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- Creators: Dean, W.P. Carey School of Business
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Description
As crystalline silicon solar cells continue to get thinner, the recombination of carriers at the surfaces of the cell plays an ever-important role in controlling the cell efficiency. One tool to minimize surface recombination is field effect passivation from the charges present in the thin films applied on the cell surfaces. The focus of this work is to understand the properties of charges present in the SiNx films and then to develop a mechanism to manipulate the polarity of charges to either negative or positive based on the end-application. Specific silicon-nitrogen dangling bonds (·Si-N), known as K center defects, are the primary charge trapping defects present in the SiNx films. A custom built corona charging tool was used to externally inject positive or negative charges in the SiNx film. Detailed Capacitance-Voltage (C-V) measurements taken on corona charged SiNx samples confirmed the presence of a net positive or negative charge density, as high as +/- 8 x 1012 cm-2, present in the SiNx film. High-energy (~ 4.9 eV) UV radiation was used to control and neutralize the charges in the SiNx films. Electron-Spin-Resonance (ESR) technique was used to detect and quantify the density of neutral K0 defects that are paramagnetically active. The density of the neutral K0 defects increased after UV treatment and decreased after high temperature annealing and charging treatments. Etch-back C-V measurements on SiNx films showed that the K centers are spread throughout the bulk of the SiNx film and not just near the SiNx-Si interface. It was also shown that the negative injected charges in the SiNx film were stable and present even after 1 year under indoor room-temperature conditions. Lastly, a stack of SiO2/SiNx dielectric layers applicable to standard commercial solar cells was developed using a low temperature (< 400 °C) PECVD process. Excellent surface passivation on FZ and CZ Si substrates for both n- and p-type samples was achieved by manipulating and controlling the charge in SiNx films.
ContributorsSharma, Vivek (Author) / Bowden, Stuart (Thesis advisor) / Schroder, Dieter (Committee member) / Honsberg, Christiana (Committee member) / Roedel, Ronald (Committee member) / Alford, Terry (Committee member) / Arizona State University (Publisher)
Created2013
Description
Photodetectors in the 1.7 to 4.0 μm range are being commercially developed on InP substrates to meet the needs of longer wavelength applications such as thermal and medical sensing. Currently, these devices utilize high indium content metamorphic Ga1-xInxAs (x > 0.53) layers to extend the wavelength range beyond the 1.7 μm achievable using lattice matched GaInAs. The large lattice mismatch required to reach the extended wavelengths results in photodetector materials that contain a large number of misfit dislocations. The low quality of these materials results in a large nonradiative Shockley Read Hall generation/recombination rate that is manifested as an undesirable large thermal noise level in these photodetectors. This work focuses on utilizing the different band structure engineering methods to design more efficient devices on InP substrates. One prospective way to improve photodetector performance at the extended wavelengths is to utilize lattice matched GaInAs/GaAsSb structures that have a type-II band alignment, where the ground state transition energy of the superlattice is smaller than the bandgap of either constituent material. Over the extended wavelength range of 2 to 3 μm this superlattice structure has an optimal period thickness of 3.4 to 5.2 nm and a wavefunction overlap of 0.8 to 0.4, respectively. In using a type-II superlattice to extend the cutoff wavelength there is a tradeoff between the wavelength reached and the electron-hole wavefunction overlap realized, and hence absorption coefficient achieved. This tradeoff and the subsequent reduction in performance can be overcome by two methods: adding bismuth to this type-II material system; applying strain on both layers in the system to attain strain-balanced condition. These allow the valance band alignment and hence the wavefunction overlap to be tuned independently of the wavelength cutoff. Adding 3% bismuth to the GaInAs constituent material, the resulting lattice matched Ga0.516In0.484As0.970Bi0.030/GaAs0.511Sb0.489superlattice realizes a 50% larger absorption coefficient. While as, similar results can be achieved with strain-balanced condition with strain limited to 1.9% on either layer. The optimal design rules derived from the different possibilities make it feasible to extract superlattice period thickness with the best absorption coefficient for any cutoff wavelength in the range.
ContributorsSharma, Ankur R (Author) / Johnson, Shane (Thesis advisor) / Goryll, Michael (Committee member) / Roedel, Ronald (Committee member) / Arizona State University (Publisher)
Created2013
Description
Increasing the conversion efficiencies of photovoltaic (PV) cells beyond the single junction theoretical limit is the driving force behind much of third generation solar cell research. Over the last half century, the experimental conversion efficiency of both single junction and tandem solar cells has plateaued as manufacturers and researchers have optimized various materials and structures. While existing materials and technologies have remarkably good conversion efficiencies, they are approaching their own limits. For example, tandem solar cells are currently well developed commercially but further improvements through increasing the number of junctions struggle with various issues related to material interfacial defects. Thus, there is a need for novel theoretical and experimental approaches leading to new third generation cell structures. Multiple exciton generation (MEG) and intermediate band (IB) solar cells have been proposed as third generation alternatives and theoretical modeling suggests they can surpass the detailed balance efficiency limits of single junction and tandem solar cells. MEG or IB solar cell has a variety of advantages enabling the use of low bandgap materials. Integrating MEG and IB with other cell types to make novel solar cells (such as MEG with tandem, IB with tandem or MEG with IB) potentially offers improvements by employing multi-physics effects in one device. This hybrid solar cell should improve the properties of conventional solar cells with a reduced number of junction, increased light-generated current and extended material selections. These multi-physics effects in hybrid solar cells can be achieved through the use of nanostructures taking advantage of the carrier confinement while using existing solar cell materials with excellent characteristics. This reduces the additional cost to develop novel materials and structures. In this dissertation, the author develops thermodynamic models for several novel types of solar cells and uses these models to optimize and compare their properties to those of existing PV cells. The results demonstrate multiple advantages from combining MEG and IB technology with existing solar cell structures.
ContributorsLee, Jongwon (Author) / Honsberg, C. (Christiana B.) (Thesis advisor) / Bowden, Stuart (Committee member) / Roedel, Ronald (Committee member) / Goodnick, Stephen (Committee member) / Schroder, Dieter (Committee member) / Arizona State University (Publisher)
Created2014
Description
This dissertation examines the ways ABC/Disney's Ugly Betty (ABC 2006-2010) manufactures diversity to create an illusion of the U.S. as a site of multiple pluralisms and equality by re-scripting the ugly duckling parable as a Latino de-racialization project and assimilation narrative. The success of the show's original version, Colombian telenovela, Yo Soy Betty, La Fea (RCN 1999-2001), escalated into an international franchise, licensed by and culturally adapted for television markets around the globe. The image the United States promotes of itself, as seen through its media products (especially Disney products) valorize and export discourses of The American Dream around the globe. In order to maintain this carefully crafted self-image, one that masks the ongoing racial oppression and colonial holdings, depictions of diversity are manufactured.
This study examines the Disney affiliated series Ugly Betty to assess how the culture and identity of Betty Suarez, its titular character, as a Mexican-American woman is manufactured. Of particular interest is how she is coded as a diverse member of U.S. workforce, and how her transformative makeover from ugly duckling can be read as an assimilation narrative from racialized ethnic invader to white American professional. Using criteria extracted from scholarship and cultural production regarding Latina identity formation, I locate Betty within what I call the spectrum of assimilation among U.S. Latinas. Because there are various ways in which one negotiates, expresses and balances the multiple cultural, racial and classed components of their self-identity, I tease out markers from existing theories to locate Betty's self-projected cultural identity within the series narrative.
Building on the evidence gathered regarding Betty's rejection of a politicized Latina identity, this project analyzes the implications of the choice of New York City as site of Betty's transformation and how the use of queer visibility and American Dream discourse inform a reading of Betty as assimilation narrative. This dissertation concludes with a brief analysis of two shows featuring Latina titular characters. Both Cristela (ABC 2014-) and Jane the Virgin (CW 2014-) are successors of Ugly Betty yet diverge in the way their portrayals of Latinidades include more nuanced and pluralistic representations.
This study examines the Disney affiliated series Ugly Betty to assess how the culture and identity of Betty Suarez, its titular character, as a Mexican-American woman is manufactured. Of particular interest is how she is coded as a diverse member of U.S. workforce, and how her transformative makeover from ugly duckling can be read as an assimilation narrative from racialized ethnic invader to white American professional. Using criteria extracted from scholarship and cultural production regarding Latina identity formation, I locate Betty within what I call the spectrum of assimilation among U.S. Latinas. Because there are various ways in which one negotiates, expresses and balances the multiple cultural, racial and classed components of their self-identity, I tease out markers from existing theories to locate Betty's self-projected cultural identity within the series narrative.
Building on the evidence gathered regarding Betty's rejection of a politicized Latina identity, this project analyzes the implications of the choice of New York City as site of Betty's transformation and how the use of queer visibility and American Dream discourse inform a reading of Betty as assimilation narrative. This dissertation concludes with a brief analysis of two shows featuring Latina titular characters. Both Cristela (ABC 2014-) and Jane the Virgin (CW 2014-) are successors of Ugly Betty yet diverge in the way their portrayals of Latinidades include more nuanced and pluralistic representations.
ContributorsMartinez, Michelle (Author) / Haggins, Bambi (Thesis advisor) / Danielson, Marivel (Committee member) / Himberg, Julia (Committee member) / Arizona State University (Publisher)
Created2015
Description
As existing solar cell technologies come closer to their theoretical efficiency, new concepts that overcome the Shockley-Queisser limit and exceed 50% efficiency need to be explored. New materials systems are often investigated to achieve this, but the use of existing solar cell materials in advanced concept approaches is compelling for multiple theoretical and practical reasons. In order to include advanced concept approaches into existing materials, nanostructures are used as they alter the physical properties of these materials. To explore advanced nanostructured concepts with existing materials such as III-V alloys, silicon and/or silicon/germanium and associated alloys, fundamental aspects of using these materials in advanced concept nanostructured solar cells must be understood. Chief among these is the determination and predication of optimum electronic band structures, including effects such as strain on the band structure, and the material's opto-electronic properties. Nanostructures have a large impact on band structure and electronic properties through quantum confinement. An additional large effect is the change in band structure due to elastic strain caused by lattice mismatch between the barrier and nanostructured (usually self-assembled QDs) materials. To develop a material model for advanced concept solar cells, the band structure is calculated for single as well as vertical array of quantum dots with the realistic effects such as strain, associated with the epitaxial growth of these materials. The results show significant effect of strain in band structure. More importantly, the band diagram of a vertical array of QDs with different spacer layer thickness show significant change in band offsets, especially for heavy and light hole valence bands when the spacer layer thickness is reduced. These results, ultimately, have significance to develop a material model for advance concept solar cells that use the QD nanostructures as absorbing medium. The band structure calculations serve as the basis for multiple other calculations. Chief among these is that the model allows the design of a practical QD advanced concept solar cell, which meets key design criteria such as a negligible valence band offset between the QD/barrier materials and close to optimum band gaps, resulting in the predication of optimum material combinations.
ContributorsDahal, Som Nath (Author) / Honsberg, Christiana (Thesis advisor) / Goodnick, Stephen (Committee member) / Roedel, Ronald (Committee member) / Ponce, Fernando (Committee member) / Arizona State University (Publisher)
Created2011
Description
Programmable Metallization Cell (PMC) is a technology platform which utilizes mass transport in solid or liquid electrolyte coupled with electrochemical (redox) reactions to form or remove nanoscale metallic electrodeposits on or in the electrolyte. The ability to redistribute metal mass and form metallic nanostructure in or on a structure in situ, via the application of a bias on laterally placed electrodes, creates a large number of promising applications. A novel PMC-based lateral microwave switch was fabricated and characterized for use in microwave systems. It has demonstrated low insertion loss, high isolation, low voltage operation, low power and low energy consumption, and excellent linearity. Due to its non-volatile nature the switch operates with fewer biases and its simple planar geometry makes possible innovative device structures which can be potentially integrated into microwave power distribution circuits. PMC technology is also used to develop lateral dendritic metal electrodes. A lateral metallic dendritic network can be grown in a solid electrolyte (GeSe) or electrodeposited on SiO2 or Si using a water-mediated method. These dendritic electrodes grown in a solid electrolyte (GeSe) can be used to lower resistances for applications like self-healing interconnects despite its relatively low light transparency; while the dendritic electrodes grown using water-mediated method can be potentially integrated into solar cell applications, like replacing conventional Ag screen-printed top electrodes as they not only reduce resistances but also are highly transparent. This research effort also laid a solid foundation for developing dendritic plasmonic structures. A PMC-based lateral dendritic plasmonic structure is a device that has metallic dendritic networks grown electrochemically on SiO2 with a thin layer of surface metal nanoparticles in liquid electrolyte. These structures increase the distribution of particle sizes by connecting pre-deposited Ag nanoparticles into fractal structures and result in three significant effects, resonance red-shift, resonance broadening and resonance enhancement, on surface plasmon resonance for light trapping simultaneously, which can potentially enhance thin film solar cells' performance at longer wavelengths.
ContributorsRen, Minghan (Author) / Kozicki, Michael (Thesis advisor) / Schroder, Dieter (Committee member) / Roedel, Ronald (Committee member) / Barnaby, Hugh (Committee member) / Arizona State University (Publisher)
Created2011
Description
This study explored the perspectives and experiences of eight women active within a particular location of the collective social media landscape. One aspect of the research centered around critiquing mainstream media diets for encouraging fat stigma and deepening the negative effects of stereotyping larger bodies. The research questions centered around transgressive media diets, specifically those that were body positive, and focused on if they could help to eradicate fat stigma and educate the masses on false stereotypes. To examine this, eight plus-size fashion bloggers and/or plus-size models were interviewed following a semi-structured format. These women, as bloggers and Instagrammers with a strong presence in the plus-size fashion industry, were both content producers as well as consumers, and their personal narratives enabled the study to better understand the complex interconnections between production and consumption, self-expression and the politics of self-representation, the cooptation of these self-representations by profit-oriented media interest, and how commodification shapes the transgressive potential of these representations. The research also found that many content creators came to transgressive media diets because they saw a lack of representation and decided that they must make that representation for themselves. The study also examined what community building meant within the porous landscape of social media platforms and the relationship between identity building and community building as social processes. Many of the participants brought up examples of fat discrimination yet many defined themselves as "confident" or "badass", thus finding ways to empower themselves despite the pressure of societal norms. Some of this empowerment came from finding a community online. Finally, these plus-size models and fashion bloggers moved through a thin ideal industry by demanding and being examples of diversity.
ContributorsValentine, Erin (Author) / Katsulis, Yasmina (Thesis advisor) / Himberg, Julia (Committee member) / McGibbney, Michelle (Committee member) / Arizona State University (Publisher)
Created2018
Description
Aside from uplifting and tearing down the mood of a young LGBTQ+ kid, journalistic media has the potential to alter the way audiences understand and react to individuals of the LGBTQ+ community. Looking at the rhetorical approaches, frameworks, and expanded narratives of news sources, this project engages with the concepts of same-sex marriage, lifestyles, bans, and children in education in order to attain an understanding of what media messages are being shared, how they are being communicated, and what the implications of such rhetoric are. Summary of the findings:
• Same-sex marriage as the win that cannot be repeated.
Infamously known as the central legal battle for the LGBTQ+ community, same-sex marriage finds itself in many political speeches, campaigns, and social commentaries. Interestingly, after being legalized through a Supreme Court decision in the United States, Same-Sex Marriage finds itself framed as the social inevitability that should not be repeated in politics or any legal shift. In other words, “the gays have won this battle, but not the war.”
• There are risks around the “LGBTQ+ lifestyle” and its careful catering to an elite minority and the mediation through bans.
The risks of the LGBTQ+ “lifestyle” date back far, with many connotations being attached to being LGBTQ+ (AIDS epidemics, etc.). In modern journalism, many media outlets portray LGBTQ+ individuals to be a tiny minority (.001% according to some) that demands the whole society to adhere to their requests. This framework portrays the LGBTQ+ community as oppressors and obsessed advocates that can never “seem to get enough” (ex: more than just marriage). The bans are framed as the neutralizing factor to the catering.
• LGBTQ+ children and topics in academic and social spaces are the extreme degree.
When it comes to LGBTQ+ issues and conversations as they revolve around children, media outlets have some of the most passionate opinions about them. Often portrayed as “the line that shouldn’t be crossed,” LGBTQ+ issues, as they find themselves in schools and other spaces, are thus portrayed as bearable to a certain degree, never completely. Claims of indoctrination are also presented prominently even when institutional efforts are to protect LGBTQ+ kids.
• Same-sex marriage as the win that cannot be repeated.
Infamously known as the central legal battle for the LGBTQ+ community, same-sex marriage finds itself in many political speeches, campaigns, and social commentaries. Interestingly, after being legalized through a Supreme Court decision in the United States, Same-Sex Marriage finds itself framed as the social inevitability that should not be repeated in politics or any legal shift. In other words, “the gays have won this battle, but not the war.”
• There are risks around the “LGBTQ+ lifestyle” and its careful catering to an elite minority and the mediation through bans.
The risks of the LGBTQ+ “lifestyle” date back far, with many connotations being attached to being LGBTQ+ (AIDS epidemics, etc.). In modern journalism, many media outlets portray LGBTQ+ individuals to be a tiny minority (.001% according to some) that demands the whole society to adhere to their requests. This framework portrays the LGBTQ+ community as oppressors and obsessed advocates that can never “seem to get enough” (ex: more than just marriage). The bans are framed as the neutralizing factor to the catering.
• LGBTQ+ children and topics in academic and social spaces are the extreme degree.
When it comes to LGBTQ+ issues and conversations as they revolve around children, media outlets have some of the most passionate opinions about them. Often portrayed as “the line that shouldn’t be crossed,” LGBTQ+ issues, as they find themselves in schools and other spaces, are thus portrayed as bearable to a certain degree, never completely. Claims of indoctrination are also presented prominently even when institutional efforts are to protect LGBTQ+ kids.
ContributorsNieto Calderon, Ramon Antonio (Author) / Himberg, Julia (Thesis director) / Sturges, Robert (Committee member) / Department of English (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
This project uses Kenneth Burke’s theory of dramatism and the pentad to analyze popular narrative films about human sex trafficking. It seeks to understand the relationship between a film’s dominant philosophy (as highlighted by utilizing Burke’s pentad), its inherently suggested solutions to trafficking, and the effect that the film has on viewers’ perception of trafficking. 20 narrative feature films about sex trafficking such as the 2008 film Taken were analyzed for this study. Three out of five of Burke’s philosophies were uncovered after analysis: idealism, mysticism, and materialism. Films that aligned with idealism were found to implicitly blame women for their own trafficking. Films that aligned with mysticism were found to rally audiences around violence and racism as opposed to women’s freedom. Films that aligned with materialism were found to be the most empathetic towards trafficked women. The conclusion of this paper is that films about sex trafficking have a high potential to be harmful to women who have exited trafficking. This paper asserts that the most valuable films about trafficking are those that are not simply based on a true story but are created by trafficking survivors themselves, such as the 2016 film Apartment 407.
ContributorsHamby, Hannah Mary (Co-author) / Raum, Brionna (Co-author) / Edson, Belle (Thesis director) / Zanin, Alaina (Committee member) / Dean, W.P. Carey School of Business (Contributor) / Hugh Downs School of Human Communication (Contributor) / School of Film, Dance and Theatre (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This document is a proposal for a research project, submitted as an Honors Thesis to Barrett, The Honors College at Arizona State University. The proposal summarizes previous findings and literature about women survivors of domestic violence who are suffering from post-traumatic stress disorder as well as outlining the design and measures of the study. At this time, the study has not been completed. However, it may be completed at a future time.
ContributorsKunst, Jessica (Author) / Hernandez Ruiz, Eugenia (Thesis director) / Belgrave, Melita (Committee member) / School of Music (Contributor) / Dean, W.P. Carey School of Business (Contributor) / School of International Letters and Cultures (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05