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

Cécile Delacour (1) , L. Ortega (2) , M. Faucher , T. Crozes (3) , T. Fournier (3) , B. Pannetier (4) , V. Bouchiat (5)

1 NEEL - TPS - Thermodynamique et biophysique des petits systèmes
2 NEEL - POM - Optique & Microscopies
3 NEEL - Nanofab - Nanofabrication
4 NEEL - QuantECA - Circuits électroniques quantiques Alpes
5 NEEL - Quan2m - Interactions modulables dans des états quantiques 2D

We report on a combined structural and electronic analysis of niobium ultrathin films (from 2 to 10 nm) deposited in ultra-high vacuum on atomically flat Rplane sapphire wafers. A textured polycrystalline morphology is observed for the thinnest films showing that hetero-epitaxy is not achieved under a thickness of 3.3nm , 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/9ML) has an offset critical temperature above 4.2K and can be processed by standard nanofabrication techniques to generate air- and time-stable superconducting nanostructures, useful for quantum devices.

Mots clés: Superconducting films and low-dimensional structures; Vapor phase epitaxy; growth from vapor phase; Superconducting films and low-dimensional structures

Domaines: Physique [physics]

Cécile Delacour, L. Ortega, M. Faucher, T. Crozes, T. Fournier, et al.. Persistence of superconductivity in niobium ultrathin films grown on R-plane sapphire. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2011, 83 (14), pp.144504. ⟨10.1103/PhysRevB.83.144504⟩. ⟨hal-00591335⟩