Theory of elasticity and electric polarization effects in the group-III nitrides

In this work, the properties of strained tetrahedrally bonded materials are explored theoretically, with special focus on group-III nitrides. In order to do so, a multiscale approach is taken: accurate quantitative calculations of material properties are carried out in a quantum first-principles frame, for small systems. These properties are then extrapolated and empirical methods are employed to make predictions for larger systems, such as alloys or nanostructures. We focus our attention on elasticity and electric polarization in semiconductors. These quantities serve as input for the calculation of the optoelectronic properties of these systems. Regarding the methods employed, our first-principles calculations use highly- accurate density functional theory (DFT) within both standard Kohn-Sham and generalized (hybrid functional) Kohn-Sham approaches. We have developed our own empirical methods, including valence force field (VFF) and a point-dipole model for the calculation of local polarization and local polarization potential. Our local polarization model gives insight for the first time to local fluctuations of the electric polarization at an atomistic level. At the continuum level, we have studied composition-engineering optimization of nitride nanostructures for built-in electrostatic field reduction, and have developed a highly efficient hybrid analytical-numerical staggered-grid computational implementation of continuum elasticity theory, that is used to treat larger systems, such as quantum dots.

Atomic layer deposition of copper – study through density functional theory

The wonder of the last century has been the rapid development in technology. One of the sectors that it has touched immensely is the electronic industry. There has been exponential development in the field and scientists are pushing new horizons. There is an increased dependence in technology for every individual from different strata in the society. Atomic Layer Deposition (ALD) is a unique technique for growing thin films. It is widely used in the semiconductor industry. Films as thin as few nanometers can be deposited using this technique. Although this process has been explored for a variety of oxides, sulphides and nitrides, a proper method for deposition of many metals is missing. Metals are often used in the semiconductor industry and hence are of significant importance. A deficiency in understanding the basic chemistry at the nanoscale for possible reactions has delayed the improvement in metal ALD. In this thesis, we study the intrinsic chemistry involved for Cu ALD. This work reports computational study using Density Functional Theory as implemented in TURBOMOLE program. Both the gas phase and surface reactions are studied in most of the cases. The merits and demerits of a promising transmetallation reaction have been evaluated at the beginning of the study. Further improvements in the structure of precursors and coreagent have been proposed. This has led to the proposal of metallocenes as co-reagents and Cu(I) carbene compounds as new set of precursors. A three step process for Cu ALD that generates ligand free Cu layer after every ALD pulse has also been studied. Although the chemistry has been studied under the umbrella of Cu ALD the basic principles hold true for ALD of other metals (e.g. Co, Ni, Fe ) and also for other branches of science like thin film deposition other than ALD, electrochemical reactions, etc.

The defining characteristics of alternative food initiatives in Ireland: a social movement battling for an alternative food future?

Alternative food initiatives (AFIs) have been described as an attempt to change and improve aspects of how the food system operates. They are focused around more traditional, local and sustainable food production and circulation. AFIs such as farmers’ markets, allotments and community gardens, share a desire to reduce the number of steps food goes through from production to plate. The role of these initiatives in the food system, and their potential to impact real change, has however been questioned. Working to better understand this issue is a central concern of this research. To do this a two tier analysis has been deployed. The first tier involves identifying the characteristics and general dynamics of AFIs. Bourdieu’s theory of practice, and the theories of field and capital, are the concepts applied. The research then uses these findings in the second tier of analysis concerned with relating AFI characteristics and dynamics back to their key traits, positive and negative, as well as arguments made about AFI’s role identified from previous research. Another part of this second tier of analysis is exploring if AFIs, the producers, consumers, organisations and groups that make up this phenomenon, can be considered a social movement. AFIs can be referred to collectively as a social movement, but are not often explored theoretically from this perspective. AFIs in Ireland provide the empirical context for this research. A series of qualitative interviews in four areas of Ireland, as well as evidence from primary and secondary sources are analysed. The research finds that AFIs can be understood as the potential beginnings of a lifestyle social movement. Leaders are of central importance to its development. It is also found that an important role of AFIs is revitalising, supporting and contributing to food culture.

ITSM ProcessGuide – a longitudinal and multi-method field study for real-world DSR artifact evaluation

Process guidance supports users to increase their process model understanding, process execution effectiveness as well as efficiency, and process compliance performance. This paper presents a research in progress encompassing our ongoing DSR project on Process Guidance Systems and a field evaluation of the resulting artifact in cooperation with a company. Building on three theory-grounded design principles, a Process Guidance System artifact for the company’s IT service ticketing process is developed, deployed and used. Fol-lowing a multi-method approach, we plan to evaluate the artifact in a longitudinal field study. Thereby, we will not only gather self-reported but also real usage data. This article describes the development of the artifact and discusses an innovative evaluation approach.