Study on Ca Segregation toward an Epitaxial Interface between Bismuth Ferrite and Strontium Titanate

Ulrich Haselmann, Georg Haberfehlner, Weijie Pei, Maxim N. Popov, Lorenz Romaner, Daniel Knez, Jian Chen, Arsham Ghasemi, Yunbin He*, Gerald Kothleitner, Zaoli Zhang

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Segregation is a crucial phenomenon, which has to be considered in functional material design. Segregation processes in perovskite oxides have been the subject of ongoing scientific interest, since they can lead to a modification of properties and a loss of functionality. Many studies in oxide thin films have focused on segregation toward the surface using a variety of surface-sensitive analysis techniques. In contrast, here we report a Ca segregation toward an in-plane compressively strained heterostructure interface in a Ca- and Mn-codoped bismuth ferrite film. We are using advanced transmission electron microscopy techniques, X-ray photoelectron spectroscopy, and density functional theory (DFT) calculations. Ca segregation is found to trigger atomic and electronic structure changes at the interface. This includes the reduction of the interface strain according to the Ca concentration gradient, interplanar spacing variations, and oxygen vacancies at the interface. The experimental results are supported by DFT calculations, which explore two segregation scenarios, i.e., one without oxygen vacancies and Fe oxidation from 3+ to 4+ and one with vacancies for charge compensation. Comparison with electron energy loss spectroscopy (EELS) measurements confirms the second segregation scenario with vacancy formation. The findings contribute to the understanding of segregation and indicate promising effects of a Ca-rich buffer layer in this heterostructure system.

Original languageEnglish
Pages (from-to)12264-12274
Number of pages11
JournalACS Applied Materials and Interfaces
Volume12
Issue number10
DOIs
Publication statusPublished - 11 Mar 2020

Keywords

  • atomic-resolution TEM
  • BiFeO
  • density functional theory (DFT)
  • EELS and EDS
  • oxide heterostructure interface
  • oxygen vacancy
  • segregation

ASJC Scopus subject areas

  • Materials Science(all)

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