# Offcut Substrate-Induced Defect Trapping at Step Edges

## TL;DR

This study shows how step edges in a layered oxide structure can trap defects, preventing unwanted boundaries and allowing control at the nanoscale.

## Contribution

The novel finding is that step edges in trilayer oxide heterostructures can localize and trap defects, preventing antiphase boundary formation.

## Key findings

- Localized defects form exclusively at step edges due to lattice mismatch.
- Oxygen vacancies are induced near the step edge in the second La0.66Sr0.34MnO3 unit cell.
- Strained step edges suppress antiphase boundary formation in the bulk structure.

## Abstract

We report step edge-induced
localized defects suppressing subsequent
antiphase boundary formation in the bulk structure of a trilayer oxide
heterostructure. The heterostructure encompasses a layer of La0.66Sr0.34MnO3 sandwiched between a superconducting
La1.84Sr0.16CuO4 bottom layer and
an insulating La2CuO4 top layer. The combination
of a minor a-axis mismatch (0.11 Å) and a pronounced c-axis mismatch (2.73 Å) at the step edges leads to
the emergence of localized defects exclusively forming at the step
edge. Employing atomically resolved electron energy-loss spectroscopy
maps, we discern the electronic state of those structures in the second
La0.66Sr0.34MnO3 unit cell near the
step edge. In particular, a reduction in the pre-edge region of the
O-K edge indicates the formation of oxygen vacancies
induced by the strained step edge. This study underscores our capability
to control defects at the nanoscale.