Thermal annealing of RF sputtered NbN

Carter, W.; Cukauskas, E. J.

doi:10.1109/tmag.1987.1065019

Cited by 9 publications

(3 citation statements)

References 8 publications

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“…The reduction of N( F ) weakens the electron-phonon coupling strength and hence the T C reduces. Earlier reports revealed that the T C of as deposited NbN films can be enhanced by vacuum annealing [38][39][40] but not in N 2 atmosphere [41,42]. These experiments further support our proposed mechanism of suppression of the T C in δ − NbN.…”

supporting

confidence: 89%

“…Formation of the N-interstitial defect complex in δ − NbN causes strong smearing of electronic structure by creating atomic disorder in the films and thus a significant reduction in the N( F ) which strongly influencing the electron-phonon coupling strength and consequently reduces the T C . Increase in the T C of vacuum annealed δ − NbN [38,39,40] and degradation of superconducting properties at N 2 atmosphere [41,42] further support our proposed mechanism. Based on above analysis we suggest that to obtain δ − NbN with high T C , films should be grown at Nb-rich conditions to avoid N interstitial defects and annealing of samples in a vacuum is recommended to eliminate residual N atoms.…”

supporting

confidence: 61%

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Effect of disorder on superconductivity of NbN thin films studied using x-ray absorption spectroscopy

Kalal¹,

Nayak²,

Tayal³

et al. 2021

J. Phys.: Condens. Matter

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The superconducting transition temperature (T C ) of rock-salt type niobium nitride (δ − NbN) has been reported to vary in a large range (between 9 to 17 K) and the theoretically predicted value of 18 K has not achieved hitherto. Such a variation in the T C has been assigned to disorder present in δ − NbN irrespective of microstructure (polycrystalline or epitaxial), methods or conditions applied during the growth of NbN thin films. In this work, we investigate the atomic origin such suppression of T C in δ − NbN thin film by employing combined methods of experiments and abinitio simulations. Sputtered δ − NbN thin films with different disorder were studied using N and Nb K-edge x-ray absorption spectroscopy. A strong correlation between the superconductivity and the atomic distortion induced electronic reconstruction was observed. The theoretical analysis revealed that under N-rich conditions, atomic and molecular N-interstitial defects assisted by cation vacancies form spontaneously. As a result, the electronic densities of states around the Fermi level get smeared leading to a suppression of the T C in δ − NbN.

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supporting

confidence: 89%

supporting

confidence: 61%

Effect of disorder on superconductivity of NbN thin films studied using x-ray absorption spectroscopy

Kalal¹,

Nayak²,

Tayal³

et al. 2021

J. Phys.: Condens. Matter

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show abstract

“…Formation of the Ninterstitial defect complex in δ − NbN causes strong smearing of electronic structure by creating atomic disorder in the films and thus a significant reduction in the N(ǫ F ) which strongly influencing the electronphonon coupling strength and consequently reduces the T C . Increase in the T C of vacuum annealed δ − NbN [29][30][31] and degradation of superconducting properties at N 2 atmosphere [32,33] further support our proposed mechanism. Based on above analysis we suggest that to obtain δ − NbN with high T C , films should be grown at Nb-rich conditions to avoid N interstitial defects and annealing of samples in a vacuum is recommended to eliminate residual N atoms.…”

mentioning

confidence: 54%

Microscopic Origin of Structural Disorder in $δ$-NbN: Correlation of Superconductivity and Electronic Structure

Kalal,

Nayak,

Tayal

et al. 2020

Preprint

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Rock-salt type niobium nitride (δ − NbN) is a well-known superconductor having superconducting transition temperature (TC) ≈ 18 K and a large superconducting gap ≈ 3 meV. The TC of δ − NbN thin film exhibits a large scattering irrespective of the growth conditions and lattice parameter. In this work, we investigate the atomic origin of suppression of TC in δ − NbN thin film by employing combined methods of experiments and ab-initio simulations. Sputtered δ − NbN thin films with different disorder were analyzed through electrical resistivity and x-ray absorption spectroscopy. A strong correlation between the superconductivity and the atomic distortion induced electronic reconstruction was observed. The theoretical analysis revealed that under N-rich growth conditions, atomic and molecular N-interstitial defects assisted by cation vacancies form spontaneously and are responsible for the suppression of TC in δ − NbN by smearing its electronic densities of states around Fermi level.

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30Mei1 - 73Kit1

Flükiger¹,

Wolf²

Nb, Nb-Al - Nb-Ge

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Thermal annealing of RF sputtered NbN

Cited by 9 publications

References 8 publications

Effect of disorder on superconductivity of NbN thin films studied using x-ray absorption spectroscopy

Effect of disorder on superconductivity of NbN thin films studied using x-ray absorption spectroscopy

Microscopic Origin of Structural Disorder in $δ$-NbN: Correlation of Superconductivity and Electronic Structure

30Mei1 - 73Kit1

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