Origin of the metallic to insulating transition of an epitaxial Bi(111) film grown on Si(111)

TL;DR

This paper investigates the transition from metallic to insulating behavior in epitaxial Bi(111) films on Si(111), revealing the roles of film thickness, interface states, and quantum size effects in this transition.

Contribution

It uncovers the origin of the metallic-insulating transition in Bi films, emphasizing the influence of interface states and quantum size effects at different temperatures.

Findings

Insulating behavior arises from states inside the film.

Metallic behavior originates from interface states.

Quantum size effects are only observable above the transition temperature.

Abstract

Transport characteristics of single crystal bismuth films on Si(111)-7 \times 7 are found to be metallic or insulating at temperature below or above TC, respectively. The transition temperature TC decreases as the film thickness increases. By combining thickness dependence of the films resistivity, we find the insulating behavior results from the states inside film, while the metallic behavior originates from the interface states. We show that quantum size effect in a Bi film, such as the semimetal-to-semiconductor transition, is only observable at a temperature higher than TC. In addition, the metallic interface state is shown to result from the large SO-splitting at interfaces.