Quantum mechanical analysis of the elastic propagation of electrons in the Au/Si system: application to Ballistic Electron Emission Microscopy

TL;DR

This paper develops a Green's function method using a LCAO scheme to model elastic electron propagation in the Au/Si system, improving understanding of BEEM currents and resolving previous experimental discrepancies.

Contribution

It introduces a novel Green's function approach that incorporates metal band structure effects into BEEM current modeling, enhancing accuracy over prior methods.

Findings

Band structure effects explain BEEM spectral similarities

Method accurately models near-threshold electron currents

Results reconcile nanometric resolution with spectral data

Abstract

We present a Green's function approach based on a LCAO scheme to compute the elastic propagation of electrons injected from a STM tip into a metallic film. The obtained 2D current distribution in real and reciprocal space furnish a good representation of the elastic component of Ballistic Electron Emission Microscopy (BEEM) currents. Since this component accurately approximates the total current in the near threshold region, this procedure allows --in contrast to prior analyses-- to take into account effects of the metal band structure in the modeling of these experiments. The Au band structure, and in particular its gaps appearing in the [111] and [100] directions provides a good explanation for the previously irreconcilable results of nanometric resolution and similarity of BEEM spectra on both Au/Si(111) and Au/Si(100).