An analysis of photoemission and inverse photoemission spectra of Si(111) and sulphur-passivated InP(001) surfaces

TL;DR

This study compares experimental photoemission spectra of sulphur-passivated InP(001) and Si(111) surfaces with density-functional theory predictions, revealing good agreement when considering mixed surface phases and highlighting limitations of the density-of-states approximation.

Contribution

It provides a detailed comparison between experimental spectra and theoretical calculations for passivated semiconductor surfaces, introducing a mixed-phase surface model.

Findings

Spectra for InP(001)-S match calculations with mixed phases.

The Si(111) surface results agree with recent total-energy calculations.

Density-of-states approximation is invalid for these systems.

Abstract

Photoemission (PES) and inverse-photoemission spectra (IPES) for the sulphur-passivated InP(001) surface are compared with theoretical predictions based on density-functional calculations. As a test case for our methods, we also present a corresponding study of the better known Si(111) surface. The reported spectra for InP(001)-S agree well with the calculated ones if the surface is assumed to consist of a mixture of two phases, namely, the fully S-covered $(2\times2)$-reconstructed structure, which contains four S atoms in the surface unit-cell, and a $(2\times2)$ structure containing two S and two P atoms per unit cell. The latter has recently been identified in total-energy calculations as well as in core-level spectra of S-passivated Si(111)-$(2\times1)$ is in excellent agreement with the calculations. The comparison of the experimental-PES with our calculations provides additional considerations regarding the nature of the sample surface. It is also found that the commonly-used density-of-states approximation to the photo- and inverse- photoemission spectra is not valid for these systems.