High-density electron gas at the KTaO3/TbScO3 (001) interface

Author: Bhubnesh Lama, Department of Physics

Mentor: Dr. Tula Paudel, Department of Physics

The interface between 3d and 5d polar oxides has potentials for thickness independent high-density electron gas that is highly tunable in terms of spatial localization, orbital distribution, and density, much of which are not available widely studied interfaces between polar-nonpolar oxide interfaces. As a model system for observing such behavior, we studied the (001) interface between KTaO₃(KTO) and TbScO3 (TSO). We found a large density (> 1e/uc) two-dimensional electron gas (2DEG) at the interface between polar KTaO3 (KTO) and TbScO3 (TSO) oxide interfaces. We found the interface to be metallic irrespective of thickness due to a large positive ionic charge at the interface. While the electron gas density at the TSO side of the interface is small (3% of total) and localized within the unit cell (less than half a nm), the concentration of electron gas in the KTO side of the interface is much larger (remaining ~97%). The spread is much longer (at least 3 nm). An applied external voltage can tune the spatial location of electron gas across the interface. The metallic nature of KTO across the interface and eventual charge compensation may need a capping layer for experimental detection of 2DEG when the KTO thickness is less than two unit cells, similar to what is required for detecting hole gas at the surface of LAO/STO (001) heterostructure.