  The behavior of a disordered amorphous thin film of superconducting Indium
Oxide has been studied as a function of temperature and magnetic field applied
perpendicular to its plane. A superconductor-insulator transition has been
observed, though the isotherms do not cross at a single point. The curves of
resistance vs. temperature on the putative superconducting side of this
transition, where the resistance decreases with decreasing temperature, obey
two-dimensional Mott variable-range hopping of vortices over wide ranges of
temperature and resistance. To estimate the parameters of hopping, the film is
modeled as a granular system and the hopping of vortices is treated in a manner
analogous to hopping of charges. The reason the long range interaction between
vortices over the range of magnetic fields investigated does not lead to a
stronger variation of resistance with temperature than that of two-dimensional
Mott variable-range hopping remains unresolved.
