The effect of the structural properties on the SEY of C materials

We review here the dependence of the secondary electronyield (SEY) of carbon materials on the structural ordering ofthe C lattice and surface damage. We followed the SEY evo-lution during the thermal graphitization of thin amorphouscarbon layers and during the amorphization of highly ori-ented pyrolytic graphite by means of Ar+bombardment. C1score level and valence band spectroscopy, used to follow thestructural modification, were measured in parallel with SEYcurves. In the first case the SEY decrease observed with theprogressive conversion ofsp3hybrids into six-fold aromaticdomains was related to the electronic structure of the C-filmsclose to the Fermi level. We found that a moderate structuralquality of the C layer, corresponding to aromatic clustersof limited size, is sucient to obtain a SEY as low as⇠1.For the bombarded graphite, the strong lattice damagingremains limited to the near surface layer, where the highdensity of defects reduces the transport of incoming and sec-ondary electrons. Then, the SEY curves resulted dierentlymodified in the low and high primary energy regions, buttheir maximum values remained favorably low. Our findingsdemonstrate that SEY, besides being an indispensable meansto qualify technical materials in many technological fields,can be also used as a flexible and advantageous diagnosticsto probe surfaces and interfaces.