Tunneling measurements of ultrathin superconducting Ga films in high magnetic fields

Tunneling measurements in magnetic fields up to 15 T were made on Ga films about 10 nm thick deposited at T≈1 K. The values of the spin-orbit scattering parameter b≡3τₛₒΔ and the orbital depairing parameter ζ were determined for as-deposited amorphous films and for polycrystalline films obtained by annealing at T≈77 K. The tunneling conductance agreed closely with predictions of the theory of Maki and Fulde. For the best Ga-film tunnel junction a value of b=0.2±0.02 was obtained and this value did not change significantly during annealing, even though the resistively determined transport scattering time increased by a factor of 7.8 during annealing. Orbital depairing was found to follow a relation ζ=ζ₀+αH² and to increase with annealing in a manner expected from the change in mean free path determined from measurements of H_c⊥.