Insulator-superconductor transition on solid inert gas substrates

We present observations of the insulator-superconductor transition in ultrathin films of Bi on solid xenon condensed on quartz and on Ge on quartz. The relative permeability E, ranges from 1.5 for Xe to 15 for Ge. Although we find screening effects as expected, the I-S transition is robust, and unmodified by the substrate. The resistance separatrix is found to be close to h/4e(2) and the crossover thickness close to 25 Angstrom for all substrates. I-V studies and Aslamazov-Larkin analyses indicate superconductivity is inhomogeneous. The transition is best described in terms of a percolation model. (C) 2003 Elsevier Science B.V. All rights reserved.