Using a surface x-ray diffraction technique, we investigated the atomic structure of two types of interfaces between ${\mathrm{LaAlO}}_3$ and ${\mathrm{SrTiO}}_3$, that is, $p$-type ($\mathrm{SrO}/{\mathrm{AlO}}_2$) and $n$-type (${\mathrm{TiO}}_2/\mathrm{LaO}$) interfaces. Our results demonstrate that the ${\mathrm{SrTiO}}_3$ in the sample with the $n$-type interface has a large polarized region, while that with the $p$-type interface has a limited polarized region. In addition, atomic intermixing was observed to extend deeper into the ${\mathrm{SrTiO}}_3$ substrate at the $n$-type interface compared to the $p$ type. These differences result in distinct degrees of band bending, which likely contributes to the striking contrast in electrical conductivity between the two types of interfaces.

• Received 16 February 2011

DOI:https://doi.org/10.1103/PhysRevLett.107.036104