Matching Items (114)
Description
Semiconductor nanowires are featured by their unique one-dimensional structure which makes them promising for small scale electronic and photonic device applications. Among them, III-V material nanowires are particularly outstanding due to their good electronic properties. In bulk, these materials reveal electron mobility much higher than conventional silicon based devices, for example at room temperature, InAs field effect transistor (FET) has electron mobility of 40,000 cm2/Vs more than 10 times of Si FET. This makes such materials promising for high speed nanowire FETs. With small bandgap, such as 0.354 eV for InAs and 1.52 eV for GaAs, it does not need high voltage to turn on such devices which leads to low power consumption devices. Another feature of direct bandgap allows their applications of optoelectronic devices such as avalanche photodiodes. However, there are challenges to face up. Due to their large surface to volume ratio, nanowire devices typically are strongly affected by the surface states. Although nanowires can be grown into single crystal structure, people observe crystal defects along the wires which can significantly affect the performance of devices. In this work, FETs made of two types of III-V nanowire, GaAs and InAs, are demonstrated. These nanowires are grown by catalyst-free MOCVD growth method. Vertically nanowires are transferred onto patterned substrates for coordinate calibration. Then electrodes are defined by e-beam lithography followed by deposition of contact metals. Prior to metal deposition, however, the substrates are dipped in ammonium hydroxide solution to remove native oxide layer formed on nanowire surface. Current vs. source-drain voltage with different gate bias are measured at room temperature. GaAs nanowire FETs show photo response while InAs nanowire FETs do not show that. Surface passivation is performed on GaAs FETs by using ammonium surfide solution. The best results on current increase is observed with around 20-30 minutes chemical treatment time. Gate response measurements are performed at room temperature, from which field effect mobility as high as 1490 cm2/Vs is extracted for InAs FETs. One major contributor for this is stacking faults defect existing along nanowires. For InAs FETs, thermal excitations observed from temperature dependent results which leads us to investigate potential barriers.
ContributorsLiang, Hanshuang (Author) / Yu, Hongbin (Thesis advisor) / Ferry, David (Committee member) / Tracy, Clarence (Committee member) / Arizona State University (Publisher)
Created2011
Description
ABSTRACT An Ensemble Monte Carlo (EMC) computer code has been developed to simulate, semi-classically, spin-dependent electron transport in quasi two-dimensional (2D) III-V semiconductors. The code accounts for both three-dimensional (3D) and quasi-2D transport, utilizing either 3D or 2D scattering mechanisms, as appropriate. Phonon, alloy, interface roughness, and impurity scattering mechanisms are included, accounting for the Pauli Exclusion Principle via a rejection algorithm. The 2D carrier states are calculated via a self-consistent 1D Schrödinger-3D-Poisson solution in which the charge distribution of the 2D carriers in the quantization direction is taken as the spatial distribution of the squared envelope functions within the Hartree approximation. The wavefunctions, subband energies, and 2D scattering rates are updated periodically by solving a series of 1D Schrödinger wave equations (SWE) over the real-space domain of the device at fixed time intervals. The electrostatic potential is updated by periodically solving the 3D Poisson equation. Spin-polarized transport is modeled via a spin density-matrix formalism that accounts for D'yakanov-Perel (DP) scattering. Also, the code allows for the easy inclusion of additional scattering mechanisms and structural modifications to devices. As an application of the simulator, the current voltage characteristics of an InGaAs/InAlAs HEMT are simulated, corresponding to nanoscale III-V HEMTs currently being fabricated by Intel Corporation. The comparative effects of various scattering parameters, material properties and structural attributes are investigated and compared with experiments where reasonable agreement is obtained. The spatial evolution of spin-polarized carriers in prototypical Spin Field Effect Transistor (SpinFET) devices is then simulated. Studies of the spin coherence times in quasi-2D structures is first investigated and compared to experimental results. It is found that the simulated spin coherence times for GaAs structures are in reasonable agreement with experiment. The SpinFET structure studied is a scaled-down version of the InGaAs/InAlAs HEMT discussed in this work, in which spin-polarized carriers are injected at the source, and the coherence length is studied as a function of gate voltage via the Rashba effect.
ContributorsTierney, Brian David (Author) / Goodnick, Stephen (Thesis advisor) / Ferry, David (Committee member) / Akis, Richard (Committee member) / Saraniti, Marco (Committee member) / Vasileska, Dragica (Committee member) / Arizona State University (Publisher)
Created2011
Description
The purpose of this study is to first investigate the role of political socialization on young men and women and what motivates them to become politically active and make the ultimate decision to run for elected office. These effects include parental attitudes, exposure to political shows and news sources, participation in voluntary organizations, and overall community involvement. After understanding these direct and indirect effects of political socialization, I can attempt to explain the causes for the gender gap in political ambition \u2014 meaning that significantly more men are running for elected office compared to women.
ContributorsOsgood, Shannon Marie (Author) / Woodall, Gina (Thesis director) / Herrera, Richard (Committee member) / Barrett, The Honors College (Contributor) / College of Public Service and Community Solutions (Contributor) / School of Public Affairs (Contributor) / School of Politics and Global Studies (Contributor)
Created2015-05
Description
The Undoing Project is an ongoing educational feminist YouTube channel that serves as an introduction to feminism and feminist theory. The objective for this project is to present feminist theory and feminist ideology in an accessible and entertaining way. Through this project I sought to accomplish three goals: to challenge the negative image of feminism, bridge the gap between the language of academia and the public, and to acknowledge and unlearn ingrained prejudices. The videos focus on theory, history, legislation, current events, and pop culture. The initial project consists of ten videos addressing the feminist wave models, a brief history of the feminist movement, and discussions of concepts like hegemony, intersectionality, masculinity, femininity, and race.
ContributorsBuchholtz, Kaylee Marie (Author) / Brian, Jennifer (Thesis director) / Grzanka, Patrick (Committee member) / Brouwer, Dan (Committee member) / Barrett, The Honors College (Contributor) / College of Public Service and Community Solutions (Contributor) / School of Social Transformation (Contributor) / Department of English (Contributor)
Created2015-05
Description
Late life domestic violence is essentially synonymous with domestic violence except that it specifically refers to older adults. Although there are many similarities between younger victims and older victims, there are also distinct differences. Older victims have unique risk factors and barriers, including generational factors that stem from socialization. Unfortunately, society lacks awareness of late life domestic violence. This is reflected in current state statutes as well as the limited services provided to victims of domestic violence. For example, there are currently elder abuse or dependent abuse adult statutes in every state, yet there is no statute that specifically addresses late life domestic violence. When it comes to services, many programs are geared toward younger victims and staff is typically not trained to work with older victims, so older victims often do not get the resources they need. Yet about 1 in 10 women over the age of 50 experience abuse by an intimate partner. This is a prevalent issue needing more attention. To bring awareness and educate people on this topic, a user friendly website was created that will provide information on late life domestic violence, resources for victims, and ways to share the information with others. The website provides information that will educate people on this issue, and also promotes advocacy for older victims.
ContributorsGarcia, Brittany Nicole (Author) / Bonifas, Robin (Thesis director) / Dodge, Nancie (Committee member) / Barrett, The Honors College (Contributor) / School of Social Work (Contributor)
Created2015-05
Description
Previous research has found improvements in motor and cognitive measures following Assisted Cycle Therapy (AC) in adolescence with Down syndrome (DS). Our study investigated whether we would find improvements in older adults with DS on measures of leisure physical activity (GLTEQ) and sleep, which are early indicators of Alzheimer's disease (AD) in persons with Down syndrome. This study consisted of eight participants with Down syndrome between 31 and 51 years old that cycled for 30 minutes 3 x/week for eight weeks either at their voluntary cycling rate (VC) or approximately 35% faster with the help of a mechanical motor (AC). We predicted that, based on pilot data (Gomez, 2015), GLTEQ would either maintain or improve after AC, but would decrease after VC and would stay the same after NC. We predicted that the sleep score may improve after both VC or AC or it may improve more after VC than AC based on pilot data related to leisure activity. Our results were consistent with our prediction that GLTEQ will either maintain or improve after AC but will decrease after VC. Our results were not consistent with our prediction that sleep may improve after both VC or AC or it may improve more after VC than AC, possibly because we did not pre-screen for sleep disorders. Future research should focus on recruiting more participants and using both objective and subjective measures of sleep and physical activity to improve the efficacy of the study.
ContributorsParker, Lucas Maury (Author) / Ringenbach, Shannon (Thesis director) / Buman, Matthew (Committee member) / Holzapfel, Simon (Committee member) / School of Social and Behavioral Sciences (Contributor) / School of Nutrition and Health Promotion (Contributor) / College of Public Service and Community Solutions (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Homelessness has grown throughout America, rendering the former stereotypes about the homeless largely inaccurate and invalid. In addition to this, poverty has grown despite the country's wealth. As such, social services have become increasingly relevant to the lives of more and more Americans. Rather than serve as punishment and reminders of one's own personal failures, these services need to empower their clients. This is most likely to be done from a place of solidarity, a horizontal orientation that recognizes that economic positions are subject to change and that instead favors human rights and unity. From this review of the literature, I argue that service groups with an ethic of solidarity or a horizontal orientation honor the dignity of the clients, something that is more likely to inspire positive changes. In addition, I will use the case study of the non-hierarchical service organization Food Not Bombs to demonstrate the importance of respecting the dignity and inherent rights of the clients.
ContributorsPagan, Stephen Marcus (Author) / Keahey, Jennifer (Thesis director) / Cronin, Travis (Committee member) / School of Social and Behavioral Sciences (Contributor) / School of Social Work (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12
Description
Sex trafficking is a problem in Arizona that affects both minors and adults. There are hundreds of people who have the desire to counter trafficking in Arizona, and out of that desire numerous organizations have been created. While this can be beneficial to the cause, it can also become a hindrance by diluting resources and creating an atmosphere of competitiveness between organizations. The Inter-Faith Sex Trafficking Summit was an attempt to build unity and community between these organizations and to raise awareness of existing groups to those who are newly involved. Attendees represented over 108 different agencies, organizations, and faiths. Throughout the day, speakers shared their experiences and expertise on the results of collaborative efforts to promote change in community awareness, legislation, and service provision. Themes emerged including \u2014 1) no one can do this alone; we are stronger together, 2) regardless of our affiliation or theology we are on the same team and need to work as a team, and 3) the bad guys are strategic; we have to be strategic, too. Since the summit was held, numerous individuals have set up meetings to continue to discuss how they can work together. An attendee directory has been circulated, and a blog, Inter-faith Strategy to Stop Trafficking has been created to enhance connectivity. An exit survey reveals that the majority of attendees are interested in pursuing more opportunity for connecting and building a stronger alliance as well as discovering ways to become more strategic.
ContributorsWarren, Angela Mae (Author) / Roe-Sepowitz, Dominique (Thesis director) / Galliano, Grace (Committee member) / Wood, Nicole (Committee member) / Barrett, The Honors College (Contributor) / School of Social Work (Contributor)
Created2013-12
Description
This study was conducted to look at the possible effects of art intervention on anxiety levels of homeless young adults in a local drop-in shelter. While there is a fair amount of literature on art intervention and its applicability with vulnerable populations, its specific effect on anxiety has not been extensively examined. Researchers conducted two art interventions where state-trait anxiety (STAI Inventory) was measured before and after the interventions. Researchers hypothesized that anxiety would decrease after the art sessions. Some significant results were found. Participants reported feeling less strained (p = .041), worrying less over possible misfortunes (p = .02), feeling less nervous (p = .007) and feeling more decisive (p = .001). Future research recommendations are discussed.
ContributorsWille, Emma Margaret (Author) / Roe-Sepowitz, Dominique (Thesis director) / Mendoza, Natasha (Committee member) / Agliano, Stefania (Committee member) / Barrett, The Honors College (Contributor) / School of International Letters and Cultures (Contributor) / School of Social Work (Contributor) / Department of Psychology (Contributor)
Created2014-05
Description
This paper introduces the causes and effects of domestic violence in a general sense, and further focuses on the specific consequences experienced by Latinos of traditional culture in regards to partner abuse. While it is unclear why rates of intimate partner violence are higher for Latinas, their cultural values associated with gender roles and spiritual beliefs are complicating factors that are further magnified by socioeconomic challenges many Latinas experience. This paper examines the interplay between Latino cultural values and intimate partner violence, and highlights the relevance of this knowledge to inform effective social work practice in the Latino community.
ContributorsBennett, Brittney Kay (Author) / Bonifas, Robin (Thesis director) / Parsai, Monica (Committee member) / Kennedy, Teri (Committee member) / Barrett, The Honors College (Contributor) / School of Criminology and Criminal Justice (Contributor) / School of Social Work (Contributor)
Created2013-05