Relationship between the physical and structural properties of NbzSiyNx thin films deposited by dc reactive magnetron sputtering

Abstract

The optical and electrical properties of NbzSiyNx thin films deposited by dc reactive magnetron sputtering have been investigated as a function of the Si content (CSi). Optical properties were studied by both specular reflectivity and spectroscopic ellipsometry. Electrical resistivity was measured by the van der Pauw method at room temperature and as a function of the temperature down to 10K. Both the optical and electrical properties of NbzSiyNx films are closely related with the chemical composition and microstructure evolution caused by Si addition. For CSi up to 4at.% the Si atoms are soluble in the lattice of the NbN crystallites. In this compositional regime, the optical and electrical properties show little dependence on the Si content. Between 4 and 7at.% the surplus of Si atoms segregates at the grain boundaries, builds an insulating SiNx layer, and originates important modifications in the optical and electrical properties of these films. Further increase of CSi leads to the formation of nanocomposite structures. The electrical properties of these films are well described by the grain-boundary scattering model with low probability for electrons to cross the grain boundary. The appearance of the intragranular-insulating SiNx layer and the reduction of the grain size are noticed in the dielectric function mainly as a strong damping of the plasma oscillation.