Photoemission from polycrystalline diamond films irradiated with the harmonics of a Nd:YAG laser indicates that the amorphous or quasi-amorphous zones (patches) of sp(2)-C on the external surface of the diamond grains make a dominant contribution to the emission yield. This is deduced from: (a) the strong reduction of the yield as a consequence, of the partial removal of amorphous carbon (a-C) patches by etching with acid and (b) the correlation between the yield and the a-C content determined by Raman spectroscopy. The junction between the a-C patches and the diamond determines a configuration of the energy bands, which allows one-photon emission with an energy of 4.7 eV (4th harmonic). We have measured samples with variable a-C content and found an efficient emission, with values of quantum efficiency on the order of 10(-6). A phenomenological picture of the electron emission process leads us to locate it at the a-C-diamond-vacuum triple border. This indicates a high local efficiency and suggests that a diamond film with an appropriate distribution of a-C patches on the surface could be a very efficient material. Moreover it could work in moderate vacuum and have a high laser-radiation damage-threshold. Such a material would therefore be interesting as a robust photocathode.
Photoemission from diamond films illuminated by intense Nd : YAG laser harmonics / I., Boscolo; L., Catani; S., Cialdi; S., Orlanducci; Rossi, Marco; V., Sessa; F., Tazziolo; M. L., Terranova; C., Vicario. - In: APPLIED PHYSICS. A, MATERIALS SCIENCE & PROCESSING. - ISSN 0947-8396. - STAMPA. - 77:6(2003), pp. 805-809. [10.1007/s00339-003-2160-2]
Photoemission from diamond films illuminated by intense Nd : YAG laser harmonics
ROSSI, Marco;
2003
Abstract
Photoemission from polycrystalline diamond films irradiated with the harmonics of a Nd:YAG laser indicates that the amorphous or quasi-amorphous zones (patches) of sp(2)-C on the external surface of the diamond grains make a dominant contribution to the emission yield. This is deduced from: (a) the strong reduction of the yield as a consequence, of the partial removal of amorphous carbon (a-C) patches by etching with acid and (b) the correlation between the yield and the a-C content determined by Raman spectroscopy. The junction between the a-C patches and the diamond determines a configuration of the energy bands, which allows one-photon emission with an energy of 4.7 eV (4th harmonic). We have measured samples with variable a-C content and found an efficient emission, with values of quantum efficiency on the order of 10(-6). A phenomenological picture of the electron emission process leads us to locate it at the a-C-diamond-vacuum triple border. This indicates a high local efficiency and suggests that a diamond film with an appropriate distribution of a-C patches on the surface could be a very efficient material. Moreover it could work in moderate vacuum and have a high laser-radiation damage-threshold. Such a material would therefore be interesting as a robust photocathode.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
