Superconducting Tungsten Silicide Thin Film – High Kinetic Inductance Material

  Ori Hachmo  ,  Nadav Katz  
Hebrew University

Bulk crystalline tungsten is known to have a critical temperature of about 100mK. But, in a paper from 92’ Kondo showed [1] that a tungsten film which contains 5 to 70 percents of silicon exhibits a great enhancement in Tc and loses its crystal structure in favor of an amorphous one. Tungsten silicide has proven to be a useful material in the field of single photon detection based onnanowires. Our measurements of coplanar microwave resonators made from a 30nm film of this material show it has a huge kinetic inductance fraction (α) of about 0.94, while still having quality factors of 20,000 to 40,000 which makes it potentially highly nonlinear while not being dissipative. In addition, surprising results include a positive resonance frequency shift at high power as opposed to known theories about kinetic inductance.