Energy gap revealed by low-temperature scanning-tunnelling spectroscopy of Si(111)-7x7 surface in illuminated slightly-doped crystals

TL;DR

This study uses low-temperature scanning tunnelling spectroscopy with illumination to reveal an energy gap in the Si(111)-7x7 surface, providing insights into its electronic properties.

Contribution

It demonstrates that illumination can remove band bending and reveal an intrinsic energy gap in the Si(111)-7x7 surface at low temperatures.

Findings

Energy gap of 40 ± 10 meV identified in Si(111)-7x7 surface.

Illumination restores surface state populations and removes band bending.

Surface electronic properties characterized at liquid helium temperatures.

Abstract

Physical properties of Si(111)-7x7 surface of low-doped n- and p-type Si samples is studied in the liquid helium temperature region by the scanning-tunnelling microscopy and spectroscopy. Conduction required for the study is provided by illumination of the surface. Application of illumination removes completely the band bending near the surface and restores initial population of the surface states. Our results indicate the existence of the energy gap 2{\Delta} = 40 \pm 10 meV in intrinsically-populated Si(111)-7x7 surface.