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.

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.

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