Metallic interfaces in a CaTiO${}_3$/LaTiO${}_3$ heterostructure

Abstract

Almost all oxide two-dimensional electron gases are formed in SrTiO${}_3$-based heterostructures and the study of non-SrTiO${}_3$ systems is extremely rare. Here, we report the realization of a two-dimensional electron gas in a CaTiO${}_3$-based heterostructure, CaTiO${}_3$/LaTiO${}_3$, grown epitaxially layer-by-layer on a NdGaO${}_3$ (110) substrate via pulsed laser deposition. The high quality of the crystal and electronic structures are characterized by in-situ reflection high-energy electron diffraction, X-ray diffraction, and X-ray photoemission spectroscopy. Measurement of electrical transport validates the formation of a two-dimensional electron gas in the CaTiO${}_3$/LaTiO${}_3$ superlattice. It is revealed the room-temperature carrier mobility in CaTiO${}_3$/LaTiO${}_3$ is nearly 3 times higher than in CaTiO${}_3$/YTiO${}_3$, demonstrating the effect of TiO${}_6$ octahedral tilts and rotations on carrier mobility of two-dimensional electron gases. Due to doped CaTiO${}_3$ being an A-site polar metal, our results provide a new route to design novel A-site two-dimensional polar metals.