Correlated Lattice Instability and Emergent Charged Domain Walls at Oxide Heterointerfaces

Abstract

Charged domain walls provide possibilities in effectively manipulating electrons at nanoscales for developing next-generation electronic devices. Here, using the atom-resolved imaging and spectroscopy on LaAlO3/SrTiO3//NdGaO3 heterostructures, the evolution of correlated lattice instability and charged domain walls is visualized crossing the conducting LaAlO3/SrTiO3 heterointerface. When increasing the SrTiO3 layer thickness to 20 unit cells and above, both LaAlO3 and SrTiO3 layers begin to exhibit measurable polar displacements to form a tail-to-tail charged domain wall at the LaAlO3/SrTiO3 interface, resulting in the charged redistribution within the 2-nm-thick SrTiO3 layer close to the LaAlO3/SrTiO3 interface. The mobile charges in different heterostructures can be estimated by summing up Ti3+ concentrations in the conducting channel, which is sandwiched by SrTiO3 layers with interdiffusion and/or oxygen octahedral rotations. Those estimated mobile charges are quantitatively consistent with results from Hall measurements. The results not only shed light on complex oxide heterointerfaces, but also pave a new path to nanoscale charge engineering. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim