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 $T\approx 1$ K. The values of the spin-orbit scattering parameter $b\equiv \frac{\hslash }{3{\tau }_{\mathrm{so}}\Delta }$ and the orbital depairing parameter $\zeta$ were determined for as-deposited amorphous films and for polycrystalline films obtained by annealing at $T\approx 77$ 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 $b=0.2\mathrm{}\pm 0.02$ 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 $\zeta ={\zeta }_0+\alpha H^2$ and to increase with annealing in a manner expected from the change in mean free path determined from measurements of $H_{c\perp }$.