The effect of structural disorder on the secondary electron emission of graphite

The dependance of the secondary electron yield (SEY) on the degree of crystallinity of graphite has been investigated during the amorphization of a highly oriented pyrolytic graphite (HOPG) samples by means of Ar+ bombardment. Photoemission and Raman spectroscopies were used to follow the structural damage while the SEY curves were measured from very low energies up to 1000 eV. We found that the increase of lattice defects lowers the contribution of the π electrons in the valence band and loss spectra and smears out the intense modulations in the low energy secondary electron yield (LE-SEY) curve. Raman spectroscopy results showed that ion induced lattice amorphization is confined in a near-surface layer. The evolution of SEY curves was observed with the progressive Ar+ dosage after crystal damage as due to the modification of the electronic transport properties within the damaged near surface layer.