Structure and properties of nanostructured NbN and Nb-Si-N films depending on the conditions of deposition: Experiment and theory
The first results of studying the phase–structural state, properties, sizes of nanograins, hardness, and microstresses in nanocomposite NbN and Nb-Si-N films are given. The investigated films were obtained by the method of the magnetron sputtering of Nb and Si targets onto silicon substrates at different negative potentials at the substrate (from 0 to–70 V), nitrogen pressures P N, and discharge powers at the targets. To determine the thermal stability of the films, they were annealed at 600, 800, and 1000°C in a vacuum. It was revealed for the first time that the NbN films have a two-phase nanocomposite structure, which consists of δ-NbN (NaCl structure type) and α'-NbN. The δ-NbN phase is also formed in Nb-Si-N films, where it is enveloped by an amorphous Si3N4 phase The hardness of the Nb-Si-N films reaches 46 GPa, which corresponds to the level of superhardness, while the hardness of the NbN nanocomposites is somewhat lower, but also very high (34 GPa). The experimental results for the Nb-Si-N films were explained based on the data obtained from the first-principles calculations of the NbN/Si x N y heterostructures by the moleculardynamics method.
KeywordsNbN Nb-Si-N molecular dynamics superhardness nanocomposite
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