Controlling Soil-Borne Diseases in Ohio Nurseries

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Polarity-dependent reversible resistance switching in Ge–Sb–Te phase-change thin films

In this paper, we demonstrate reversible resistance switching in a capacitorlike cell using a Ge–Sb–Te film that does not rely on amorphous-crystalline phase change. The polarity of the applied electric field switches the cell resistance between lower- and higher-resistance states, as was observed in current-voltage characteristics. Moreover, voltage pulses less than 1.25 V showed this switching within time scales of microseconds with more than 40% contrast between the resistance states. The latter are found to be nonvolatile for months. The switching could also be achieved at nanoscales with atomic force microscopy with a better resistance contrast of three orders of magnitude.

Size-dependent and tunable crystallization of GeSbTe phasechange nanoparticles

Chalcogenide-based nanostructured phase-change materials (PCMs) are considered promising building blocks for non-volatile memory due to their high write and read speeds, high data-storage density, and low power consumption. Top-down fabrication of PCM nanoparticles (NPs), however, often results in damage and deterioration of their useful properties. Gas-phase condensation based on magnetron sputtering offers an attractive and straightforward solution to continuously down-scale the PCMs into sub-lithographic sizes. Here we unprecedentedly present the size dependence of crystallization for Ge2Sb2Te5 (GST) NPs, whose production is currently highly challenging for chemical synthesis or top-down fabrication. Both amorphous and crystalline NPs have been produced with excellent size and composition control with average diameters varying between 8 and 17 nm. The size-dependent crystallization of these NPs was carefully analyzed through in-situ heating in a transmission electron microscope, where the crystallization temperatures (Tc) decrease when the NPs become smaller. Moreover, methane incorporation has been observed as an effective method to enhance the amorphous phase stability of the NPs. This work therefore elucidates that GST NPs synthesized by gas-phase condensation with tailored properties are promising alternatives in designing phase-change memories constrained by optical lithography limitations

Tailoring Growth Kinetics toward a Size-Dependent Work Function of Ge Nanocrystals Synthesized by Inert Gas Condensation

Understanding the size-dependent electronic properties of germanium nanocrystals (Ge NCs) is of fundamental importance for improving the efficiency of optoelectronic devices based on such NCs. Here, Ge NCs with a tunable size were synthesized by magnetron-sputtering cluster-beam deposition, where the size of the as-deposited Ge NCs can be finely controlled between 6 and 36 nm by helium gas flow rates and variable magnetic field configurations above the target surface. Because the size of the as-deposited Ge NCs highly depends on the nucleation process inside the plasma region, a detailed comparison between these two process parameters on the size control was formulated from the perspective of the growth kinetic mechanism. Furthermore, the local surface potential of different-sized Ge NCs deposited on n-type silicon substrates was measured by Kelvin probe force microscopy. The surface potential fluctuation of n-type Si covered by Ge NCs shows a strong size-dependent relationship with the size of the Ge NCs, whereas the surface potential fluctuation increases when their size reduced. Because the surface potential fluctuation between the intrinsic Ge NCs and the n-type silicon substrate tends to get smaller as the NCs' size decreases due to the quantum confinement effect, the number of charges transferred between the electronic bands will reduce as the size of Ge NCs decreases. The latter exactly explains the observed experimental results. Therefore, this work offers a perspective to understand the behavior of charge transfer, which plays an important role in the performance of optoelectronic devices

An Extensible Framework for Query Optimization on TripleT-Based RDF Stores

ABSTRACT The RDF data model is a key technology in the Linked Data vision. Given its graph structure, even relatively simple RDF queries often involve a large number of joins. Join evaluation poses a significant performance challenge on all state-of-the-art RDF engines. TripleT is a novel RDF index data structure, demonstrated to be competitive with the current state-of-the-art for join processing. Query optimization on TripleT, however, has not been systematically studied up to this point. In this paper we investigate how the use of (i) heuristics and (ii) data statistics can contribute towards a more intelligent way of generating query plans over TripleT-based RDF stores. We propose a generic framework for query optimization, and show through an extensive empirical study that our framework consistently produces efficient query evaluation plans

Effect of Airborne Hydrocarbons on the Wettability of Phase Change Nanoparticle Decorated Surfaces

We present here a detailed study of the wettability of surfaces nanostructured with amorphous and crystalline nanoparticles (NPs) derived from the phase-change material Ge2Sb2Te5 (GST). Particular attention was devoted to the effect of airborne surface hydrocarbons on surface wetting. Our analysis illustrates that a reversible hydrophilic-hydrophobic wettability switch is revealed by combined ultraviolet-ozone (UV-O-3) treatments and exposure to hydrocarbon atmospheres. Indeed, the as prepared surfaces exhibited a hydrophilic state after thermal annealing or UV-O-3 treatment which can partially remove hydrocarbon contaminants, while a hydrophobic state was realized after exposure to hydrocarbon atmosphere. Using high-angle annular dark-field scanning transmission electron microscopy for the specially designed GST NP decorated graphene substrates, a network of hydrocarbon connecting GST NPs was observed. Our findings indicate that airborne hydrocarbons can significantly enhance the hydrophobicity of nanostructured surfaces. Finally, the experiments reveal that previously defined hydrophilic materials can be used for the design of hydrophobic surfaces even if the meniscus is highly adhered to a solid surface, which is in agreement with our qualitative model involving the contribution of the nanomeniscus formed between the substrate and a decorating NP

Nanostructure and thermal power of highly-textured and single-crystal-like Bi2Te3 thin films

Bi2Te3-based alloys are known to have outstanding thermoelectric properties. Although structure-property relations have been studied, still, detailed analysis of the atomic and nano-scale structure of Bi2Te3 thin film in relation to their thermoelectric properties remains poorly explored. Herein, highly-textured (HT) and single-crystal-like (SCL) Bi2Te3 films have been grown using pulsed laser deposition (PLD) on Si wafer covered with (native or thermal) SiOx and mica substrates. All films are highly textured with c-axis out-of-plane, but the in-plane orientation is random for the films grown on oxide and single-crystal-like for the ones grown on mica. The power factor of the film on thermal oxide is about four times higher (56.8 mu W.cm(-1).K-2) than that of the film on mica (12.8 mu W.cm(-1).K-2), which is comparable to the one of the polycrystalline ingot at room temperature (RT). Reduced electron scattering in the textured thin films results in high electrical conductivity, where the SCL film shows the highest conductivity. However, its Seebeck coefficient shows a low value. The measured properties are correlated with the atomic structure details unveiled by scanning transmission electron microscopy. For instance, the high concentration of stacking defects observed in the HT film is considered responsible for the increase of Seebeck coefficient compared to the SCL film. This study demonstrates the influence of nanoscale structural effects on thermoelectric properties, which sheds light on tailoring thermoelectric thin films towards high performance

A novel role for XIAP in copper homeostasis through regulation of MURR1

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102131/1/emboj7600031.pd