Nanoscale control of the LaAlO$_3$/SrTiO$_3$ metal-insulator transition using a self-assembled monolayer of APTES

Nanoscale control over the metal-insulator transition at oxide interfaces represents an exciting opportunity for science and technology. Nanostructures created from 3-unit-cell LaAlO$_3$/SrTiO$_3$ heterostructures via a conductive AFM technique typically decay within hours under ambient conditions, representing a challenge for some technologies. By chemically modifying the top LaAlO$_3$ surface with a self-assembled monolayer of (3-Aminopropyl)triethoxysilane (APTES), normally conductive 4-unit-cell LaAlO$_3$/SrTiO$_3$ can be made highly insulating. The APTES layer can be locally patterned, revealing a highly stable conductive nanoregion. Four-terminal measurements show that nanowires created by selective desorption of APTES remain conductive indefinitely under ambient conditions. The results suggest a robust mechanism for creating long-lived nanostructures at oxide interfaces.