Growth, electronic and electrical characterization of Ge-Rich Ge-Sb-Te alloy

In this study, we deposit a Ge-rich Ge-Sb-Te alloy by physical vapor deposition (PVD) in the amorphous phase on silicon substrates. We study in-situ, by X-ray and ultraviolet photoemission spectroscopies (XPS and UPS), the electronic properties and carefully ascertain the alloy composition to be GST 29 20 28. Subsequently, Raman spectroscopy is employed to corroborate the results from the photoemission study. X-ray diffraction is used upon annealing to study the crystallization of such an alloy and identify the effects of phase separation and segregation of crystalline Ge with the formation of grains along the [111] direction, as expected for such Ge-rich Ge-Sb-Te alloys. In addition, we report on the electrical characterization of single memory cells containing the Ge-rich Ge-Sb-Te alloy, including I-V characteristic curves, programming curves, and SET and RESET operation performance, as well as upon annealing temperature. A fair alignment of the electrical parameters with the current state-of-the-art of conventional (GeTe)n-(Sb2Te3)m alloys, deposited by PVD, is found, but with enhanced thermal stability, which allows for data retention up to 230 °C

Diversity and ethics in trauma and acute care surgery teams: results from an international survey

Background Investigating the context of trauma and acute care surgery, the article aims at understanding the factors that can enhance some ethical aspects, namely the importance of patient consent, the perceptiveness of the ethical role of the trauma leader, and the perceived importance of ethics as an educational subject. Methods The article employs an international questionnaire promoted by the World Society of Emergency Surgery. Results Through the analysis of 402 fully filled questionnaires by surgeons from 72 different countries, the three main ethical topics are investigated through the lens of gender, membership of an academic or non-academic institution, an official trauma team, and a diverse group. In general terms, results highlight greater attention paid by surgeons belonging to academic institutions, official trauma teams, and diverse groups. Conclusions Our results underline that some organizational factors (e.g., the fact that the team belongs to a university context or is more diverse) might lead to the development of a higher sensibility on ethical matters. Embracing cultural diversity forces trauma teams to deal with different mindsets. Organizations should, therefore, consider those elements in defining their organizational procedures. Level of evidence Trauma and acute care teams work under tremendous pressure and complex circumstances, with their members needing to make ethical decisions quickly. The international survey allowed to shed light on how team assembly decisions might represent an opportunity to coordinate team member actions and increase performance

Synthesis, Properties and Applications of Germanium Chalcogenides

Germanium (Ge) chalcogenides are characterized by unique properties which make these materials interesting for a very wide range of applications, from phase change memories to ovonic threshold switches, from photonics to thermoelectric and photovoltaic devices [...

The Effects of Module Temperature on the Energy Yield of Bifacial Photovoltaics: Data and Model

Bifacial photovoltaics (BPVs) are emerging with large momentum as promising solutions to improve energy yield and cost of PV systems. To reach its full potential, an accurate understanding of the physical characteristics of BPV technology is required. For this reason, we collected experimental data to refine a physical model of BPV. In particular, we simultaneously measured the module temperature, short circuit current (Isc), open-circuit voltage (Voc), power at the maximum power point (Pmpp), and the energy yield of a bifacial and a monofacial minimodule. Such minimodules, realised with the same geometry, cell technology, and module lamination, were tested under the same clear sky outdoor conditions, from morning to afternoon, for three days. The bifacial system experimentally shows higher module temperatures under operation, about 10 °C on a daily average of about 40 °C. Nevertheless, its energy yield is about 15% larger than the monofacial one. We propose a physical quantitative model that fits the experimental data of module temperature, Isc, Voc, Pmpp, and energy yield. The model was then applied to predict the annual energy yield of PV module strings. The effect of different PV module temperature coefficients on the energy yield is also discussed

Crystallization and Electrical Properties of Ge-Rich GeSbTe Alloys

Enrichment of GeSbTe alloys with germanium has been proposed as a valid approach to increase the crystallization temperature and therefore to address high-temperature applications of non-volatile phase change memories, such as embedded or automotive applications. However, the tendency of Ge-rich GeSbTe alloys to decompose with the segregation of pure Ge still calls for investigations on the basic mechanisms leading to element diffusion and compositional variations. With the purpose of identifying some possible routes to limit the Ge segregation, in this study, we investigate Ge-rich Sb2Te3 and Ge-rich Ge2Sb2Te5 with low (40 at %) amounts of Ge. The formation of the crystalline phases has been followed as a function of annealing temperature by X-ray diffraction. The temperature dependence of electrical properties has been evaluated by in situ resistance measurements upon annealing up to 300 °C. The segregation and decomposition processes have been studied by scanning transmission electron microscopy (STEM) and discussed on the basis of density functional theory calculations. Among the studied compositions, Ge-rich Ge2Sb2Te5 is found to be less prone to decompose with Ge segregation

Highly efficient solar hydrogen production through the use of bifacial photovoltaics and membrane electrolysis

The large-scale implementation of solar hydrogen production requires an optimal combination of photovoltaic systems with suitably-designed electrochemical cells, possibly avoiding power electronics for DC-DC conversion, to decrease costs. Here, a stable, solar-driven water splitting system is presented, obtained through the direct connection of a state-of-the-art proton exchange membrane (PEM) electrolyzer to a bifacial silicon heterojunction (SHJ) solar module of three cells in series with total area of 730 cm2. The bifaciality of the solar module has been optimized through modeling in terms of the number of cells, module height and inclination. During outdoor operation in the standard monofacial configuration, the system is able to produce 3.7 gr of H2 h−1m−2 with an irradiation of 1000 W m−2 and a solar-to-hydrogen efficiency (STH) of 11.55%. The same system operating in bifacial mode gives rise to a higher H2 flux and STH efficiency, reaching values of 4.2 gr of H2 h−1m−2 and STH of 13.5%. Such a noticeable difference is achieved through the collection of albedo radiation from the ground by the bifacial PV system. The system has been tested outdoors for more than 55 h, exhibiting very good endurance, with no appreciable change in production and efficiency

Development of Various Photovoltaic‐Driven Water Electrolysis Technologies for Green Solar Hydrogen Generation

Direct solar hydrogen generation via a combination of photovoltaics (PV) and water electrolysis can potentially ensure a sustainable energy supply while minimizing greenhouse emissions. The PECSYS project aims at demonstrating a solar-driven electrochemical hydrogen generation system with an area >10 m2 with high efficiency and at reasonable cost. Thermally integrated PV electrolyzers (ECs) using thin-film silicon, undoped, and silver-doped Cu(In,Ga)Se2 and silicon heterojunction PV combined with alkaline electrolysis to form one unit are developed on a prototype level with solar collection areas in the range from 64 to 2600 cm2 with the solar-to-hydrogen (StH) efficiency ranging from ≈4 to 13%. Electrical direct coupling of PV modules to a proton exchange membrane EC to test the effects of bifaciality (730 cm2 solar collection area) and to study the long-term operation under outdoor conditions (10 m2 collection area) is also investigated. In both cases, StH efficiencies exceeding 10% can be maintained over the test periods used. All the StH efficiencies reported are based on measured gas outflow using mass flow meters

Analysis of shared common genetic risk between amyotrophic lateral sclerosis and epilepsy

Because hyper-excitability has been shown to be a shared pathophysiological mechanism, we used the latest and largest genome-wide studies in amyotrophic lateral sclerosis (n = 36,052) and epilepsy (n = 38,349) to determine genetic overlap between these conditions. First, we showed no significant genetic correlation, also when binned on minor allele frequency. Second, we confirmed the absence of polygenic overlap using genomic risk score analysis. Finally, we did not identify pleiotropic variants in meta-analyses of the 2 diseases. Our findings indicate that amyotrophic lateral sclerosis and epilepsy do not share common genetic risk, showing that hyper-excitability in both disorders has distinct origins