Studies of ultra-thin Bi films quench-condensed on solid inert gas and other substrates

This paper reports an experimental study of quench-condensed disordered ultra-thin films of Bi, where localization effects and superconductivity compete. Experiments are done with bare substrates and/or underlayers of solid Xe, Ge and Sb. The deposition temperature is also varied. We have observed absence of superconductivity in low dielectric constant substrates even though the sheet resistance is varied over 5 orders of magnitude. RHEED studies indicate that quantum size effects are important in these systems. Apart from stabilizing the amorphous phase in Bi, the Ge underlayer is found to nucleate superconductivity when the Bi was quench-condensed at 15 K. The macroscopic properties of the film are dependent both on the underlayer as well as the deposition temperature.