Influence of PH3 exposure on silicon substrate morphology in the MOVPE growth of III-V on silicon multijunction solar cells

Dual-junction solar cells formed by a GaAsP or GaInP top cell and a silicon bottom cell seem to be attractive candidates to materialize the long sought-for integration of III-V materials on silicon for photovoltaic applications. One of the first issues to be considered in the development of this structure will be the strategy to create the silicon emitter of the bottom subcell. In this study, we explore the possibility of forming the silicon emitter by phosphorus diffusion (i.e. exposing the wafer to PH3 in a MOVPE reactor) and still obtain good surface morphologies to achieve a successful III-V heteroepitaxy as occurs in conventional III-V on germanium solar cell technology. Consequently, we explore the parameter space (PH3 partial pressure, time and temperature) that is needed to create optimized emitter designs and assess the impact of such treatments on surface morphology using atomic force microscopy. Although a strong degradation of surface morphology caused by prolonged exposure of silicon to PH3 is corroborated, it is also shown that subsequent anneals under H-2 can recover silicon surface morphology and minimize its RMS roughness and the presence of pits and spikes

Physics and Technology Research for Liquid-Metal Divertor Development, Focused on a Tin-Capillary Porous System Solution, at the OLMAT High Heat-Flux Facility

The operation of the Optimization of Liquid Metal Advanced Targets (OLMAT) facility began in April 2021 with the scientific objective of exposing liquid-metal plasma facing components (PFCs) to the particle and power fluxes provided by one of the hydrogen neutral beam injectors of the TJ-II stellarator. The system can deliver heat fluxes from 5 to 58 MW m−2 of high energy hydrogen neutral particles (≤ 33 keV) with fluxes up to 1022m2s−1 (containing an ion fraction ≤ 33% in some instances), pulsed operation of 30–150 ms duration and repetition rates up to 2 min−1. These characteristics enable OLMAT as a high heat flux (HHF) facility for PFC evaluation in terms of power exhaust capabilities, thermal fatigue and resilience to material damage. Additionally, the facility is equipped with a wide range of diagnostics that includes tools for analyzing the thermal response of the targets as well as for monitoring atomic/plasma physics phenomena. These include spectroscopy, pyrometry, electrical probing and visualization (fast and IR cameras) units. Such particularities make OLMAT a unique installation that can combine pure technological PFC research with the investigation of physical phenomena such as vapor shielding, thermal sputtering, the formation/characterization of plasma plumes with significant content of evaporated metal and the detection of impurities in front of the studied targets. Additionally, a myriad of surface characterization techniques as SEM/EDX for material characterization of the exposed PFC prototypes are available at CIEMAT. In this article, first we provide an overview of the current facility upgrade in which a high-power CW laser, that can be operated in continuous and pulsed modes (0.2–10 ms), dump and electrical (single Langmuir) probe embedded on the target surface have been installed. This laser operation will allow simulating more relevant heat loading scenarios such as nominal steady-state divertor heat fluxes (10–20 MW m−2 in continuous mode) and transients including ELM loading and disruption-like events (ms time scales and power densities up to GW m−2 range). The work later focuses on the more recent experimentation (2022 fall campaign) where a 3D printed Tungsten (W) Capillary Porous System (CPS) target, with approximated 30 μm pore size and a 37% porosity and filled with liquid tin. This porous surface was a mock-up of the PFC investigated in the ASDEX Upgrade divertor manipulator. The target composed with this element was eventually exposed to a sequence of shots with the maximum heat flux that OLMAT provides (58 ± 14 MWm−2). Key questions as resilience to dry-out and particle ejection of the liquid metal layer, its refilling, the induced damage/modification of the porous W matrix and the global performance of the component are addressed, attempting to shed light on the issues encountered with the PFC at tokamak scale testing.</p

Deuterium retention in tin (Sn) and lithium–tin (Li–Sn) samples exposed to ISTTOK plasmas

The use of lithium (Li) or tin (Sn) as a liquid metal plasma facing component is proposed as a solution to the high power load issue on the divertor region of nuclear fusion reactors. The possibility to use these materials depends on their compatibility with hydrogen plasmas. With the purpose of realizing deuterium retention studies, specimens of pure Sn (99.999% Sn) and Li–Sn alloy (30 at.% Li) were exposed in the ISTTOK edge plasma. Ex situ analysis of the samples was performed by means of ion beam diagnostics. Nuclear reaction analysis (NRA) technique was applied using the D(3He,p)4He reaction to quantify the fuel retention on the samples.In this work the deuterium retention is compared between pure Sn and Li–Sn alloy samples in both liquid and solid states. All the samples were found to have retention ratios smaller than 0.1 at.%. This low retention ratio is expected for pure tin given its high mass and the instability of tin hydrides. However the retention was unexpectedly low for the case of Li–Sn which was thought to be dominated by the lithium fraction in the alloy. These results suggest that tin has a role in the retention mechanism in this material. Keywords: Liquid metals, Plasma-surface interaction, Lithium, Tin, Deuterium retention, Tokamak ISTTO

Advanced transmission electron microscopy investigation of defect formation in movpe-growth of gap on silicon using arsenic initial coverage

Integration of GaP layers on silicon substrates using AsH3 pre-exposure followed by a PH3-based GaP epitaxial growth allows the development of very promising processes for the photovoltaic industry, although many of the growth routines using this approach suffer from reproducibility issues when transferred to a new epitaxial system, leading to poor quality layers. This fact reveals a lack of knowledge on the mechanisms behind the formation of the most common planar defects (stacking faults and microtwins) and their dynamics for GaP/Si Metal Organic Vapor Phase Epitaxy using AsH3 and PH3. Therefore, in this work, a set of GaP/Si samples with a similarly high defect density grown between 700 °C and 725 °C, are analyzed by means of high-resolution scanning transmission electron microscopy and electron energy loss spectroscopy. The results presented show contaminant-free Si surfaces for temperatures above 725 °C, ruling out the hypothesis of contaminant as the origin of these planar defects. Regarding the interface Si/GaP, the GaP growth starts, in all the samples, with Ga Si bonds. Additionally, no traces of As are found, which reinforces the hypothesis of an effectively displacement of As on Si surface by Ga atoms at high temperature. Finally, it is observed complex chemical structures in the origin of the microtwins and the cause of the origin of these defects seems to be a localized gallium depletion at the GaP/Si interface

Anorexia nervosa and cancer: a protocol for a systematic review and meta-analysis of observational studies

This is the final version of the article. Available from the publisher via the DOI in this record.BACKGROUND: Anorexia nervosa is characterized by a severe restriction of caloric intake, low body weight, fear of gaining weight or of becoming fat, and disturbance of body image. Pathogenesis of the disorder may include genetic predisposition, hormonal changes and a combination of environmental, psychosocial, and cultural factors. Cancer is the second leading cause of death worldwide. At present, no systematic reviews and meta-analyses have evaluated the risk of cancer in people with anorexia nervosa. The objective of this study will be to evaluate the association between anorexia nervosa and the risk of developing or dying from cancer. METHODS/DESIGN: This study protocol is part of a systematic collection and assessment of multiple systematic reviews and meta-analyses (umbrella review) evaluating the association of cancer and multiple central nervous system disorders. We designed a specific protocol for a new systematic review and meta-analysis of observational studies of anorexia nervosa with risk of developing or dying from any cancer. Data sources will be PubMed, Embase, Scopus, Web of Science, and manual screening of references. Observational studies (case-control and cohort) in humans that examined the association between anorexia nervosa and risk of developing or dying from cancer will be sought. The primary outcomes will be cancer incidence and cancer mortality in association with anorexia nervosa. Secondary outcomes will be site-specific cancer incidence and mortality, respectively. Screening of abstracts and full texts, and data abstraction will be performed by two team members independently. Conflicts at all levels of screening and abstraction will be resolved through discussion. The quality of studies will be assessed by using the Ottawa-Newcastle scale by two team members independently. Random effects models will be conducted where appropriate. Subgroup and additional analyses will be conducted to explore the potential sources of heterogeneity. The World Cancer Research Fund (WCRF)/American Institute for Cancer Research (AICR) criteria and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach will be used for determining the quality of evidence for cancer outcomes. DISCUSSION: Findings from this systematic review will inform an ongoing umbrella review on cancer and central nervous system disorders. Our systematic review and meta-analysis of observational studies will establish the extent of the epidemiological evidence underlying the association between anorexia nervosa and cancer. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42017067462.Specific funding from the Generalitat Valenciana (PROMETEOII/2015/021) and CIBERSAM/Institute of Health Carlos III was received for this work. The funders were not involved in the design of the protocol or decision to submit the protocol for publication, nor will they be involved in any aspect of the conduct of the review. BH is supported by a New Investigator Award from the Canadian Institutes of Health Research and the Drug Safety and Effectiveness Network. MR is partially funded by the Spanish Health Services Research on Chronic Patients Network (REDISSEC)/Institute of Health Carlos III. The views expressed in this article are the views of the authors and may not be understood or quoted as being made on behalf of, or reflecting the position of, the funder(s) or any institution

Effect of strain rate on tensile mechanical properties of high-purity niobium single crystals for SRF applications

An investigation of the mechanical properties of high-purity niobium single crystals is presented. Specimens were cut with different crystallographic orientations from a large grain niobium disk and uniaxial tensile tests were conducted at strain rates between 10-4 and 103 s-1. The logarithmic strain rate sensitivity for crystals oriented close to the center of a tensile axis inverse pole figure (IPF) is ~0.14 for all strain rates. The strain at failure (ranging from 0.4 to 0.9) is very sensitive to crystal orientation and maximal at ~10-2 s-1 for crystals oriented close to the center of an IPF. The high anisotropy observed at quasi-static strain rates decreased with increasing strain rate. The activation of multiple slip systems in the dynamic tests could account for this reduction in anisotropy. A transition from strain hardening to softening in the plastic domain was observed at strain rates greater than approximately 6 × 10-2 s-1 for crystals oriented close to the center of a tensile axis IPF. Shear bands were observed in specimens with orientations having similarly high Schmid factors on both {110} and {112} slip families, and they are correlated with reduced ductility. Crystal rotations at fracture are compared for the different orientations using scanning electron microscopy images and EBSD orientation maps. A rotation toward the terminal stable [101] orientation was measured for the majority of specimens (with tensile axes more than ~17° from the [001] direction) at strain rates between 1.28 × 10-2 and 1000 s-1.The authors would like to acknowledge the work of CERN's Materials, Metrology and Non-Destructive Testing (EN-MME-MM) section for granting access to their equipment for specimen preparation and scanning electron microscope (SEM) analyses. The authors would also like to thank Mr. Larry Vladic of Elite Motion LLC for lending us the high-speed camera during the high strain rate tests performed ASU. This Marie Sklodowska-Curie Action (MSCA) Innovative Training Network (ITN) receives funding from the European Union's H2020 Framework Programme under grant agreement no. 764879. T.R. Bieler, D. Kang, E. Pai Kulyadi, P. Eisenlohr, C. Kale, and K.N. Solanki acknowledge support from DOE/OHEP grant DE-SC0009962

Global and regional cortical thinning in first-episode psychosis patients: relationships with clinical and cognitive features

BackgroundThe thickness of the cortical mantle is a sensitive measure for identifying alterations in cortical structure. We aimed to explore whether first episode schizophrenia patients already show a significant cortical thinning and whether cortical thickness anomalies may significantly influence clinical and cognitive features.MethodWe investigated regional changes in cortical thickness in a large and heterogeneous sample of schizophrenia spectrum patients (n=142) at their first break of the illness and healthy controls (n=83). Magnetic resonance imaging brain scans (1.5 T) were obtained and images were analyzed by using BRAINS2. The contribution of sociodemographic, cognitive and clinical characterictics was investigated.ResultsPatients showed a significant total cortical thinning (F=17.55, d=−0.62, p0.53). No significant group × gender interactions were observed (all p’s>0.15). There were no significant associations between the clinical and pre-morbid variables and cortical thickness measurements (all r’s<0.12). A weak significant negative correlation between attention and total (r=−0.24, p=0.021) and parietal cortical thickness (r=−0.27, p=0.009) was found in patients (thicker cortex was associated with lower attention). Our data revealed a similar pattern of cortical thickness changes related to age in patients and controls.ConclusionsCortical thinning is independent of gender, age, age of onset and duration of the illness and does not seem to significantly influence clinical and functional symptomatology. These findings support a primary neuro-development disorder affecting the normal cerebral cortex development in schizophrenia

Clinical usefulness of the screen for cognitive impairment in psychiatry (SCIP-S) scale in patients with type I bipolar disorder

Background: The relevance of persistent cognitive deficits to the pathogenesis and prognosis of bipolar disorders (BD) is understudied, and its translation into clinical practice has been limited by the absence of brief methods assessing cognitive status in Psychiatry. This investigation assessed the psychometric properties of the Spanish version of the Screen for Cognitive Impairment in Psychiatry (SCIP-S) for the detection of cognitive impairment in BD. Methods: After short training, psychiatrists at 40 outpatient clinics administered the SCIP three times over two weeks to a total of 76 consecutive type I BD admissions. Experienced psychologists also administered a comprehensive battery of standard neuropsychological instruments to clinical sample and 45 healthy control subjects. Results: Feasibility was supported by a brief administration time (approximately 15 minutes) and minimal scoring errors. The reliability of the SCIP was confirmed by good equivalence of forms, acceptable stability (ICC range 0.59 to 0.87) and adequate internal consistency (Chronbach's alpha of 0.74). Construct validity was granted by extraction of a single factor (accounting 52% of the variance), acceptable correlations with conventional neuropsychological instruments, and a clear differentiation between bipolar I and normal samples. Efficiency was also provided by the adequate sensitivity and specificity. Limitations: The sample size is not very large. The SCIP and the neurocognitive battery do not cover all potentially relevant cognitive domains. Also, sensitivity to change remains unexplored. Conclusion: With minimal training, physicians obtained a reliable and valid estimate of cognitive impairment in approximately 15 minutes from an application of the SCIP to type I BD patients

Spanish version of the Screen for Cognitive Impairment in Psychiatry (SCIP-S): Psychometric properties of a brief scale for cognitive evaluation in schizophrenia

[EN] Objective: The Screen for Cognitive Impairment in Psychiatry (SCIP) is a brief scale designed for detecting cognitive deficits in several psychotic and affective disorders. This study examined the psychometric properties of the Spanish version of the SCIP in a sample of outpatients suffering schizophrenia-spectrum disorders. Methods: Psychometric properties were evaluated in a sample of 126 stable patients with schizophrenia. Men and women 18 to 55 years of age were recruited from consecutive admissions to 40 psychiatric outpatient clinics in Spain and asked to complete a series of cognitive measures at baseline, as well as three versions of the SCIP separated by one week intervals. A matched sample of 39 healthy controls was also subjected to the baseline examination. The feasibility, reliability and validity of the SCIP was examined; concurrent validity was assessed by means of a complete neuropsychological battery. Results: Average time for SCIP administration was 16.02 (SD=5.01) minutes. Test–retest reliability intra-class correlation coefficients ranged from 0.74 to 0.90, with an internal consistency Cronbach's alpha value of 0.73. The three parallel forms of SCIP were shown to be equivalent. The SCIP scales were correlated with corresponding neuropsychological instruments, with Pearson's r between 0.38 and 0.60, pb0.01. The SCIP effectively discriminated between the patient and control samples. Factor analysis revealed one significant dimension, cognitive performance, that accounted for 49.8% of the total variance. Conclusions: The Spanish version of the SCIP is a simple, brief, valid and reliable tool for detection of cognitive impairment in patients with schizophrenia by minimally trained healthcare personnel