Origin of negative temperature coefficient of resistivity in polycrystalline Ti-N films

Abstract

A negative temperature coefficient of electrical resistivity (TCR) has been observed in Ti-N films prepared by reactive evaporation or sputtering. Some samples measured had a resistivity minimum and the minimum temperature changing with varying nitrogen contents. To study the origin of this anomalous temperature dependence of resistivity, the crystallographic structures of Ti-N films were measured by x-ray diffraction. The resistivity data could be analyzed in terms of the existing theory based on the structural Kondo effect. The results demonstrated that the negative TCR originated from higher concentration of interstitial nitrogen atoms in the Ti-Nx solid-solution phase, and nitrogen vacancies and/or intrinsic stacking faults in the fcc TiNx compounds.