Dresden 2011 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 60: SC \& MLT: Cryodetectors

TT 60.1: Talk

Friday, March 18, 2011, 10:30–10:45, HSZ 301

Ultra-thin TaN films for infrared Superconducting Nanowire Single-Photon Detectors — •Konstantin Ilin¹, Dagmar Rall^1,4, Matthias Hofherr¹, Michael Siegel^1,5, Alexei Semenov², Heinz-Wilhelm Hübers², Andreas Engel³, Kevin Inderbitzin³, Adrian Aeschbacher³, and Andreas Schilling³ — ¹IMS, Karlsuher Institut für Technologie, Karlsruhe, Deutschland — ²DLR Institut für Planetenforschung, Berlin, Deutschland — ³Physik-Institut der Universität Zürich, Zürich, Schweiz — ⁴LTI, KIT, Karlsruhe, Deutschland — ⁵DFG CFN, Karlsruhe, Deutschland

The quest for the development of superconducting nanowire single-photon detectors (SNSPD) with higher intrinsic detection efficiency in a wider spectral range stimulates the study of ultra-thin films of different superconducting materials. Tantalum nitride (TaN) is considered as a promising candidate for the development of SNSPDs for infra-red radiation. Thin superconducting TaN films were deposited by reactive magnetron sputtering from a pure Ta target in a gas mixture of Ar and N₂. The films were deposited on sapphire substrates heated to about 550 C. The transition temperature T_c of the thickest films (15 nm) was about 9.6 K. It decreased with the thickness remaining larger than 7 K for films with a thickness of 4 nm. SNSPDs made from TaN films have a critical current density of a few MA/cm² at 4.2K and T_c only slightly less than T_c of non-patterned films. Superconducting and normal state properties of micrometer and sub-micrometer sized TaN structures will be discussed in details. The single-photon response of TaN SNSPDs will be presented for the first time.