Influence of surface roughness on secondary electron emission from graphite

In this study, the authors address how surface roughness alters secondary electron emission. By using specific grades of metallographic polishing pads, controlled levels of roughness and surface features were imparted. As expected, the smoothest surface (root mean square roughness 0.110 ± 0.022 μm) produced the highest secondary electron yield; however, a moderate rough surface (0.990 ± 0.019 μm) produced a slightly lower yield as compared to a rougher surface (7.10 ± 1.23 μm) at lower primary electron energies. This inversion, that a macroscopic rougher surface yields a higher emission, has been explained by differences between large and small scale variations in the surface roughness and the frequency that these features appeared on the surface. The surface roughness was quantified using optical profilometry and a fast Fourier transform of the surface topology.