Electronic structure of InSb (001), (110), and (111)B surfaces

TL;DR

This study investigates the electronic surface structures of InSb (001), (110), and (111)B orientations, revealing how Sb termination influences Fermi-level pinning and surface states, with implications for surface charge control.

Contribution

It provides detailed experimental insights into how Sb termination shifts Fermi-level pinning and surface states on various InSb surfaces, a novel understanding for surface engineering.

Findings

Fermi-level pinning near valence band edge across surfaces

Sb termination shifts Fermi-level towards conduction band

Disordered (111)B (3x1) surface exhibits many sub-gap states

Abstract

The electronic structure of various (001), (110), and (111)B surfaces of n-type InSb were studied with scanning tunneling microscopy and spectroscopy. The InSb(111)B (3x1) surface reconstruction is determined to be a disordered (111)B (3x3) surface reconstruction. The surface Fermi-level of the In rich and the equal In:Sb (001), (110), and (111)B surface reconstructions was observed to be pinned near the valence band edge. This observed pinning is consistent with a charge neutrality level lying near the valence band maximum. Sb termination was observed to shift the surface Fermi-level position by up to $254 \pm 35$ meV towards the conduction band on the InSb (001) surface and $60 \pm 35$ meV towards the conduction band on the InSb(111)B surface. The surface Sb on the (001) can shift the surface from electron depletion to electron accumulation. We propose the shift in the Fermi-level pinning is due to charge transfer from Sb clusters on the Sb terminated surfaces. Additionally, many sub-gap states were observed for the (111)B (3x1) surface, which are attributed to the disordered nature of this surface. This work demonstrates the tuning of the Fermi-level pinning position of InSb surfaces with Sb termination.