Secondary electron generation mechanisms in carbon allotropes at low impact electron energies

More than a century after the discovery of the electron, there are still fundamental, yet unresolved, questions concerning the generation-ejection mechanism of the ubiquitous Secondary Electrons (SEs) from a solid surface. Broadness of the field of application for these SEs makes it desirable to be able to control this phenomenon, which requires the understanding of the elementary physical mechanism leading to their generation and emission. This paper reports on the dissection of such a tangled process operated by the help of spectroscopic tools of increasing finesse; measuring differential cross sections with an increasing degree of differentiation. These results demonstrate that single ionising scattering events, assisted by collective excitations, constitute the fundamental ingredient leading to SE-generation and -emission. To this end, the interaction of Low Energy Electrons (LEEs) with various Carbon allotropes has been investigated by means of Total Electron Yield (TEY) and (e,2e)-coincidence spectroscopy measurements. Carbon allotropes are chosen as targets since they are important in technological applications where both minimisation and maximisation of the SE-yield is a relevant issue. This is the first time that such complete set of benchmarks on the SE-yield from well characterised surfaces has been gathered, interpreted and is made available to the scientific community. This comprehensive investigation has led to the disentanglement of the elementary processes relevant for the understanding of the SE-generation probability, that fully take into account both energy and momentum conservation in the collision and the band structure of the solid as well as many-body effects.