Superconductor films based on metal oxides are protected against acids in the atmosphere by solution application of 2 um passivation coatings of DuPont Teflon® AF amorphous fluoroplastic resin.
Unlike conventional niobium superconductors, films pioneered by DuPont function effectively at temperatures readily achieved by cooling with liquid nitrogen or mechanical refrigeration equipment. The photo shows a sapphire wafer with a superconductive film that functions as the entire front end of a two-channel microwave receiver.
Teflon® AF provides more protection against atmospheric acids and better adhesion than typical polyimide passivation coatings.
Tests show the coating's good resistance to boiling water, and there has been no breakage of brittle oxide films during thermal cycling tests.
Solutions of Teflon® AF are applied by conventional spin coating techniques to controlled thickness down to 1 Rm. They dry at 100°C (212°F) by solvent evaporation.
Higher electrical performance
Superconductorbased devices under development gain increased velocity of propagation and reduced crosstalk, thanks to the very low dielectric constant (1.89-1.93) of Teflon® AF.
Material Selected and Why
Teflon® AF provides effective circuit protection, improved dielectrics and easy application.