Matching Items (67)
Description
The current research examines the influence of disciplines, advisors, committees, language, culture, and previous experiences in students' search and selection of dissertation topics, as well as whether and how students react to those influences during this process. Invention has been an area of research for rhetoricians for centuries, but most modern research focuses exclusively on the pre-writing process in first composition classrooms (Young, 1976). The current research collected survey and interview data from second- and third-year Ph.D. students in natural sciences, social sciences, and humanities at a large research university in the United States. 80 second- and third-year Ph.D. students completed an online survey; 11 students and four of their advisors participated in a semi-structured interview. The results demonstrate that the majority of students spent over three months in the selection of dissertation topics, and the humanities students tended to spend longer time in this process than social sciences or humanities students. Additionally, students have much in common in their perception of the criteria they would use in the selection of dissertation topics, and those criteria are similar to what previous researchers (Isaac, Koenigsknecht, Malaney, & Karras, 1989; Kozma, 1997; Sessions, 1971) have identified. However, when it comes to the actual selection experiences, the interviews show that students do not necessarily apply those criteria rationally. Moreover, disciplines appear to have an overarching effect on students' topic selection. Natural sciences advisors appeared to have more direct involvement in students' topic choice than advisors in social sciences or humanities. The linguistic and cultural backgrounds of the eleven doctoral participants were not found influential in their selection of dissertation topics. Finally, although Ph.D. advisors generally have a good understanding of students' academic progress, their knowledge of the students' personal and professional concerns may differ, and the latter knowledge is crucial in their advising on students' dissertation topic choice. The current study suggests invention in the scholar and researcher level is significantly different from that of first-year composition classrooms. The successful invention of dissertation topics is indispensable of the influence of disciplines, programs as well as the intellectual and practical support students can receive.
ContributorsXia, Jing (Author) / Matsuda, Paul K (Thesis advisor) / James, Mark (Committee member) / Renaud, Claire (Committee member) / Arizona State University (Publisher)
Created2013
Description
In this dissertation, remote plasma interactions with the surfaces of low-k interlayer dielectric (ILD), Cu and Cu adhesion layers are investigated. The first part of the study focuses on the simultaneous plasma treatment of ILD and chemical mechanical polishing (CMP) Cu surfaces using N2/H2 plasma processes. H atoms and radicals in the plasma react with the carbon groups leading to carbon removal for the ILD films. Results indicate that an N2 plasma forms an amide-like layer on the surface which apparently leads to reduced carbon abstraction from an H2 plasma process. In addition, FTIR spectra indicate the formation of hydroxyl (Si-OH) groups following the plasma exposure. Increased temperature (380 °C) processing leads to a reduction of the hydroxyl group formation compared to ambient temperature processes, resulting in reduced changes of the dielectric constant. For CMP Cu surfaces, the carbonate contamination was removed by an H2 plasma process at elevated temperature while the C-C and C-H contamination was removed by an N2 plasma process at elevated temperature. The second part of this study examined oxide stability and cleaning of Ru surfaces as well as consequent Cu film thermal stability with the Ru layers. The ~2 monolayer native Ru oxide was reduced after H-plasma processing. The thermal stability or islanding of the Cu film on the Ru substrate was characterized by in-situ XPS. After plasma cleaning of the Ru adhesion layer, the deposited Cu exhibited full coverage. In contrast, for Cu deposition on the Ru native oxide substrate, Cu islanding was detected and was described in terms of grain boundary grooving and surface and interface energies. The thermal stability of 7 nm Ti, Pt and Ru ii interfacial adhesion layers between a Cu film (10 nm) and a Ta barrier layer (4 nm) have been investigated in the third part. The barrier properties and interfacial stability have been evaluated by Rutherford backscattering spectrometry (RBS). Atomic force microscopy (AFM) was used to measure the surfaces before and after annealing, and all the surfaces are relatively smooth excluding islanding or de-wetting phenomena as a cause of the instability. The RBS showed no discernible diffusion across the adhesion layer/Ta and Ta/Si interfaces which provides a stable underlying layer. For a Ti interfacial layer RBS indicates that during 400 °C annealing Ti interdiffuses through the Cu film and accumulates at the surface. For the Pt/Cu system Pt interdiffuion is detected which is less evident than Ti. Among the three adhesion layer candidates, Ru shows negligible diffusion into the Cu film indicating thermal stability at 400 °C.
ContributorsLiu, Xin (Author) / Nemanich, Robert (Thesis advisor) / Chamberlin, Ralph (Committee member) / Chen, Tingyong (Committee member) / Smith, David (Committee member) / Ponce, Fernando (Committee member) / Arizona State University (Publisher)
Created2012
Description
In this dissertation, the interface chemistry and electronic structure of plasma-enhanced atomic layer deposited (PEALD) dielectrics on GaN are investigated with x-ray and ultraviolet photoemission spectroscopy (XPS and UPS). Three interrelated issues are discussed in this study: (1) PEALD dielectric growth process optimization, (2) interface electronic structure of comparative PEALD dielectrics on GaN, and (3) interface electronic structure of PEALD dielectrics on Ga- and N-face GaN. The first study involved an in-depth case study of PEALD Al2O3 growth using dimethylaluminum isopropoxide, with a special focus on oxygen plasma effects. Saturated and self-limiting growth of Al2O3 films were obtained with an enhanced growth rate within the PEALD temperature window (25-220 ºC). The properties of Al2O3 deposited at various temperatures were characterized to better understand the relation between the growth parameters and film properties. In the second study, the interface electronic structures of PEALD dielectrics on Ga-face GaN films were measured. Five promising dielectrics (Al2O3, HfO2, SiO2, La2O3, and ZnO) with a range of band gap energies were chosen. Prior to dielectric growth, a combined wet chemical and in-situ H2/N2 plasma clean process was employed to remove the carbon contamination and prepare the surface for dielectric deposition. The surface band bending and band offsets were measured by XPS and UPS for dielectrics on GaN. The trends of the experimental band offsets on GaN were related to the dielectric band gap energies. In addition, the experimental band offsets were near the calculated values based on the charge neutrality level model. The third study focused on the effect of the polarization bound charge of the Ga- and N-face GaN on interface electronic structures. A surface pretreatment process consisting of a NH4OH wet chemical and an in-situ NH3 plasma treatment was applied to remove carbon contamination, retain monolayer oxygen coverage, and potentially passivate N-vacancy related defects. The surface band bending and polarization charge compensation of Ga- and N-face GaN were investigated. The surface band bending and band offsets were determined for Al2O3, HfO2, and SiO2 on Ga- and N-face GaN. Different dielectric thicknesses and post deposition processing were investigated to understand process related defect formation and/or reduction.
ContributorsYang, Jialing (Author) / Nemanich, Robert J (Thesis advisor) / Chen, Tingyong (Committee member) / Peng, Xihong (Committee member) / Ponce, Fernando (Committee member) / Smith, David (Committee member) / Arizona State University (Publisher)
Created2014
Description
This dissertation presents research findings on the three materials systems: lateral Si nanowires (SiNW), In2Se3/Bi2Se3 heterostructures and graphene. The first part of the thesis was focused on the growth and characterization of lateral SiNW. Lateral here refers to wires growing along the plane of substrate; vertical NW on the other hand grow out of the plane of substrate. It was found, using the Au-seeded vapor – liquid – solid technique, that epitaxial single-crystal SiNW can be grown laterally along Si(111) substrates that have been miscut toward [11− 2]. The ratio of lateral-to-vertical NW was found to increase as the miscut angle increased and as disilane pressure and substrate temperature decreased. Based on this observation, growth parameters were identified whereby all of the deposited Au seeds formed lateral NW. Furthermore, the nanofaceted substrate guided the growth via a mechanism that involved pinning of the trijunction at the liquid/solid interface of the growing nanowire.
Next, the growth of selenide heterostructures was explored. Specifically, molecular beam epitaxy was utilized to grow In2Se3 and Bi2Se3 films on h-BN, highly oriented pyrolytic graphite and Si(111) substrates. Growth optimizations of In2Se3 and Bi2Se3 films were carried out by systematically varying the growth parameters. While the growth of these films was demonstrated on h-BN and HOPG surface, the majority of the effort was focused on growth on Si(111). Atomically flat terraces that extended laterally for several hundred nm, which were separated by single quintuple layer high steps characterized surface of the best In2Se3 films grown on Si(111). These In2Se3 films were suitable for subsequent high quality epitaxy of Bi2Se3 .
The last part of this dissertation was focused on a recently initiated and ongoing study of graphene growth on liquid metal surfaces. The initial part of the study comprised a successful modification of an existing growth system to accommodate graphene synthesis and process development for reproducible graphene growth. Graphene was grown on Cu, Au and AuCu alloys at varioua conditions. Preliminary results showed triangular features on the liquid part of the Cu metal surface. For Au, and AuCu alloys, hexagonal features were noticed both on the solid and liquid parts.
Next, the growth of selenide heterostructures was explored. Specifically, molecular beam epitaxy was utilized to grow In2Se3 and Bi2Se3 films on h-BN, highly oriented pyrolytic graphite and Si(111) substrates. Growth optimizations of In2Se3 and Bi2Se3 films were carried out by systematically varying the growth parameters. While the growth of these films was demonstrated on h-BN and HOPG surface, the majority of the effort was focused on growth on Si(111). Atomically flat terraces that extended laterally for several hundred nm, which were separated by single quintuple layer high steps characterized surface of the best In2Se3 films grown on Si(111). These In2Se3 films were suitable for subsequent high quality epitaxy of Bi2Se3 .
The last part of this dissertation was focused on a recently initiated and ongoing study of graphene growth on liquid metal surfaces. The initial part of the study comprised a successful modification of an existing growth system to accommodate graphene synthesis and process development for reproducible graphene growth. Graphene was grown on Cu, Au and AuCu alloys at varioua conditions. Preliminary results showed triangular features on the liquid part of the Cu metal surface. For Au, and AuCu alloys, hexagonal features were noticed both on the solid and liquid parts.
ContributorsRathi, Somilkumar J (Author) / Drucker, Jeffery (Thesis advisor) / Smith, David (Committee member) / Chen, Tingyong (Committee member) / Arizona State University (Publisher)
Created2014
Description
Abstract
Grammaticalization theory provides a framework for analyzing language change. This thesis uses the concepts relevant to grammaticalization theory in an examination of ‘only’ and ‘just’ to determine how changes in their usage conform to the theory. After an introduction providing a sampling of the myriad ways ‘only’ and ‘just’ are used in Modern English, I provide an overview of grammaticalization theory in Chapter 2. Included in this chapter are a history of the major concepts of grammaticalization theory, an explanation of the commonly-accepted parameters and tools used to test and demonstrate grammaticalization, and a brief discussion of current arguments against grammaticalization theory. Chapter 3 presents my analysis of ‘only’ and ‘just’. I show that ‘only’ has grammaticalized from an adjective to a more grammatical adjective, from an adjective to an adverb, and from an adjective to a complementizer. I then show that ‘just’ has grammaticalized from an adjective to a more grammatical adjective and from an adjective to an adverb. Although some proponents of grammaticalization theory question the grammaticalization pathways leading from adjective to adverb and from adjective to complementizer, I argue that in the cases of ‘only’ and ‘just’ these pathways do indeed exist. I use the Oxford English Dictionary and corpora to support and demonstrate the validity of my argument.
Grammaticalization theory provides a framework for analyzing language change. This thesis uses the concepts relevant to grammaticalization theory in an examination of ‘only’ and ‘just’ to determine how changes in their usage conform to the theory. After an introduction providing a sampling of the myriad ways ‘only’ and ‘just’ are used in Modern English, I provide an overview of grammaticalization theory in Chapter 2. Included in this chapter are a history of the major concepts of grammaticalization theory, an explanation of the commonly-accepted parameters and tools used to test and demonstrate grammaticalization, and a brief discussion of current arguments against grammaticalization theory. Chapter 3 presents my analysis of ‘only’ and ‘just’. I show that ‘only’ has grammaticalized from an adjective to a more grammatical adjective, from an adjective to an adverb, and from an adjective to a complementizer. I then show that ‘just’ has grammaticalized from an adjective to a more grammatical adjective and from an adjective to an adverb. Although some proponents of grammaticalization theory question the grammaticalization pathways leading from adjective to adverb and from adjective to complementizer, I argue that in the cases of ‘only’ and ‘just’ these pathways do indeed exist. I use the Oxford English Dictionary and corpora to support and demonstrate the validity of my argument.
ContributorsBrubaker, Heidi (Author) / Gelderen, Elly van (Thesis advisor) / Adams, Karen (Committee member) / James, Mark (Committee member) / Arizona State University (Publisher)
Created2015
Description
South Sudanese refugees are among the most vulnerable immigrants to the U.S.. Many have spent years in refugee camps, experienced trauma, lost members of their families and have had minimal or no schooling or literacy prior to their arrival in the U.S. Although most South Sudanese aspire to become U.S. citizens, finally giving them a sense of belonging and participation in a land they can call their own, they constitute a group that faces great challenges in terms of their educational adaptation and English-language learning skills that would lead them to success on the U.S. citizenship examination. This dissertation reports findings from a qualitative research project involving case studies of South Sudanese students in a citizenship preparation program at a South Sudanese refugee community center in Phoenix, Arizona. It focuses on the links between the motivations of students seeking citizenship and the barriers they face in gaining it. Though the South Sudanese refugee students aspiring to become U.S. citizens face many of the same challenges as other immigrant groups, there are some factors that in combination make the participants in this study different from other groups. These include: long periods spent in refugee camps, advanced ages, war trauma, absence of intact families, no schooling or severe disruption from schooling, no first language literacy, and hybridized forms of second languages (e.g. Juba Arabic). This study reports on the motivations students have for seeking citizenship and the challenges they face in attaining it from the perspective of teachers working with those students, community leaders of the South Sudanese community, and particularly the students enrolled in the citizenship program.
ContributorsJohnson, Erik (Author) / Adams, Karen (Thesis advisor) / Renaud, Claire (Committee member) / James, Mark (Committee member) / Arizona State University (Publisher)
Created2014
Description
This study investigates the relationships between ESL teachers' beliefs about writing instruction and their use of computer technology in the first-year composition classroom. Utilizing a sociocultural approach, the study analyzes the connections between ESL teachers' instructional beliefs and the technological practices that emerge as a result of these beliefs and decisions. Qualitative research was conducted, and data was collected through classroom observations, teacher interviews, and course materials. Data analysis reveals that regardless of teachers' differing beliefs about writing instruction, they use computer technology when it enhances their teaching and students' learning. It also reveals that factors such as teacher attitude toward technology and adequate training affect the extent to which they incorporate technology into class.
ContributorsErdem, Ebru (Author) / Gelderen, Elly van (Thesis advisor) / Nilsen, Don (Committee member) / James, Mark (Committee member) / Arizona State University (Publisher)
Created2014
Description
This yearlong project examines how multilingual undergraduate writers--including international visa students and U.S. permanent residents or citizens who are non-native English speakers--exercise agency in their first-year composition placement decisions. Agency is defined as the capacity to act or not to act contingent upon various conditions. The goal of the project is to demonstrate how student agency can inform the overall programmatic placement decisions, which can lead to more effective placement practices for multilingual writers. To explore the role of agency in students' placement decisions, I conducted a series of four in-depth interviews with eleven multilingual writers between Fall 2010 and Spring 2011 in the Writing Programs at Arizona State University. To triangulate these placement decisions, I interviewed some of the multilingual student participants' academic advisors and writing teachers as well as writing program administrators. Findings showed that when conditions for agency were appropriate, the multilingual student participants were able to negotiate placement, choose to accept or deny their original placement, self-assess their proficiency level as deciding to choose a writing course, plan on their placement, question about placement, and finally make decisions about a writing course they wanted to take. In the context of this study, conditions for agency include the freedom to choose writing courses and information about placement that is distributed by the following sources: advisors' recommendations, other students' past experience in taking first-year composition, the new student orientation, and other sources that provide placement related information such as an online freshman orientation and a major map. Other findings suggested that the academic advisor participants did not provide the multilingual students with complete placement information; and this affected the way the multilingual students chose which section of first-year composition to enroll in. Meanwhile, there was no formal communication about placement options and placement procedures between the Writing Programs and writing teachers. Building on these findings, I argue for improving conditions for agency by providing placement options, making placement information more readily available, and communicating placement information and options with academic advisors, writing teachers, and multilingual students.
ContributorsSaenkhum, Tanita, 1976- (Author) / Matsuda, Paul Kei (Thesis advisor) / Rose, Shirley (Committee member) / James, Mark (Committee member) / Arizona State University (Publisher)
Created2012
Description
Group III-nitride semiconductors have wide application in optoelectronic devices. Spontaneous and piezoelectric polarization effects have been found to be critical for electric and optical properties of group III-nitrides. In this dissertation, firstly, the crystal orientation dependence of the polarization is calculated and in-plane polarization is revealed. The in-plane polarization is sensitive to the lateral characteristic dimension determined by the microstructure. Specific semi-polar plane growth is suggested for reducing quantum-confined Stark effect. The macroscopic electrostatic field from the polarization discontinuity in the heterostructures is discussed, b ased on that, the band diagram of InGaN/GaN quantum well/barrier and AlGaN/GaN heterojunction is obtained from the self-consistent solution of Schrodinger and Poisson equations. New device design such as triangular quantum well with the quenched polarization field is proposed. Electron holography in the transmission electron microscopy is used to examine the electrostatic potential under polarization effects. The measured potential energy profiles of heterostructure are compared with the band simulation, and evidences of two-dimensional hole gas (2DHG) in a wurtzite AlGaN/ AlN/ GaN superlattice, as well as quasi two-dimensional electron gas (2DEG) in a zinc-blende AlGaN/GaN are found. The large polarization discontinuity of AlN/GaN is the main source of the 2DHG of wurtzite nitrides, while the impurity introduced during the growth of AlGaN layer provides the donor states that to a great extent balance the free electrons in zinc-blende nitrides. It is also found that the quasi-2DEG concentration in zinc-blende AlGaN/GaN is about one order of magnitude lower than the wurtzite AlGaN/GaN, due to the absence of polarization. Finally, the InAlN/GaN lattice-matched epitaxy, which ideally has a zero piezoelectric polarization and strong spontaneous polarization, is experimentally studied. The breakdown in compositional homogeneity is triggered by threading dislocations with a screw component propagating from the GaN underlayer, which tend to open up into V-grooves at a certain thickness of the InxAl1-xN layer. The V-grooves coalesce at 200 nm and are filled with material that exhibits a significant drop in indium content and a broad luminescence peak. The structural breakdown is due to heterogeneous nucleation and growth at the facets of the V-grooves.
ContributorsWei, Qiyuan (Author) / Ponce, Fernando A. (Thesis advisor) / Tsen, Kong-Thon (Committee member) / Shumway, John (Committee member) / Menéndez, Jose (Committee member) / Smith, David (Committee member) / Arizona State University (Publisher)
Created2012
Description
Increasing numbers of courses are offered online and increasing numbers of students are pursuing post-secondary studies. At broad-access institutions, such as land grant universities and community colleges, this presents a particular concern around student persistence--that is, the number of students who complete diploma, certificate, or degree requirements from an institution. Such increased access and increased enrollment also present unique challenges to first-year writing instructors, who are often the first professionals with whom first-year students are in contact. Here I explore the many reasons why student persistence should interest first-year writing instructors, in particular, those who are teaching online. Student persistence has important civic, economic, ethical, institutional, and disciplinary implications that first-year instructors cannot ignore. I propose a persistence-based pedagogy that involves six essential elements: designing learner-centered online writing courses, demonstrating mattering by valuing student writing, fostering self-efficacy by making assignments relevant, fostering student connections through collaboration and community, engaging virtual learners by fostering a sense of place and presence, and recognizing the challenges and minimizing the risks of teaching online. Such an undertaking is necessarily transdisciplinary and draws on scholarship in rhetoric and composition, instructional design, educational psychology, applied linguistics, and higher education administration. It connects pedagogical principles advanced nearly fifty years ago with digital pedagogies that are in their infancy and attempts to balance the social epistemic nature of writing instruction with the real-world demands of diverse student populations, increasing course sizes, and ever-changing technologies. Perhaps most importantly, this dissertation focuses on strategies that online writing instructors can adopt regardless of their theoretical leanings, academic training, or institutional requirements. While persistence-based instruction does not change the purpose or outcomes of first-year composition and does not replace proper placement measures or address early-term drop rates, it does provide a framework for facilitating online courses that is rooted in rhetorical theory and composition pedagogy and promotes informed teaching and lifelong learning.
ContributorsBergin, Jeffrey R (Author) / Roen, Duane (Thesis advisor) / Miller, Keith (Committee member) / James, Mark (Committee member) / Arizona State University (Publisher)
Created2012