Nanoscale electronic inhomogeneity in ZrNx thin films growth by reactive sputtering at room temperature

Abstract

We report on the structural and electrical properties of nanocrystalline zirconium nitride films grown by reactive sputtering on Si (100) substrates at room temperature. The samples were grown with a N2/Ar mixture varying the N2 concentration between 8 and 60% of the total atmosphere. The films are nanocrystalline with the coexistence of conducting and insulator phases. The electrical resistivity evolves from ZrN with a metallic state to an insulating rich nitrogen phase, passing through a semiconductor-like behavior as N2 in the mixture increases. A variable-range-hopping regime describes the temperature dependence of the resistivity for mixtures between 30 and 40%. Reactive mixtures of 50 and 60% of N2 give more insulator films. Beyond these macroscopic properties, the films display inhomogeneity electrical properties at the nanoscale with coexistence regions of different conductivity. The inhomogeneities reduce as nitrogen stoichiometry increases and the films become more insulators. Our results are relevant for applications including conducting electrodes and insulator barriers in tunneling devices.