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The development of neuromorphic devices is a pivotal step in the pursuit of low‐power artificial intelligence. A synaptic analog is one of the building blocks of this vision. The synaptic behavior of molecular La0.7Sr0.3MnO3/tris(8‐hydroxyquinolinato)gallium/AlOx/Co spintronic devices is studied, where the conductance plays the role of the synaptic weight. These devices are arranged in a crossbar configuration, the most effective architecture for the purpose. The conductance of each cross point is controlled separately by the application of voltage pulses: when set in the high conductance potentiated state, the devices show a spin‐valve magnetoresistance, while in the low conductance depressed state, no magnetoresistance is observed. The time dependence of the resistive switching behavior is an important parameter of the synaptic behavior and is very revealing of the underlying physical mechanisms. To study the time dynamics of the resistive switching after the voltage pulses, the response of the device to trains of potentiation and depression pulses, and the time‐resolved conductivity relaxation after the pulses are measured. The results are described with the conductivity model based on impurity energy levels in the organic semiconductor's gap. A flat distribution of the activation energies necessary to move these impurities is hypothesized, which can explain the observed glassy behavior. [ABSTRACT FROM AUTHOR]

Photothermal energy has been widely used in high-tech applications, such as heating/cooling systems, bio-imaging, bio-sensing, and medical therapies. However, conventional photothermal materials have narrow photo-absorption bandwidth and low photothermal conversion efficiency. Innovative materials that can more efficiently harvest photothermal energy are highly demanded. Topological insulator materials with excellent optical properties hold great potential in photo-absorption and photothermal conversion. This work investigated and engineered photo-absorption and photothermal effect in Sb2Te3 topological insulator nanograting. The TI material was grown by metal-organic chemical vapor deposition to exploit the benefits of the process, yielding high material quality and large deposition areas. Through a meticulous process encompassing material synthesis, engineering, and characterization, highly absorptive Sb2Te3 topological insulator nanograting and efficient photothermal conversion have been achieved. This research contributes to the advancement of the fundamental knowledge of light–matter interaction and photothermal effects in topological insulator materials. The outcomes of this study can benefit the development of efficient photothermal materials for high-performance nano-energy and biomedical technologies. [ABSTRACT FROM AUTHOR]

Spin‐charge interconversion phenomena at the interface between magnetic materials and topological insulators (TIs) are attracting enormous interest in the research effort toward the development of fast and ultra‐low power devices for future information and communication technology. A large spin‐to‐charge (S2C) conversion efficiency in Au/Co/Au/Sb2Te3/Si(111) heterostructures based on Sb2Te3 TIs grown by metal–organic chemical vapor deposition on 4″ Si(111) substrates is reported. By conducting room temperature spin pumping ferromagnetic resonance, a 250% enhanced charge current due to spin pumping in the Sb2Te3‐containing system is measured when compared to the reference Au/Co/Au/Si(111). The corresponding inverse Edelstein effect length λIEE ranges from 0.28 to 0.61 nm, depending on the adopted methodological analysis, with the upper value being so far the largest observed for the second generation of 3D chalcogenide‐based TIs. These results open the path toward the use of chemical methods to produce TIs on large area Si substrates and characterized by highly performing S2C conversion, thus marking a milestone toward future technology‐transfer. [ABSTRACT FROM AUTHOR]

When coupled with ferromagnetic layers (FM), topological insulators (TI) are expected to boost the charge‐to‐spin conversion efficiency across the FM/TI interface. In this context, a thorough control and optimization of the FM/TI interface quality are requested. Here, the evolution of the chemical, structural, and magnetic properties of the Fe/Sb2Te3 heterostructure is presented as a function of a rapid mild thermal annealing conducted on the Sb2Te3‐TI (up to 200 °C). While the bilayer is not subjected to any thermal treatment upon Fe deposition, the annealing of Sb2Te3 markedly improves its crystalline quality, leading to an increase in the fraction of ferromagnetic Fe atoms at the buried Fe/Sb2Te3 interface and a slight lowering of the magnetic coercivity of the Fe layer. The method is an efficient tool to clean up the Fe/Sb2Te3 interface, which may be extended to different FM/TI heterostructures. Simultaneously to the interface reconstruction, a constant ≈20% fraction of FeTe develops at the interface. Since FeTe can display superconductivity, the Fe/Sb2Te3 system could have potentialities for exploiting phenomena at the edge of magnetism, superconductivity and topology. [ABSTRACT FROM AUTHOR]

Topological insulator (TI) properties of granular Sb2Te3 thin films, grown by MOCVD at room temperature on 4″ SiO2/Si substrates, are investigated. The negative magneto‐conductance (MC), analyzed in terms of the Hikami–Larkin–Nagaoka theory, reveals the presence of a clear weak antilocalization (WAL) effect, thus demonstrating the TI character of our system. The extracted WAL prefactor (α) values are explained in terms of the film conductance, in agreement with the existing models for WAL in transport disordered systems. The dephasing length ( l ϕ) dependence on temperature is affected by the grain size of the film and might in turn explain the observed temperature dependence of α and of the conductance. These results demonstrate the feasibility of technologically‐relevant processes to synthesize TIs films, at the same time providing a tool to investigate the effects of the film microstructure on the topological character of their transport properties. [ABSTRACT FROM AUTHOR]

We report on the self-assembly of core--shell Ge/In--Te nanowires (NWs) on single crystal Si substrates by Metalorganic Chemical Vapour Deposition (MOCVD), coupled to the Vapour--Liquid--Solid (VLS) mechanism, catalysed by Au nanoparticles (NPs). The NWs are formed by a crystalline Ge core and an InTe (II) shell, have diameters down to 15 nm and show <110> oriented growth direction. The role of the MOCVD process parameters and of the NPs size in determining the NWs core--shell microstructure and their alignment was investigated by high-resolution TEM, EDX, XRD and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

The outgrowth formation in inorganic thin films is a dramatic problem that has limited the technological impact of many techniques and materials. Outgrowths are often themselves part of the films, but are detrimental for vertical junctions since they cause short-circuits or work as defects, compromising the reproducibility and in some cases the operation of the corresponding devices. The problem of outgrowth is particularly relevant in ablation-based methods and in some complex oxides, but is present in a large variety of systems and techniques. Here we propose an efficient local electrochemical method to selectively decompose the outgrowths of conductive oxide thin films by electrochemical decomposition, without altering the properties of the background film. The process is carried out using the same set-up as for local oxidation nanolithography, except for the sign of the voltage bias and it works at the nanoscale both as serial method using a scanning probe and as parallel method using conductive stamps. We demonstrated our process using La0.7Sr0.3MnO3 perovskite as a representative material but in principle it can be extended to many other conductive systems. [ABSTRACT FROM AUTHOR]