Aluminium-oxide wires for superconducting high kinetic inductance circuits. (30th November 2016)

• Record Type: Journal Article
• Authors: Rotzinger, H; Skacel, S T; Pfirrmann, M; Voss, J N; Münzberg, J; Probst, S; Bushev, P; Weides, M P; Ustinov, A V; Mooij, J E
• Is Part Of: Superconductor science & technology. Volume 30:Number 2(2017:Feb.)
• Publication Date: 2016-11-30
• Subjects: superconductivity -- kinetic inductance -- thin film; 85.25.Am -- 74.81.Bd -- 78.70.Gq; Superconductivity -- Periodicals; Superconductors -- Periodicals; 537.623
• DOI: 10.1088/0953-2048/30/2/025002
• Languages: English
• ISSNs: 0953-2048

Abstract

Abstract: We investigate thin films of conducting aluminium-oxide, also known as granular aluminium, as a material for superconducting high quality, high kinetic inductance circuits. The films are deposited by an optimised reactive DC magnetron sputter process and characterised using microwave measurement techniques at milli-Kelvin temperatures. We show that, by precise control of the reactive sputter conditions, a high room temperature sheet resistance and therefore high kinetic inductance at low temperatures can be obtained. For a coplanar waveguide resonator with 1.5 kΩ sheet resistance and a kinetic inductance fraction close to unity, we measure a quality factor in the order of 700 000 at 20 mK. Furthermore, we observe a sheet resistance reduction by gentle heat treatment in air. This behaviour is exploited to study the kinetic inductance change using the microwave response of a coplanar wave guide resonator. We find the correlation between the kinetic inductance and the sheet resistance to be in good agreement with theoretical expectations.