Ferroelectric Polarization-Modulated Interfacial Fine Structures Involving Two-Dimensional Electron Gases in Pb(Zr,Ti)O/LaAlO/SrTiO Heterostructures.

Interfacial fine structures of bare LaAlO/SrTiO (LAO/STO) heterostructures are compared with those of LAO/STO heterostructures capped with upward-polarized Pb(Zr,Ti)O (PZT) or downward-polarized Pb(Zr,Ti)O (PZT) overlayers by aberration-corrected scanning transmission electron microscopy experiments. By combining the acquired electron energy-loss spectroscopy mapping, we are able to directly observe electron transfer from Ti to Ti and ionic displacements at the interface of bare LAO/STO and PZT/LAO/STO heterostructure unit cell by unit cell. No evidence of Ti is observed at the interface of the PZT/LAO/STO samples.