Microstructure of NbN epitaxial ultrathin films grown on A-, M-, and R-plane sapphire

Journal Article · Mon Dec 03 04:00:00 EST 2007 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.2820607· OSTI ID:21016199

Espiau de Lamaeestre, R; Odier, Ph; Villegier, J -C ^[1]

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1. CEA-LETI, MINATEC, 17 Avenue des Martyrs, 38054 Grenoble Cedex 9 (France)

We compared ultrathin NbN films (2.5-10 nm) simultaneously grown by dc reactive sputtering at 600 deg. C on A, M, and R orientations of sapphire substrates. Film structures and superconducting properties were characterized. We show that actual NbN device films on R-Al{sub 2}O{sub 3} are (135) oriented and suffer from detrimental disoriented twin domains. On the contrary, NbN on M-Al{sub 2}O{sub 3} is shown to be untwined, leading to a lower resistivity, an increased critical current density J{sub c} (>4 MA cm{sup -2} at 4.2 K), and a higher critical temperature T{sub c} (11.3 K for 4.4 nm). These results offer promising alternative for better performances of superconducting detectors and mixers.

• OSTI ID: 21016199
• Journal Information: Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 23 Vol. 91; ISSN APPLAB; ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CRITICAL CURRENT
CRITICAL TEMPERATURE
CURRENT DENSITY
DEPOSITION
EPITAXY
GRAIN ORIENTATION
LAYERS
NANOSTRUCTURES
NIOBIUM NITRIDES
SAPPHIRE
SPUTTERING
SUBSTRATES
SUPERCONDUCTIVITY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0400-1000 K
THIN FILMS