic experimental complexity to control and detect very low energy electrons. Furthermore, several results published in the past have been recently questioned to suffer from experimental systematic errors. In this paper, we critically review the experimental method used to study LE-SEY and define more precisely the energy region, in which the experimental data can be considered valid. By analyzing the significantly different behavior of LE-SEY in atomically clean polycrystalline Cu and in its as-received technical counterpart, we solve most, if not all, of the apparent controversy present in the literature, producing important inputs for better understanding the devices performances related to their LE-SEY.