Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 9: SC: Poster Session

TT 9.43: Poster

Monday, March 22, 2010, 14:00–18:00, Poster A

Measurement of Dielectric Losses in Amorphous Thin Films at GHz Frequencies Using Superconducting Resonators — •Sebastian Skacel¹, Christoph Kaiser¹, Stefan Wünsch^1,2, Michael Siegel^1,2, Ralf Dolata³, Brigitte Mackrodt³, and Alexander Zorin³ — ¹Institut für Mikro- und Nanoelektronische Systeme (IMS), Karlsruher Institut für Technologie — ²Center for Functional Nanostructures, Karlsruher Institut für Technologie — ³Physikalisch-Technische Bundesanstalt (PTB), Braunschweig

Josephson junctions (JJs) are employed for many applications involving microwave signals, so that low microwave losses in the structures are desirable. We have developed a reliable method for the direct measurement of dielectric losses in thin films. Thus we obtain quantitative values for the losses in the film volume as well as the metal/dielectric interfaces. Using different resonator geometries we studied the losses in dielectric thin films usually used for JJ fabrication, such as Nb₂O₅, SiO, SiO₂ and SiN_x, at 4.2K and low GHz frequencies. The results show that for such amorphous materials, the bulk losses clearly exceed the interface losses. Furthermore, the frequency dependence of the losses in this working regime was studied for the first time. Our results are in good agreement with the universal law and suggest that the losses are due to many-body interacting dipoles, which is an important fact for the theoretical modelling of two-level-fluctuators. Further investigations of dielectric multi-layer films are in good agreement with the theoretical expectations, which allows the optimisation of such multi-layers usually used in JJ and qubit fabrication.