Superconducting Beryllium Films

Resistance-vs.-temperature measurements were made on a series of beryllium films condensed on liquid-helium cooled surfaces. Two vapor sources designed to reduce contamination were used and films were prepared on both crystalline quartz and glass substrates. The samples were superconducting with a transition temperature of T-c = 9.6 0.1 K as indicated by a sharp falloff of resistance on cooling. This qualitatively confirms earlier reports of the superconductivity of quenched beryllium films. The transition curves were, however, appreciably sharper and the transition temperature about a degree higher than previously reported. Good agreement found from sample to sample indicates that the residual impurity concentration was small enough to be unimportant and that the observed transition temperature is characteristic of pure beryllium. The phase of ber yllium responsible for the high T-c value disappeared on annealing in the range 40-60 K. No indication was found of a reported T-c approximate to 6-K phase. Beryllium films thicker than about 750 angstrom broke up during deposition, indicating the presence of large stresses.