Gallium-based Solid Liquid Interdiffusion Bonding of Semiconductor Substrates near room temperature

Within this work, bonding technologies based upon the alloying of gallium with other metals to assemble semiconductor substrates for the possible application of encapsulation and 3D-integration of micro systems and devices have been researched. Motivated by the important demand to achieve low temperature processes, methods with bonding temperatures below 200°C were investigated. Necessary technologies like the deposition of gallium as thin film and subsequent micro structuring have been developed. The alloying between gallium and gold as well as gallium and copper was analysed in detail. A good correlation between the elemental composition of the interface and its mechanical and electrical parameters was established, particularly regarding its thermal dependence. It emerged that in case of combination Au/Ga Kirkendall void are extensively formed whereby serious problems with mechanical strength as well as hermeticity emerged. In case of Cu/Ga, this problem is existent to a much lesser degree; it was possible to create hermetic tight bonds. For the necessary pre-treatment of copper, several methods could be successfully demonstrated. In summary, the development of bonding technologies based upon metallic interfaces that exhibit electric conductance, high strength and hermetic seal could be demonstrated.In dieser Arbeit werden Bondverfahren zum Fügen von Halbleitersubstraten für mögliche Anwendungen für die Verkapselung und 3D-Integration von Bauelementen der Mikrosystemtechnik erforscht, die auf der Legierungsbildung von Gallium mit anderen Metallen beruhen. Motiviert von der zentralen Anforderung an niedrige Prozesstemperaturen wurden Methoden mit Fügetemperaturen deutlich unter 200°C untersucht. Dafür nötige Technologien zum Abscheiden von Gallium als Dünnschicht und das anschließende Mikrostrukturieren wurden entwickelt. Die Legierungsbildung zwischen Gallium und Gold sowie zwischen Gallium und Kupfer wurde im experimentell im Detail analysiert. Dabei konnte eine gute Korrelation zwischen der stofflichen Zusammensetzung und den mechanischen bzw. elektrischen Parametern der Zwischenschicht, auch und insbesondere hinsichtlich ihrer Temperaturabhängigkeit gefunden werden. Es stellte sich heraus, dass im Falle der Kombination Au/Ga Kirkendall Hohlräume in einer Menge entstehen, die zu erheblichen Problemen bezüglich mechanischer Festigkeit und Dichtheit der Fügeverbindung führen. Bei der Materialkombination Cu/Ga hingegen trat dieses Problem nur begrenzt auf; es war möglich hermetisch dichte Verbindungen herzustellen. Für die bei Kupfer nötige Vorbehandlung wurden mehrere Methoden erfolgreich getestet. Insgesamt konnte die Entwicklung von Fügetechnologien gezeigt werden, die metallische Zwischenschichten verwenden, elektrisch leitfähig sind, sehr gute Festigkeiten aufweisen und hermetisch dicht sind

The Transmission of Saga at West Virginia University

Changes in the higher education landscape continue to bring new regulations which enforce standardization and similarities in organizational behavior. Because of these pressures, institutional identities and differentiations are more dependent on the unique way students experience an institution rather than the structure of the organization. Through focus groups and interviews, this phenomenological study seeks to understand the ways in which the traditional undergraduate experience impacts the transmission of organizational saga at West Virginia University. To do so, it examines stories told by students through thematic analysis to connect student experiences with symbols of the university. Focusing on these connections and the ways in which students derive meaning from symbols and embed their own meanings into symbols of the university, can bring greater clarity to the elements of student experience which are significant and transmittable within organizational saga

Teacher Retention in Secure Residential Settings

A phenomenological study was conducted to identify the factors associated with job retention among teachers in secure residential treatment centers in Tennessee. Central to this investigation was the exploration of how residential teachers perceive they are supported in their position, how teachers in residential settings perceive the culture of the facility, and what factors are associated with teacher retention in secure residential settings. Through a series of fifteen interviews, common themes emerged from the coding that provided insight into these questions. Teachers who had worked in residential settings for more than five years seemed to have very strong internal belief systems that drove them and were rewarded by the successes of their students, despite what else might be occurring at the facility. Success for the teachers did not always seem to depend administrative support, but they relied heavily on their peers for support. Administrators may be able to improve teacher retention by focusing on these factors, as well as ensuring that education is a valued component of the residential program and that teachers are compensated on a level equal to their peers in public education. Suggestions for future research include quantitative studies to examine the differences between for profit and non-profit programs, differences in retention that depend on the size of the program, and an analysis of retention as it correlates to teacher compensation

La efectividad y la eficacia de las mediciones estandarizadas y de las evaluaciones en educación

El artículo comienza definiendo la medición estandarizada y la evaluación, en educación y describiendo el estado de su situación global en la actualidad, particularmente en lo relacionado con los estudios internacionales de evaluación del rendimiento. Explora la relación entre validez y confiabilidad versus efectividad y eficacia, respectivamente, profundizando en la validez. Luego discute las limitaciones intrínsecas de la medición estandarizada a través de un ejemplo concreto. Señala las diferencias entre medición y evaluación en educación, como también aquellas entre medición referida a normas y medición referida a criterios. Discute, seguidamente, la real posibilidad de integrar ambos tipos de medición en un sólo instrumento. Revisa los pros y los contras de expresar los resultados de las mediciones en forma cuantitativa o cualitativa, enfatizando las ventajas de esta última. Enumera y comenta las formas técnicas para establecer la comparabilidad de los resultados de las mediciones estandarizadas y plantea las condiciones para que estas últimas se constituyan en reales herramientas para la política en educación. Finalmente, el artículo plantea, comenta y discute críticamente, dos recientes expresiones acerca de la medición y evaluación en educación: el supuesto resurgimiento de la evaluación formativa y la distinción artificial entre evaluación del aprendizaje y para el aprendizaj

The Earned Income Tax Credit: Targeting the Poor but Crowding Out Wealth

In this paper, we quantify the effects of the Earned Income Tax Credit (EITC) from a macroeconomic perspective. We use an incomplete markets model to analyze jointly the labor supply and saving responses to changes in tax credit generosity and their aggregate and distributional implications. In line with existing literature, our results show that the EITC is an effective policy instrument to raise labor force participation and provide insurance to working poor households. However, we show that the EITC also disincentivizes private savings for a large part of the population, except for the poorest transfer recipients. Furthermore, since unskilled labor supply reacts more strongly than skilled workers’ labor supply, wages for low skilled workers fall relative to high skilled workers. Whilst reducing post-tax earnings inequality, the EITC contributes to both a higher skill premium and wealth inequality. Finally, our welfare analysis suggests that EITC expansions are welfare improving for the majority of the population, both ex ante and when accounting for transitional dynamics

Correlations in hypernuclear matter

We investigate short range correlations in nuclear and hypernuclear matter. Self-energies due to short range correlations and their influence on the nucleon and $\Lambda$-hyperon spectral functions are described in an approach accounting for a realistic treatment of mean-field dynamics and a self-consistently derived quasi-particle interaction. Landau-Migdal theory is used to derived the short range interaction from a phenomenological Skyrme energy density functional, subtracting the long range pionic contributions to the nucleonic spectral functions. We discuss our results for different hyperon-baryon ratios to show the influence of strangeness on the correlations in hypernuclear matter.Comment: 7 pages, 5 figures, proceedings for HYP06 in Main

Cultures and Traditions of Wordplay and Wordplay Research

This volume focuses on realisations of wordplay in different cultures and social and historical contexts, and brings together various research traditions of approaching wordplay. Together with the volume DWP7, it assembles selected papers presented at the interdisciplinary conference The Dynamics of Wordplay / La dynamique du jeu de mots (Trier, 2016) and stresses the inherent dynamicity of wordplay and wordplay research