Low-Energy Electron Energy Loss Spectroscopy on Evaporated Films of Metal-Free and Metal Phthalocyanines

Non-derivative energy loss spectra of low energy electrons reflected from the surface of evaporated films of phthalocyanines (MPc; M=H2, Cu, VO, Pb) have been measured in the loss energy region up to 30 eV. The observed peaks in the π-π* excitations region are in good agreement with the optical absorption maxima. Two broad structures are observed in common above 10 eV. The peak around 14 eV is considered to be due to the σ-σ* excitation. The collective excitation of valence electrons (plasmonlike oscillation) is observed at 20 eV. Electron radiation damage and the surface activity have also been investigated.