Influence of the SiO underlayer on the superconductor-insulator transitionin amorphous Bi films

We have measured the temperature (T) dependence of the resistance per squar e R for a series of ultrathin Bi films quench-condensed onto different SiO underlayers ranging in thickness from zero to similar to 20 Angstrom. The R -T characteristics of Bi films on a 4.3 Angstrom -thick layer of SiO are di fferent from those on the layers thicker than 10 Angstrom, possibly because of the inhomogeneity in Bi films. The results suggest that insufficient th ickness of an underlayer causes a larger value of the critical resistance f or the superconductor-insulator transition in quench-condensed Bi films.