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.Comment: 16 pages, 7 figure
