Recovery of Semiconductor and Defect Properties from Charge-Collection Measurements

This paper discusses the modeling of the measurements which are performed with the charge-collection, or Electron Beam Induced Current (EBIC) technique of the scanning electron microscope, and the use of the related theoretical results for recovering bulk and local recombination properties of semi conductors. A general description of different EBIC measurements can be given on the basis of the notion of charge-collection probability (r) in the device being examined. This function can be calculated by solving a stationary diffusion equation and the induced current results from the convolution of (r) with the generation function of the electron beam. According to this approach, EBIC experiments give information about or the essential semiconductor or defect parameters upon which is dependent. The more usual procedures to recover this information from actual measurements are reviewed and some new possibilities are examined

Differences in verbal and visuospatial forward and backward order recall: A review of the literature

How sequential, verbal and visuospatial stimuli are encoded and stored in memory is not clear in cognitive psychology. Studies with order recall tasks, such as the digit, and Corsi span, indicate that order of presentation is a crucial element for verbal memory, but not for visuospatial memory. This seems to be due to the different effects of forward and backward recall in verbal and visuospatial tasks. In verbal span tasks, performance is worse when recalling things in backward sequence rather than the original forward sequence. In contrast, when it comes to visuospatial tasks, performance is not always worse for a modified backward sequence. However, worse performance in backward visuospatial recall is evident in individuals with weak visuospatial abilities; such individuals perform worse in the backward version of visuospatial tasks than in the forward version. The main aim of the present review is to summarize findings on order recall in verbal and visuospatial materials by considering both cognitive and neural correlates. The results of this review will be considered in the light of the current models of WM, and will be used to make recommendations for future studie

Understanding how excess lead iodide precursor improves halide perovskite solar cell performance

The presence of excess lead iodide in halide perovskites has been key for surpassing 20% photon-to-power conversion efficiency. To achieve even higher power conversion efficiencies, it is important to understand the role of remnant lead iodide in these perovskites. To that end, we explored the mechanism facilitating this effect by identifying the impact of excess lead iodide within the perovskite film on charge diffusion length, using electron-beam-induced current measurements, and on film formation properties, from grazing-incidence wide-angle X-ray scattering and high-resolution transmission electron microscopy. Based on our results, we propose that excess lead iodide in the perovskite precursors can reduce the halide vacancy concentration and lead to formation of azimuthal angle-oriented cubic alpha-perovskite crystals in-between 0 degrees and 90 degrees. We further identify a higher perovskite carrier concentration inside the nanostructured titanium dioxide layer than in the capping layer. These effects are consistent with enhanced lead iodide-rich perovskite solar cell performance and illustrate the role of lead iodide

Controlled Release of Doxorubicin Loaded within Magnetic Thermo-responsive Nanocarriers under Magnetic and Thermal Actuation in a Microfluidic Channel

We report a procedure to grow thermo-responsive polymer shells at the surface of magnetic nanocarriers made of multiple iron oxide superparamagnetic nanoparticles embedded in poly(maleic anhydride-alt-1-ocatadecene) polymer nanobeads. Depending on the comonomers and on their relative composition, tunable phase transition temperatures in the range between 26 and 47 °C under physiological conditions could be achieved. Using a suitable microfluidic platform combining magnetic nanostructures and channels mimicking capillaries of the circulatory system, we demonstrate that thermo-responsive nanobeads are suitable for localized drug delivery with combined thermal and magnetic activation. Below the critical temperature nanobeads are stable in suspension, retain their cargo, and cannot be easily trapped by magnetic fields. Increasing the temperature above the critical temperature causes the aggregation of nanobeads, forming clusters with a magnetic moment high enough to permit their capture by suitable magnetic g..

Micro-spectroscopy on silicon wafers and solar cells

Micro-Raman (μRS) and micro-photoluminescence spectroscopy (μPLS) are demonstrated as valuable characterization techniques for fundamental research on silicon as well as for technological issues in the photovoltaic production. We measure the quantitative carrier recombination lifetime and the doping density with submicron resolution by μPLS and μRS. μPLS utilizes the carrier diffusion from a point excitation source and μRS the hole density-dependent Fano resonances of the first order Raman peak. This is demonstrated on micro defects in multicrystalline silicon. In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates. This can be attributed to the strong stress dependence of the carrier mobility (piezoresistance) of silicon. With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the doping density and the carrier lifetime in selective emitters, laser fired doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes

Anxiety profiles and protective factors: A latent profile analysis in children

The current study investigated the presence of different anxiety profiles in schoolchildren in order to understand whether Mathematics and Test Anxiety are a manifestation of a general form of anxiety, or the expression of specific forms of anxiety. Moreover, we also examined the influence of personal protective factors. The results of a latent profile analysis, conducted on 664 children attending grades 3 to 6, clearly identified three different profiles distinguished on the basis of the level of general, test and mathematics anxiety. Protective factors, such as self-concept and resilience, were differently related to anxiety: the former was clearly lower when the risk profile was higher, whereas students were able to maintain a certain level of resilience up to an average risk of developing forms of anxiety. The implications of these findings may lead to the development of specific intervention programs aimed at reducing students’ anxiety and fostering self-concept and resilience. © 2017 Elsevier Lt

Communication and visiting policies in Italian intensive care units during the first COVID-19 pandemic wave and lockdown: a nationwide survey

Background: During the first coronavirus disease 2019 (COVID-19) pandemic wave, an unprecedented number of patients with respiratory failure due to a new, highly contagious virus needed hospitalization and intensive care unit (ICU) admission. The aim of the present study was to describe the communication and visiting policies of Italian intensive care units (ICUs) during the first COVID-19 pandemic wave and national lockdown and compare these data with prepandemic conditions. Methods: A national web-based survey was conducted among 290 Italian hospitals. Each ICU (active between February 24 and May 31, 2020) was encouraged to complete an individual questionnaire inquiring the hospital/ICU structure/organization, communication/visiting habits and the role of clinical psychology prior to, and during the first COVID-19 pandemic wave. Results: Two hundred and nine ICUs from 154 hospitals (53% of the contacted hospitals) completed the survey (202 adult and 7 pediatric ICUs). Among adult ICUs, 60% were dedicated to COVID-19 patients, 21% were dedicated to patients without COVID-19 and 19% were dedicated to both categories (Mixed). A total of 11,102 adult patients were admitted to the participating ICUs during the study period and only approximately 6% of patients received at least one visit. Communication with family members was guaranteed daily through an increased use of electronic devices and was preferentially addressed to the same family member. Compared to the prepandemic period, clinical psychologists supported physicians more often regarding communication with family members. Fewer patients received at least one visit from family members in COVID and mixed-ICUs than in non-COVID ICUs, l (0 [0–6]%, 0 [0–4]% and 11 [2–25]%, respectively, p < 0.001). Habits of pediatric ICUs were less affected by the pandemic. Conclusions: Visiting policies of Italian ICUs dedicated to adult patients were markedly altered during the first COVID-19 wave. Remote communication was widely adopted as a surrogate for family meetings. New strategies to favor a family-centered approach during the current and future pandemics are warranted

Harmonization of Zika neutralization assays by using the WHO International Standard for anti-Zika virus antibody

During outbreaks of emerging viruses, such as the Zika outbreak in 2015–2016, speed and accuracy in detection of infection are critical factors to control the spread of the disease; often serological and diagnostic methods for emerging viruses are not well developed and validated. Thus, vaccines and treatments are difficult to evaluate due to the lack of comparable methods. In this study, we show how the 1st WHO International Standard for anti-Zika antibody was able to harmonize the neutralization titres of a panel of serological Zika-positive samples from laboratories worldwide. Expression of the titres in International Unit per millilitre reduced the inter-laboratory variance, allowing for greater comparability between laboratories. We advocate the use of the International Standard for anti-Zika virus antibodies for the calibration of neutralization assays to create a common language, which will permit a clear evaluation of the results of different clinical trials and expedite the vaccine/treatment development

MODELING THE EBIC MEASUREMENTS OF DIFFUSION LENGTHS AND THE RECOMBINATION CONTRAST AT EXTENDED DEFECTS

Une description alternative, basée sur le concept de probabilité de collecte, est proposée pour l'interprétation d'expériences typiques réalisées par la technique du courant induit par faisceau d'électrons (EBIC) associée au microscope électronique à balayage. On montre que la distribution φ (r) de cette probabilité dans l'échantillon obéit à une équation de diffusion homogène et que le courant induit résulte de l'excitation des propriétés de l'échantillon par la fonction de génération du faisceau électronique. L'objectif des expériences EBIC est de déterminer les paramètres essentiels caractérisant le semiconducteur ou le défaut, dont φ dépend. Différentes méthodes d'accès à cette information sont discutées et quelques nouvelles possibilités sont présentées.An alternative description is proposed of typical experiments that are performed with the electron beam induced current (EBIC) technique of the scanning electron microscope, on the basis of the notion of charge-collection probability. It is shown that the distribution φ (r) of this probability in the specimen obeys a homogeneous diffusion equation, and the induced current results from probing this sample property with the generation function of the electron beam. EBIC experiments aim at determining the essential semiconductor or defect parameters upon which φ is dependent. Different methods of recovering this information are discussed and some new possibilities are presented

On the temperature dependence of the EBIC contrast of dislocations in silicon

In some recent papers the measurements by Ourmazd et al. (J. Physique Colloq. 44 (1983) C4-289) of the temperature dependence of the electron beam induced current contrast of dislocations in silicon have been interpreted as being in disagreement with the predictions of the linear contrast model proposed by Donolato. Here it is shown that this conclusion was based on an improper assumption regarding the functional form of the recombination strength of a dislocation; omitting this assumption removes the discrepancy.Dans certains articles récents, les mesures par Ourmazd et al. (J. Physique Colloq. 44 (1983) C4-289) de la variation en fonction de la température du contraste des images obtenues par EBIC des dislocations dans le silicium ont été interprétées comme contredisant les prédictions du modèle de contraste linéaire que nous avions proposé. Nous montrons ici que cette conclusion était basée sur une hypothèse incorrecte concernant la forme fonctionnelle de la force de recombinaison de la dislocation