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.

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Resistive switching and its suppression in Pt/Nb:SrTiO3 junctions

The interfaces of polar oxide heterostructures can display electronic properties unique from the oxides they border, as they require screening from either internal or external sources of charge. The screening mechanism depends on a variety of factors, including the band structure at the interface, the presence of point defects or adsorbates, whether or not the oxide is ferroelectric, and whether or not an external field is applied. In this review, we discuss both theoretical and experimental aspects of different screening mechanisms, giving special emphasis to ways in which the mechanism can be altered to provide novel or tunable functionalities. We begin with a theoretical introduction to the problem and highlight recent progress in understanding the impact of point defects on polar interfaces. Different case studies are then discussed, for both the high thickness regime, where interfaces must be screened and each interface can be considered separately, and the low thickness regime, where the degree and nature of screening can be manipulated and the interfaces are close enough to interact. We end with a brief outlook toward new developments in this rapidly progressing field.

https://iopscience.iop.org/article/10.1088/0034-4885/79/7/076501/pdf

Screening mechanisms at polar oxide heterointerfaces.

The reactivity of water with the (001)pc surface of epitaxial LaCoO3 (LCO) thin films was investigated as a function of relative humidity (RH) by ambient pressure X-ray photoelectron spectroscopy. ...

Water Reactivity on the LaCoO3 (001) Surface: An Ambient Pressure X-ray Photoelectron Spectroscopy Study

In addition to composition, the structure of a catalyst is another fundamental determinant of its catalytic reactivity. Recently, anomalous Ti oxide-rich surface phases of ternary oxides have been stabilized as nonstoichiometric epitaxial overlayers. These structures give rise to different modes of oxygen binding, which may lead to different oxidative chemistry. Through density functional theory investigations and electrochemical measurements, we predict and subsequently show that such a TiO2 double-layer surface reconstruction enhances the oxygen evolving activity of the perovskite-type oxide SrTiO3. Our theoretical work suggests that the improved activity of the restructured TiO2(001) surface toward oxygen formation stems from (i) having two Ti sites with distinct oxidation activity and (ii) being able to form a strong O–O moiety (which reduces overbonding at Ti sites), which is a direct consequence of (iii) having a labile lattice O that is able to directly participate in the reaction. Here, we demonst...

https://www.sas.upenn.edu/rappegroup/publications/Papers/Martirez15p2939.pdf

Synergistic Oxygen Evolving Activity of a TiO2-Rich Reconstructed SrTiO3(001) Surface

Cost effective and efficient methods for CO2 capture are the need of the hour to render the clean environment in the era of rising energy demand. Here, we report the physicochemical adsorption of carbon dioxide (CO2) in iron oxide decorated graphene nanocomposite at elevated pressures and temperatures. Nanocomposite was prepared by scalable and cost effective technique and its suitability for CO2 capture was studied at elevated pressures (3–13 bar) and temperatures (25–100 °C) using Sieverts apparatus. The higher CO2 capture capacities of 60, 35, and 24 mmol g−1 were observed at 11 bar pressure and 25, 50, and 100 °C, respectively, compared to other studied porous materials. Nature of interaction (Physicochemical adsorption) of CO2 with nanocomposite was identified using Fourier transform infrared spectroscopy. Degassing was performed to examine the recovery of nanocomposite.

Enhanced CO2 capture in Fe3O4-graphene nanocomposite by physicochemical adsorption

The interaction of water and carbon dioxide with nanostructured epitaxial (Ba,Sr)TiO3(001) thin film and bulk single crystal SrTiO3(001) surfaces was studied using x-ray photoemission spectroscopy (XPS), thermal desorption spectroscopy (TDS), and density functional theory (DFT). On both surfaces, XPS and TDS indicate D2O and CO2 chemisorb at room temperature with broad thermal desorption peaks (423–723 K) and a peak desorption temperature near 573 K. A comparison of thermal desorption Redhead activation energies to adsorption energies calculated using DFT indicates that defect surface sites are important for the observed strong adsorbate-surface reactivity. Numerical calculations of the competetive adsorption/desorption equilibria for H2O and CO2 on SrTiO3(001) surfaces show that for typical atmospheric concentrations of 0.038% carbon dioxide and 0.247% water vapor the surfaces are covered to a large extent with both adsorbates. The high desorption temperature indicates that these adsorbates have the pote...

Y. Kobayashi

Papers

Chemisorption of water and carbon dioxide on nanostructured BaTiO3–SrTiO3(001) surfaces