In this work, we propose a reliability analysis targeting the evaluation of the suitability of a Phase-Change Memory (PCM) device for Storage Class Memory (SCM) applications. Thanks to the analysis ...of programming and endurance characteristics in single devices and 4 kb arrays we compare two different GeTe and GeSbTe (αGST) based PCM. The evolution of the phase-change material along cycling is explained by the analysis of subthreshold characteristics and analytical equations based on experimental data for the description of electrical parameters evolution are given. An extrapolation method to evaluate endurance at more than 109 cycles required for SCM is described and applied, showing the intrinsic high endurance capability and suitability for SCM applications of αGST wrt GeTe.
•Phase-Change Memory based on αGeSbTe alloy shows higher suitability for Storage Class Memory applications than GeTe.•Subthreshold conduction and data retention trends give important hints on material evolution along cycling.•The total lifetime of the Phase-Change Memory device depends on the energy of the single programming pulse.•The subthreshold conduction slope evolution is correlated to the cumulative programming energy along cycling by a power law.
The hydroxyl radical (OH) fuels atmospheric chemical cycling as the main sink for methane and a driver of the formation and loss of many air pollutants, but direct OH observations are sparse. We ...develop and evaluate an observation-based proxy for short term, spatial variations in OH (ProxyOH) in the remote marine troposphere using unprecedented and comprehensive measurements from the NASA Atmospheric Tomography (ATom) airborne campaign. ProxyOH is a reduced form of the OH steady-state equation representing the dominant OH production and loss pathways in the remote marine troposphere, according to box model simulations of OH constrained with ATom observations. ProxyOH comprises only eight variables that are generally observed by routine ground- or satellite-based instruments. ProxyOH scales linearly with in situ OH spatial variations along the ATom flight tracks (median r2 = 0.90, interquartile range = 0.80 – 0.94 across 2 km altitude by 20° latitudinal regions). We deconstruct spatial variations in ProxyOH as a first-order approximation of the sensitivity of OH variations to individual terms. Two terms modulate within-region ProxyOH variations—water vapor (H2O) and, to a lesser extent, nitric oxide (NO). This implies that a limited set of observations could offer a novel avenue for observation-based mapping of OH spatial variations over much of the remote marine troposphere. Both H2O and NO are expected to change with climate, while NO also varies strongly with human activities. We also illustrate the utility of ProxyOH as a process-based approach for evaluating inter-model differences in remote marine tropospheric OH.
Mechanisms of void shrinkage in aluminium Zhang, Zezhong; Liu, Tianyu; Smith, Andrew E. ...
Journal of applied crystallography,
10/2016, Letnik:
49, Številka:
5
Journal Article
Recenzirano
Voids can significantly affect the performance of materials and a key question is how voids form and evolve. Voids also provide a rare opportunity to study the fundamental interplay between surface ...crystallography and atomic diffusion at the nanoscale. In the present work, the shrinkage of voids in aluminium from 20 to 1 nm in diameter through in situ annealing is imaged in a transmission electron microscope. It is found that voids first shrink anisotropically from a non‐equilibrium to an equilibrium shape and then shrink while maintaining their equilibrium shape until they collapse. It is revealed that this process maximizes the reduction in total surface energy per vacancy emitted. It is also observed that shrinkage is quantized, taking place one atomic layer and one void facet at a time. By taking the quantization and electron irradiation into account, the measured void shrinkage rates can be modelled satisfactorily for voids down to 5 nm using bulk diffusion kinetics. Continuous electron irradiation accelerates the shrinkage kinetics significantly; however, it does not affect the energetics, which control void shape.
The shrinkage of voids in aluminium through in situ annealing is imaged in a transmission electron microscope. It is found that voids first shrink anisotropically from a non‐equilibrium to an equilibrium shape and then shrink while maintaining their equilibrium shape until they collapse. It is also observed that shrinkage is quantized, taking place one atomic layer and one void facet at a time.
We report recent developments at Commissariat à l’Energie Atomique-Laboratoire d’Electronique des Technologies de l’Information Infrared Laboratory on the processing and characterization of
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...HgCdTe (MCT) planar infrared focal plane arrays (FPAs) operating in the long-wavelength infrared (LWIR) and very-long-wavelength infrared (VLWIR) spectral bands. The active layers in these FPAs were grown by liquid phase epitaxy (LPE) on a lattice-matched CdZnTe substrate. This technological process results in lower dark current and lower serial resistance than for
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-on-
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vacancy-doped architecture and thus is better adapted for lower flux detection or higher operating temperature. This architecture was evaluated for space applications in the LWIR and VLWIR spectral bands with cutoff wavelengths from 10 to 17
μ
m at 78 K. Innovations have been introduced to the technological process to form a heterojunction by use of an LPE growth technique. The initial objective was to reduce the dark current at low temperatures, by reducing the transition temperature from diffusion-limited to depletion-limited dark current. Another advantage is that the wider bandgap obtained in the vicinity of the junction ensures less sensitivity to the defects present at the interface between MCT and passivation layers. Electro-optical characterization of
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photodiodes was performed on quarter video graphics array format FPAs with 25 and 30
μ
m pixel pitches. The results revealed excellent operabilities in current and responsivity, with low dispersion, and noise limited by current shot noise. Studies performed on the dark current show that dark current densities at 78 K are consistent with the heuristic prediction law “Rule 07”. Below this temperature, dark current varies as a pure diffusion current for a variety of devices from different manufacturers, introducing a temperature range limitation in the description of the “Rule 07” law.
In this work, we present the extensive electrical characterization of 4kb Phase-Change Memory (PCM) arrays based on "Wall" structure and Ge-rich GeSbTe (GST) material, integrating a SiC dielectric ...with low thermal conductivity surrounding the heater element for enhanced cell thermal efficiency. We investigate the effects of the introduction of such dielectrics on the electrical performances of the device and we provide a promising path to achieve energy-efficient PCM cells supporting our results by electro-thermal TCAD simulations.
Micro-Abstract The paucity of randomized breast cancer trials in elderly patients limits the data available for optimal treatment selection in this patient population, especially in elderly patients ...with comorbidities and increased susceptibility to adverse events. In the BOLERO-2 (Breast Cancer Trials of Oral Everolimus-2) phase III trial (N = 724) everolimus (EVE) plus exemestane (EXE) provided substantial clinical benefit in elderly patients with hormone receptor–positive (HR+ ) advanced breast cancer and was generally well tolerated.
Students look forward to their clinical practicum to learn within the context of reality nursing. As educators we need to actively develop models of clinical practicum whereby students are supported ...to engage and learn in the clinical learning environment. The aim of this paper is to describe an innovative model of supportive clinical teaching and learning for undergraduate nursing students as implemented in a large teaching hospital in New South Wales, Australia. The model of supportive clinical teaching and learning situates eight students at a time, across a shift, on one ward, with an experienced registered nurse from the ward specialty, who is employed as the clinical teacher to support nursing students during their one to two week block practicum. Results from written evaluation statements inform the discussion component of the paper for a model that has proved to be successful in this large healthcare facility.
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