Improved critical temperature of superconducting plasma-enhanced atomic layer deposition of niobium nitride thin films by thermal annealing

Abstract

The efficiency of the superconducting radio frequency cavities composed of Nb required the deposition of thickness-controlled multilayer coatings of superconductor-insulator-superconductor (S-IS) on the internal surfaces of the cavities. Herein, we report the plasma-enhanced atomic layer deposition of carbon-free NbN (50 µm thick), followed by a thermal treatment, to obtain the superconducting layer in the S-IS structure. Using (tert-butylimido)-tris(diethylamino)-niobium as the niobium precursor and H 2 and NH 3 plasma as reactive gases, the deposition and annealing parameters were optimized by studying their effects on the film properties (crystallinity, density, and composition). We demonstrated that the superconducting critical temperature (Tc) can be improved after thermal annealing up to 13.8 K, a value compatible with the targeted application. In addition to the expected densified layers and increased grain size, we observed a partial transformation of the oxide present in the as-deposited layer into niobium oxynitride, which could indicate the origin of the improvement of the superconducting properties. With low carbon and oxygen impurity concentrations in the films, this study contributes to the understanding of the relationship between the structure, composition, and superconductivity in NbN.

Multistep atomic layer deposition process for ultrathin superconducting NbN films with high critical current density on amorphous substrate

“…Subsequent to the completion of the NH 3 /Ar reactant exposure, the H 2 /Ar reactant was fed to restrict oxygen inclusion into a film. A similar approach was implemented in the studies [28,29], where first the H 2 reactant was fed, and second the NH 3 reactant was fed to produce the films free of carbon and oxygen inclusions. Our primary focus was on the modification of operating parameters, such as the duration of exposure to the H 2 /Ar reactant plasma and relation of the gas mixture, the duration of exposure to the gas mixture plasma, the power of the ICP source for the NH 3 /Ar reactant.…”

Structures, properties and applications of two-dimensional metal nitrides: from nitride MXene to other metal nitrides

“…Plasma-assisted pulsed laser deposition Zn3N2 [402] HfN [404] Plasma-enhanced atomic layer deposition Mo2N [419] NbN [421,422] TaN [423] Plasma-enhanced chemical vapor deposition AlN [183,184] Pulsed laser deposition Zn3N2 [401] TiN [403] NbN [405] Cu3N [406] AlN [188,190] Zn3N2 [370][371][372][373][374][375] CrN [377] CoN (Co target) [493] HfN [494] Hf3N4 [494,495] RF reactive magnetron sputtering HfN (HfN target) [367][368][369] ZnN (ZnN target) [366] TiN (Ti target) [376] AuN2 (Au target) [378] Zr3N4 [379] Co3N [380] Room temperature ion beam assisted sputtering NbN [496] Thermal decomposition Ca2N [497] Thermal evaporation Zn3N2 [398,399] Cu3N [400] Topochemical nitridation of TMD by NH3 at high temperature Mo2N [438] MoN [435,438] The common methods for synthesizing MNs thin films include radio frequency (RF) magnetron sputtering [366][367]…”