Preparation of clean surfaces and Se vacancy formation in Bi$_{2}$Se$_{3}$ by ion bombardment and annealing

TL;DR

This study demonstrates that low energy Ar$^{+}$ ion bombardment and annealing can produce clean, well-ordered Bi$_{2}$Se$_{3}$ surfaces with controlled selenium vacancy formation, comparable to traditional cleaving methods.

Contribution

It introduces a reproducible ion bombardment and annealing technique for preparing Bi$_{2}$Se$_{3}$ surfaces with controlled vacancy formation, offering an alternative to mechanical cleaving.

Findings

Well-ordered surfaces achieved with 1 keV Ar$^{+}$ ion bombardment and 30 min annealing.

Surface Se vacancies form at annealing temperatures above 520°C.

Optimal annealing temperature identified as 450°C.

Abstract

Bismuth Selenide (Bi$_{2}$Se$_{3}$) is a topological insulator (TI) with a structure consisting of stacked quintuple layers. Single crystal surfaces are commonly prepared by mechanical cleaving. This work explores the use of low energy Ar$^{+}$ ion bombardment and annealing (IBA) as an alternative method to produce reproducible and stable Bi$_{2}$Se$_{3}$ surfaces under ultra-high vacuum (UHV). It is found that a well-ordered surface can be prepared by a single cycle of 1 keV Ar$^{+}$ ion bombardment and 30 min of annealing. Low energy electron diffraction (LEED) and detailed low energy ion scattering (LEIS) measurements show no differences between IBA-prepared surfaces and those prepared by $\textit{in situ}$ cleaving in UHV. Analysis of the LEED patterns shows that the optimal annealing temperature is 450{\deg}C. Angular LEIS scans reveal the formation of surface Se vacancies when the annealing temperature exceeds 520{\deg}C.