Interpretation of Absolute Laser Reflectance During Optical Monitoring of Polycrystalline GaAs Deposition on Quartz Using Metalorganic Chemical Vapor Deposition

Gallium arsenide was deposited by metal organic chemical vapor deposition in a horizontal quartz reactor tube using trimethylgallium and arsine at 400oC - 500oC. Nucleation time and deposition rate were monitored using in situ laser reflectometry. This allowed differentiation between film and parasitic growth, which was not possible with other optical techniques. An absolute reflectance model was developed using measurements prior to GaAs deposition, and then employed to calculate values for GaAs on quartz. Detected reflectance intensities during experimental GaAs deposition were low compared to the model due to 3-dimensional island growth, causing scattering of the incident laser radiation

Jumble Java Byte Code to Measure the Effectiveness of Unit Tests

Jumble is a byte code level mutation testing tool for Java which inter-operates with JUnit. It has been designed to operate in an industrial setting with large projects. Heuristics have been included to speed the checking of mutations, for example, noting which test fails for each mutation and running this first in subsequent mutation checks. Significant effort has been put into ensuring that it can test code which uses custom class loading and reflection. This requires careful attention to class path handling and coexistence with foreign class-loaders. Jumble is currently used on a continuous basis within an agile programming environment with approximately 370,000 lines of Java code under source control. This checks out project code every fifteen minutes and runs an incremental set of unit tests and mutation tests for modified classes. Jumble is being made available as open source

Materials Challenges: Inorganic Photovoltaic Solar Energy

This authoritative reference covers the various aspects of materials science that will impact on the next generation of photovoltaic (PV) module technology. The emphasis on materials brings a fresh perspective to the literature and highlights crucial issues. Special attention is given to thin film PV materials, an area that is growing more rapidly than crystalline silicon and could dominate in the long term. The book addresses the fundamental aspects of PV solar cell materials and gives a comprehensive description of each major thin film material, either in research or production. Particular weight is given to the key materials drivers of solar conversion efficiency, long term stability, materials costs, and materials sustainability

Cadmium Telluride Solar Cells on Ultrathin Glass for Space Applications

This paper details the preliminary findings of a study to achieve a durable thin film CdTe photovoltaic device structure onto ultra-thin space qualified cover glass. An aluminium doped zinc oxide (AZO) transparent conducting oxide (TCO) was deposited directly onto cover glass using metal organic chemical vapour deposition (MOCVD). The AZO demonstrated a low sheet resistance of 10 Ω/□ and high optical transparency of 85% as well as an excellent adherence and environmental stability. Preliminary deposition of the photovoltaic layers onto the AZO on cover glass, by MOCVD, showed the possibility of such a structure yielding a device conversion efficiency of 7.2 %. High series resistance (10 Ω.cm2) and low Voc (586 mV) were identified as the limiting factors when compared to the authors platform process on indium tin oxide (ITO) coated aluminosilicate. The coverage of the Cd1-xZnxS window layer along with the front contacting of the device was shown to be the major cause of the low efficiency. Further deposition of the AZO/CdTe employing an oxygen plasma cleaning step to the cover glass and evaporated gold front contacts significantly improved the device performance. A best conversion efficiency of 10.2 % with series resistance improved to 4.4 Ω.cm2 and open circuit voltage (Voc) up to 667 mV and good adhesion has demonstrated for the first time direct deposition of CdTe solar cells onto 100 μm thick space qualified cover glass

CdCl2 treatment related diffusion phenomena in Cd1xZnxS/CdTe solar cells

Utilisation of wide bandgap Cd1_xZnxS alloys as an alternative to the CdS window layer is an attractive route to enhance the performance of CdTe thin film solar cells. For successful implementation, however, it is vital to control the composition and properties of Cd1_xZnxS through device fabrication processes involving the relatively high-temperature CdTe deposition and CdCl2 activation steps. In this study, cross-sectional scanning transmission electron microscopy and depth profiling methods were employed to investigate chemical and structural changes in CdTe/Cd1_xZnxS/CdS superstrate device structures deposited on an ITO/boro-aluminosilicate substrate. Comparison of three devices in different states of completion—fully processed (CdCl2 activated), annealed only (without CdCl2 activation), and a control (without CdCl2 activation or anneal)—revealed cation diffusion phenomena within the window layer, their effects closely coupled to the CdCl2 treatment. As a result, the initial Cd1_xZnxS/CdS bilayer structure was observed to unify into a single Cd1_xZnxS layer with an increased Cd/Zn atomic ratio; these changes defining the properties and performance of the Cd1_xZnxS/CdTe device

Inhaled methoxyflurane (Penthrox®) versus placebo for injury-associated analgesia in children - The MAGPIE trial (MEOF-002): Study protocol for a randomised controlled trial

BackgroundPain from injuries is one of the commonest symptoms in children attending emergency departments (EDs), and this is often inadequately treated in both the pre-hospital and ED settings, in part due to challenges of continual assessment and availability of easily administered analgesic options. Pain practices are therefore a key research priority, including within the field of paediatric emergency medicine. Methoxyflurane, delivered via a self-administered Penthrox® inhaler, belongs to the fluorinated hydrocarbon group of volatile anaesthetics and is unique among the group in having analgesic properties at low doses. Despite over 30 years of clinical acute analgesia use, and a large volume of evidence supporting its safety and efficacy, there is a paucity of randomised controlled trial data for Penthrox®.MethodsThis is an international multi-centre randomised, double-blind, placebo-controlled phase III trial assessing the efficacy and safety of methoxyflurane delivered via the Penthrox® inhaler for the management of moderate to severe acute traumatic pain in children and young people aged 6–17 years. Following written informed consent, eligible participants are randomised to self-administer either inhaled methoxyflurane (maximum dose of 2 × 3 ml) or normal saline placebo (maximum dose 2 × 5 ml). Patients, treating clinicians and research nurses are blinded to the treatment. The primary outcome is the change in pain intensity at 15 min after the commencement of treatment, as measured by the Visual Analogue Scale (VAS) or the Wong-Baker FACES® Pain Rating scale, with the latter converted to VAS values. Secondary outcome measures include the number and proportion of responders who achieve a 30% reduction in VAS score compared to baseline, rescue medication requested, time and number of inhalations to first pain relief, global medication performance assessment by the patient, clinician and research nurse, and evaluation of adverse events experienced during treatment and during the subsequent 14 ± 2 days. The primary analysis will be by intention to treat. The total sample size is 110 randomised and treated patients per treatment arm.DiscussionThe Methoxyflurane AnalGesia for Paediatric InjuriEs (MAGPIE) trial will provide efficacy and safety data for methoxyflurane administered via the Penthrox® inhaler, in children and adolescents who present to EDs with moderate to severe injury-related pain.Trial registrationEudraCT, 2016–004290-41. Registered on 11 April 2017.ClinicalTrials.gov, NCT03215056. Registered on 12 July 2017

MOCVD of Cd(1-x)Zn(x)S/CdTe PV cells using an ultra-thin absorber layer

Ultra-thin Cd(₁ ₋ ₓ)Zn(ₓ)S/CdTe devices were produced by atmospheric pressure metal organic chemical vapour deposition (AP-MOCVD) with varying CdTe absorber thicknesses ranging from 1.0 to 0.2 mm and compared to baseline cells with total CdTe thickness of 2.25μ. The ultra-thin CdTe layers (≤1 μm) were intentionally doped with As to induce p-type conductivity in the absorber. Cell performance reduced with CdTe thickness, with the magnitude of photo-current generation loss becoming more significant for the very thin CdTe layers. The decline in cell performance was lower than the optically limited performance relating to a decrease in shunt resistance, Rsh, especially for the thinnest cells due to areas of incomplete CdTe coverage and large presence of pin-holes leading to micro-shorts. Incorporation of Zn into the CdS window layer improved cell performance for all devices except when 0.2 μm thick CdTe was used. This improvement was markedly in the blue region owing to enhanced optical transparency of the window layer. External quantum efficiency (EQE) measurements showed a red-shift of the window layer absorption edge due to leaching out of Zn during the CdCl₂ treatment. Reduction of the CdCl₂ deposition time was demonstrated to recover the blue response of the ultra-thin cells

Chemical analysis of Cd12xZnxS/CdTe solar cells by plasma profiling TOFMS

Thin film CdTe photovoltaic (PV) devices and reference layers obtained by the atmospheric pressure metalorganic vapour deposition (AP-MOCVD) method have been studied for their chemical structure using plasma profiling time-of-flight-mass spectroscopy (PP-TOFMS, also called glow discharge TOFMS). Different levels of arsenic (As) dopant in CdTe films were measured by PP-TOFMS and compared to results obtained from a more conventional depth profiling method (secondary ion mass spectrometry or SIMS). This comparison showed that PPTOFMS has the sufficient sensitivity towards detection of the As dopant in CdTe and hence is suited as a rapid, low vacuum tool in controlling the large scale production of CdTe PV materials

Capacity challenges in water quality monitoring: understanding the role of human development

Monitoring the qualitative status of freshwaters is an important goal of the international community, as stated in the Sustainable Development Goal (SDGs) indicator 6.3.2 on good ambient water quality. Monitoring data are, however, lacking in many countries, allegedly because of capacity challenges of less-developed countries. So far, however, the relationship between human development and capacity challenges for water quality monitoring have not been analysed systematically. This hinders the implementation of fine-tuned capacity development programmes for water quality monitoring. Against this background, this study takes a global perspective in analysing the link between human development and the capacity challenges countries face in their national water quality monitoring programmes. The analysis is based on the latest data on the human development index and an international online survey amongst experts from science and practice. Results provide evidence of a negative relationship between human development and the capacity challenges to meet SDG 6.3.2 monitoring requirements. This negative relationship increases along the course of the monitoring process, from defining the enabling environment, choosing parameters for the collection of field data, to the analytics and analysis of five commonly used parameters (DO, EC, pH, TP and TN). Our assessment can be used to help practitioners improve technical capacity development activities and to identify and target investment in capacity development for monitoring

MOCVD of ultra-thin PV solar cell devices using a pyrite based p-i-n structure

Ultra-thin photovoltaic (PV) devices were produced by atmospheric pressure metal organic chemical vapour deposition (AP-MOCVD) incorporating a highly absorbing intermediate sulphurised FeSₓ layer into a CdS/CdTe structure. X ray diffraction (XRD) confirmed a transitional phase change to pyrite FeS₂ after post growth sulphur (S) annealing of the FeSₓ layer between 400⁰C and 500⁰C. Devices using a superstrate configuration incorporating a sulphurised or non sulphurised FeSₓ layer were compared to p-n devices with only a CdS/CdTe structure. Devices with sulphurised FeSₓ layers performed least efficiently, even though pyrite fractions were present. Rutherford back scattering (RBS) confirmed deterioration of the CdS/FeSₓ interface due to S inter-diffusion during the annealing process