Fabrication and properties of rf niobium-on-sapphire superconducting resonators

Niobium-on-sapphire resonators have been constructed as sensor elements for accelerometers in gravitational wave antennae. In their present form the resonators constitute small simple sensor elements for a wide range of applications where displacements take place, such as seismometry, gravimetry, thermal expansion measurements, as well as gravitational wave antennae. Radio-frequency losses in the niobium-sapphire interface have been observed. These limit the resonator Q to less than 10(5) and show a strong power dependence. Several methods of fabrication of the niobium-on-sapphire circuits have been investigated. Complete details for construction are given. An accelerometer based on these resonators is described in an accompanying paper.