Offcut Substrate-Induced Defect Trapping at Step Edges.

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 La 0.66 Sr 0.34 MnO 3 sandwiched between a superconducting La 1.84 Sr 0.16 CuO 4 bottom layer and an insulating La 2 CuO 4 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 La 0.66 Sr 0.34 MnO 3 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.