Now showing items 12154-12173 of 19641

    • naat ?a hemkank'la maqlaqsyalank: Toward a Tribal Methodology in Language Research

      Zepeda, Ofelia; Dupris, Joseph James; Warner, Natasha; Fountain, Amy; Silva, Wilson; Zhang, Qing (The University of Arizona., 2020)
      The historical diminishment and contemporary revitalization of indigenous languages are underwritten by universalizing discourses set into motion three thousand years ago in the Antiquarian Mediterranean. Tribes, which are immanent polities with inherent rights to govern and protect their lands and peoples, have historically been deemed to be a barrier to empire-building and colonization. The salient colonial response to tribal polity has been forced detribalization, or the disaggregation of indigenous polities into governable state subjects. The factors underwriting indigenous status and identity are not interchangeable, though they overlap significantly. This research disambiguates indigenous race and nation under a “tribal” label. Ultimately, this dissertation offers a tribal methodology for language research that recognizes and respects indigenous polities. The research project aligns multiyear collaboration by the Klamath Tribes and American Indian Language Development Institute with the Klamath Tribes’ long-term commitment to restore the languages of the Klamath, Modoc, and Yahooskin Paiute peoples. Tribal language research conducted with tribal community members informed and articulated principles for future tribally-based language research. Further, the research validated the portability of Where Are Your Keys? Techniques and assessed them as valuable and important for enhancing tribal community members’ language immersion experiences. The first chapter gives a brief political history of western linguistic inquiry, demonstrating language’s primary role in coloniality. Coloniality relies on language as a vital supplement to visions of empire in indigenous homelands. Language research, regimentation of linguistic elements, and evaluation of language speakers through the Middle Ages proved an effective means for usurpation of lands, minds and bodies from existing polities. Those practices proved foundational to praxes of empire in the Americas. Colonizers sought to consume and appropriate indigenous knowledges in synergy with state-sponsored violence and alienation of non-IndoEuropean language users in conjunction with existing racial, religious and class orders. At the end of the chapter, the purpose of tying language to political or racial status and concerns about ambiguations of identity and polity under “indigenous” labels in language science paradigms are examined. The second chapter argues for limiting indigenous labels to tribes and similar transnational political entities underlying colonial nations. This scholarly reframing of polity and identity in relation to land claims enables critical examination of political differences between citizens of indigenous polity and persons of Indigene heritage in the formation of the United States and Mexico. The territorialization of the states of Oregon and California importantly drew on indigenized notions of race, religion and class to privilege European-Indigene metissage, initiate genocide and decolonial revolution, and attempt to preclude Black-tribal association west of the continental divide. The third chapter examines the interplay of federal Indian policy, language research and race science in political actions aimed at detribalization in the United States. Language research was an important aspect of 19th century federal Indian policy. That research incorporated ideas about the relationship between race, citizenship and tribes in the mid-20th century, eventually motivating the federal termination policy, or the legislative erasure of tribes de jure. From Termination through Restoration and the present, the Klamath Tribes have mobilized transcommunal activities to assert nationhood and mitigate state subjugation in the face of socioeconomic siege and formal legislative erasure. The chapter provides focused attention to maqlaqsyals and its diminished use in response to modern racism and Klamath termination, incorporating community thoughts and efforts pertaining to language revitalization. The fourth chapter outlines a research paradigm that centers indigenous polities and suggests the methodological tenets of a tribal paradigm can mobilize language research in sustenance of the political integrity of indigenous nations. The components of a paradigmatic approach to research are discussed, emphasizing cooperative political action through tribal consultation and formal cooperative agreements. Next, insights and experiences are recounted in operationalizing a preliminary tribal research methodology, and methodological reframing based on pilot research carried out in 2016 and 2017 with Klamath tribal community members. Methodological insights gained from the 2018 Summer Language Intensive internship with Where Are Your Keys? (WAYK) and Aleutian Pribilof Island Association are presented with regard to their contribution to a prototype of tribal language research. The chapter concludes with information underwriting the present research project. The fifth chapter describes a study that was carried out with Klamath Tribes community members from December 2018 to August 2019 on the Klamath Reservation in Chiloquin, Oregon. It provides a detailed explanation of research design, methods, and interpretation of outcomes operationalizing the prototype research methodology described in chapter four. The research was carried out to better understand which members of the language community would be interested in participating in tribal language research and what their attitudes are towards maqlaqsyals language and restoration efforts, and to formally test the portability of Where Are Your Keys? Techniques to pedagogical components of tribal language research. The findings of the research are presented, with insights to better understand tribally-centered research. It is hoped that this project leaves the Klamath Tribes well-positioned to facilitate further language research reflective of tribal community guidance. Concluding thoughts are given in the final chapter.
    • Nabla spaces, the theory of the locally convex topologies (2-norms, etc.) which arise from the mensuration of triangles.

      Lomont, John; Griesan, Raymond William.; Suchanek, Amy; Wright, A. Larry; Benson, Clark; Laetsch, Theodore (The University of Arizona., 1988)
      Metric topologies can be viewed as one-dimensional measures. This dissertation is a topological study of two-dimensional measures. Attention is focused on locally convex vector topologies on infinite dimensional real spaces. A nabla (referred to in the literature as a 2-norm) is the analogue of a norm which assigns areas to the parallelograms. Nablas are defined for the classical normed spaces and techniques are developed for defining nablas on arbitrary spaces. The work here brings out a strong connection with tensor and wedge products. Aside from the normable theory, it is shown that nabla topologies need not be metrizable or Mackey. A class of concretely given non-Mackey nablas on the ℓp and Lp spaces is introduced and extensively analyzed. Among other results it is found that the topological dual of ℓ₁ with respect to these nabla topologies is C₀, one of the spaces infamous for having no normed predual. Also, a connection is made with the theory of two-norm convergence (not to be confused with 2-norms). In addition to the hard analysis on the classical spaces, a duality framework from which to study the softer aspects is introduced. This theory is developed in analogy with polar duality. The ideas corresponding to barrelledness, quasi-barrelledness, equicontinuity and so on are developed. This dissertation concludes with a discussion of angles in arbitrary normed spaces and a list of open questions.
    • Nacionalismo en la obra literaria de José Antonio Ramos

      McElroy, Onyria Herrera (The University of Arizona., 1981)
    • The NAFTA Spectacle: Envisioning Borders, Migrants and the U.S.-Mexico Neoliberal Relation in Visual Culture

      Gutierrez, Laura; Wilson, Jamie; Briggs, Laura; Duran, Javier (The University of Arizona., 2013)
      This dissertation brings critical visual culture studies to bear on mediatized representations of borders and migration in U.S. and Mexican contexts. In particular, this study examines how the human price of the North American Free Trade Agreement is represented and/or disappeared in popular visual culture. I deploy an eclectic methodological framework whose elements emerge from the confluence of Border Studies, Visual Cultural Studies and theorizations of neoliberalism in order to study how television, print media and narrative and documentary film serve as sites for both the visual constitution and critical contestation of neoliberal agendas. For example, I view objects of visual culture such as the Border Wars television program, Backpacker magazine and films Sin dejar huella and AbUSed: The Postville Raid as powerful and privileged sites for the analysis of political discourses.
    • NAFTA, globalization, and higher education departments of business administration: Case studies from northwestern Mexico

      Rhoades, Gary; Acosta Fuller, Jose Blas, 1956- (The University of Arizona., 1998)
      One of the major developments marking the global economy is the emergence of regional trading blocks. This study takes into account this trend and it addresses a question about business administration departments in Mexican universities: To what extent and in what ways do they reflect the influence of NAFTA and globalization on their curriculum, structure, and mission? Conceptually, the study draws on dependency theory and institutional theory. Dependency theory was useful for understanding globalization in Mexican business administration as affected through business and linkages to the U.S. Institutional theory was useful in understanding and explaining specific mechanisms experienced by the departments as they relate to the different professional organizations in society. This study considered four departments located in large public and private universities in Northwestern Mexico. Documents and interviews were the two principal sources of data. This investigation involved the analysis of 46 documents, and 26 interviews conducted with administrators and faculty in Business Administration programs. The analysis of data indicated that private departments hold national and international relationships that influence curriculum change while the public departments are more nationally oriented in relationships and curriculum change.
    • Naive Psychology: Preschoolers' Understanding of Intention and False Belief and Its Relationship to Mental Word

      Rosser, Rosemary; Jian, Jianhua; Rosser, Rosemary; Aleamoni, Lawrence M.; Bauman, Sheri; Wilkes, Glenda (The University of Arizona., 2006)
      In the current study, children’s understanding of false belief, intention, and their ability to distinguish the appearance of a character from its reality was investigated. Seventy-two three to five years olds were recruited from several preschools in the Silicon Valley in California. During the experiment, children were shown an animated movie in a computer and asked the false belief, intention, and appearance-reality distinction questions. Following the animated movie, children were also asked if they understand 10 mental words that depicted the human mind, such as think, want, believe, etc. The relationship between the children’s knowledge of the human mind and the mental words they understood was explored. Results of the current study revealed that children who were four and half to five performed better than children three and half to four on false belief tasks. Children’s performance on intention and appearance-reality distinction questions did not differ significantly across age. However, girls’ performance was superior to boys’ performance on intention questions. Similarly, girls’ knowledge of overall naïve psychology was also superior to that of boys. Moreover, the order of the naïve psychology concepts that children passed in current study was from intention to appearance-reality distinction and then false belief. Finally, the regression analysis of the data revealed that the mental word vocabulary children processed was closely related to naïve psychology development. More specifically, the number of total mental words that were reported by children or assessed by contextual questions was a significant predictor of naïve psychology knowledge.
    • NAME WRITING AND THE PRESCHOOL CHILD (LANGUAGE ACQUISITION, PREOPERATIONAL, CONSTRUCTION OF KNOWLEDGE, PIAGET).

      LIEBERMAN, EVELYN JACKSON.; Goodman, Yetta; Abraham, Kitty; Paul, Alice (The University of Arizona., 1985)
      This study explored the construction of written language knowledge as evidenced by the changes in forty-seven preschool children's autographs. Throughout the school year children were asked to "write your name and draw a picture of yourself." The resulting name writing samples indicated that changes in children's autographs were not idiosyncratic but identifiable transitions in a cognitive constructive process as children gradually attempted to make sense out of written language by writing their names. Transitions identified in children's autographs included: graphic actions (scribbling); random graphemes dispersed within drawing; spatial differentiation between writing and drawing; zigzag lines; zigzag lines with graphemes; linear and eventually horizontal, discrete, letterlike strings; reduced number of graphemes; increasing number of pertinent letters in and/or out of order; appropriate number of placeholders and pertinent letters; recognizable letters; and, eventually conventional signatures. As children's autographs evolved over time they provided evidence that children construct knowledge about written language much as Piaget and others have suggested young children construct logico-mathematical knowledge; not by using adult logic but by trying to make sense of and understand written language. Conventional or even recognizable autographs did not suddenly appear or result from the copying of models. Rather, autographs evolved over time as children devised strategies and followed intuitive rules while solving the problem of distinguishing writing from drawing, generating the culturally significant actions involved in writing, discovering the distinctive orthographic features of letters, and eventually controlling the orthographic conventions of name writing. In addition to providing evidence for name writing as a constructive process, this study also presented information indicating that initially, name writing is ideographic and is not based on knowledge of letter names or understanding letter/sound correspondences. Name writing was also discussed as a significant sign of young children's emerging use of symbols. The conclusion was reached that name writing, when approached as a constructive process, is an appropriate curriculum component in preschool programs and an essential ingredient in the emerging literacy of young children.
    • Named Data Networking in Local Area Networks

      Zhang, Beichuan; Shi, Junxiao; Zhang, Beichuan; Gniady, Chris; Hartman, John; Efrat, Alon (The University of Arizona., 2017)
      The Named Data Networking (NDN) is a new Internet architecture that changes the network semantic from packet delivery to content retrieval and promises benefits in areas such as content distribution, security, mobility support, and application development. While the basic NDN architecture applies to any network environment, local area networks (LANs) are of particular interest because of their prevalence on the Internet and the relatively low barrier to deployment. In this dissertation, I design NDN protocols and implement NDN software, to make NDN communication in LAN robust and efficient. My contributions include: (a) a forwarding behavior specification required on every NDN node; (b) a secure and efficient self-learning strategy for switched Ethernet, which discovers available contents via occasional flooding, so that the network can operate without manual configuration, and does not require a routing protocol or a centralized controller; (c) NDN-NIC, a network interface card that performs name-based packet filtering, to reduce CPU overhead and power consumption of the main system during broadcast communication on shared media; (d) the NDN Link Protocol (NDNLP), which allows the forwarding plane to add hop-by-hop headers, and provides a fragmentation-reassembly feature so that large NDN packets can be sent directly over Ethernet with limited MTU.
    • Naming the Dead: Identification and Ambiguity Along the U.S.-Mexico Border

      Sheridan, Thomas E.; Reineke, Robin Christine; Sheridan, Thomas E.; Nichter, Mark; Pike, Ivy; Anderson, Bruce; Braitberg, Victor (The University of Arizona., 2016)
      Since the beginning of the 21st century, the deaths of migrants have become a regular occurrence in southern Arizona where an average of 170 bodies are recovered from the desert each year. This dissertation examines the causes and effects of death and disappearance along the U.S.-Mexico border, seeking to address the contradiction present in the fact that thousands of people have died or disappeared in one of the world’s most heavily surveilled landscapes. It interrogates the ways in which the dead, the missing, and their families are simultaneously erased and exposed in a biopolitical process that has powerful implications beyond the space of the borderlands. The observations for this dissertation are drawn from nearly a decade of both ethnographic research and applied humanitarian assistance in the field of forensic human identification, primarily at the Pima County Office of the Medical Examiner, in Tucson, Arizona. Although the majority of migrant fatalities have been determined by the medical examiner to be accidental, resulting from exposure to the elements or unknown causes, a historical analysis reveals the violent nature of these deaths and disappearances, which are a structured result of U.S. border and immigration policies. From their homes to their destinations, migrants in the Americas face a particular kind of structural violence and social invisibility that is revealed when they disappear at the border. This disappearance is then made more thorough by the structured lack of access for families of the missing to services to assist them in their search. Practices of care, whether occurring within families of the missing and dead, during the desert crossing itself, or in the forensic work to identify the dead, powerfully contest the invisibility and erasure experienced by migrants in the Americas today.
    • Nano-Particle Removal from Surface of Materials Used in EUV Mask Fabrication

      Parks, Harold G; Raghavan, Srini; Pandit, Viraj Sadanand; Parks, Harold G; Raghavan, Srini; O'Hanlon, John F.; Wang Roveda, Janet (The University of Arizona., 2006)
      With device scaling, the current optical lithography technique is reaching its technological limit to print small features. Extreme Ultra-Violet (EUV) lithography has shown promise to print extremely thin lines reliably and cost-effectively. Many challenges remain before introducing EUV to large scale manufacturing. The main challenge addressed in this study is particle removal from EUV mask surfaces (CrON1, CrON2, and fused silica) and thermal oxide (SiO₂). Effective pre-clean procedures were developed for each surface. As chemical cleaning methods fail to meet SEMATECH criteria, addition of megasonic energy to EUV mask cleaning baths is seen as a promising cleaning methodology. As the requirement to print fine lines needs to be met, all materials used in EUV mask fabrication either absorb the incident EUV wavelength light or reflect it. Therefore, the masks used in the industry will be reflective instead of the conventional transmissive masks. Also, for the same reason, no protective pellicle can be used leading to all the surfaces unprotected from particle contamination. To avoid the detrimental effect of the particle contamination, a cleaning study for nano-particle removal was performed. A dark field microscope was utilized to study the removal of gold nano-particles from surfaces. The cleaning procedures utilized H₂SO₄ and NH₄OH chemistries with and without megasonic irradiation. The cleaning variables were bath concentration, temperature, and megasonic power. The contamination variables were the gold nanoparticles charge and size, from 40nm to 100nm. For 100 nm negatively charged gold nano-particles deposited on a CrON1 surface, a 1:10 H₂SO₄:DI bath at boiling temperature (101°C) without megasonics gave high particle removal efficiency (PRE) values as did a 1:10 H₂SO₄:DI bath at 35°C with 100W megasonics. Comparison of removal of poly diallyl-dimethyl ammonium chloride (PDAC) coated and uncoated gold nano-particles deposited on a CrON1 surface using dilute H₂SO₄ baths indicated that the coated, positively charged nano-particles were more difficult to remove. PRE trends for different baths indicate surface dissolution (shown to be thermodynamically favorable) as the particle removal mechanism. However, experimental etch rates indicated minimal surface etching in a 10 minute bath. Increased surface roughness indicated possible local galvanic corrosion at particle sites. Low surface etching results meet SEMATECH requirements. During the fused silica surface cleaning study, particle charge (negative) and size (100 nm) of the contamination source and cleaning bath chemistry (NH₄OH) were kept constant. Low PREs were obtained at room temperature for all NH₄OH bath concentrations; however, high PREs were obtained at an elevated temperature (78°C) without megasonics and at room temperature in more dilute chemistries with megasonic power applied. Similar PRE trends were demonstrated for thermal SiO₂ surfaces. The experimental etch rates of the thermal SiO₂ agree with published values.
    • Nano-Scale Investigation of Structural and Electrical Properties of Self-Organized Thin Films of Phthalocyanines: A Progress towards New Photovoltaic Material

      Armstrong, Neal R.; Kumaran, Niranjani; Armstrong, Neal R.; Armstrong, Neal R.; Aspinwall, Craig A.; Mash, Eugene A., Jr.; McGrath, Dominic V.; Wysocki, Vicki H. (The University of Arizona., 2008)
      Ongoing efforts to improve the efficiency of organic photovoltaic cells emphasize the significance of the architecture of molecular assemblies in thin films, at nanometer and micron length scales, to enhance both exciton diffusion and charge transport, in donor and acceptor layers. Controlled growth of molecules via self-assembly techniques presents new opportunities to develop nano-structured organic thin films for electronic devices. This thesis is focused on controlling the orientation of phthalocyanine molecular assemblies in thin films in order to demonstrate the impact of microscopic control of molecular order on electrical properties and organic solar cell device performance.The studies performed here provide insights into the self-assembling behavior, film morphology, nanoscale electrical conductivity, and photovoltaic properties of a disk-shaped peripherally substituted phthalocyanine (Pc) molecule possessing amide functional groups in the side chains. Amide functionality was integrated in the side chains of this phthalocyanine molecule with the purpose of increasing the intra-columnar interaction through formation of a hydrogen bonding network between molecules, and to guide columnar orientation in a preferred direction via specific surface-molecule interactions. It is realized that molecule-substrate interactions must dominate over molecule-molecule interactions to achieve control over the deposition of molecules in a preferred direction for organic solar cell applications. Microscopic imaging and spectroscopic studies confirm the formation of flat-lying, well ordered, layered phthalocyanine films as anticipated.The remarkable electrical conductivity of the flat-lying phthalocyanine molecules, as studied by Conducting tip Atomic Force Microscopy (C-AFM) provide the impetus for the formation of organic solar cells based on layers of these hydrogen bonding phthalocyanine molecules. The photocurrent from devices that are made with the ordered Pc molecules and disordered Pc molecules as the primary photoactive donor layer, and vacuum deposited C60 as the acceptor material, were evaluated. The results presented here demonstrate the feasibility of increasing the photogenerated current by controlling the molecular organization in the photo active layer.
    • Nanocomposites for High-Speed Optical Modulators and Plasmonic Thermal Mid-Infrared Emitters

      Peyghambarian, Nasser; Demir, Veysi; Peyghambarian, Nasser; Norwood, Robert A.; Pau, Stanley (The University of Arizona., 2015)
      Demand for high-speed optical modulators and narrow-bandwidth infrared thermal emitters for numerous applications continues to rise and new optical devices are needed to deal with massive data flows, processing powers, and fabrication costs. Conventional techniques are usually hindered by material limitations or electronic interconnects and advances in organic nanocomposite materials and their integration into photonic integrated circuits (PICs) have been acknowledged as a promising alternative to single crystal techniques. The work presented in this thesis uses plasmonic and magneto-optic effects towards the development of novel optical devices for harnessing light and generating high bandwidth signals (> 40GHz) at room and cryogenic temperatures (4.2°K). Several publications have resulted from these efforts and are listed at the end of the abstract. In our first published research we developed a narrow-bandwidth mid-infrared thermal emitter using an Ag/dielectric/Ag thin film structure arranged in hexagonal planar lattice structures. PECVD produced nanoamorphous carbon (NAC) is used as a dielectric layer. Spectrally tunable (>2 μm) and narrow bandwidth (<0.5 μm) emission peaks in the range of 4-7μm were demonstrated by decreasing the resistivity of NAC from 10¹² and 10⁹ Ω.cm with an MoSi₂ dopant and increasing the emitter lattice constant from 4 to 7 μm. This technique offers excellent flexibility for developing cost-effective mid-IR sources as compared to costly fiber and quantum cascade lasers (QCLs). Next, the effect of temperature on the Verdet constant for cobalt-ferrite polymer nanocomposites was measured for a series of temperatures ranging from 40 to 200°K with a Faraday rotation polarimeter. No visual change was observed in the films during thermal cycling, and ~4x improvement was achieved at 40°K. The results are promising and further analysis is merited at 4.2°K to assess the performance of this material for cryogenic magneto-optic modulators for supercomputers. Finally, the dielectric constant and loss tangent of MAPTMS sol-gel films were measured over a wide range of microwave frequencies. The test structures were prepared by spin-coating sol-gel films onto metallized glass substrates. The dielectric properties of the sol-gel were probed with several different sets of coplanar waveguides (CPWs) electroplated onto sol-gel films. The dielectric constant and loss-tangent of these films were determined to be ~3.1 and 3 x 10⁻³ at 35GHz. These results are very promising indicating that sol-gels are viable cladding materials for high-speed electro-optic polymer modulators (>40GHz).
    • Nanoporous glass-ceramics transparent in infrared range to be used as optical sensor-Mechanical and viscoelastic properties of the TAS (Te-As-Se) glass

      Delaizir, Gaelle; Lucas, Pierre; Lucas, Pierre; Potter, B. G.; Uhlmann, Donald R.; Zhang, Xiang-Hua; Sangleboeuf, Jean-Christophe; Bureau, Bruno (The University of Arizona., 2007)
      GeS₂-Sb₂S₃-CsCl glass-ceramics with nanoporous surfaces were synthesized and tested as optical elements. The nanoporosity is obtained through a two-step process, including controlled nucleation of CsCl nuclei in the glass matrix followed by selective etching of the nuclei with an acid solution. The porous surface is several hundred nanometers thick and results in a surface area increase of almost four orders of magnitudes. The pores size is approximately 150 nm and can be tailored by controlling the nucleation process and the etching time. It is shown that the creation of the nanoporous surface does not critically affect the optical transmission of these infrared transparent glass-ceramics. These materials can therefore be used for the design of optical elements and an ATR (Attenuated Total Reflections) plate with nanoporous surface was fabricated and tested as an optical infrared sensor. The porous element shows higher detection sensitivity in initial experiments with a coating of silane molecules. The TAS (Te₂As₃Se₅) infrared glass, used as optical sensor in many fields of applications (medicine, environment, etc), exhibits poor mechanical properties rapidly that enable it to be used. Its mechanical properties have been investigated as a function of time and environment. From a general observation, air and vacuum have dramatic effects on TAS fibers tensile strength. When ageing under static stress, they exhibit an increase of tensile strength. The structural relaxation phenomenon is hypothesized to explain these results. The coordination number, , which is a rough measure of the network rigidity, has an influence on the TAS mechanical properties. It is shown that the TAS glass exhibits photosensitive effects. This effect seems to be only a surface effect, not a volume effect in the sense that light has no influence on the kinetic of a stress relaxation experiment. Due to their low glass transition temperature, TAS fibers exhibit viscoelastic behavior at room temperature. The study of the change of radius curvature allows for the determination of constitutive laws both for the stress relaxation kinetics and the delayed elasticity process which are well described by a stretched exponential function KWW (Kolraush-Williams-Watt).
    • Nanoscale Characterization of the Electrical Properties of Oxide Electrodes at the Organic Semiconductor-Oxide Electrode Interface in Organic Solar Cells

      Armstrong, Neal R.; MacDonald, Gordon Alex; Armstrong, Neal R.; Pemberton, Jeanne E.; Saavedra, S. Scott; Monti, Oliver L.A.; Loy, Douglas A. (The University of Arizona., 2015)
      This dissertation focuses on characterizing the nanoscale and surface averaged electrical properties of transparent conducting oxide (TCO) electrodes such as indium tin oxide (ITO) and transparent metal-oxide (MO) electron selective interlayers (ESLs), such as zinc oxide (ZnO), the ability of these materials to rapidly extract photogenerated charges from organic semiconductors (OSCs) used in organic photovoltaic (OPV) cells, and evaluating their impact on the power conversion efficiency (PCE) of OPV devices. In Chapter 1, we will introduce the fundamental principles regarding the need for low cost power generation, the benefits of OPV technologies, as well as the key principles that govern the operation of OPV devices and the key innovations that have advanced this technology. In Chapter 2 of this dissertation, we demonstrate an innovative application of conductive probe atomic force microscopy (CAFM) to map the nanoscale electrical heterogeneity at the interface between an electrode, such as ITO, and an OSC such as the p-type OSC copper phthalocyanine (CuPc).(MacDonald et al. (2012) ACS Nano, 6, p. 9623) In this work we collected arrays of J-V curves, using a CAFM probe as the top contact of CuPc/ITO systems, to map the local J-V responses. By comparing J-V responses to known models for charge transport, we were able to determine if the local rate-limiting step for charge transport is through the OSC (ohmic) or the CuPc/ITO interface (nonohmic). These results strongly correlate with device PCE, as demonstrated through the controlled addition of insulating alkylphosphonic acid self-assembled monolayers (SAMs) at the ITO/CuPc interface. Subsequent chapters focus on the electrical property characterization of RF-magnetron sputtered ZnO (sp-ZnO) ESL films on ITO substrates. We have shown that the energetic alignment of ESLs and the organic semiconducting (OSC) active materials plays a critical role in determining the PCE of OPV devices and the appearance of, or lack thereof, UV light soaking sensitivity. For ZnO and fullerene interfaces, we have shown that either minimizing the oxygen partial pressure during ZnO deposition or exposure of ZnO to UV light minimizes the energetic offset at this interface and maximizes device PCE. We have used a combination of device testing, device modeling, and impedance spectroscopy to fully characterize the effects that energetic alignment has on the charge carrier transport and charge carrier distribution within the OPV device. This work can be found in Chapter 3 of this dissertation and is in preparation for publication. We have also shown that the local properties of sp-ZnO films varies as a function of the underlying ITO crystal face. We show that the local ITO crystal face determines the local nucleation and growth of the sp-ZnO films. We demonstrate that this effects the morphology, the chemical resistance to etching as well as the surface electrical properties of the sp-ZnO films. This is likely due to differences in the surface mobility of sputtered Zn and O atoms on these crystal faces during film nucleation. This affects the nanoscale distribution of electrical and chemical properties. As a result we demonstrate that the PCE, and UV sensitivity of the J-V response of OPVs using sp-ZnO ESLs are strongly impacted by the distribution of ITO crystal faces at the surface of the substrate. This work can be found in Chapter 4 of this dissertation and is in preparation for publication. These studies have contributed to a detailed understanding of the role that electrical heterogeneity, insulating barriers and energetic alignment at the MO/OSC interface play in OPV PCE.
    • Nanoscale Feature Composite: An Ensemble Surface for Enhancing Cardiovascular Implant Endothelialization

      Yoon, Jeong-Yeol; Tran, Phat L.; Slepian, Marvin J.; Riley, Mark R.; Wong, Pak K.; Wu, Xiaoyi; Yoon, Jeong-Yeol (The University of Arizona., 2011)
      The establishment and maintenance of functional endothelial cells (ECs) on an engineered surface is central to tissue engineering. As the field advances, the role of cellular mechanisms, particularly the adhesive interaction between the surface of implantable devices and biological systems, becomes more relevant in both research and clinical practice. Knowledge of these interactions can address many fundamental biological questions and would provide key design parameters for medical implants. It has been shown that EC functionality and adhesivity, crucial for the re-endothelialization process, can be induced by nanotopographical modification. Therefore, the goal of this dissertation research was to develop an ensemble surface composing of nanoscale features for the enhancement of endothelial cell adhesion. Without adhesion, subsequent vital mechanism involved in cell alignment, elongation or spreading, proliferation, migration, and ECM proteins deposition will not occur.Experiments in support of this goal were broken down into three specific aims. The first aim was to characterize and develop a size-dependent self-assembly (SDSA) nanoarray of Octamer transcription factor 4 as a demonstration to the fabrication of nanoscale feature surface. This nanoparticle array platform was a pilot studied for the second aim, which was the development of an ensemble surface of nanoscale features for endothelial cell adhesion. The third aim was to evaluate and assess EC response to the ensemble surface.Hence, we developed an ensemble surface composed of nanoscale features and adhesive elements for EC adhesivity. By using shear stress as a detachment force, we demonstrated greater cell retention by the ensemble surface than uniform controls. Adhesive interactions and cellular migration through integrin expressions, which are critical to tissue development and wound healing process was also observed. Furthermore, cell viability was relatively sustainable, as indicated by the low expression of apoptotic signaling molecules. The findings presented within this dissertation research can be applicable to blood-contact medical implants and possess the potential for future clinical translation.
    • Nanoscale Insight and Control of Structural and Electronic Properties of Organic Semiconductor / Metal Interfaces

      Monti, Oliver L.A.; Maughan, Bret; Monti, Oliver L.A.; Armstrong, Neal R.; Brown, Michael F.; Schwartz, Steven D. (The University of Arizona., 2017)
      Organic semiconductor interfaces are promising materials for use in next-generation electronic and optoelectronic devices. Current models for metal-organic interfacial electronic structure and dynamics are inadequate for strongly hybridized systems. This work aims to address this issue by identifying the factors most important for understanding chemisorbed interfaces with an eye towards tuning the interfacial properties. Here, I present the results of my research on chemisorbed interfaces formed between thin-films of phthalocyanine molecules grown on monocrystalline Cu(110). Using atomically-resolved nanoscale imaging in combination with surface-sensitive photoemission techniques, I show that single-molecule level interactions control the structural and electronic properties of the interface. I then demonstrate that surface modifications aimed at controlling interfacial interactions are an effective way to tailor the physical and electronic structure of the interface. This dissertation details a systematic investigation of the effect of molecular and surface functionalization on interfacial interactions. To understand the role of molecular structure, two types of phthalocyanine (Pc) molecules are studied: non-planar, dipolar molecules (TiOPc), and planar, non-polar molecules (H2Pc and CuPc). Multiple adsorption configurations for TiOPc lead to configuration-dependent self-assembly, Kondo screening, and electronic energy-level alignment. To understand the role of surface structure, the Cu(110) surface is textured and passivated by oxygen chemisorption prior to molecular deposition, which gives control over thin-film growth and interfacial electronic structure in H2Pc and CuPc films. Overall, the work presented here demonstrates a method for understanding interfacial electronic structure of strongly hybridized interfaces, an important first step towards developing more robust models for metal-organic interfaces, and reliable, predictive tuning of interfacial properties.
    • Nanostructure and Optoelectronic Phenomena in Germanium-Transparent Conductive Oxide (Ge:TCO) Composites

      Potter, Barrett G., Jr.; Shih, Grace Hwei-Pyng; Uhlmann, Donald R.; Lucas, Pierre; Potter, Barrett G., Jr. (The University of Arizona., 2012)
      Nanostructured composites are attracting intense interest for electronic and optoelectronic device applications, specifically as active elements in thin film photovoltaic (PV) device architectures. These systems implement fundamentally different concepts of enhancing energy conversion efficiencies compared to those seen in current commercial devices. This is possible through considerable flexibility in the manipulation of device-relevant properties through control of the interplay between the nanostructure and the optoelectronic response. In the present work, inorganic nanocomposites of semiconductor Ge embedded in transparent conductive indium tin oxide (ITO) as well as Ge in zinc oxide (ZnO) were produced by a single step RF-magnetron sputter deposition process.It is shown that, by controlling the design of the nanocomposites as well as heat treatment conditions, decreases in the physical dimensions of Ge nanophase size provided an effective tuning of the optical absorption and charge transport properties. This effect of changes in the optical properties of nanophase semiconductors with respect to size is known as the quantum confinement effect. Variation in the embedding matrix material between ITO and ZnO with corresponding characterization of optoelectronic properties exhibit notable differences in the presence and evolution of an interfacial oxide within these composites. Further studies of interfacial structures were performed using depth-profiling XPS and Raman spectroscopy, while study of the corresponding electronic effects were performed using room temperature and temperature-dependent Hall Effect. Optical absorption was noted to shift to higher onset energies upon heat treatment with a decrease in the observed Ge domain size, indicating quantum confinement effects within these systems. This contrasts to previous investigations that have involved the introduction of nanoscale Ge into insulating, amorphous oxides. Comparison of these different matrix chemistries highlights the overarching role of interfacial structures on quantum-size characteristics. The opportunity to tune the spectral response of these PV materials, via control of semiconductor phase assembly in the nanocomposite, directly impacts the potential for the use of these materials as sensitizing elements for enhanced solar cell conversion efficiency.
    • Nanostructured Si and Sn-Based Anodes for Lithium-Ion Batteries

      Aifantis, Katerina E.; Deng, Haokun; Potter, Barrett G.; Raghavan, Srini; Aifantis, Katerina E. (The University of Arizona., 2016)
      Lithium-ion batteries (LIBs) are receiving significant attention from both academia and industry as one of the most promising energy storage and conservation devices due to their high energy density and excellent safety. Graphite, the most widely used anode material, with limitations on energy density, can no longer satisfy the requirements proposed by new applications. Therefore, further improvement on the electrochemical performance of anodes has been long pursued, along with the development of new anode materials. Among potential candidates, Si and Sn based anodes are believed to be the most promising. However, the dramatic volume expansion upon Li-intercalation and contraction upon Li de-intercalation cause mechanical instability, and thus cracking of the electrodes. To overcome this issue, many strategies have been explored. Among them the most efficient strategies include introduction of a nanostructure, coupled with a buffering matrix and coating with a protective film. However, although cycling life has been significantly increased using these three strategies, the capacity retention still needs improvement, especially over extensive charge-discharge cycles. In addition, more efforts are still needed to develop new fabrication methods with low costs and high efficiency. To further improve mechanical stability of electrodes, understanding of the failure mechanisms, particularly, the failure mechanisms of Si and Sn nanomaterials is essential. Therefore, some of the key factors including materials fabrication and microstructural changes during cycling are studied in this work. Hollow Si nanospheres have proved to be have a superior electrochemical performance when applied as anode materials. However, most of fabrication methods either involve use of processing methods with low throughput, or expensive temporary templates, which severely prohibits large-scale use of hollow Si spheres. This work designed a new template-free chemical synthesis method with high throughput and simple procedures to fabricate Si hollow spheres with a nanoporous surface. The characterization results showed good crystallinity and a uniform hollow sphere structure. The substructure of pores on the surface provides pathways for electrolyte diffusion and can alleviate the damage by the volume expansion during lithiation. The success of this synthesis method provides valuable inspiration for developing industrial manufacturing method of hollow Si spheres.3D graphene is the most promising matrix that can provide the necessary mechanical support to Sn and Si nanoparticles during lithiation. 2D graphene, however, results in Sn/graphene nanocomposites with a continuous capacity fade during cycling. It is anticipated that this is due to microstructural changes of Sn, however, no studies have been performed to examine the morphology of such cycled anodes. Hence, a new Sn/2D graphene nanocomposite was fabricated via a simple chemical synthesis, in which Sn nanoparticles (20-200 nm) were attached onto the graphene surface. The content of Sn was 10 wt.% and 20 wt.%. These nanopowders were cycled against pure Li-metal and, as in previous studies, a significant capacity decrease occurred during the first several cycles. Transmission and scanning electron microscopy revealed that during long term cycling electrochemical coarsening took place, which resulted in an increased Sn particle size of over 200 nm, which could form clusters that were 1 m. Such clusters result in a poor electrochemical performance since it is difficult for complete lithiation of the Sn to occur. It is hence concluded that the inability of Sn/2D graphene anodes to retain high capacities is due to coarsening that occurs during cycling. In addition to using forms of carbon to buffer the Sn expansion, it has been proposed to alloy Sn with S, which has a low redox potential vs Li⁰/Li⁺. Therefore, another new anode proposed here is that of SnS attached to graphite. The as prepared powders had a flower-like structure of the SnS alloy. Electrochemical cycling and subsequent microstructural analysis showed that after electrochemical cycling this pattern was destroyed and replaced by Sn and SnS nanoparticles. Based on the electron microscopy and XRD analysis, it was concluded that selective leaching of S occurs during lithiation of SnS particles, which results into nano SnS and Sn particles to be distributed throughout the electrolyte or SEI layer, without being able to take part in the electrochemical reactions. This mechanism has not been noted before for SnS anodes and indicates that it may not be possible to retain the initial morphology of SnS alloy during cycling, or the ability of SnS to be active throughout long term cycling. To conclude it should be stated that the goal and novelty of this thesis was (i) the fabrication of new Si, Sn/graphene and SnS/C nanostructures that can be used as anodes in Li-ion batteries and (ii) the documentation of the mechanisms that disrupt the initial structural stability of Sn/2D graphene and SnS/C anodes and result in severe capacity loss during long term cycling (over 100 cycles). These systems are of high interest to the electrochemistry community and battery developers.
    • Nanowire Growth Process Modeling and Reliability Models for Nanodevices

      Liao, Haitao; Fathi Aghdam, Faranak; Liu, Jian; Fan, Neng; An, Lingling; Liao, Haitao (The University of Arizona., 2016)
      Nowadays, nanotechnology is becoming an inescapable part of everyday life. The big barrier in front of its rapid growth is our incapability of producing nanoscale materials in a reliable and cost-effective way. In fact, the current yield of nano-devices is very low (around 10 %), which makes fabrications of nano-devices very expensive and uncertain. To overcome this challenge, the first and most important step is to investigate how to control nano-structure synthesis variations. The main directions of reliability research in nanotechnology can be classified either from a material perspective or from a device perspective. The first direction focuses on restructuring materials and/or optimizing process conditions at the nano-level (nanomaterials). The other direction is linked to nano-devices and includes the creation of nano-electronic and electro-mechanical systems at nano-level architectures by taking into account the reliability of future products. In this dissertation, we have investigated two topics on both nano-materials and nano-devices. In the first research work, we have studied the optimization of one of the most important nanowire growth processes using statistical methods. Research on nanowire growth with patterned arrays of catalyst has shown that the wire-to-wire spacing is an important factor affecting the quality of resulting nanowires. To improve the process yield and the length uniformity of fabricated nanowires, it is important to reduce the resource competition between nanowires during the growth process. We have proposed a physical-statistical nanowire-interaction model considering the shadowing effect and shared substrate diffusion area to determine the optimal pitch that would ensure the minimum competition between nanowires. A sigmoid function is used in the model, and the least squares estimation method is used to estimate the model parameters. The estimated model is then used to determine the optimal spatial arrangement of catalyst arrays. This work is an early attempt that uses a physical-statistical modeling approach to studying selective nanowire growth for the improvement of process yield. In the second research work, the reliability of nano-dielectrics is investigated. As electronic devices get smaller, reliability issues pose new challenges due to unknown underlying physics of failure (i.e., failure mechanisms and modes). This necessitates new reliability analysis approaches related to nano-scale devices. One of the most important nano-devices is the transistor that is subject to various failure mechanisms. Dielectric breakdown is known to be the most critical one and has become a major barrier for reliable circuit design in nano-scale. Due to the need for aggressive downscaling of transistors, dielectric films are being made extremely thin, and this has led to adopting high permittivity (k) dielectrics as an alternative to widely used SiO₂ in recent years. Since most time-dependent dielectric breakdown test data on bilayer stacks show significant deviations from a Weibull trend, we have proposed two new approaches to modeling the time to breakdown of bi-layer high-k dielectrics. In the first approach, we have used a marked space-time self-exciting point process to model the defect generation rate. A simulation algorithm is used to generate defects within the dielectric space, and an optimization algorithm is employed to minimize the Kullback-Leibler divergence between the empirical distribution obtained from the real data and the one based on the simulated data to find the best parameter values and to predict the total time to failure. The novelty of the presented approach lies in using a conditional intensity for trap generation in dielectric that is a function of time, space and size of the previous defects. In addition, in the second approach, a k-out-of-n system framework is proposed to estimate the total failure time after the generation of more than one soft breakdown.
    • NAPASKIAK: AN ESKIMO VILLAGE IN WESTERN ALASKA

      Spicer, E. H.; Oswalt, Wendell H. (The University of Arizona., 1959)