The charging of small metallic clusters forming discontinuous gold and gallium films, condensed in vacuum onto an insulating substrate (sapphire), was experimentally studied by the method of ultraviolet photoelectron spectroscopy (UPS) for a photon energy of 5.4 eV. It seems that the charging is due to electron emission as well as to electron transfer from metal islands to the empty electron states in the metal-insulator interface. © 1995.
Lewowski, T., & Wieczorek, P. (1995). Photoelectron spectroscopy of thin discontinuous metal films deposited onto a sapphire substrate. Vacuum, 46(5–6), 523–525. https://doi.org/10.1016/0042-207X(94)00121-9