Matching Items (11)

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Wet NanoBonding of Semiconducting Surfaces Optimized via Surface Energy Modification using Three Liquid Contact Angle Analysis as a Metrology

Description

Semiconductor wafers are analyzed and their total surface energy γT is measured in three components according to the van Oss theory: (1) γLW, surface energy due to Lifshitz-van der Waals

Semiconductor wafers are analyzed and their total surface energy γT is measured in three components according to the van Oss theory: (1) γLW, surface energy due to Lifshitz-van der Waals forces or dipole interactions, (2) γ+, surface energy due to interactions with electron donors, and (3) γ–, surface energy due to interactions with electron acceptors. Surface energy is measured via Three Liquid Contact Angle Analysis (3LCAA), a method of contact angle measurement using the sessile drop technique and three liquids: water, glycerin, and α-bromonaphthalene. This research optimizes the experimental methods of 3LCAA, proving that the technique produces reproducible measurements for surface energy on a variety of surfaces. Wafer surfaces are prepared via thermal oxidation, rapid thermal oxidation, ion beam oxidation, rapid thermal annealing, hydrofluoric acid etching, the RCA clean, the Herbots-Atluri (H-A) process, and the dry and wet anneals used for Dry and Wet NanoBonding™, respectively.
NanoBonding™ is a process for growing molecular bonds between semiconducting surfaces to create a hermetic seal. NanoBonding™ prevents fluid percolation, protecting integrated electronic sensors from corrosive mobile ion species such as sodium. This can extend the lifetime of marine sensors and glucose sensors from less than one week to over two years, dramatically reducing costs and improving quality of life for diabetic patients. Surface energy measurement is critical to understanding and optimizing NanoBonding™. Surface energies are modified through variations on the H-A process, and measured via 3LCAA. The majority of this research focuses on silicon oxide surfaces.
This is the first quantitative measurement of gallium arsenide surface energy in three components. GaAs is a III-V semiconductor with potential commercial use in transistors, but its oxide layer slowly evaporates over time. In subsequent research, 3LCAA may prove key to developing a stable GaAs oxide layer.

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Date Created
  • 2016-05

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Physics Secondary Education: How Perception Creates Educational Realities

Description

This study explores the significant roles and responsibilities of Arizona physics teachers as well as the effect that these teachers have on students and thus their futures. In a two-fold

This study explores the significant roles and responsibilities of Arizona physics teachers as well as the effect that these teachers have on students and thus their futures. In a two-fold survey administered to all 194 public comprehensive high school physics teachers with 60% participation, questions regarding the perception and expectations that physics teachers hold for themselves, students, and school counselors are addressed as well as the corresponding practices. This survey reveals that generally, teachers feel that students have preconceptions about what physics is and what the course requires, and yet approximately half of the teachers do not make significant recruitment efforts. It is pertinent to ask why physics has one of the lowest enrollment statuses out of all the sciences in high school. Even more so, it is crucial to ask why there is a teacher shortage in the subject of physics. In exploring these questions, results to the previously mentioned genres of questions will speak to the issues at hand and are intended to give a robust explanation as to why physics is fading away in Arizona.

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Date Created
  • 2018-05

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Analyzing the Challenges and Solutions of Living on Mars

Description

This paper addresses many of the problems that will be encountered when travelling to Mars and discusses the possibility of different solutions. Protection from radiation, oxygen production, and water sources

This paper addresses many of the problems that will be encountered when travelling to Mars and discusses the possibility of different solutions. Protection from radiation, oxygen production, and water sources are some of the major problems and the solution to these problems are vital for the success of future space travel. By utilizing technology that has already been used in space travel and implementing the use of technology that is successful on Earth, humans will be able to live on Mars successfully.

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Date Created
  • 2020-05

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Wet NanoBonding™: Catalyzing Molecular Cross-Bridges and Interphases Between Nanoscopically Smoothed Si-Based Surfaces and Tailoring Surface Energy Components

Description

Dry and steam NanoBonding™ are conceived and researched to bond Si-based surfaces, via nucleation and growth of a two-dimensional SiOxHy or hydrated SiOxHy interphase connecting surfaces at the nanoscale

Dry and steam NanoBonding™ are conceived and researched to bond Si-based surfaces, via nucleation and growth of a two-dimensional SiOxHy or hydrated SiOxHy interphase connecting surfaces at the nanoscale across macroscopic domains. The motivation is to create strong, long lasting, hermetically bonded sensors with their electronics for the development of an artificial pancreas and to bond solar cells to glass panels for robust photovoltaic technology. The first step in NanoBonding™ is to synthesize smooth surfaces with 20 nm wide atomic terraces via a precursor phase, ß-cSiO2 on Si(100) and oxygen-deficient SiOx on the silica using the Herbots-Atluri process and Entrepix’s spin etching. Smooth precursor phases act as geometric and chemical template to nucleate and grow macroscopic contacting domains where cross bridging occurs via arrays of molecular strands in the hydrated SiOxHy interphase. Steam pressurization is found to catalyze NanoBonding™ consistently, eliminating the need for direct mechanical compression that limits the size and shape of wafers to be bonded in turn, reducing the cost of processing. Total surface energy measurements via 3 Liquids Contact Angle Analysis (3L CAA) enables accurate quantitative analysis of the total surface energy and each of its components. 3L CAA at each step in the process shows that surface energy drops to 42.4 ± 0.6 mJ/m2 from 57.5 ± 1.4 mJ/m2 after the Herbots-Atluri clean of an “As Received” wafer. 3L CAA after steam pressurization Nanobonding™ shows almost complete elimination from 13.8 mJ/m2 ± 1.0 to 0.002 ±- 0.0002 mJ/m2 in the contribution of acceptors to the total free surface energy, and an increase from 0.2 ± .03 to 23.8± 1.6 mJ/m2 in the contribution of donors. This is consistent with an increase in hydroxylation of the ß-cSiO2 surface as a consistent precursor phase for cross-bridging. This research optimizes the use of glycerin, water, and α-bromo-naphtalene in the use of 3L CAA to effectively quantify the components of total free surface energy which helps to better understand the most consistent method for NanoBonding™.

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Created

Date Created
  • 2013-05

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In Vivo Clinical Animal Trials for an Anti-Fog Coating on Surgical Lenses

Description

One major issue that surgeons face during closed body cavity surgery is fogging of the lens surfaces. The cloudy and opaque lens surface caused by water vapor present in closed

One major issue that surgeons face during closed body cavity surgery is fogging of the lens surfaces. The cloudy and opaque lens surface caused by water vapor present in closed body cavities forces the surgeon to repeatedly remove the endoscope, wipe it, and reinsert it back into the patient. This presents several risks such as increased surgery time, greater scarring, and an increased chance of infection. In order to address this issue, the development of the Thin Fluid Film Device (TFFD™) VitreOx™ aims to render the lens surface hydrophilic, whereas it is typically hydrophobic. By creating a hydrophilic polymeric nanomesh, the 3-D water droplets can be trapped to lie flatter, thus resulting in a flatter 2-D sheeting effect. The light can no longer be refracted at different angles off of the 3-dimensional water beads, thus eliminating the opacity of the lens surface.
Two animal trials were performed involving a rat and two pigs in order to prove the efficacy of VitreOx™ in addition to being compared with competitor, Covidien Clearify. A laparoscopy was performed on each animal, and the length of time that the endoscope took to fog was measured post product application. The results of the optimized animal clinical trials involving two Yucatan pigs showed that the scope treated with Covidien’s Clearify began fogging within 8 minutes and continued to do so for the remained of the surgery, as opposed to the scope with VitreOx™ which remained fog free for the full 90-minute procedure. The results proved the efficacy of our product.
The second part of the thesis aimed to optimize HemoClear™, the blood evacuating TFFD™. This was done by testing a higher concentration of 6 mg/mL fibrinogen as compared to previous work. After conducting an experiment designed to mimic closed-body cavity surgery it was determined that the HemoClear™ eliminated fog 67% of the time and evacuated blood with a success of 83%. Future work aims to continue testing at this concentration with variances in mixing and application technique.

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Date Created
  • 2015-05

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Optical characterization of III nitride semiconductors using cathodoluminescence techniques

Description

Group III-nitride semiconductors have attracted much attention for applications on high brightness light-emitting diodes (LEDs) and laser diodes (LDs) operating in the visible and ultra-violet spectral range using indium gallium

Group III-nitride semiconductors have attracted much attention for applications on high brightness light-emitting diodes (LEDs) and laser diodes (LDs) operating in the visible and ultra-violet spectral range using indium gallium nitride in the active layer. However, the device efficiency in the green to red range is limited by quantum-confined Stark effects resulting from the lattice mismatch between GaN and InGaN. In this dissertation, the optical and micro-structural properties of GaN-based light emitting structures have been analyzed and correlated by utilizing cathodoluminescence and transmission electron microscopy techniques. In the first section, optimization of the design of GaN-based lasers diode structures is presented. The thermal strain present in the GaN underlayer grown on sapphire substrates causes a strain-induced wavelength shift. The insertion of an InGaN waveguide mitigates the mismatch strain at the interface between the InGaN quantum well and the GaN quantum barrier. The second section of the thesis presents a study of the characteristics of thick non-polar m-plane InGaN films and of LED structures containing InGaN quantum wells, which minimize polarization-related electric fields. It is found that in some cases the in-plane piezoelectric fields can still occur due to the existence of misfit dislocations which break the continuity of the film. In the final section, the optical and structural properties of InGaAlN quaternary alloys are analyzed and correlated. The composition of the components of the film is accurately determined by Rutherford backscattering spectroscopy.

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Created

Date Created
  • 2011

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Conceptualizing and Reasoning with Frames of Reference in Three Studies

Description

This dissertation reports three studies about what it means for teachers and students to reason with frames of reference: to conceptualize a reference frame, to coordinate multiple frames of reference,

This dissertation reports three studies about what it means for teachers and students to reason with frames of reference: to conceptualize a reference frame, to coordinate multiple frames of reference, and to combine multiple frames of reference. Each paper expands on the previous one to illustrate and utilize the construct of frame of reference. The first paper is a theory paper that introduces the mental actions involved in reasoning with frames of reference. The concept of frames of reference, though commonly used in mathematics and physics, is not described cognitively in any literature. The paper offers a theoretical model of mental actions involved in conceptualizing a frame of reference. Additionally, it posits mental actions that are necessary for a student to reason with multiple frames of reference. It also extends the theory of quantitative reasoning with the construct of a ‘framed quantity’. The second paper investigates how two introductory calculus students who participated in teaching experiments reasoned about changes (variations). The data was analyzed to see to what extent each student conceptualized the variations within a conceptualized frame of reference as described in the first paper. The study found that the extent to which each student conceptualized, coordinated, and combined reference frames significantly affected his ability to reason productively about variations and to make sense of his own answers. The paper ends by analyzing 123 calculus students’ written responses to one of the tasks to build hypotheses about how calculus students reason about variations within frames of reference. The third paper reports how U.S. and Korean secondary mathematics teachers reason with frame of reference on open-response items. An assessment with five frame of reference tasks was given to 539 teachers in the US and Korea, and the responses were coded with rubrics intended to categorize responses by the extent to which they demonstrated conceptualized and coordinated frames of reference. The results show that the theory in the first study is useful in analyzing teachers’ reasoning with frames of reference, and that the items and rubrics function as useful tools in investigating teachers’ meanings for quantities within a frame of reference.

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Created

Date Created
  • 2019

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Fidelity of implementation of research experience for teachers in the classroom

Description

In this study, the Arizona State University Mathematics and Science Teaching Fellows 2010 program was analyzed qualitatively from start to finish to determine the impact of the research experience on

In this study, the Arizona State University Mathematics and Science Teaching Fellows 2010 program was analyzed qualitatively from start to finish to determine the impact of the research experience on teachers in the classroom. The sample for the study was the 2010 cohort of eight high school science teachers. Erickson's (1986) interpretive, participant observational fieldwork method was used to report data by means of detailed descriptions of the research experience and classroom implementation. Data was collected from teacher documents, interviews, and observations. The findings revealed various factors that were responsible for an ineffective implementation of the research experience in the classroom such as research experience, curriculum support, availability of resources, and school curriculum. Implications and recommendations for future programs are discussed in the study.

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Date Created
  • 2012

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Nature or nurture?: a characterization of the knowledge and practices of in- and out-of-field beginning secondary physics teachers

Description

Previous studies have shown that adequate content knowledge is a necessary, but not sufficient, requirement for affective teaching. While legislation requests teachers to be "highly qualified" in a subject area,

Previous studies have shown that adequate content knowledge is a necessary, but not sufficient, requirement for affective teaching. While legislation requests teachers to be "highly qualified" in a subject area, such as physics, many teachers are frequently asked to teach in an area when they are not certified through a teaching license to do so. This study uses mixed methods to examine the knowledge of beginning physics teachers. Through semi-structured interviews, classroom observations, and concept maps, the pedagogical content knowledge, subject matter knowledge, and practices of three groups of beginning secondary physics teachers were explored. Data were analyzed qualitatively using cases and quantitatively using descriptive statistics and t-tests, the results of which were combined during the interpretation phase of the research process. The study indicated that, over the first two years of teaching, the in-field group of teachers showed stronger physics content knowledge, a consideration for student difficulties with physics topics, and a positive shift in pedagogical content knowledge impacted by working with students, as compared to the rest of the teachers in the study. This research has implications in the development of secondary physics teachers and in the field of physics education research. Specifically, this research has implications in the physics content support for beginning secondary science teachers, the novice/expert research in physics education research, and the pedagogical preparation of undergraduate students, graduate students, and faculty in physics.

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Date Created
  • 2010

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The optical properties of nitride semiconductors for visible light emission

Description

Nitride semiconductors have wide applications in electronics and optoelectronics technologies. Understanding the nature of the optical recombination process and its effects on luminescence efficiency is important for the development of

Nitride semiconductors have wide applications in electronics and optoelectronics technologies. Understanding the nature of the optical recombination process and its effects on luminescence efficiency is important for the development of novel devices. This dissertation deals with the optical properties of nitride semiconductors, including GaN epitaxial layers and more complex heterostructures. The emission characteristics are examined by cathodoluminescence spectroscopy and imaging, and are correlated with the structural and electrical properties studied by transmission electron microscopy and electron holography. Four major areas are covered in this dissertation, which are described next. The effect of strain on the emission characteristics in wurtzite GaN has been studied. The values of the residual strain in GaN epilayers with different dislocation densities are determined by x-ray diffraction, and the relationship between exciton emission energy and the in-plane residual strain is demonstrated. It shows that the emission energy increases withthe magnitude of the in-plane compressive strain. The temperature dependence of the emission characteristics in cubic GaN has been studied. It is observed that the exciton emission and donor-acceptor pair recombination behave differently with temperature. The donor-bound exciton binding energy has been measured to be 13 meV from the temperature dependence of the emission spectrum. It is also found that the ionization energies for both acceptors and donors are smaller in cubic compared with hexagonal structures, which should contribute to higher doping efficiencies. A comprehensive study on the structural and optical properties is presented for InGaN/GaN quantum wells emitting in the blue, green, and yellow regions of the electromagnetic spectrum. Transmission electron microscopy images indicate the presence of indium inhomogeneties which should be responsible for carrier localization. The temperature dependence of emission luminescence shows that the carrier localization effects become more significant with increasing emission wavelength. On the other hand, the effect of non-radiative recombination on luminescence efficiency also varies with the emission wavelength. The fast increase of the non-radiative recombination rate with temperature in the green emitting QWs contributes to the lower efficiency compared with the blue emitting QWs. The possible saturation of non-radiative recombination above 100 K may explain the unexpected high emission efficiency for the yellow emitting QWs Finally, the effects of InGaN underlayers on the electronic and optical properties of InGaN/GaN quantum wells emitting in visible spectral regions have been studied. A significant improvement of the emission efficiency is observed, which is associated with a blue shift in the emission energy, a reduced recombination lifetime, an increased spatial homogeneity in the luminescence, and a weaker internal field across the quantum wells. These are explained by a partial strain relaxation introduced by the InGaN underlayer, which is measured by reciprocal space mapping of the x-ray diffraction intensity.

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Date Created
  • 2012