Direct observation and consequences of dopant segregation inside and outside dislocation cores in perovskite BaSnO3

TL;DR

This study uses atomic-resolution electron microscopy to reveal how La dopants segregate differently inside and outside dislocation cores in BaSnO3, significantly affecting local atomic structures and electronic properties, including an insulator-metal transition.

Contribution

It provides direct atomic-scale observations of dopant segregation behaviors and their electronic consequences in BaSnO3 dislocations, a novel insight into defect-dopant interactions.

Findings

La dopants segregate at dislocation cores driven by elastic strain.

Segregation causes formation of Ba-vacancies and core reconstruction.

Dopant segregation dramatically alters electronic structure, inducing insulator-metal transition.

Abstract

Distinct dopant behaviors inside and outside dislocation cores are identified by atomic-resolution electron microscopy in perovskite BaSnO3 with considerable consequences on local atomic and electronic structures. Driven by elastic strain, when A-site designated La dopants segregate near a dislocation core, the dopant atoms accumulate at the Ba sites in compressively strained regions. This triggers formation of Ba-vacancies adjacent to the core atomic sites resulting in reconstruction of the core. Notwithstanding the presence of extremely large tensile strain fields, when La atoms segregate inside the dislocation core, they become B-site dopants, replacing Sn atoms and compensating the positive charge of the core oxygen vacancies. Electron energy-loss spectroscopy shows that the local electronic structure of these dislocations changes dramatically due to the segregation of the dopants inside and around the core ranging from formation of strong La-O hybridized electronic states near the conduction band minimum to insulator-to-metal transition.