Abstract:Nanoscale control of the metal-insulator transition in LaAlO 3 / SrTiO 3 heterostructures can be achieved using local voltages applied by a conductive atomic-force microscope probe. One proposed mechanism for the writing and erasing process involves an adsorbed H 2 O layer at the top LaAlO 3 surface. In this picture, water molecules dissociates into OH -and H + which are then selectively removed by a biased AFM probe. To test this mechanism, writing and erasing experiments are performed in a vacuum AFM using various gas mixtures. Writing ability is suppressed in those environments where H 2 O is not present. The stability of written nanostructures is found to be strongly associated with the ambient environment. The self-erasure process in air can be strongly suppressed by creating a modest vacuum or replacing the humid air with dry inert gas. These experiments provide strong constraints for theories of both the writing process as well as the origin of interfacial conductance. an insulating state. We refer to this process as a "water cycle" because it permits multiple writing and erasing without physical modification of the oxide heterostructure.Here we investigate the writing and erasing process on 3uc-LAO/STO heterostructures under a variety of atmospheric conditions, in order to constrain physical models of the writing and erasing procedure and the origin of the interfacial electron gas. Thin films (3 u.c.) of LaAlO 3 were deposited on a TiO 2 -terminated (001) SrTiO 3 substrates by pulsed laser deposition with in situ high pressure reflection high energy electron diffraction (RHEED) [18]. Growth was at a temperature of 550°C and O 2 pressure of 1×10 -3 Torr. 4After growth, electrical contacts to the interface were prepared by milling 25nm deep trenches via an Ar-ion mill and filling them with Au/Ti bilayer (2nm adhesion Ti layer and 23nm Au layer).To perform c-AFM experiments, a vacuum AFM ( FIG. 1(a)) is employed that is capable of operation down to 10 -5 Torr and allows controlled introduction of various gases. Writing and erasing experiments (

Reports of emergent conductivity, superconductivity and magnetism have helped to fuel intense interest in the rich physics and technological potential of complex-oxide interfaces. Here we employ magnetic force microscopy to search for room-temperature magnetism in the well-studied LaAlO 3 /SrTiO 3 system. Using electrical top gating to control the electron density at the oxide interface, we directly observe the emergence of an in-plane ferromagnetic phase as electrons are depleted from the interface. Itinerant electrons that are reintroduced into the interface align antiferromagnetically with the magnetization at first screening and then destabilizing it as the conductive regime is approached. Repeated cycling of the gate voltage results in new, uncorrelated magnetic patterns. This newfound control over emergent magnetism at the interface between two non-magnetic oxides portends a number of important technological applications.

Devices that confine and process single electrons represent an important scaling limit of electronics. Such devices have been realized in a variety of materials and exhibit remarkable electronic, optical and spintronic properties. Here, we use an atomic force microscope tip to reversibly 'sketch' single-electron transistors by controlling a metal-insulator transition at the interface of two oxides. In these devices, single electrons tunnel resonantly between source and drain electrodes through a conducting oxide island with a diameter of ∼1.5 nm. We demonstrate control over the number of electrons on the island using bottom- and side-gate electrodes, and observe hysteresis in electron occupation that is attributed to ferroelectricity within the oxide heterostructure. These single-electron devices may find use as ultradense non-volatile memories, nanoscale hybrid piezoelectric and charge sensors, as well as building blocks in quantum information processing and simulation platforms.

The synergistic control of multipollutants is the frontier of environmental catalysis. This research is in the infancy stage, and many uncertainties still remain. Herein, we investigated the reaction characteristics of synergistic elimination of NO x and chloroaromatics on a commercial V2O5–WO3/TiO2 catalyst. The reaction byproducts were qualitatively and quantitatively analyzed, and their origins were clarified. In particular, the origins of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the synergistic reaction with or without SO2 were first explored; this is crucial for assessing the environmental risk by applying such a synergistic system. Experimental results indicate that during the synergistic reaction, the V2O5–WO3/TiO2 catalyst was deactivated at 200 and 250 °C, whereas the 300 °C was sufficient to durably convert the NO and chlorobenzene at the turnover frequency (TOF) of 7.23 × 10–4 and 1.32 × 10–4 s–1, respectively. A range of aromatics, alkenes, and alkanes, particularly their chlorinated congeners, were observed in the off-gases and on the catalyst surface, where those of 3-chlorobenzonitrile, 4-chloro-2-nitrophenol, and inorganic CS2 were first discovered. In the time-on-stream test at 250 °C, the PCDD/Fs collected from the off-gases was measured at 0.0514 ng I-TEQ Nm–3, but the most toxic dioxins congener, 2,3,7,8-TCDD, was not observed. The alkalinity of selective catalytic reduction reaction likely facilitated the chlorophenol formation, which eventually promoted PCDD/F generation. The SO2 was found to benefit polychlorinated byproduct generation, but the addition of which distinctly inhibited PCDD/F formation.

Core-shell Ag@ZIF-8 nanowires, where single Ag nanowires are coated with uniform zeolitic-imidazolate-framework-8 (ZIF-8) shells, successfully realize renewable adsorptive separation of low concentrations of butanol from an aqueous medium under solar light irradiation by taking advantage of the exceptional adsorption capability of the ZIF-8 shells toward butanol and the unique plasmonic photothermal effect of the Ag nanowire cores. Impressively, the high separation efficiency is maintained as almost unchanged, even after 10 adsorption/desorption cycles.

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Abstract:We report superconductivity in quasi-1D nanostructures created at the LaAlO 3 /SrTiO 3 interface. Nanostructures having line widths w~10 nm are formed from the parent twodimensional electron liquid using conductive atomic force microscope lithography. Nanowire cross-sections are small compared to the superconducting coherence length in LaAlO 3 /SrTiO 3 (w << SC~1 00 nm), placing them in the quasi-1D regime. Broad superconducting transitions with temperature and finite resistances in the superconducting state well below T c ≈200 mK are observed. V-I curves show switching between the superconducting and normal states that are characteristic of superconducting nanowires.The four-terminal resistance in the superconducting state shows an unusual dependence on the current path, varying by as much as an order of magnitude.

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