Influence of Nitride Buffer Layers on Superconducting Properties of Niobium Nitride

Document Type

Article

Publication Date

11-1-2018

Identifier/URL

41071274 (Pure)

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Abstract

Niobium nitride thin films were deposited using reactive magnetron sputtering simultaneously on sapphire substrates with TiN, VN, and AlN buffer layers. Deposition temperature was varied from 400 to 840 °C. It was found that the crystal structure, surface roughness, and transition temperatures of the resulting NbN films depend strongly on both the growth temperature and the type of the buffer layer. The use of VN and TiN buffer layers for growing NbN at 400 °C improved transition temperatures compared to NbN grown at 840 °C on sapphire. While increasing the temperature improved the superconducting performance of films grown directly on sapphire, it caused hexagonal δ′-NbN and ε-NbN phases to emerge on the buffered films. A highly oriented hexagonal ε-NbN film was achieved by using a TiN buffer and an 840 °C deposition temperature. The ability to deposit high performance NbN at a lower temperature will improve and simplify the fabrication of advanced superconducting devices such as superconducting single photon detectors.

DOI

10.1116/1.5044276

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