Correlated Lattice Instability and Emergent Charged Domain Walls at Oxide Heterointerfaces

Abstract

AbstractCharged 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.