Search for: All records

Charge transfer or redistribution at oxide heterointerfaces is a critical phenomenon, often leading to remarkable properties such as two-dimensional electron gas and interfacial ferromagnetism. Despite studies on LaNiO₃/LaFeO₃superlattices and heterostructures, the direction and magnitude of the charge transfer remain debated, with some suggesting no charge transfer due to the high stability of Fe³⁺(3d⁵). Here, we synthesized a series of epitaxial LaNiO₃/LaFeO₃superlattices and demonstrated partial (up to ~0.5 e⁻/interface unit cell) charge transfer from Fe to Ni near the interface, supported by density functional theory simulations and spectroscopic evidence of changes in Ni and Fe oxidation states. The electron transfer from LaFeO₃to LaNiO₃and the subsequent rearrangement of the Fe 3d band create an unexpected metallic ground state within the LaFeO₃layer, strongly influencing the in-plane transport properties across the superlattice. Moreover, we establish a direct correlation between interfacial charge transfer and in-plane electrical transport properties, providing insights for designing functional oxide heterostructures with emerging properties. 

Low-dimensional materials with chain-like (one-dimensional) or layered (two-dimensional) structures are of significant interest due to their anisotropic electrical, optical, and thermal properties. One material with a chain-like structure, BaTiS3 (BTS), was recently shown to possess giant in-plane optical anisotropy and glass-like thermal conductivity. To understand the origin of these effects, it is necessary to fully characterize the optical, thermal, and electronic anisotropy of BTS. To this end, BTS crystals with different orientations (a- and c-axis orientations) were grown by chemical vapor transport. X-ray absorption spectroscopy was used to characterize the local structure and electronic anisotropy of BTS. Fourier transform infrared reflection/transmission spectra show a large in-plane optical anisotropy in the a-oriented crystals, while the c-axis oriented crystals were nearly isotropic in-plane. BTS platelet crystals are promising uniaxial materials for infrared optics with their optic axis parallel to the c-axis. The thermal conductivity measurements revealed a thermal anisotropy of ∼4.5 between the c- and a-axis. Time-domain Brillouin scattering showed that the longitudinal sound speed along the two axes is nearly the same, suggesting that the thermal anisotropy is a result of different phonon scattering rates.