Correction of systematic errors in scanning tunnelling spectra on semiconductor surfaces: the energy gap of Si(111)-7x7 at 0.3 K

TL;DR

This paper introduces a correction method for systematic errors in scanning tunnelling spectroscopy of semiconductor surfaces, demonstrated on Si(111)-(7x7) at 0.3 K, revealing an energy gap consistent with prior estimates.

Contribution

A new correction technique for systematic errors in STS data is proposed and applied to accurately measure the energy gap of Si(111)-(7x7) surface at low temperature.

Findings

Corrected STS data shows a 70 meV energy gap.

No sharp density of states peak at the Fermi level.

Results align with previous less precise estimates.

Abstract

The investigation of the electronic properties of semiconductor surfaces using scanning tunnelling spectroscopy (STS) is often hindered by non-equilibrium transport of the injected charge carriers. We propose a correction method for the resulting systematic errors in STS data, which is demonstrated for the well known Si(111)-(7x7) surface. The surface has an odd number of electrons per surface unit cell and is metallic above 20 K. We observe an energy gap in the ground state of this surface by STS at 0.3 K. After correction, the measured width of the gap is (70 +- 15) meV which is compatible with previous less precise estimates. No sharp peak of the density of states at the Fermi level is observed, in contrast to proposed models for the Si(111)-(7x7) surface.