Secondary electron emission of 10-100 keV electrons from transparent films of Al and Au

Measurements of the secondary electron yields delta and delta T on the incident and the opposite surfaces respectively of transparent Al and Au films are reported for the normal incidence of 10-100 keV electrons, using an apparatus with accurate separation of secondary, backscattered and transmitted electrons. Results are discussed for the ratios beta and beta T of the mean secondary electron yield of respectively backscattered and transmitted electrons for one incident primary electron. The results are compared with calculated values using the energy and angular distributions of the backscattered and transmitted electrons. They can be explained by the assumption that the mean secondary electron yield of one primary, backscattered or transmitted electron is proportional to the Bethe energy loss inside the exit depth of the secondaries. There is no experimental evidence the conservation of momentum causes an additional factor r to be used for the secondary electron emission of electrons with a momentum directed outside the surface.