Magnetoresistance and conductivity exponents of quench-condensed ultra-thin films of Bi

TL;DR

This study investigates how magnetoresistance and conductivity evolve in ultra-thin quench-condensed Bismuth films, revealing a 2-D percolation behavior influenced by substrate dielectric properties.

Contribution

It demonstrates the dependence of magnetoresistance and conductivity exponents on substrate dielectric constant and film thickness in quench-condensed Bi films.

Findings

Negative initial MR proportional to magnetic field squared

Conductance follows a power-law with an exponent near 1.33 on Ge underlayers

Percolation behavior observed only on specific substrates

Abstract

We have studied the magnetoresistance (MR) and evolution of conductivity with thickness of quench-condensed Bismuth films on substrates of various dielectric constants. Our results indicate a negative intial MR proportional to the square of the magnetic field. The conductance shows a power-law kind of dependence on thickness, with an exponent close to 1.33, characterisitic of a 2-D percolating system, only when the films are grown on a thin ($\sim 10${\rm \AA} Germanium underlayer but not otherwise.