Tracking the polar properties at LaTiO3/KTaO3 heterostructures

Abstract

This study investigates oxide heterostructures where electrons are confined to a two-dimensional plane at LaTiO₃/KTaO₃ (LTO–KTO) interfaces. LTO thin films were deposited on KTO via a polymeric precursor method, followed by rapid thermal annealing and heat treatment at 800 °C under oxygen, nitrogen, or air. Nitrogen-treated films exhibited smooth surfaces (0.3 nm roughness) and layer-by-layer growth. Two-dimensional sheet resistance measurements revealed metallic behavior for 20 nm and 50 nm films, while magnetotransport data showed spin-polarized hysteresis from magnetic islands in LTO. The Two-Dimensional Electron Gas (2DEG) region exhibited ferroelectric-like polarization switching, and the 20 nm film achieved a high carrier density of 1.8 × 10¹⁴ cm-2 , exceeding that of KTO-based systems. XPS identified Ti clustering linked to ferroelectric and 2DEG phenomena. Strong photoluminescence was observed, arising from defect levels within the band gap, with spectra varying by atmosphere due to Ti–O bond displacements and polarization-induced resistance hysteresis.