The atomic composition, structural, morphological, and optical properties of N-rich copper nitride thin films were investigated prior to and after annealing them in vacuum at temperatures up to 300 C. Films were characterized by means of ion-beam analysis, X-ray diffraction, atomic force microscopy, and spectroscopic ellipsometry techniques. The data revealed that even when the total (integrated over the whole thickness) atomic composition of the films remained constant, nitrogen starts to migrate from the bulk to the film surface, without out-diffusing, at temperatures as low as 100 C. This migration led to two chemical phases with different atomic concentration of nitrogen, lattice parameters, and crystallographic orientation but with the same crystal structure. X-ray diffraction experimental and Rietveld refined data seemed to confirm that nitrogen excess accommodates in interstitial locations within the anti-ReO3 crystal lattice forming a solid solution.

Thermal Stability of Copper Nitride Thin Films: the Role of Nitrogen Migration. R.Gonzalez-Arrabal, N.Gordillo, M.S.Martin-Gonzalez, R.Ruiz-Bustos, F.Agulló-López: Journal of Applied Physics, 2010, 107[10], 103513