REPRODUCIBILITY STUDIES ON CIRCUITS EMPLOYING THIN FILM SUPERCONDUCTORS FORMED BY VACUUM DEPOSITION
TRW SPACE TECHNOLOGY LABS LOS ANGELES CA
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Thin-film cryotrons with Sn gate thickness reproducible to within 5 and Pb control films having less than one micron penumbra were fabricated. For such films, formed under carefully controlled evaporation conditions, Sn critical temperatures are reproducible to within 0.005 K and critical currents for the cryotron to about 5 with comparable tolerances for the low temperature resistivity of the Sn. A detailed discussion of apparatus designed for control of evaporation parameters and film geometry is given. Study of film formation through monitoring of film conductance yielded information regarding the nature of the scattering of conduction electrons at the walls of the film. Films formed at or annealed at room temperature show purely spectral scattering. In addition, such studies reveal a minimum critical thickness for onset of electrical conduction of about 90 Angstroms for both Sn and Pb. This value is obtained for very large deposition rates independent of substrate temperature.
- Electricity and Magnetism