Point defects at cleaved Sr$_{n+1}$Ru$_n$O$_{3n+1}$(001) surfaces

TL;DR

This study combines experimental STM imaging and DFT calculations to analyze surface defects on cleaved Sr$_{n+1}$Ru$_n$O$_{3n+1}$(001), revealing that intrinsic defects are not formed during cleaving, but surface vacancies can be induced by electron bombardment.

Contribution

The paper provides the first combined experimental and theoretical analysis of surface point defects on Sr$_{n+1}$Ru$_n$O$_{3n+1}$(001) surfaces, highlighting the high formation energy of intrinsic vacancies and the conditions for creating surface oxygen vacancies.

Findings

Intrinsic defects are not created during cleaving.

Surface oxygen vacancies can be induced by electron bombardment.

Observed point defects originate from impurities and residual gas adsorption.

Abstract

The (001) surfaces of cleaved Sr$_3$Ru$_2$O$_7$ and Sr$_2$RuO$_4$ samples were investigated using low-temperature scanning tunneling microscopy and density functional theory calculations. Intrinsic defects are not created during cleaving. This experimental observation is consistent with calculations, where the formation energy for a Sr and O vacancy, 4.19 eV and 3.81 eV, respectively, is significantly larger than that required to cleave the crystal, 1.11 eV/(1 $\times$ 1) unit cell. Surface oxygen vacancies can be created through electron bombardment, however, and their appearance is shown to vary strongly with the imaging conditions. Point defects observed on as-cleaved surfaces result from bulk impurities and adsorption from the residual gas.