Development of Monte-Carlo simulations for nano-patterning surfaces associated with MM-EPES analysis

EPES (elastic peak electron spectroscopy) allows measuring the percentage of elastic backscattered electrons ηe from a surface excited by primary electrons. However, this method must be combined with Monte Carlo simulations to get quantitative information. After a brief description of the algorithm used in this work (named MC2), we focused on the adaptation of this simulation for nanoporous surfaces (named MC2-NP). The theoretical results obtained put in evidence the dependence of ηe versus pore diameter (d), depth of the pores (h) and covering rate (CR) of the pores on the surface. Results obtained on surfaces having cylinder-shaped and cone-shaped holes with nanometer dimensions are presented too. To validate theoretical results obtained with MC2-NP, silicon(111) nanoporous surfaces have been prepared with an anodized aluminum oxide (AAO) template and by argon ion bombardment in an UHV chamber. Uniform nanohole arrays were formed as a replica of ordered lattice pattern of the template. Then EPES experimental measurements have been performed on planar and nanoporous Si(111) surfaces using a retarding field analyzer (RFA). The experimental results put in evidence that the percentage of the elastically backscattered electrons is influenced by the patterning of the surface. Then comparing values of ηe obtained experimentally with those obtained with MC2-NP simulations, we show the sensitivity of the EPES method for studying nanoporous surfaces. In this way, we expect fast estimation of nanohole's dimensions by in-situ MM-EPES (Multi-Mode EPES) without other techniques such as for example scanning electron microscopy.