Aluminium-oxide wires for superconducting high kinetic inductance   circuits
  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\,k$\Omega$ 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. 
H. Rotzinger, S. T. Skacel, M. Pfirrmann, J. N. Voss, J. M\"unzberg,   S. Probst, P. Bushev, M. P. Weides, A. V. Ustinov and...
cond-mat.supr-con