Thin-film cryotrons with tin gate thickness reproducible to within 5% and lead control films having less than one micron penumbra have been fabricated. For such films, formed under carefully controlled evaporation conditions, tin critical temperatures are reproducible to within 0. 0050 K and critical currents for the cryotron to about ± 5% with comparable tolerances for the low temperature resistivity of the tin. A detailed discussion of apparatus designed for control of evaporation parameters

more »

... nd film geometry is given. Study of film formation through monitoring of film conductance has yielded infqrmation 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 for both tin and lead. This value is obtained for very large deposition rates independent of substrate temperature.