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This thesis focuses on the theoretical work done to determine thermodynamic properties of a chalcopyrite thin-film material for use as a photovoltaic material in a tandem device. The material of main focus here is ZnGeAs2, which was chosen for the relative abundance of constituents, favorable photovoltaic properties, and good lattice matching with ZnSnP2, the other component in this tandem device. This work is divided into two main chapters, which will cover: calculations and method to determine the formation energy and abundance of native point defects, and a model to calculate the vapor pressure over a ternary material from first-principles. The purpose of this work is to guide experimental work being done in tandem to synthesize ZnGeAs2 in thin-film form with high enough quality such that it can be used as a photovoltaic. Since properties of photovoltaic depend greatly on defect concentrations and film quality, a theoretical understanding of how laboratory conditions affect these properties is very valuable. The work done here is from first-principles and utilizes density functional theory using the local density approximation. Results from the native point defect study show that the zinc vacancy (VZn) and the germanium antisite (GeZn) are the more prominent defects; which most likely produce non-stoichiometric films. The vapor pressure model for a ternary system is validated using known vapor pressure for monatomic and binary test systems. With a valid ternary system vapor pressure model, results show there is a kinetic barrier to decomposition for ZnGeAs2.
ContributorsTucker, Jon R (Author) / Van Schilfgaarde, Mark (Thesis advisor) / Newman, Nathan (Committee member) / Adams, James (Committee member) / Arizona State University (Publisher)
Created2011
Description
Electromigration in metal interconnects is the most pernicious failure mechanism in semiconductor integrated circuits (ICs). Early electromigration investigations were primarily focused on aluminum interconnects for silicon-based ICs. An alternative metallization compatible with gallium arsenide (GaAs) was required in the development of high-powered radio frequency (RF) compound semiconductor devices operating at higher current densities and elevated temperatures. Gold-based metallization was implemented on GaAs devices because it uniquely forms a very low resistance ohmic contact and gold interconnects have superior electrical and thermal conductivity properties. Gold (Au) was also believed to have improved resistance to electromigration due to its higher melting temperature, yet electromigration reliability data on passivated Au interconnects is scarce and inadequate in the literature. Therefore, the objective of this research was to characterize the electromigration lifetimes of passivated Au interconnects under precisely controlled stress conditions with statistically relevant quantities to obtain accurate model parameters essential for extrapolation to normal operational conditions. This research objective was accomplished through measurement of electromigration lifetimes of large quantities of passivated electroplated Au interconnects utilizing high-resolution in-situ resistance monitoring equipment. Application of moderate accelerated stress conditions with a current density limited to 2 MA/cm2 and oven temperatures in the range of 300°C to 375°C avoided electrical overstress and severe Joule-heated temperature gradients. Temperature coefficients of resistance (TCRs) were measured to determine accurate Joule-heated Au interconnect film temperatures. A failure criterion of 50% resistance degradation was selected to prevent thermal runaway and catastrophic metal ruptures that are problematic of open circuit failure tests. Test structure design was optimized to reduce resistance variation and facilitate failure analysis. Characterization of the Au microstructure yielded a median grain size of 0.91 ìm. All Au lifetime distributions followed log-normal distributions and Black's model was found to be applicable. An activation energy of 0.80 ± 0.05 eV was measured from constant current electromigration tests at multiple temperatures. A current density exponent of 1.91 was extracted from multiple current densities at a constant temperature. Electromigration-induced void morphology along with these model parameters indicated grain boundary diffusion is dominant and the void nucleation mechanism controlled the failure time.
ContributorsKilgore, Stephen (Author) / Adams, James (Thesis advisor) / Schroder, Dieter (Thesis advisor) / Krause, Stephen (Committee member) / Gaw, Craig (Committee member) / Arizona State University (Publisher)
Created2013
Description
"Culture talk" figures prominently in the discussions of and about Muslims, both locally and globally. Culture, in these discussions, is considered to be the underlying cause of gender and generational divides giving rise to an alleged "identity crisis." Culture also presumably conceals and contaminates "pure/true Islam." Culture serves as the scaffold on which all that divides Muslim American immigrants and converts is built; furthermore, the fear of a Muslim cultural takeover underpins the "Islamization of America" narrative. This dissertation engages these generational and "immigrant"-"indigenous" fissures and the current narratives that dominate Muslim and public spheres. It does so through the perspectives of the offspring of converts and immigrants. As the children and grandchildren of immigrants and converts come of age, and distant as they are from historical processes and experiences that shaped the parents' generations while having shared a socialization process as both Muslim and American, what role do they play in the current chapter of Islam in post-9/11 America? Will the younger generation be able to cross the divides, mend the fissures, and play a pivotal role in an "American Muslim community"? Examining how younger generations of both backgrounds view each other and their respective roles in forging an American Muslim belonging, agenda and discourse is a timely and much needed inquiry. This project aims to contribute by shedding more light on the identities, perspectives and roles of these younger generations through the four dominant narratives of identity crisis, pure/true Islam vs. Cultural Islam, the Islamization of America, and creation of an American Muslim community/identity/culture. These narratives are both part of public discourse and themes generated from interviews, a questionnaire\survey, and personal observation. This ethnographic study examines how American born and/or raised offspring of both converts to Islam and immigrant Muslims in the Phoenix and Chicago metropolitan areas define self and community, how they negotiate fissures and fault lines (ethnicity, race, class, gender, and religious interpretation) within their communities, and how their faith informs daily life and envisions a future. I utilize participant observation, interviews, and surveys and examine digital, visual and published media to answer these questions.
ContributorsAli, Muna (Author) / Eder, James (Thesis advisor) / Jackson, Sherman (Committee member) / Hjorleifur Jonsson (Committee member) / Tsuda, Takeyuki (Committee member) / Arizona State University (Publisher)
Created2013
Description
Food system and health characteristics were evaluated across the last Waorani hunter-gatherer group in Amazonian Ecuador and a remote neighboring Kichwa indigenous subsistence agriculture community. Hunter-gatherer food systems like the Waorani foragers may not only be nutritionally, but also pharmaceutically beneficial because of high dietary intake of varied plant phytochemical compounds. A modern diet that reduces these dietary plant defense phytochemicals below levels typical in human evolutionary history may leave humans vulnerable to diseases that were controlled through a foraging diet. Few studies consider the health impact of the recent drastic reduction of plant phytochemical content in the modern global food system, which has eliminated essential components of food because they are not considered "nutrients". The antimicrobial and anti-inflammatory nature of the food system may not only regulate infectious pathogens and inflammatory disease, but also support beneficial microbes in human hosts, reducing vulnerability to chronic diseases. Waorani foragers seem immune to certain infections with very low rates of chronic disease. Does returning to certain characteristics of a foraging food system begin to restore the human body microbe balance and inflammatory response to evolutionary norms, and if so, what implication does this have for the treatment of disease? Several years of data on dietary and health differences across the foragers and the farmers was gathered. There were major differences in health outcomes across the board. In the Waorani forager group there were no signs of infection in serious wounds such as 3rd degree burns and spear wounds. The foragers had one-degree lower body temperature than the farmers. The Waorani had an absence of signs of chronic diseases including vision and blood pressure that did not change markedly with age while Kichwa farmers suffered from both chronic diseases and physiological indicators of aging. In the Waorani forager population, there was an absence of many common regional infectious diseases, from helminthes to staphylococcus. Study design helped control for confounders (exercise, environment, genetic factors, non-phytochemical dietary intake). This study provides evidence of the major role total phytochemical dietary intake plays in human health, often not considered by policymakers and nutritional and agricultural scientists.
ContributorsLondon, Douglas (Author) / Tsuda, Takeyuki (Thesis advisor) / Beezhold, Bonnie L (Committee member) / Hruschka, Daniel (Committee member) / Eder, James (Committee member) / Arizona State University (Publisher)
Created2012
Description
This dissertation examines incidents of conflict and violence amid communities of the Maya Tzotzil Chamula in Chiapas, Mexico. Despite ostensible homogeneity, or more social and cultural resemblances than differences, conflicts arise between many Chamula because of how they acquire desire according to others who mediate what is desirable. These conflicts relate well to Rene Girard's hypothesis that mimetic desire influences identity yet generates conflict as imitation fosters rivalry. Qualitative methods of participant observation, interviews, and document research depict how desire, identity, and conflict interrelate. Ethnographic cases show how conflict emerges "interdividually" as rivals compete to obtain objects imputed desirable. The study begins with how young Tzotzils today appropriate the desires of others, becoming lawyer, spiritual guide, rock and roll singer, or anthropologist. Complex examples exhibit groups struggling for power and privilege within or between members of communities as they vie over "objects of desire" such as status, land, water, or representations of power and pecuniary interests. For some Chamula, mimetic rivalry works to deny resemblances with others despite being alike as neighbor, relative, farmer, carpenter, or member of the same political or religious affiliation. The study also highlights mimetic interactions that have shaped Maya struggles in the past, such as the uprisings of 1712, 1867, and 1911. Interpretive analysis explores how identity formation (structures), imitative desire (motivated interaction), and practice (habitual agency) together galvanize material and psychosocial variables for conflict. Imitative desire is worth observing because of its long-term implications for human adaptation and social change. As a contribution to social conflict theory, this dissertation offers a critical perspective to current research on mimetic desire as a significant force in human relations.
ContributorsRolland, Michael (Author) / Chance, John K. (Thesis advisor) / Eder, James (Committee member) / Hjorleifur Jonsson (Committee member) / Rus Iii, Jan (Committee member) / Arizona State University (Publisher)
Created2012
Description
This thesis is a qualitative research study that focuses on siblings of children with Autistic Spectrum Disorder (ASD). Even though it is expected that having a child with ASD in the family will influence the whole family including siblings of the child with ASD, the sibling population is rarely included in research related to children with ASD, and there is only limited services available for them. This exploratory study (n=6) is aimed at better understanding the siblings' lives in their family settings in order to identify the siblings' unmet needs and determine how they have been influenced by the child with ASD. This study is also aimed at identifying the most appropriate support for the siblings to help them cope better. The study followed the Resiliency Model of Family Stress, Adjustment, and Adaptation and a narrative theory approach. An in-depth interview with the parents was conducted for the study, so the findings reflect the parents' perception of the siblings. All the themes emerged into two categories: life in the family setting and supports. The findings indicate that the families are striving for balance between the siblings and the children with ASD, but still tend to focus more on the children with ASD. Also, the families tend to have autonomous personal support systems. The parents tend to perceive that these personal support systems are good enough for the siblings; therefore, the parents do not feel that formal support for the siblings was necessary. As a result of the findings, recommendations are made for the organizations that work with individuals with ASD to provide more appropriate services for the families of children with ASD, including siblings. Also, recommendations are made for future studies to clarify more factors related to the siblings due to the limitation of this study; the siblings' lives were reflected vicariously via the parents.
ContributorsJeong, Seong Hae (Author) / Marsiglia, Flavio F (Thesis advisor) / Ayers, Stephanie (Committee member) / Adams, James (Committee member) / Arizona State University (Publisher)
Created2013
Description
The children of immigrants who arrived in the United States in the 1980s now make up one of the fastest growing components of American society. They face unique and interesting pressures as they incorporate aspects of their parents' heritage into their contemporary American lives. The purpose of this dissertation is to offer an in-depth look at the 1.5 and second generation by examining how the immigrant descendants negotiate assimilative pressures, transnational practices, and ethnic identification. Using ethnographic research methods, such as participant observation and in-depth interviews, I researched the children of immigrants, ages 18-30, living in northwest Arkansas, who have at least one immigrant parent from Latin America. This research is important because non-traditional receiving towns, especially more rural localities, are often overlooked by scholarly studies of migration in favor of larger metropolitan centers (e.g., Los Angeles, Chicago). Studying immigrant descendants in smaller towns that are becoming increasingly populated by Hispanic/Latinos will create a better understanding of how a new generation of immigrants is assimilating into American society and culture. To increase awareness on the Hispanic/Latino 1.5 and second generation living in small town America and to offer potential solutions to facilitate an upwardly mobile future for this population, my dissertation explores a number of research questions. First, how is this population assimilating to the U.S.? Second, are members of the 1.5 and second generation transnational? How active is this transnational lifestyle? Will transnationalism persist as they grow older? Third, how does this population identify themselves ethnically? I also pay particular attention to the relationships among assimilation, transnationalism, and ethnic identity. My dissertation documents the lived experiences of the 1.5 and second generation in northwest Arkansas. The children of immigrants are one of the fastest growing groups nationwide. To understand their world and the lives they lead is to understand the new fabric of American society. I anticipate that the results from this research can be used to facilitate easier transitions to the U.S. among current and prospective immigrant generations, ensuring a brighter outlook for the future of the newest members of U.S. society.
ContributorsSmith, Claire M. (Author) / Tsuda, Takeyuki (Thesis advisor) / Eder, James (Committee member) / Chance, John K. (Committee member) / Arizona State University (Publisher)
Created2014
Description
The dissertation is based on 15 months of ethnographically-informed qualitative research at a liberal arts college in the Himalayan nation of Bhutan. It seeks to provide a sense of daily life and experience of schooling in general and for female students in particular. Access to literacy and the opportunities that formal education can provide are comparatively recent for most Bhutanese women. This dissertation will look at how state-sponsored schooling has shaped gender relations and experiences in Bhutan where non-monastic, co-educational institutions were unknown before the 1960s. While Bhutanese women continue to be under-represented in politics, upper level government positions and public life in general, it is frequently claimed at a variety of different levels (for instance in local media and government reports), that Bhutan, unlike it South Asian neighbors, has a high degree of gender equity. It is argued that any under-representation does not reflect access or opportunity but is instead the result of women's decision not to "come up" and participate. However this dissertation will dispute the claim that female students could choose to be more visible, vocal and mobile in classrooms and on campus without being challenged or discouraged. I will show that school is a gendered context, in which female students are consistently reminded of their "limitations" and their "appropriate place" through the use of familiar social practices such as teasing, gossip, and harassment. Schooling, particularly in developing nations like Bhutan, is usually implicitly and uncritically understood to be a neutral resource, often evaluated in relation to development aims such as creating a more educated and skilled workforce. While Bhutanese schools do seem to promote new kind of opportunity and new understandings of success, they also continue to recognize, maintain and reproduce conventional values around hierarchy, knowledge transmission, cooperation (or group identity) and gender norms. This dissertation will also show how emergent disparities in wealth and opportunity in the nation at large are beginning to be reflected and reproduced in both the experience of schooling and the job market in ways that Bhutanese development policy is not yet able to adequately address.
ContributorsRoder, Dolma Choden (Author) / Eder, James (Thesis advisor) / Hjorleifur Jonsson (Committee member) / Mccarty, Teresa (Committee member) / Arizona State University (Publisher)
Created2012
Description
This report will review the mechanical and microstructural properties of the refractory element rhenium (Re) deposited using Laser Additive Manufacturing (LAM). With useable structural strength over 2200 °C, existing applications up to 2760 °C, very high strength, ductility and chemical resistance, interest in Re is understandable. This study includes data about tensile properties including tensile data up to 1925 °C, fracture modes, fatigue and microstructure including deformation systems and potential applications of that information. The bulk mechanical test data will be correlated with nanoindentation and crystallographic examination. LAM properties are compared to the existing properties found in the literature for other manufacturing processes. The literature indicates that Re has three significant slip systems but also twins as part of its deformation mechanisms. While it follows the hcp metal characteristics for deformation, it has interesting and valuable extremes such as high work hardening, potentially high strength, excellent wear resistance and superior elevated temperature strength. These characteristics are discussed in detail.
ContributorsAdams, Robbie (Author) / Chawla, Nikhilesh (Thesis advisor) / Adams, James (Committee member) / Krause, Stephen (Committee member) / Arizona State University (Publisher)
Created2012
Description
This dissertation is intended to tie together a body of work which utilizes a variety of methods to study applied mathematical models involving heterogeneity often omitted with classical modeling techniques. I posit three cogent classifications of heterogeneity: physiological, behavioral, and local (specifically connectivity in this work). I consider physiological heterogeneity using the method of transport equations to study heterogeneous susceptibility to diseases in open populations (those with births and deaths). I then present three separate models of behavioral heterogeneity. An SIS/SAS model of gonorrhea transmission in a population of highly active men-who-have-sex-with-men (MSM) is presented to study the impact of safe behavior (prevention and self-awareness) on the prevalence of this endemic disease. Behavior is modeled in this examples via static parameters describing consistent condom use and frequency of STD testing. In an example of behavioral heterogeneity, in the absence of underlying dynamics, I present a generalization to ``test theory without an answer key" (also known as cultural consensus modeling or CCM). CCM is commonly used to study the distribution of cultural knowledge within a population. The generalized framework presented allows for selecting the best model among various extensions of CCM: multiple subcultures, estimating the degree to which individuals guess yes, and making competence homogenous in the population. This permits model selection based on the principle of information criteria. The third behaviorally heterogeneous model studies adaptive behavioral response based on epidemiological-economic theory within an $SIR$ epidemic setting. Theorems used to analyze the stability of such models with a generalized, non-linear incidence structure are adapted and applied to the case of standard incidence and adaptive incidence. As an example of study in spatial heterogeneity I provide an explicit solution to a generalization of the continuous time approximation of the Albert-Barabasi scale-free network algorithm. The solution is found by recursively solving the differential equations via integrating factors, identifying a pattern for the coefficients and then proving this observed pattern is consistent using induction. An application to disease dynamics on such evolving structures is then studied.
ContributorsMorin, Benjamin (Author) / Castillo-Chavez, Carlos (Thesis advisor) / Hiebeler, David (Thesis advisor) / Hruschka, Daniel (Committee member) / Suslov, Sergei (Committee member) / Arizona State University (Publisher)
Created2012