Effect of surface defects and few-atomic steps on the local density of states of the atomically-clean surface of topological insulator Bi$_2$Se$_3$

TL;DR

This study uses low-temperature STM and STS to analyze the surface defects, steps, and local density of states of atomically clean Bi$_2$Se$_3$, revealing p-type conduction and electronic shifts near surface features.

Contribution

It provides new insights into how surface defects and atomic steps influence the local electronic structure of Bi$_2$Se$_3$ topological insulator surfaces.

Findings

Identification of subsurface defects linked to p-type conduction.

Observation of the chemical potential within the bulk band gap.

Detection of local density of states shifts near surface steps.

Abstract

The results of ultra-high vacuum low-temperature scanning-tunneling microscopy (STM) and spectroscopy (STS) of atomically clean (111) surface of the topological insulator Bi$_2$Se$_3$ are presented. We observed several types of new subsurface defects whose location and charge correspond to p-type conduction of grown crystals. The sign of the thermoelectric effect also indicates p-type conduction. STM and STS measurements demonstrate that the chemical potential is always located inside the bulk band gap. We also observed changes in the local density of states in the vicinity of the quintuple layer steps at the studied surface. This changes correspond either to the shift of the Dirac cone position or to the shift of the chemical potential near the step edge.