A TiN thin film was grown by the DC-Sputtering technique was characterized by EELS spectroscopy in order to obtain the optical quantities, ε1,ε2 and the refractive index η. Optical properties were obtained analyzing the low loss window located at an energy less to 50 eV respect to the elastic peak. A primary energy of 200 keV and a spot size of 440 nm with an average acquisition time of 5 min were used. The optical properties were calculated using the Kramers - Kronig relations.

Figure 1 shows the PEELS spectra in the low loss region for TiN thin film. As we can see, the most prominent plasmon loss peak characterizing TiN appears at an energy loss of 24 eV. The origin of the loss peak located at 17 eV is interpreted as surface plasmon. in order to obtain a better approximation, we use a near-free electron model and we have compared with the respective optical quantities calculated with the conventional formalism.