Matching Items (122)
Description
Solid-state lithium-ion batteries are a major area of research due to their increased safety characteristics over conventional liquid electrolyte batteries. Lithium lanthanum zirconate (LLZO) is a promising garnet-type ceramic for use as a solid-state electrolyte due to its high ionic conductivity. The material exists in two dierent phases, one that is cubic in structure and one that is tetragonal. One potential synthesis method that results in LLZO in the more useful, cubic phase, is electrospinning, where a mat of nanowires is spun and then calcined into LLZO. A phase containing lanthanum zirconate (LZO) and amorphous lithium occursas an intermediate during the calcination process. LZO has been shown to be a sintering aid for LLZO, allowing for lower sintering temperatures. Here it is shown the eects of internal LZO on the sintered pellets. This is done by varying the 700C calcination time to transform diering amounts of LZO and LLZO in electrospun nanowires, and then using the same sintering parameters for each sample. X-ray diraction was used to get structural and compositional analysis of both the calcined powders and sintered pellets. Pellets formed from wires calcined at 1 hour or longer contained only LLZO even if the calcined powder had only undergone the rst phase transformation. The relative density of the pellet with no initial LLZO of 61.0% was higher than that of the pellet with no LZO, which had a relative density of 57.7%. This allows for the same, or slightly higher, quality material to be synthesized with a shorter amount of processing time.
ContributorsLondon, Nathan Harry (Author) / Chan, Candace (Thesis director) / Tongay, Sefaattin (Committee member) / Department of Physics (Contributor) / Materials Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Horizon is a young adult dystopian fiction piece that addresses issues of gender and LGBTQIA+ identity. In the story, the world has been divided into two separate societies: earth, inhabited by females, and a platform in the sky, inhabited by males. This physical division is the result of a war between the two groups. Ever since this war, there has been limited communication between the two societies, and the members of each society have animosity for those who are of a different sex or gender. The plot follows two main characters, Andrea and Susumu, as they come to understand the corruption of their societies and attempt to cross the gender divide. They are joined on their journey by other characters of varied gender and LGBTQIA+ identities, each of them unable to fit into their society's parameters of appropriate gendered behavior. This creative project looks critically at the ways in which members of different genders can become alienated from each other through societal pressure. It also analyzes how LGBTQIA+ identity may factor into the gendering of an individual, explores how people can be ostracized because of their identity, and critiques the gender binary. The second component of this creative project is a detailed reflection on the creative writing process. It outlines the steps of creating Horizon, from brainstorming through writing and editing. An explanation of the purpose the project and a discussion of writing challenges and future goals is included. The reflection also puts Horizon in context with other LGBTQIA+ media and dystopian novels and explains some of the most crucial decisions that were made in the creation of this story.
ContributorsPerry, Samantha Lynn (Author) / Himberg, Julia (Thesis director) / Dove-Viebahn, Aviva (Committee member) / Hugh Downs School of Human Communication (Contributor) / College of Public Service and Community Solutions (Contributor) / Department of English (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Arizona and Florida are unique venues are they are the only two locations in the world to host the preseason leagues known as Spring Training for all thirty Major League Baseball teams. With fan bases willing to travel and spend disposable income to follow their favorite teams and/or escape the cold spells of their home state, the sports and tourism industries in Arizona and Florida have been able to captivate a status as top spring destinations. This study takes a focus on the economic impact that Spring Training in March has on the state of Arizona; specifically the Phoenix Metropolitan area. Consumer research is presented and a SWOT analysis is generated to further assess the condition of the Cactus League and Arizona as a host state. An economic impact study driven by the Strengths, Weaknesses, Opportunities & Threats (SWOT) analysis method is the primary focuses of research due to the sum and quality of usable data that can be organized using the SWOT structure. The scope of this research aims to support the argument that Spring Training impacts the host city in which it resides in. In conjunction with the SWOT analysis, third parties will be able to get a sense of the overall effectiveness and impact of Cactus League Spring Training in the Valley of the Sun. Integration of findings from a Tampa Bay sight visit will also be assessed to determine the health of the competition. This study will take an interdisciplinary approach as it views the topics at hand from the lenses of the consumer, baseball professional, and investor.
ContributorsOlden, Kyle (Co-author) / Farmer, James (Co-author) / Eaton, John (Thesis director) / Mokwa, Michael (Committee member) / T. Denny Sanford School of Social and Family Dynamics (Contributor) / College of Public Service and Community Solutions (Contributor) / Department of Information Systems (Contributor) / Department of Economics (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
This study investigates how the patient-provider relationship between lesbian, gay, and bisexual women and their healthcare providers influences their access to, utilization of, and experiences within healthcare environments. Nineteen participants, ages 18 to 34, were recruited using convenience and snowball sampling. Interviews were conducted inquiring about their health history and their experiences within the healthcare system in the context of their sexual orientation. The data collected from these interviews was used to create an analysis of the healthcare experiences of those who identify as queer. Although the original intention of the project was to chronicle the experiences of LGB women specifically, there were four non-binary gender respondents who contributed interviews. In an effort to not privilege any orientation over another, the respondents were collectively referred to as queer, given the inclusive and an encompassing nature of the term. The general conclusion of this study is that respondents most often experienced heterosexism rather than outright homophobia when accessing healthcare. If heterosexism was present within the healthcare setting, it made respondents feel uncomfortable with their providers and less likely to inform them of their sexuality even if it was medically relevant to their health outcomes. Gender, race, and,socioeconomic differences also had an effect on the patient-provider relationship. Non-binary respondents acknowledged the need for inclusion of more gender options outside of male or female on the reporting forms often seen in medical offices. By doing so, medical professionals are acknowledging their awareness and knowledge of people outside of the binary gender system, thus improving the experience of these patients. While race and socioeconomic status were less relevant to the context of this study, it was found that these factors have an affect on the patient-provider relationship. There are many suggestions for providers to improve the experiences of queer patients within the healthcare setting. This includes nonverbal indications of acknowledgement and acceptance, such as signs in the office that indicate it to be a queer friendly space. This will help in eliminating the fear and miscommunication that can often happen when a queer patient sees a practitioner for the first time. In addition, better education on medically relevant topics to queer patients, is necessary in order to eliminate disparities in health outcomes. This is particularly evident in trans health, where specialized education is necessary in order to decrease poor health outcomes in trans patients. Future directions of this study necessitate a closer look on how race and socioeconomic status have an effect on a queer patient's relationship with their provider.
ContributorsRajan, Sindhu (Co-author) / Bradley, Arianna (Co-author) / Larson, Michelle (Co-author) / Alvarado, Aimee (Co-author) / Ingram-Waters, Mary (Thesis director) / Arnold, Michelle (Committee member) / School of Molecular Sciences (Contributor) / School of Social Transformation (Contributor) / T. Denny Sanford School of Social and Family Dynamics (Contributor) / College of Public Service and Community Solutions (Contributor) / School of Human Evolution and Social Change (Contributor) / School of Historical, Philosophical and Religious Studies (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Netflix has positioned itself at the forefront of the future of television with its original programming, which has been rolled out in greater and more frequent amounts just in the last couple of years. The streaming service has already experimented with creativity in ways most other shows and creators haven't, playing with the pacing of overall seasons as well as the length of episodes. So, too, Netflix has been at the forefront of increasing visibility for minority characters on television. Many of its shows incorporate racially diverse casts and depict lots of LGBTQ characters, a refreshingly realistic view of the world that many of its viewers have always lived in but haven't yet witnessed on television. Visibility and representation are critical concepts for analyzing minority characters on television. It is important for diverse characters to be seen, first and foremost, but also to be seen in positive or at least realistic lights. Care must be taken to avoid fulfilling stereotypes or tropes, and attention must be paid to what has happened to other characters who have come before. However, many of Netflix's portrayals of these characters, particularly bisexual characters, leave much to be desired. With the original dramas House of Cards, Hemlock Grove, Orange is the New Black, and Sense8, all of which include characters who identify as or behave bisexually, Netflix has been reluctant to use the specific word bisexual to describe characters, and many don't even identify their sexuality with a synonym for the term. Many of the bisexual characters that I identified died or were killed on the shows, and nearly all of them fulfilled stereotypes or tropes in some way. There were multiple scenes of threesomes or other distinctly kinky sexual encounters, which served to exoticize bisexuality and distance it from the more normatively viewed identities of heterosexuality and homosexuality. Ultimately, while Netflix's original programming has offered increased visibility to bisexual characters, it has yet to reflect the real community it seeks to portray. In particular, Netflix's refusal to label characters as bisexual is frustrating and limiting. It can be argued that this is a progressive move toward more ideas of sexual fluidity and a post-modern lack of sexual labels, but there are not enough depictions of identified bisexual characters on television yet for this to make sense. Until bisexual characters and their identities are not invisibilized or stigmatized, more work has to be done to ensure that bisexual people are represented fairly and accurately on television and in all media.
ContributorsKoerth, Kimberly Marie (Author) / Himberg, Julia (Thesis director) / Sturges, Robert (Committee member) / Department of English (Contributor) / College of Public Service and Community Solutions (Contributor) / Walter Cronkite School of Journalism and Mass Communication (Contributor) / School of Social Transformation (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
In the Rare-earth-Tri-telluride family, (RTe3s) [R=La, Ce, Nd, Sm, Gd, Tb, Dy, Er, Ho, Tm] the emergence of Charge Density Waves, (CDW) has been under investigation for a long time due to broadly tunable properties by either chemical substitution or pressure application. These quasi 2D Layered materials RTe3s undergo Fermi Surface Nesting leading to CDW instability. CDWs are electronic instabilities found in low-dimensional materials with highly anisotropic electronic structures. Since the CDW is predominantly driven by Fermi-surface (FS) nesting, it is especially sensitive to pressure-induced changes in the electronic structure. The FS of RTe3s is a function of p-orbitals of Tellurium atoms, which are arranged in two adjacent planes in the crystal structure. Although the FS and electronic structure possess a nearly four-fold symmetry, RTe3s form an incommensurate CDW.This dissertation is structured as follows: Chapter 1 includes basic ideas of Quantum materials, followed by an introduction to CDW and RTe3s. In Chapter 2, there are fundamentals of crystal growth by Chemical Vapor Transport, including various precursors, transport agent, temperature gradient, and rate of the reaction. After the growth, the crystals were confirmed for lattice vibrations by Raman, for composition by Energy Dispersive Spectroscopy; crystal structure and orientation were confirmed by X-ray Diffraction; magnetic ordering was established by Vibrating sample measurement. Detailed CDW study was done on various RTe3s by Raman spectroscopy. The basic mechanism and instrumentations used in these characterizations are explained in Chapter 3. Chapter 4 includes experimental data for crystal growth and results of these characterizations for Parent RTe3s. Chapter 5 includes fundamental insights on Cationic alloying of RTe3s, along with one alloy system’s crystal growth and characterization. This work tries to explain the behavior of CDW by a Temperature-dependent Raman study of RTe3s established the CDW transition temperature accompanied by Phonon softening; Angle-resolved Raman data confirming the nearly four-fold symmetry; thickness-dependent Raman spectroscopy resulting in the conclusion that as thickness decreases CDW transition temperature increases. Also, CDW transition is analyzed as a function of alloying.
ContributorsAttarde, Yashika (Author) / Tongay, Sefaattin (Thesis advisor) / Botana, Antia (Committee member) / Alford, Terry (Committee member) / Arizona State University (Publisher)
Created2021
Description
In the last few decades, extensive research efforts have been focused on scaling down silicon-based complementary metal-oxide semiconductor (CMOS) technology to enable the continuation of Moore’s law. State-of-art CMOS includes fully depleted silicon-on-insulator (FDSOI) field-effect-transistors (FETs) with ultra-thin silicon channels (6 nm), as well as other three-dimensional (3D) device architectures like Fin-FETs, nanosheet FETs, etc. Significant research efforts have characterized these technologies towards various applications, and at different conditions including a wide range of temperatures from room temperature (300 K) down to cryogenic temperatures. Theoretical efforts have studied ultrascaled devices using Landauer theory to further understand their transport properties and predict their performance in the quasi-ballistic regime.Further scaling of CMOS devices requires the introduction of new semiconducting channel materials, as now established by the research community. Here, two-dimensional (2D) semiconductors have emerged as a promising candidate to replace silicon for next-generation ultrascaled CMOS devices. These emerging 2D semiconductors also have applications beyond CMOS, for example in novel memory, neuromorphic, and spintronic devices. Graphene is a promising candidate for spintronic devices due to its outstanding spin transport properties as evidenced by numerous studies in non-local lateral spin valve (LSV) geometries. The essential components of graphene-based LSV, such as graphene FETs, metal-graphene contacts, and tunneling barriers, were individually investigated as part of this doctoral dissertation.
In this work, several contributions were made to these CMOS and beyond CMOS technologies. This includes comprehensive characterization and modeling of FDSOI nanoscale FETs from room temperature down to cryogenic temperatures. Using Landauer theory for nanoscale transistors, FDSOI devices were analyzed and modeled under quasi-ballistic operation. This was extended towards a virtual-source modeling approach that accounts for temperature-dependent quasi-ballistic transport and back-gate biasing effects. Additionally, graphene devices with ultrathin high-k gate dielectrics were investigated towards FETs, non-volatile memory, and spintronic devices. New contributions were made relating to charge trapping effects and their impact on graphene device electrostatics (Dirac voltage shifts) and transport properties (impact on mobility and conductivity). This work also studied contact resistance and tunneling effects using transfer length method (TLM) graphene FET structures and magnetic tunneling junction (MTJ) towards graphene-based LSV.
ContributorsZhou, Guantong (Author) / Sanchez Esqueda, Ivan (Thesis advisor) / Vasileska, Dragica (Committee member) / Tongay, Sefaattin (Committee member) / Thornton, Trevor (Committee member) / Arizona State University (Publisher)
Created2023
Description
The research of alternative materials and new device architectures to exceed the limits of conventional silicon-based devices has been sparked by the persistent pursuit of semiconductor technology scaling. The development of tungsten diselenide (WSe2) and molybdenum disulfide (MoS2), well-known member of the transition metal dichalcogenide (TMD) family, has made great strides towards ultrascaled two-dimensional (2D) field-effect-transistors (FETs). The scaling issues facing silicon-based complementary metal-oxide-semiconductor (CMOS) technologies can be solved by 2D FETs, which show extraordinary potential.This dissertation provides a comprehensive experimental analysis relating to improvements in p-type metal-oxide-semiconductor (PMOS) FETs with few-layer WSe2 and high-κ metal gate (HKMG) stacks. Compared to this works improved methods, standard metallization (more damaging to underlying channel) results in significant Fermi-level pinning, although Schottky barrier heights remain small (< 100 meV) when using high work function metals. Temperature-dependent analysis reveals a dominant contribution to contact resistance from the damaged channel access region. Thus, through less damaging metallization methods combined with strongly scaled HKMG stacks significant improvements were achieved in contact resistance and PMOS FET overall performance. A clean contact/channel interface was achieved through high-vacuum evaporation and temperature-controlled stepped deposition. Theoretical analysis using a Landauer transport adapted to WSe2 Schottky barrier FETs (SB-FETs) elucidates the prospects of nanoscale 2D PMOS FETs indicating high-performance towards the ultimate CMOS scaling limit.
Next, this dissertation discusses how device electrical characteristics are affected by scaling of equivalent oxide thickness (EOT) and by adopting double-gate FET architectures, as well as how this might support CMOS scaling. An improved gate control over the channel is made possible by scaling EOT, improving on-off current ratios, carrier mobility, and subthreshold swing. This study also elucidates the impact of EOT scaling on FET gate hysteresis attributed to charge-trapping effects in high-κ-dielectrics prepared by atomic layer deposition (ALD). These developments in 2D FETs offer a compelling alternative to conventional silicon-based devices and a path for continued transistor scaling. This research contributes to ongoing efforts in 2D materials for future semiconductor technologies. Finally, this work introduces devices based on emerging Janus TMDs and bismuth oxyselenide (Bi2O2Se) layered semiconductors.
ContributorsPatoary, Md Naim Hossain (Author) / Sanchez Esqueda, Ivan (Thesis advisor) / Tongay, Sefaattin (Committee member) / Vasileska, Dragica (Committee member) / Goodnick, Stephen (Committee member) / Arizona State University (Publisher)
Created2023
Description
Doping is the cornerstone of Semiconductor technology, enabling the functionalities of modern digital electronics. Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have tunable direct bandgaps, strong many-body interactions, and promising applications in future quantum information sciences, optoelectronic, spintronic, and valleytronic devices. However, their wafer-scale synthesis and precisely controllable doping are challenging. Moreover, there is no fixed framework to identify the doping concentration, which impedes their process integration for future commercialization. This work utilizes the Neutron Transmutation Doping technique to control the doping uniformly and precisely in TMDCs. Rhenium and Tin dopants are introduced in Tungsten- and Indium-based Chalcogenides, respectively. Fine-tuning over 0.001% doping level is achieved. Precise analytical techniques such as Gamma spectroscopy and Secondary Ion Mass Spectrometry are used to quantify ultra-low doping levels ranging from 0.005-0.01% with minimal error. Dopants in 2D TMDCs often exhibit a broad stokes-shifted emission, with high linewidths, due to extrinsic effects such as substrate disorder and surface adsorbates. A well-defined bound exciton emission induced by Rhenium dopants in monolayer WSe2 and WS2 at liquid nitrogen temperatures is reported along with specific annealing regimes to minimize the defects induced in the Neutron Transmutation process. This work demonstrates a framework for Neutron Doping in 2D materials, which can be a scalable process for controlling doping and doping-induced effects in 2D materials.
ContributorsLakhavade, Sushant Sambhaji (Author) / Tongay, Sefaattin (Thesis advisor) / Alford, Terry (Committee member) / Yang, Sui (Committee member) / Arizona State University (Publisher)
Created2023
Description
In the past decade, 2D materials especially transition metal dichalcogenides (TMDc), have been studied extensively for their remarkable optical and electrical properties arising from their reduced dimensionality. A new class of materials developed based on 2D TMDc that has gained great interest in recent years is Janus crystals. In contrast to TMDc, Janus monolayer consists of two different chalcogen atomic layers between which the transition metal layer is sandwiched. This structural asymmetry causes strain buildup or a vertically oriented electric field to form within the monolayer. The presence of strain brings questions about the materials' synthesis approach, particularly when strain begins to accumulate and whether it causes defects within monolayers.The initial research demonstrated that Janus materials could be synthesized at high temperatures inside a chemical vapor deposition (CVD) furnace. Recently, a new method (selective epitaxy atomic replacement - SEAR) for plasma-based room temperature Janus crystal synthesis was proposed. In this method etching and replacing top layer chalcogen atoms of the TMDc monolayer happens with reactive hydrogen and sulfur radicals. Based on Raman and photoluminescence studies, the SEAR method produces high-quality Janus materials. Another method used to create Janus materials was the pulsed laser deposition (PLD) technique, which utilizes the interaction of sulfur/selenium plume with monolayer to replace the top chalcogen atomic layer in a single step.
The goal of this analysis is to characterize microscale defects that appear in 2D Janus materials after they are synthesized using SEAR and PLD techniques. Various microscopic techniques were used for this purpose, as well as to understand the
mechanism of defect formation. The main mechanism of defect formation was proposed to be strain release phenomena. Furthermore, different chalcogen atom positions within the monolayer result in different types of defects, such as the appearance of cracks or wrinkles across monolayers. In addition to investigating sample topography, Kelvin probe force microscopy (KPFM) was used to examine its electrical properties to see if the formation of defects impacts work function. Further study directions have been suggested for identifying and characterizing defects and their formation mechanism in the Janus crystals to understand their fundamental properties.
ContributorsSinha, Shantanu (Author) / Tongay, Sefaattin (Thesis advisor) / Alford, Terry (Committee member) / Yang, Sui (Committee member) / Arizona State University (Publisher)
Created2022