SCALING OF CURRENT-RESISTIVITY ISOTHERMS OF INDIUM FILMS IN A MAGNETIC-FIELD

We have studied the nonlinear resistivity (J-rho characteristics) of g ranular indium films with different thicknesses (t) over bar and grain sizes (d) over bar in various constant magnetic fields B down to 0.6 K. Films 1 and 2 with (d) over bar = 14 nm are viewed as a dirty super conductor while films 3 and 4 with (d) over bar = 28 nm are modeled as a random Josephson network. The J-rho data are analyzed according to the vortex-glass (VG) theory. For film 1 with (t) over bar = 100 nm, w e have obtained the VG transition temperatures T-g(B) and scaling func tions, which are similar to those obtained in high-T-c superconductors , suggesting that the VG transition also rakes place in a conventional superconductor with sufficiently low T-c ( < 4 K). A finite-size effe ct is visible for thinner film 2 with (t) over bar = 20 nm, where T-g appears to be zero. This is in accord with the two-dimensional (2D) VG theory. The VG behavior is not observed for films 3 ((t) over bar = 6 0 nm) and 4 ((t) over bar = 200 nm) with (d) over bar = 28 nm. We ascr ibe it to the fact that the measuring current is too large to probe th e film at lengths larger than (d) over bar = 28 nm.