Investigations of the disorder in the Ta_xN thin films: On the first order Raman spectrum of the rock salt crystal structure

First order Raman absorption in materials with the rock salt crystal structure is forbidden. Its appearance in real crystals results from the presence of vacancies and other defects. For Ta_xN polycrystalline thin films, we found that imperfections that reduce the coherence length contribute to the appearance of the first order Raman spectrum. This investigation enables us to better understand the anomalous concentration dependence of the resistivity of Ta_xN polycrystalline thin films fabricated using reactive sputtering at 450°C and 4.9 mTorr nitrogen pressures on amorphous substrates.