Termination of Single Crystal Bi2Se3 Surfaces Prepared by Various Methods

TL;DR

This study compares surface termination and order of Bi2Se3 prepared by different methods, revealing that in situ cleaving and ion bombardment yield well-ordered Se-terminated surfaces, while ex situ cleaving results in less ordered, contaminated, and variable terminations.

Contribution

It provides a comparative analysis of surface preparation methods for Bi2Se3, highlighting the effects on surface termination and order using multiple surface characterization techniques.

Findings

In situ cleaving and ion bombardment produce well-ordered Se-terminated surfaces.

Ex situ cleaving results in less ordered surfaces with possible contamination.

Atmospheric contaminants may cause non-reproducible surface termination.

Abstract

Bismuth Selenide (Bi2Se3) is a topological insulator with a two-dimensional layered structure that enables clean and well-ordered surfaces to be prepared by cleaving. Although some studies have demonstrated that the cleaved surface is terminated with Se, as expected from the bulk crystal structure, other reports have indicated either a Bi- or mixed-termination. Low energy ion scattering (LEIS), low energy electron diffraction (LEED) and x-ray photoelectron spectroscopy (XPS) are used here to compare surfaces prepared by ex situ cleaving, in situ cleaving, and ion bombardment and annealing (IBA) in ultra-high vacuum (UHV). Surfaces prepared by in situ cleaving and IBA are well ordered and Se-terminated. Ex situ cleaved samples could be either Se-terminated or Bi-rich, are less well ordered and have adsorbed contaminants. This suggests that a chemical reaction involving atmospheric contaminants, which may preferentially adsorb at surface defects, could contribute to the non-reproducibility of the termination.