Influence of nitrogen background pressure on structure of niobium nitride films grown by pulsed laser deposition

Depositions of niobium nitride thin films on Nb using pulsed laser deposition (PLD) with different nitrogen background pressures (10.7 to 66.7 Pa) have been performed. The effect of nitrogen pressure on NbN formation in this process was examined. The deposited films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), and energy dispersive X-ray (EDX) analysis. Hexagonal β-Nb₂N and cubic δ-NbN phases resulted when growth was performed in low nitrogen background pressures. With an increase in nitrogen pressure, NbN films grew in single hexagonal β-Nb₂N phase. The formation of the hexagonal texture during the film growth was studied. The c/a ratio of the hexagonal β-Nb₂N unit cell parameter increases with increasing nitrogen pressure. Furthermore, the N:Nb ratio has a strong influence on the lattice parameter of the δ-NbN, where the highest value was achieved for this ratio was 1.19. It was found that increasing nitrogen background pressure leads to change in the phase structure of the NbN film. With increasing nitrogen pressure, the film structure changes from hexagonal to a mixed phase and then back to a hexagonal phase.