Permanent deactivation of boron-oxygen-related recombination centres in crystalline silicon

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Designing Cooperative Gamification: Conceptualization and Prototypical Implementation

Organizations deploy gamification in CSCW systems to enhance motivation and behavioral outcomes of users. However, gamification approaches often cause competition between users, which might be inappropriate for working environments that seek cooperation. Drawing on the social interdependence theory, this paper provides a classification for gamification features and insights about the design of cooperative gamification. Using the example of an innovation community of a German engineering company, we present the design of a cooperative gamification approach and results from a first experimental evaluation. The findings indicate that the developed gamification approach has positive effects on perceived enjoyment and the intention towards knowledge sharing in the considered innovation community. Besides our conceptual contribution , our findings suggest that cooperative gamification may be beneficial for cooperative working environments and represents a promising field for future research

Signal honesty and predation risk among a closely related group of aposematic species.

This is the final version of the article. It first appeared from NPG via http://dx.doi.org/10.1038/srep11021Many animals have bright colours to warn predators that they have defences and are not worth attacking. However, it remains unclear whether the strength of warning colours reliably indicate levels of defence. Few studies have unambiguously established if warning signals are honest, and have rarely considered predator vision or conspicuousness against the background. Importantly, little data exists either on how differences in signal strength translate into survival advantages. Ladybirds exhibit impressive variation in coloration both among and within species. Here we demonstrate that different levels of toxicity exist among and within ladybird species, and that signal contrast against the background is a good predictor of toxicity, showing that the colours are honest signals. Furthermore, field experiments with ladybird models created with regards to predator vision show that models with lower conspicuousness were attacked more frequently. This provides one of the most comprehensive studies on signal honesty in warning coloration to date.LMA was funded by the University of Cambridge and Colciencias—Colombia. MS was supported by a Biotechnology and Biological Sciences Research Council (BBSRC) David Phillips Research Fellowship (BB/G022887/1)

Understanding the Light-induced Lifetime Degradation and Regeneration in Multicrystalline Silicon

In this contribution, we focus on improving the fundamental understanding of the carrier lifetime degradation and regeneration observed in block-cast multicrystalline silicon (mc-Si) wafers under illumination at elevated temperature. We observe a pronounced degradation in lifetime at 1 sun light intensity and 75̊C after rapid thermal annealing (RTA) in a belt-firing furnace at a set peak temperature of 900̊C. However, almost no lifetime instability is detected in mc-Si wafers which are fired at a peak temperature of only 650̊C, clearly showing that the firing step is triggering the degradation effect. Lifetime spectroscopy reveals that the light-induced recombination centre is a deep-level centre with an asymmetric electron-to-hole capture cross section ratio of 20±7. After completion of the degradation, the lifetime is observed to recover and finally reaches even higher carrier lifetimes compared to the initial state. While the lifetime degradation is found to be homogeneous, the regeneration shows an inhomogeneous behaviour, which starts locally and spreads later laterally throughout the sample. Furthermore, the regeneration process is extremely slow with time constants of several hundred hours. We demonstrate, however, that by increasing the regeneration temperature, it is possible to significantly speed up the regeneration process so that it might become compatible with industrial solar cell production. To explain the observed lifetime evolution, we propose a defect model, where metal precipitates in the mc-Si bulk dissolve during the RTA treatment and the mobile metal atoms bind to a homogeneously distributed impurity. Restructuring and subsequent dissociation of this defect complex is assumed to cause the lifetime degradation, whereas a subsequent diffusion of the mobile species to the sample surfaces and crystallographic defects explains the regeneration.State of Lower SaxonyGerman Federal Ministry of Economics/0325763

Atomic-Layer-Deposited Al2O3 as Effective Barrier against the Diffusion of Hydrogen from SiNx:H Layers into Crystalline Silicon during Rapid Thermal Annealing

Stacks of hydrogen-lean aluminum oxide, deposited via plasma-assisted atomic-layer-deposition, and hydrogen-rich plasma-enhanced chemical vapor-deposited silicon nitride (SiNx) are applied to boron-doped float-zone silicon wafers. A rapid thermal annealing (RTA) step is performed in an infrared conveyor-belt furnace at different set-peak temperatures. The hydrogen content diffused into the crystalline silicon during the RTA step is quantified by measurements of the silicon resistivity increase due to hydrogen passivation of boron dopant atoms. These experiments indicate that there exists a temperature-dependent maximum in the introduced hydrogen content. The exact position of this maximum depends on the composition of the SiNx layer. The highest total hydrogen content, exceeding 1015 cm−3, is introduced into the silicon bulk from silicon-rich SiNx layers with a refractive index of 2.3 (at λ = 633 nm) at an RTA peak temperature of 800 °C, omitting the Al2O3 interlayer. Adding an Al2O3 interlayer with a thickness of 20 nm reduces the hydrogen content by a factor of four, demonstrating that Al2O3 acts as a highly effective hydrogen diffusion barrier. Measuring the hydrogen content in the silicon bulk as a function of Al2O3 thickness at different RTA peak temperatures provides the hydrogen diffusion length in Al2O3 as a function of measured temperature

Exploring optimum cut-off scores to screen for probable posttraumatic stress disorder within a sample of UK treatment-seeking veterans

Background: Previous research exploring the psychometric properties of the scores of measures of posttraumatic stress disorder (PTSD) suggests there is variation in their functioning depending on the target population. To date, there has been little study of these properties within UK veteran populations. Objective: This study aimed to determine optimally efficient cut-off values for the Impact of Event Scale-Revised (IES-R) and the PTSD Checklist for DSM-5 (PCL-5) that can be used to assess for differential diagnosis of presumptive PTSD. Methods: Data from a sample of 242 UK veterans assessed for mental health difficulties were analysed. The criterion-related validity of the PCL-5 and IES-R were evaluated against the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5). Kappa statistics were used to assess the level of agreement between the DSM-IV and DSM-5 classification systems. Results: The optimal cut-off scores observed within this sample were 34 or above on the PCL-5 and 46 or above on the IES-R. The PCL-5 cut-off is similar to the previously reported values, but the IES-R cut-off identified in this study is higher than has previously been recommended. Overall, a moderate level of agreement was found between participants screened positive using the DSM-IV and DSM-5 classification systems of PTSD. Conclusions: Our findings suggest that the PCL-5 and IES-R can be used as brief measures within veteran populations presenting at secondary care to assess for PTSD. The use of a higher cut-off for the IES-R may be helpful for differentiating between veterans who present with PTSD and those who may have some sy`mptoms of PTSD but are sub-threshold for meeting a diagnosis. Further, the use of more accurate optimal cut-offs may aid clinicians to better monitor changes in PTSD symptoms during and after treatment

Neuropsychiatric Outcomes in UK Military Veterans with Mild Traumatic Brain Injury and Vestibular Dysfunction

Objective: To estimate the frequency of vestibular dysfunction following blunt, blast, and blunt & blast mild traumatic brain injury (mTBI) and thereon assess the long-term impact of vestibular dysfunction on neurobehavioral function and disability independently of co-morbid psychiatric symptoms. Setting: Combat Stress residential and Veterans’ Outreach drop-in centres for psychological support. Participants: 162 help-seeking UK military veterans. Main measures: Self-reported frequency and severity of mTBI (using the Ohio State Identification Method), Vertigo Symptom Scale, PTSD checklist for DSM5, Kessler Psychological Distress Scale, Neurobehavioral Symptom Inventory, HIT6, Memory Complaints Inventory, WHO Disability Assessment Scale 2.0. Results: 72% of the sample reported one or more mTBI over their lifetime. Chi-square analyses indicated that vestibular disturbance, which affected 69% of participants, was equally prevalent following blunt (59%) or blast (47%) injury and most prevalent following blunt and blast combined (83%). Mediation analysis indicated that when PTSD, depression and anxiety were taken into account, vestibular dysfunction in participants with mTBI was directly and independently associated with increased postconcussive symptoms and functional disability. Conclusion: Vestibular dysfunction is common after combined blunt and blast mTBI and singularly predictive of poor long-term mental health. From a treatment perspective, vestibular rehabilitation may provide relief from postconcussive symptoms other than dizziness and imbalance

Phase transitions in electron spin resonance under continuous microwave driving

We study an ensemble of strongly coupled electrons under continuous microwave irradiation interacting with a dissipative environment, a problem of relevance to the creation of highly polarized non-equilibrium states in nuclear magnetic resonance. We analyze the stationary states of the dynamics, described within a Lindblad master equation framework, at the mean-field approximation level. This approach allows us to identify steady state phase transitions between phases of high and low polarization controlled by the distribution of disordered electronic interactions. We compare the mean-field predictions to numerically exact simulations of small systems and find good agreement. Our study highlights the possibility of observing collective phenomena, such as metastable states, phase transitions and critical behaviour in appropriately designed paramagnetic systems. These phenomena occur in a low-temperature regime which is not theoretically tractable by conventional methods, e.g., the spin-temperature approach

Light and elevated temperature induced degradation and recovery of gallium-doped Czochralski-silicon solar cells

The fast-firing step commonly applied at the end of solar cell production lines is known to trigger light-induced degradation effects on solar cells made on different silicon materials. In this study, we examine degradation phenomena on high-efficiency solar cells with poly-Si passivating contacts made on Ga-doped Czochralski-grown silicon (Cz-Si) base material under one-sun illumination at elevated temperatures ranging from 80 to 160 °C. The extent of degradation is demonstrated to increase with the applied temperature up to 140 °C. Above 140 °C, the degradation extent decreases with increasing temperature. The degradation of the energy conversion efficiency can be ascribed foremost to a reduction of the short-circuit current and the fill factor and to a lesser extent to a reduction of the open-circuit voltage. The extent of degradation at 140 °C amounts to 0.4%abs of the initial conversion efficiency of 22.1% compared to 0.15%abs at 80 °C. The extent of the efficiency degradation in the examined solar cells is significantly lower (by a factor of ~ 5) compared to solar cells made on B-doped Cz-Si wafers. Importantly, through prolonged illumination at elevated temperatures (e.g. 5 h, 1 sun, 140 °C), an improvement of the conversion efficiency by up to 0.2%abs compared to the initial value is achievable in combination with a permanent regeneration resulting in long-term stable conversion efficiencies above 22%

A spatial nine-bar linkage, possible configurations and conditions for paradoxical mobility

Abstract This paper is about a linkage consisting of nine bars connected by spherical joints, where the bars form a spatial hexagon with its main diagonals. Additionally the supporting lines of the diagonals have one proper point in common. This linkage is rigid in general. Wunderlic