Apart from a handful of exceptions, all known complex oxide two-dimensional electron gases (2DEGs) are formed in ${\mathrm{SrTiO}}_3$-based heterostructures, and microscopic information about non-${\mathrm{SrTiO}}_3$ 2DEGs systems is scarce. Here, we report on the realization of metallic conductance in a ${\mathrm{CaTiO}}_3$-based system, ${\mathrm{CaTiO}}_3$/${\mathrm{LaTiO}}_3$ superlattices, epitaxially grown in a layer-by-layer way on a ${\mathrm{NdGaO}}_3$(110) substrate by pulsed laser deposition. The high quality of the crystal and electronic structures is characterized by in situ reflection high-energy electron diffraction, x-ray diffraction, scanning transmission electron microscopy, and x-ray photoemission spectroscopy. Electrical transport confirms the formation of metallic interfaces in the ${\mathrm{CaTiO}}_3$/${\mathrm{LaTiO}}_3$ superlattice. In addition, Hall measurements reveal that in the ${\mathrm{CaTiO}}_3$/${\mathrm{LaTiO}}_3$ superlattice the room-temperature carrier mobility is nearly three times higher than that of the ${\mathrm{CaTiO}}_3$/${\mathrm{YTiO}}_3$ superlattice, implying the importance of ${\mathrm{TiO}}_6$ octahedral tilts and rotations on the carrier mobility of a 2DEG. Since doped ${\mathrm{CaTiO}}_3$ is an A-site polar metal, our results provide a materials system for designing synthetic two-dimensional polar metals.

• Received 6 July 2020
• Accepted 7 October 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.4.104008