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Characterization of HgCdTe and HgCdSe materials for third generation infrared detectors

Description
HgCdTe is the dominant material currently in use for infrared (IR) focal-plane-array (FPA) technology. In this dissertation, transmission electron microscopy (TEM) was used for the characterization of epitaxial HgCdTe epilayers and HgCdTe-based devices. The microstructure of CdTe surface passivation layers deposited either by hot-wall epitaxy (HWE) or molecular beam epitaxy…

HgCdTe is the dominant material currently in use for infrared (IR) focal-plane-array (FPA) technology. In this dissertation, transmission electron microscopy (TEM) was used for the characterization of epitaxial HgCdTe epilayers and HgCdTe-based devices. The microstructure of CdTe surface passivation layers deposited either by hot-wall epitaxy (HWE) or molecular beam epitaxy (MBE) on HgCdTe heterostructures was evaluated. The as-deposited CdTe passivation layers were polycrystalline and columnar. The CdTe grains were larger and more irregular when deposited by HWE, whereas those deposited by MBE were generally well-textured with mostly vertical grain boundaries. Observations and measurements using several TEM techniques showed that the CdTe/HgCdTe interface became considerably more abrupt after annealing, and the crystallinity of the CdTe layer was also improved. The microstructure and compositional profiles of CdTe(211)B/ZnTe/Si(211) heterostructures grown by MBE was investigated. Many inclined {111}-type stacking faults were present throughout the thin ZnTe layer, terminating near the point of initiation of CdTe growth. A rotation angle of about 3.5° was observed between lattice planes of the Si substrate and the final CdTe epilayer. Lattice parameter measurement and elemental profiles indicated that some local intermixing of Zn and Cd had taken place. The average widths of the ZnTe layer and the (Cd, Zn)Te transition region were found to be roughly 6.5 nm and 3.5 nm, respectively. Initial observations of CdTe(211)B/GaAs(211) heterostructures indicated much reduced defect densities near the vicinity of the substrate and within the CdTe epilayers. HgCdTe epilayers grown on CdTe(211)B/GaAs(211) composite substrate were generally of high quality, despite the presence of precipitates at the HgCdTe/CdTe interface. The microstructure of HgCdSe thin films grown by MBE on ZnTe/Si(112) and GaSb(112) substrates were investigated. The quality of the HgCdSe growth was dependent on the growth temperature and materials flux, independent of the substrate. The materials grown at 100°C were generally of high quality, while those grown at 140°C had {111}-type stacking defects and high dislocation densities. For epitaxial growth of HgCdSe on GaSb substrates, better preparation of the GaSb buffer layer will be essential in order to ensure that high-quality HgCdSe can be grown.
ContributorsZhao, Wenfeng (Author) / Smith, David J. (Thesis advisor) / McCartney, Martha (Committee member) / Carpenter, Ray (Committee member) / Bennett, Peter (Committee member) / Treacy, Michael J. (Committee member) / Arizona State University (Publisher)
Created2011

College Hesitancy in Minority High School Girls Interested in STEM

Description
Minority women continue to be underrepresented in STEM fields and in STEM related degrees, leading to a lack of diversity in the research conducted and voices advocated for in STEM. To understand why there continues to be a lack of representation of minority women in STEM, I conducted a survey…

Minority women continue to be underrepresented in STEM fields and in STEM related degrees, leading to a lack of diversity in the research conducted and voices advocated for in STEM. To understand why there continues to be a lack of representation of minority women in STEM, I conducted a survey of approximately 20 high school girls who identified as minorities and had an interest in science and conservation to ask questions about their hesitancy to attend college and the different barriers they face. The results of this survey show that these minority girls have low hesitancy when considering applying to and attending college. The biggest barrier these girls face is cost, with 74% of respondents citing college expense as a source of hesitancy when considering applying to college. I then discuss possible interventions that would lead to an increase in the representation of minority women in STEM in higher education. I suggest that colleges and universities should highlight scholarships, financial aid, and programs available and that minority women are eligible for, or they should reduce the cost of tuition.
ContributorsClark, Amelie (Author) / Iacona, Gwen (Thesis director) / Gerber, Leah (Committee member) / Bisgrove, Daniel (Committee member) / Barrett, The Honors College (Contributor) / Civil, Environmental and Sustainable Eng Program (Contributor)
Created2023-12
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Women in Construction: The Dwindling Numbers and the Effects of Upbringing, Background, and Culture in Abstaining from the Industry

Description

This report attempts to understand the effects of the many aspects that pertain to a woman’s path into the construction industry and their role in limiting women’s overall representation in the construction industry. More specifically, it aims to understand how upbringing, background, and culture impact women that do pursue careers…

This report attempts to understand the effects of the many aspects that pertain to a woman’s path into the construction industry and their role in limiting women’s overall representation in the construction industry. More specifically, it aims to understand how upbringing, background, and culture impact women that do pursue careers in the construction industry. This paper presents some of the current and prominent issues being faced by women in in the construction industry, including those in the trades. These issues then contribute to their lack of representation and forceful exit. Additionally, it assesses personal narratives from a localized group of women who are currently employed at a large construction company. This information and these narratives are analyzed jointly to try and gain a better understanding of the current challenges being faced by women in comparison to those reported previously. This joint comparison allows for a deeper understanding of women’s perception of the construction industry as a whole.
ContributorsContreras, Marisa (Author) / Lou, Yingyan (Thesis director) / Parrish, Kristen (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / School of Social Transformation (Contributor) / Civil, Environmental and Sustainable Eng Program (Contributor)
Created2022-05

The STEM Podcast

Description
This podcast focused on the experience of women in the field of STEM and more specifically civil engineering. The episodes will explore three main topics surrounding women in the workforce: how women navigate and succeed in a workforce with a predominantly male presence, whether or not women experience “impostor syndrome”,…

This podcast focused on the experience of women in the field of STEM and more specifically civil engineering. The episodes will explore three main topics surrounding women in the workforce: how women navigate and succeed in a workforce with a predominantly male presence, whether or not women experience “impostor syndrome”, and how to deal with being undermined in the workforce. Also available on Spotify! https://open.spotify.com/show/6iyemJ08Et4JCEATtlgNls?si=03167fd008e94bb6
ContributorsRivera, Valentina (Author) / DiCaro, Isabella (Co-author) / Hjelsmtad, Keith (Thesis director) / Boyce-Jacino, Katherine (Committee member) / Barrett, The Honors College (Contributor) / Civil, Environmental and Sustainable Eng Program (Contributor)
Created2022-05

The STEM Podcast: An Exploration of the Experiences of Women in STEM with an Emphasis on Civil Engineering

Description

The goal of this creative thesis is to focus on the experience of women in the field of STEM and more specifically civil engineering. This project will explore four main topics surrounding women in the workforce: how women navigate and succeed in a workforce with predominant male presence, how women…

The goal of this creative thesis is to focus on the experience of women in the field of STEM and more specifically civil engineering. This project will explore four main topics surrounding women in the workforce: how women navigate and succeed in a workforce with predominant male presence, how women advance their career given the gender barriers of the industry, including motherhood, and “impostor syndrome” in the workforce
ContributorsDiCaro, Isabella (Author) / Rivera, Valentina (Abridger) / Boyce-Jacino, Katherine (Thesis director) / Hjelmstad, Keith (Committee member) / Barrett, The Honors College (Contributor) / Civil, Environmental and Sustainable Eng Program (Contributor)
Created2022-05