Band structure and electronic transport across Ta2O5/Nb:SrTiO3 interfaces

Resistive switching devices promise significant progress in memory and logic technologies. One of the hurdles toward their practical realization is the high forming voltages required for their initial activation, which may be incompatible with standard microelectronic architectures. This work studies the conduction mechanisms of Ta2O5 layers, one of the most studied materials for memristive devices, in their initial, as-fabricated state (“pre-forming”). By separating this aspect and resolving the current mechanisms, we provide the input that may guide future design of resistive switching devices. For this purpose, Ta2O5 layers were sputtered on conductive Nb:SrTiO3 substrates. Ta2O5/Nb:SrTiO3 structures exhibit diode behavior with an ideality factor of n ≈ 1.3 over four current decades. X-ray photoelectron spectroscopy analysis of the interfacial band offsets reveals a barrier of 1.3 ± 0.3 eV for electrons injected from the semiconductor into Ta2O5. Temperature-dependent current–voltage analysis exhibits rectifying behavior. While several conduction mechanisms produce good fits to the data, comparing the physical parameters of these models to the expected physical parameters led us to conclude that trap-assisted tunneling (TAT) is the most likely conduction mechanism. Fitting the data using a recent TAT model and with the barrier that was measured by spectroscopy fully captures the temperature dependence, further validating this conduction mechanism.Fil: Miron, Dror. Technion - Israel Institute of Technology; IsraelFil: Cohen Azarzar, Dana. Technion - Israel Institute of Technology; IsraelFil: Segev, Noa. Technion - Israel Institute of Technology; IsraelFil: Baskin, Maria. Technion - Israel Institute of Technology; IsraelFil: Palumbo, Félix Roberto Mario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; ArgentinaFil: Yalon, Eilam. Technion - Israel Institute of Technology; IsraelFil: Kornblum, Lior. Technion - Israel Institute of Technology; Israe

Opaque Transparency: How Material Affordances Shape Intermediary Work

How do the material aspects of intermediary work affect regulators, targets, and beneficiaries? To shed light on this question, we studied an information intermediary in the form of a website and the organizations who founded it. Specifically, we analyzed FracFocus, a self‐regulatory initiative with strong industry ties, charged with disclosing data pertaining to the chemicals used in oil and gas wells completed using hydraulic fracturing technology (fracking) in the United States and Canada. We found that between 2010 and mid‐2017, the vast majority of legislation in states and provinces where fracking actively occurred was updated to mandate or encourage disclosure via FracFocus, meaning that it had a considerable effect on the trajectory of official regulation on fracking disclosure. We also found that FracFocus disclosed important data but did so in a manner that limited accessibility and reduced the comprehensibility of environmental and public health risks to beneficiaries. Our analysis suggests that the public's experience of such a device is one of opaque transparency, in which the line between official and non‐official regulation is blurred. We traced these outcomes to the material affordances created by FracFocus

Unleashing Sustainability Transformations Through Robust Action

Shifting to dramatically more sustainable systems is an unconventional or wicked problem, encompassing multiple actors, disciplines, and values. Yet to date, sustainability initiatives have been tackled primarily by means of conventional managerial approaches. We contend that these approaches are ill-suited for achieving sustainability transformations. We propose an alternative approach founded upon the sociological concept of robust action. In robust action, leaders embrace ambiguity (rather than striving for clarity), focus on short-term accomplishments (rather than long-term goals), and are satisfied with oblique movement (rather than linear progress). We elaborate on three robust strategies—participatory architecture, multivocal inscription and distributed experimentation—and investigate their effectiveness in three sustainability related contexts: wind power, sustainability reporting and microcredit. We conclude by discussing the applicability of robust action to other contexts, and the complementarities between robust action and other forms of leadership towards sustainability

The crystal structure of Mycobacterium tuberculosis adenylate kinase in complex with two molecules of ADP and Mg2+ supports an associative mechanism for phosphoryl transfer

The crystal structure of Mycobacterium tuberculosis adenylate kinase (MtAK) in complex with two ADP molecules and Mg2+ has been determined at 1.9 Å resolution. Comparison with the solution structure of the enzyme, obtained in the absence of substrates, shows significant conformational changes of the LID and NMP-binding domains upon substrate binding. The ternary complex represents the state of the enzyme at the start of the backward reaction (ATP synthesis). The structure is consistent with a direct nucleophilic attack of a terminal oxygen from the acceptor ADP molecule on the β-phosphate from the donor substrate, and both the geometry and the distribution of positive charge in the active site support the hypothesis of an associative mechanism for phosphoryl transfer