TY - JOUR
T1 - Study on Ca Segregation toward an Epitaxial Interface between Bismuth Ferrite and Strontium Titanate
AU - Haselmann, Ulrich
AU - Haberfehlner, Georg
AU - Pei, Weijie
AU - Popov, Maxim N.
AU - Romaner, Lorenz
AU - Knez, Daniel
AU - Chen, Jian
AU - Ghasemi, Arsham
AU - He, Yunbin
AU - Kothleitner, Gerald
AU - Zhang, Zaoli
PY - 2020/3/11
Y1 - 2020/3/11
N2 - 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.
AB - 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.
KW - atomic-resolution TEM
KW - BiFeO
KW - density functional theory (DFT)
KW - EELS and EDS
KW - oxide heterostructure interface
KW - oxygen vacancy
KW - segregation
UR - http://www.scopus.com/inward/record.url?scp=85081944620&partnerID=8YFLogxK
U2 - 10.1021/acsami.9b20505
DO - 10.1021/acsami.9b20505
M3 - Article
C2 - 32058684
AN - SCOPUS:85081944620
SN - 1944-8244
VL - 12
SP - 12264
EP - 12274
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 10
ER -