Oxide-based resistive switching devices are promising candidates for new memory and computing technologies. Poor understanding of the defect-based mechanisms that give rise to resistive switching is a major impediment for engineering reliable and reproducible devices. Here we identify an unintentional interface layer as the origin of resistive switching in Pt/Nb:SrTiO3 junctions. We clarify the microscopic mechanisms by which the interface layer controls the resistive switching. We show that appropriate interface processing can eliminate this contribution. These findings are an important step towards engineering more reliable resistive switching devices.

The enhancement of the functional properties of materials at reduced dimensions is crucial for continuous advancements in nanoelectronic applications. Here, we report that the scale reduction leads to the emergence of an important functional property, ferroelectricity, challenging the long-standing notion that ferroelectricity is inevitably suppressed at the scale of a few nanometers. A combination of theoretical calculations, electrical measurements, and structural analyses provides evidence of room-temperature ferroelectricity in strain-free epitaxial nanometer-thick films of otherwise nonferroelectric strontium titanate (SrTiO3). We show that electrically induced alignment of naturally existing polar nanoregions is responsible for the appearance of a stable net ferroelectric polarization in these films. This finding can be useful for the development of low-dimensional material systems with enhanced functional properties relevant to emerging nanoelectronic devices.

This work elucidates unconventional metallic behavior and metal-insulator transitions in a strongly correlated materials system.

We analyze and compare the temperature dependence of the electron mobility of two- and three-dimensional electron liquids in SrTiO3. The contributions of electron-electron scattering must be taken into account to accurately describe the mobility in both cases. For uniformly doped, three-dimensional electron liquids, the room temperature mobility crosses over from longitudinal optical (LO) phonon-scattering-limited to electron-electron-scattering-limited as a function of carrier density. In high-density, two-dimensional electron liquids, LO phonon scattering is completely screened and the mobility is dominated by electron-electron scattering up to room temperature. The possible origins of the observed behavior and the consequences for approaches to improve the mobility are discussed.

The interplay of film stoichiometry and strain on the metal-insulator transition (MIT) and Hall coefficient of NdNiO3 films grown under different conditions is investigated. Unstrained lattice parameters and lattice mismatch strains are evaluated for films grown under a range of growth pressures and on different substrates. It is shown that both the temperature of the MIT and the Hall coefficient in the metallic phase are highly sensitive to film strain. In films grown with lower oxygen/total growth pressures, very large compressive in-plane strains can be obtained, which can act to suppress the MIT. Both the Hall coefficient and the temperature of the MIT are relatively insensitive to growth pressure, provided that films under the same strain are compared. The results support an itinerant picture of the transition that is controlled by the Ni eg bands, and that is relatively insensitive to changes in film stoichiometry.