Energy loss of STEM electrons in coupled surfaces

In the frame of the self-energy formalism, the energy loss spectrum for STEM electrons moving close to a sphere coupled to a planar surface is studied. As an application the problem of the coupling between a small metallic particle and a large supporting surface is studied, as well as its dependence on both the size of the particle and the dielectric nature of the support. The coupling between both surfaces is found to be relevant only for particles of radius less than νω−1, where ω is the energy transfer and ν is the electron velocity. This result is explained in terms of the range of the Coulomb interaction. Our results are in qualitative agreement with recent experimental data.Authors gratefully thank help and support from Gipuzkoako Foru Aldundia and the Basque Country Government (PGV9114).Peer reviewe