Electron energy loss spectroscopy with subnanometer spatial resolution on compositionally modulated TiNx multilayers

Compositionally modulated TiNx multilayers (0.3 < x < 1; with a period of 8 nm) are investigated by spatially resolved electron energy loss spectroscopy with a 0.5 nm incident probe, in order to investigate systematically the evolution of the electronic structure as the nitrogen concentration varies. The difference in binding energy between Ti L and N K edges decreases substantially as the nitrogen concentration changes from the stoichiometric value (x approximate to 1) towards a non-stoichiometric one (x approximate to 0.3). This can be explained hy a re-distribution of the charge from the removed nitrogen to the surrounding titanium atoms. Furthermore the titanium L-3 peak, so-called white line, broadens in accordance with the nitrogen concentration, due to a change in the cl hand occupation. A shift of the volume plasma frequency towards lower energies when the nitrogen vacancy concentration increases is observed and explained in terms of a simple free-electron gas model, These results demonstrate the great power of spatially resolved electron energy loss spectroscopy as a probe of electronic structure with subnanometer-scale spatial resolution.