Figure 4: Model of giant conductivity switching in LAO/STO heterointerfaces.
From: Giant conductivity switching of LaAlO3/SrTiO3 heterointerfaces governed by surface protonation
(a) Initially, the conducting band (CB) and valence band (VB) of the LAO/STO interface bend to create an occupied conductive state at the interface. In addition, a mid-gap oxygen vacancy state in the STO is present below the Fermi energy EF. (b) Solvent immersion removes the proton and causes the electron to leave the interface. (c) Ultraviolet light creates electron-hole pairs at the oxygen vacancy, which are separated by the polar LAO potential. Specifically, the hole ‘bubbles up’ the VB potential in the LAO and segregates to the surface. (d) The surface hole oxidizes adsorbed water, thereby generating a proton. This proton can then interact with Lewis basic sites of the LAO.
