Tungsten Silicide Films for Kinetic Inductance Detectors

Microwave Kinetic Inductance Detectors (MKIDs) provide highly multiplexed arrays of detectors that can be configured to operate from the sub-millimeter to the X-ray regime. We have examined two tungsten silicide alloys (W5Si3 and WSi2), which are dense alloys that provide a critical temperature tunable with composition, large kinetic inductance fraction, and high normal-state resistivity. We have fabricated quarter wavelength CPW superconducting resonators and provide measurement data on critical temperature, surface resistance, quality factor, noise, and quasiparticle lifetime. Tungsten silicide appears to be very promising for kinetic inductance detectors.