Correlated Lattice Instability and Emergent Charged Domain Walls at Oxide Heterointerfaces

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 LaAlO 3 /SrTiO 3 //NdGaO 3 heterostructures, the evolution of correlated lattice instability and charged domain walls is visualized crossing the conducting LaAlO 3 /SrTiO 3 heterointerface. When increasing the SrTiO 3 layer thickness to 20 unit cells and above, both LaAlO 3 and SrTiO 3 layers begin to exhibit measurable polar displacements to form a tail‐to‐tail charged domain wall at the LaAlO 3 /SrTiO 3 interface, resulting in the charged redistribution within the 2‐nm‐thick SrTiO 3 layer close to the LaAlO 3 /SrTiO 3 interface. The mobile charges in different heterostructures can be estimated by summing up Ti 3+ concentrations in the conducting channel, which is sandwiched by SrTiO 3 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.