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Persistence of superconductivity in niobium ultrathin films grown on R-plane sapphire

Cécile Delacour, Luc Ortega, Marc Faucher, Thierry Crozes, Thierry Fournier, Bernard Pannetier, Vincent Bouchiat

DOI 10.1103/PhysRevB.83.144504 · Physical Review B

T1

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Abstract

We report on a combined structural and electronic analysis of niobium ultrathin films (from 2 to 10 nm) deposited in ultrahigh vacuum on atomically flat R-plane sapphire wafers. A textured polycrystalline morphology is observed for the thinnest films, showing that heteroepitaxy is not achieved under a thickness of 3.3 nm, which almost coincides with the first measurement of a superconducting state. The superconducting critical temperature rise takes place on a very narrow thickness range, of the order of a single monolayer (ML). The thinnest superconducting sample (3 nm/9 ML) has an offset critical temperature above 4.2 K and can be processed by standard nanofabrication techniques to generate air- and time-stable superconducting nanostructures, useful for quantum devices.

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FormulaReported Tc (K)Pressure (GPa)Type
Nb

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4.2Pressure not reportedzero_resistance

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