The effect of heat treatment on structural and electronic properties of niobium nitride prepared by a thermal diffusion method

Abstract

Niobium nitride (NbN x) coatings are were prepared onto Nb substrate by thermal diffusion at high temperatures. The formation of NbN x coating by thermal diffusion was studied in the range of 1250-1500 o C at constant nitrogen background gas pressure (1.310-3 Pa) and processing time (180 min). The electronic and crystal structures of the NbN x coatings were investigated. It was found that nitrogen diffuses into Nb forming the Nb-N solid solution (bcc) α-NbN phase that starts to appear above 1250 o C. Increasing the processing temperature gives richer -phase concentration. Besides, X-ray absorption spectroscopy (XAS) was performed to study the electronic structure of the NbN x layer. The results of the electronic structural study corroborate the crystal structural analysis. The Nb M 3,2 edge X-ray absorption spectroscopy (XAS) spectrum shows strong temperature dependence. At the highest processing temperature (1500 o C), the number of d holes increased. Nitrogen diffusion into Nb is resulting to increase electrostatic interaction between d electron and core hole. Electrostatic interaction between d electron and core hole was increased due to nitrogen diffusion into the niobium. For the studied conditions, only the α-NbN was observed in the X-ray diffraction patterns.

Superconducting niobium nitride: a perspective from processing, microstructure, and superconducting property for single photon detectors

“…These deviations can complicate the study of the NbN and their respective structures, as chemical makeup can vary quite substantially in composition from one sample to another, yet the lattice parameters do not significantly differ [11]. As the nitrogen content increases, NbN polymorphs form in the following order from the lowest N content to the highest N content: α-NbN (bcc structured solid solution Nb(N)) [12], β-NbN (hexagonal, Nb 2 N), γ-NbN (tetragonal, Nb 4 N 3±x ), δ ′ -NbN (hexagonal, Nb 5 N 6 ), and δ-NbN (cubic B1-phase) [13]. The increase in the partial pressure of N during film growth can increase the N content into interstitial sites of the forming lattice, slightly expanding the lattice parameter (a 0 ) and distorting the structure [14].…”

Niobium near-surface composition during nitrogen infusion relevant for superconducting radio-frequency cavities

“…Most of the studies found in the literature address N and Nb interactions at high temperatures [11][12][13][14]. Nonetheless, few reports detail investigations of Nb single crystals under low N 2 pressures and of cavity-grade Nb after undergoing real cavity-treatment conditions.…”

Study of Surface Modification of Niobium Caused by Nitriding and Cathodic Cage Deposition

“…In addition, these nitrides can act as protective layers against oxidation processes 9 and improve tribological performance 10 . Niobium nitride has excellent physical and chemical properties such as hardness 11 , wear resistance 12 , chemical stability 13 , and superconducting properties 14 high electrical conductivity, and superconducting transition temperature 15,16 . Furthermore, plasma nitriding can form a transition layer produced by nitrogen diffusion on the metal surface.…”