High temperature reliability of power module substrates

The thermal cycling reliability of candidate copper and aluminium power substrates has been assessed for use at temperatures exceeding 300°C peak using a combination of thermal cycling, nanoindentation and finite element modelling to understand the relative stresses and evolution of the mechanical properties. The results include the relative cycling lifetimes up to 350°C, demonstrating almost an order of magnitude higher lifetime for active metal brazed Al / AlN substrates over Cu / Si3N4, but four times more severe roughening and cracking of the Ni-P plating's on the Al / AlN (DBA) substrates. The nonlinear finite element modelling illustrated that the yield strength of the metal and the thickness of the ceramic are the main stress controlling factors, but comparisons with the cycling lifetime results demonstrated that the fracture toughness (resistance) of the ceramic is the over-riding controlling factor for the overall passive thermal cycling lifetimes. In order to achieve the highest substrate lifetime for the highly stressed high temperature thermal cycled applications, the optimum solution appears to be annealed copper, brazed on to a thicker than normal or higher fracture toughness Si3N4 ceramic

Issues and challenges in the assessment of popular music performance within the UK HE music sector

This thesis summarises that assessing popular music performance has it issues and challenges. These arise from: the interpretation of language, how we assess in group assessments versus solo performances, creating assessments within the degree framework whilst keeping it industry relevant, the differences in our expectations of what professional standards are, and the lack of training for part-time (and some full-time) members of staff. It identifies there is a definite lack of research within the field of popular music and the necessity for further research required as well as suggestions for what these areas are. The scope of future research ranges from a new template for an assessment grid that could be used for all popular music performance assessments that cross-reference with the institutions own learning outcomes, to establish what is best practice and why, understanding the student body and their concerns on a national level, as well as wider issues such as the benefits of the passing and failing at undergraduate degree, creating agreed guidelines of what professional standards are, and the best ways in which to train academic lecturers – especially those with a freelance/ portfolio career. The method of this thesis uses desktop research and analyses the research that surround the areas of contention. It applies principles of other subjects to when there is a lack of research in the area of music. It is important to note that the thesis does not look to provide answers but to open up the dialogue and discussion that is anecdotally spoken about but is not always articulated with findings and research. Further research and evidence is required to see how these scenarios could be improved and resolved

Training for a transformed service : the experience of learners in 2016

This article explores the training and early practice experience of the first cohort of probation learners trained under the auspices of ‘Transforming Rehabilitation’ (TR). It draws on interviews with learners qualifying in 2016 in order to examine the adequacy of their training and their early perceptions of delivering TR as qualified practitioners. While highlighting their training as stressful and noting issues with TR and some implications of the highly risk-focused nature of NPS work in particular, participants were generally positive about their training and early post-qualification experiences. Some inferences are drawn in relation to the future approach to training

Paranoid thinking, cognitive bias and dangerous neighbourhoods: implications for perception of threat and expectation of victimisation

Background: Paranoid thinking is prevalent in the non-clinical population and cognitive mechanisms of heuristic reasoning and jumping to conclusions bias contributes to its formation and maintenance. Aims: This study investigated the degree to which paranoia, perceived environmental risk, heuristic reasoning and jumping to conclusions bias (measured with the beads task) contribute to misinterpretation of neutral stimuli, and whether this informed judgements regarding vulnerability to threat and crime. It is also investigated whether impulsiveness is a confounding factor on the beads task. Methods: Two hundred participants were recruited using a snowball-sampling method for a quantitative cross-sectional study. Participants reported demographic information, three psychometric questionnaires and two experimental tasks via an online paradigm hosted by the Bristol Online Survey tool. Results: Participants with high paranoia scores perceived their environment to be more dangerous than those with low scores. Participants with high paranoia scores also overestimated threat in neutral stimuli and had high expectations of future victimisation. Jumping to conclusions on the beads task did not predict fear of crime outcomes, but was predicted by impulsivity. Conclusion: Participants who demonstrated paranoid thinking were more likely to reside in perceived dangerous neighbourhoods and overestimate threat. While this could indicate a paranoid heuristic, it is a potentially rational response to prior experiences of crime and victimisation. Implications and suggestions for future research are discussed

A study of temperature-related non-linearity at the metal-silicon interface

In this paper, we investigate the temperature dependencies of metal-semiconductor interfaces in an effort to better reproduce the current-voltage-temperature (IVT) characteristics of any Schottky diode, regardless of homogeneity. Four silicon Schottky diodes were fabricated for this work, each displaying different degrees of inhomogeneity; a relatively homogeneous NiV/Si diode, a Ti/Si and Cr/Si diode with double bumps at only the lowest temperatures, and a Nb/Si diode displaying extensive non-linearity. The 77–300 K IVT responses are modelled using a semi-automated implementation of Tung's electron transport model, and each of the diodes are well reproduced. However, in achieving this, it is revealed that each of the three key fitting parameters within the model display a significant temperature dependency. In analysing these dependencies, we reveal how a rise in thermal energy “activates” exponentially more interfacial patches, the activation rate being dependent on the carrier concentration at the patch saddle point (the patch's maximum barrier height), which in turn is linked to the relative homogeneity of each diode. Finally, in a review of Tung's model, problems in the divergence of the current paths at low temperature are explained to be inherent due to the simplification of an interface that will contain competing defects and inhomogeneities

Experimental and physics based study of the Schottky Barrier Height inhomogeneity and associated traps affecting 3C-SiC-on-Si Schottky Barrier Diodes

The ability of cubic phase (3C-) Silicon Carbide (SiC) to grow heteroepitaxially on Silicon (Si) substrates (3C-SiC-on-Si) is an enabling feature for cost-effective Wide Bandgap devices and homogeneous integration with Si devices. In this paper, the authors evaluated 3C-SiC-on-Si Schottky Barrier Contacts by fabricating and testing non-freestanding lateral Schottky Barrier Diodes (LSBD). To gain a deep physical insight of the complex carrier transport phenomena that take place in this material, advanced Technology Computer Aided Design (TCAD) models were developed which allowed accurately matching of measurements with simulations. The models incorporate the device geometry, an accurate representation of the bulk material properties, and complex trapping/de-trapping and tunnelling phenomena which appear to affect the device performance. The observed non-uniformities of the Schottky Barrier Height (SBH) were successfully modelled through the incorporation of interfacial traps. The combination of TCAD with fabrication and measurements enabled the identification of trap profiles and pin their influence on the electrical performance of 3C-SiC-on-Si LSBD. The effect of temperature was studied by engaging the identified trap profiles and calculating the occupation distribution of electrons in 3C-SiC at elevated temperature. The investigation constitutes an imperative knowledge step towards the development of devices that take advantage of 3C-SiC material properties

How was your day? : exploring a day in the life of probation workers across Europe using practice diaries

This paper presents a reflection upon the preliminary analysis of diary research conducted during the period 2014-2015 in five European countries (England and Wales, France, Norway, Romania and Slovakia). The authors gathered and analysed data from a pilot project which used semi-structured diaries to generate data on probation workers’ daily lives with a view to understanding ‘a day in the life’ of probation officers across jurisdictions. The findings open up questions in relation to diary research in probation practice (diary format, follow-up interview etc.) and we use this article to discuss the relative advantages and benefits of using diary research in this area. We conclude with the argument that diaries as a method of social research hold considerable potential for conducting research in the context of probation but acknowledge that the method we employed requires some development and greater clarification in terms of the aims of the research

4H-SiC trench MOSFET with integrated fast recovery MPS diode

A 4H-SiC trench metal-oxide-semiconductor field-effect-transistor (MOSFET) design with an integrated merged PiN Schottky (MPS) diode is proposed. The Schottky contact is embedded on the bottom of the trench structure for the first time. The low electric field in the oxide and Schottky contact surface can be achieved simultaneously using the proposed integration design which enhances the oxide reliability and reduces leakage from the Schottky diode. The integration of the MPS diode reduces the total chip area and the required number of dies compared with the conventional method of using an external Schottky diode