An Off-Axis Electron Holography Study of the Built-In Electric Field in LaAlO_3/SrTiO_3 Heterointerface

摘要

The built-in electric field across LaAlO_3/SrTiO_3 heterointerface, which hosts two-dimensional electron gas (2DEG), is studied by off-axis electron holography in transmission electron microscopy (TEM). On the contrary to the well-accepted polar catastrophe model, which indicates a Zener breakdown due to the strong built-in electric field in LaAlO_3 (～0.24 V/A), we find that such an internal electric field in LaAlO_3 is almost negligible (<0.1 V/A) when compared to the band bending of SrTiO_3. Our results suggest that the emergence of 2DEG should have other explanations beyond the polar catastrophe model.