Analytical model for secondary electron yield of composite layered structures

An analytical model is developed to calculate the secondary electron yield (SEY) of composite layered structures, based on two independent physical parameters of secondary electron emission. For the same material, different processing techniques can result in significant variations in material surface conditions and microstructures, resulting in discrepancies in the excitation and escape capabilities of secondary electrons. The present model integrates the secondary electron excitation mechanism with Bethe’s stopping power expression, which can calculate the average mean free path and excitation energy threshold of thin dielectric films, providing a quantitative evaluation of contributions from each layer. Good agreement is observed between model predictions and experimental results for nanometer-scale ALD-Al2O3 films on Ag substrates. The results show that SEY is strongly dependent on the film thickness. The SEY curve of the film in the composite structure resembles that of a bulk material, but with a lower peak due to the limited thickness. As the film thickness increases, a larger contribution from the top layer and a further reduced contribution from the substrate are observed. This model offers a theoretical method for SEY evaluation in layered structures and can support the film thickness design in multipactor suppression and dynode films in electron detectors.