Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 32: Postersession Superconductivity: Josephson Junctions, SQUIDs, Heterostructures, Andreev Scattering, Vortex Physics, Cryodetectors, Measuring Devices, Cryotechnique
TT 32.28: Poster
Mittwoch, 25. März 2009, 14:00–18:00, P1A
Investigation of energy relaxation processes in NbN thin film using optical and IR irradiation — •Dagmar Rall1, Matthias Hofherr2, Konstantin Ilin2, Michael Siegel2, Uli Lemmer1, Alexei Semenov3, and Heinz-Wilhelm Hübers3 — 1LTI, University of Karlsruhe, Germany — 2IMS, University of Karlsruhe, Germany — 3DLR Institute of Planetary Research, Berlin, Germany
Superconducting radiation detectors made from ultra-thin Niobium Nitride (NbN) films show high sensitivity (down to single-photon) and short response times (some ten ps), making them suitable for applications like astrophysics, spectroscopy and telecommunications. The electron energy relaxation processes and responsivity of thin NbN films and their dependence on the stoichiometry of NbN films and the critical dimensions of a device are investigated for further improvement and optimisation of the detection efficiency and speed. We present results on the study of the response of NbN thin film samples to optical and infra-red radiation. The NbN thin films with thickness from 3nm to 15nm were deposited by DC reactive magnetron sputtering onto heated sapphire substrates and patterned into lines with critical dimensions from less than 100nm up to several micrometers. The samples were kept at helium temperatures, electrically biased and excited by fs laser pulses or amplitude modulated (up to 15GHz) laser radiation. The absorbed energy is redistributed by inelastic scattering processes among electron and phonon subsystems of the NbN film. These interaction processes result in a change of resistivity of the film, which is measured as a change of voltage across the sample.