Characteristic electron energy losses in organic PTCDA films

Studies are made of the characteristic energy losses of slow electrons during the formation of thin PTCDA films on a ZnO(0001) surface. It is shown that at low primary electron energies (<100 eV) the energy loss spectrum ( _n =3.0, 6.3, and 15 eV) reflects the structure of the transitions between the valence band and the conduction band. As the primary electron energy increases, energy losses to the excitation of plasma oscillations become dominant (ħω ₁=6 eV — excitation of a π-plasmon and ħω ₂=25 eV — excitation of a σ-plasmon). Pis’ma Zh. Tekh. Fiz. 25, 19–24 (October 26, 1999)