Conductance of a STM contact on the surface of a thin film

TL;DR

This paper theoretically investigates how quantized electron energy levels in a thin metal film affect the conductance of a small STM contact, revealing a step-like G(V) dependence linked to size quantization.

Contribution

It demonstrates that the quantization of electron energy levels causes a step-like differential conductance, enabling spectroscopic mapping of energy levels above and below the Fermi surface.

Findings

Conductance G(V) exhibits step-like features due to size quantization.

The spacing between steps corresponds to energy level differences.

G(V) analysis maps energy spectrum above and below Fermi surface.

Abstract

The conductance of a contact, having a radius smaller than the Fermi wave length, on the surface of a thin metal film is investigated theoretically. It is shown that quantization of the electron energy spectrum in the film leads to a step-like dependence of differential conductance G(V) as a function of applied bias eV. The distance between neighboring steps in eV equals the energy level spacing due to size quantization. We demonstrate that a study of G(V) for both signs of the voltage maps the spectrum of energy levels above and below Fermi surface in scanning tunneling experiments.