The Study of Ohmic Contacts to Nitrogen-doped Nanocarbon Layers and Diamond Surfaces

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Description
Over the past few years, research into the use of doped diamond in electronics has seen an exponential growth. In the course of finding ways to reduce the contact resistivity, nanocarbon materials have been an interesting focus. In this work,

Over the past few years, research into the use of doped diamond in electronics has seen an exponential growth. In the course of finding ways to reduce the contact resistivity, nanocarbon materials have been an interesting focus. In this work, the transfer length method (TLM) was used to investigate Ohmic contact properties using the tri-layer stack Ti/Pt/Au on nitrogen-doped n-type conducting nano-carbon (nanoC) layers grown on (100) diamond substrates. The nanocarbon material was characterized using Secondary Ion Mass Spectrometry (SIMS), Scanning electron Microscopy (SEM) X-ray diffraction (XRD), Raman scattering and Hall effect measurements to probe the materials characteristics. Room temperature electrical measurements were taken, and samples were annealed to observe changes in electrical conductivity. Low specific contact resistivity values of 8 x 10^-5 Ωcm^2 were achieved, which was almost two orders of magnitude lower than previously reported values. The results were attributed to the increased nitrogen incorporation, and the presence of electrically active defects which leads to an increase in conduction in the nanocarbon. Further a study of light phosphorus doped layers using similar methods with Ti/Pt/Au contacts again yielded a low contact resistivity of about 9.88 x 10^-2 Ωcm^2 which is an interesting prospect among lightly doped diamond films for applications in devices such as transistors. In addition, for the first time, hafnium was substituted for Ti in the contact stack (Hf/Pt/Au) and studied on nitrogen doped nanocarbon films, which resulted in low contact resistivity values on the order of 10^-2 Ωcm^2. The implications of the results were discussed, and recommendations for improving the experimental process was outlined. Lastly, a method for the selective area growth of nanocarbon was developed and studied and the results provided an insight into how different characterizations can be used to confirm the presence of the nanocrystalline diamond material, the limitations due to the film thickness was explored and ideas for future work was proposed.
Date Created
2023
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3D Printed Device for Mechanical Fatigue Testing and Analysis of Li-ion Batteries and Electrodes

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Description

In the last several years, there has been interest in the development of flexible batteries as a substitute for traditional Li-ion batteries. Flexible batteries can fold, bend, and twist; studies have shown that mechanical stresses and fatigue may decrease battery

In the last several years, there has been interest in the development of flexible batteries as a substitute for traditional Li-ion batteries. Flexible batteries can fold, bend, and twist; studies have shown that mechanical stresses and fatigue may decrease battery performance and cause defects. In this paper, the viability of producing a mechanical fatigue-testing device from 3D printed and other off-the-shelf components was explored. The device was made using a servomotor and LCD screen controlled by a programmed Arduino board, and successfully met the expectations to be cheap, easily reproducible, versatile, and applicable to the testing of battery components. In a proof-of-concept test, the device was used to perform repeated folding tests on lithium cobalt oxide cathodes in different configurations, which were then characterized using a laser microscope. 3D topographical renderings suggested that bending at acute angles induces defects on the surface of the electrode where the electrode is creased. In future work, the device will be used to further explore the effect of mechanical fatigue on Li-ion battery components.

Date Created
2021-05
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Simulation of Atomic Structure around Defects in Anatase

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Description
Titanium dioxide is an essential material under research for energy and environmental applications, chiefly through its photocatalytic properties. These properties allow it to be used for water-splitting, detoxification, and photovoltaics, in addition to its conventional uses in pigmentation and

Titanium dioxide is an essential material under research for energy and environmental applications, chiefly through its photocatalytic properties. These properties allow it to be used for water-splitting, detoxification, and photovoltaics, in addition to its conventional uses in pigmentation and sunscreen. Titanium dioxide exists in several polymorphic structures, of which the most common are rutile and anatase. We focused on anatase for the purposes of this research, due to its promising results for hydrolysis.

Anatase exists often in its reduced form (TiO2-x), enabling it to perform redox reactions through the absorption and release of oxygen into/from the crystal lattice. These processes result in structural changes, induced by defects in the material, which can theoretically be observed using advanced characterization methods. In situ electron microscopy is one of such methods, and can provide a window into these structural changes. However, in order to interpret the structural evolution caused by defects in materials, it is often necessary and pertinent to use atomistic simulations to compare the experimental images with models.

In this thesis project, we modeled the defect structures in anatase, around oxygen vacancies and at surfaces, using molecular dynamics, benchmarked with density functional theory. Using a “reactive” forcefield designed for the simulation of interactions between anatase and water that can model and treat bonding through the use of bond orders, different vacancy structures were analyzed and simulated. To compare these theoretical, generated models with experimental data, the “multislice approach” to TEM image simulation was used. We investigated a series of different vacancy configurations and surfaces and generated fingerprints for comparison with TEM experiments. This comparison demonstrated a proof of concept for a technique suggesting the possibility for the identification of oxygen vacancy structures directly from TEM images. This research aims to improve our atomic-level understanding of oxide materials, by providing a methodology for the analysis of vacancy formation from very subtle phenomena in TEM images.
Date Created
2019-05
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The Social and Political Consequences of Autonomous Vehicles

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Description
When, in 1958, Disney aired a program titled “Magic Highway USA” featuring autonomous vehicles directed by punch-cards, few would have predicted touchscreen reprogrammable devices. None could have foreseen a battery powered car capable of fully autonomous operation and a zero

When, in 1958, Disney aired a program titled “Magic Highway USA” featuring autonomous vehicles directed by punch-cards, few would have predicted touchscreen reprogrammable devices. None could have foreseen a battery powered car capable of fully autonomous operation and a zero to sixty mph acceleration in 1.9 seconds. The 21st century has proven to be one of exponential technological advancement and stunning innovation, with few case studies more obvious than that of the progression of autonomous vehicle (AV) technology. Advances in transportation technology and robotics have, throughout history, pointed to the eventual development of fully autonomous vehicles; however, it is only within the last 10 years that innovation has met determination to leapfrog AV development to its current state. As this technology has developed, society has begun to realize its extensive social implications, both positive and negative, from extending mobility to the impaired to reducing the need to fill jobs in the transportation industry. With progress comes new challenges and as planners strive to get ahead of the pace of AV innovation, it is becoming increasingly apparent that questions of data security, privacy, regulation, and liability must be quickly addressed. Some also question the economic feasibility of AV and suggest that, unless new economic models are developed around the transportation industry, there is a significant risk of increased societal strain as a result of digital and economic inequality. As a consequence, industry, academia, and policy have all emerged to direct, manage, and govern this new and exciting space. Autonomous vehicles promise to move the world into a new era of almost limitless potential but only if society, industry, and policy are capable of moving with it.
Date Created
2019-05
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Fatigue Mechanisms of Typical Polymers and Silicone based Elastomers

Description
The goal of the paper was to examine the fatigue mechanisms of polymers and silicone based elastomers. The mechanisms of fatigue due to crazing: the alignment of polymer chains to the stress axis, and shear banding: the localized orientation of

The goal of the paper was to examine the fatigue mechanisms of polymers and silicone based elastomers. The mechanisms of fatigue due to crazing: the alignment of polymer chains to the stress axis, and shear banding: the localized orientation of the polymer by the shear stresses from two planes, were discussed in depth in this paper. Crazing only occurs in tensile stress, is initiated on the surface of the material, and only occurs in brittle polymers. Crazing also accounts for a 40-60% decrease in density, causing localized weakening of the material and a concentration in stress. This is due to a decrease in effective cross sectional area. The mechanism behind discontinuous growth bands was also discussed to be the cause of cyclic crazing. Shear banding only occurs in ductile polymers and can result in the failure of polymers via necking. Furthermore, the high fatigue resistance of silicone elastomers was discussed in this paper. This conclusion was made because of the lack of fatigue mechanisms (crazing, discontinuous growth bands, and shears banding) in the observed elastomer's microstructure after the samples had undergone fatigue tests. This was done through an analysis of room temperature vulcanized silicone adhesives, a heat-curing silicone elastomer, and a self-curing transparent silicone rubber. Fatigue of room temperature vulcanized silicon was observed, however this was reasoned to be the failure of the adhesion of the elastomer to the steel substrate instead of the microstructure itself. Additionally, the significance of fatigue in real world applications was discussed using SouthWest Airlines Flight 812 as an example.
Date Created
2016-05
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Ultra-Low-Noise Cryogenic Dipping Probe for JMRAM Applications

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Description
The vastly growing field of supercomputing is in dire need of a new measurement system to optimize JMRAM (Josephson junction magnetoresistive random access memory) devices. To effectively measure these devices, an ultra-low-noise, low cost cryogenic dipping probe with a dynamic

The vastly growing field of supercomputing is in dire need of a new measurement system to optimize JMRAM (Josephson junction magnetoresistive random access memory) devices. To effectively measure these devices, an ultra-low-noise, low cost cryogenic dipping probe with a dynamic voltage range is required. This dipping probe has been designed by ASU with <100 nVp-p noise, <10 nV offsets, 10 pV to 16 mV voltage range, and negligible thermoelectric drift. There is currently no other research group or company that can currently match both these low noise levels and wide voltage range. Two different dipping probes can be created with these specifications: one for high-use applications and one for low-use applications. The only difference between these probes is the outer shell; the high-use application probe has a shell made of G-10 fiberglass for a higher price, and the low-use application probe has a shell made of AISI 310 steel for a lower price. Both types of probes can be assembled in less than 8 hours for less than $2,500, requiring only soldering expertise. The low cost and short time to create these probes makes wide profit margins possible. The market for these cryogenic dipping probes is currently untapped, as most research groups and companies that use these probes build their own, which allows for rapid business growth. These potential consumers can be easily reached by marketing these probes at superconducting conferences. After several years of selling >50 probes, mass production can easily become possible by hiring several technicians, and still maintaining wide profit margins.
Date Created
2016-05
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The Impact of Implementing an Invariant-Based Theory of Composites on the Automotive Industry

Description
A novel approach, the Invariant Based Theory of Composites and the "Trace" method it proposes, has the potential to reduce aerospace composite development times and costs by over 30% thus reinvigorating the development process and encouraging composite technology growth. The

A novel approach, the Invariant Based Theory of Composites and the "Trace" method it proposes, has the potential to reduce aerospace composite development times and costs by over 30% thus reinvigorating the development process and encouraging composite technology growth. The "trace" method takes advantage of inherent stiffness properties of laminates, specifically carbon fiber, to make predictions of material properties used to derive design allowables. The advantages of the "trace" theory may not necessarily be specific to the aerospace industry, however many automotive manufacturers are facing environmental, social and political pressure to increase the gas mileage in their vehicles and reduce their carbon footprint. Therefore, the use of lighter materials, such as carbon fiber composites, to replace heavier metals in cars is inevitable yet as of now few auto manufacturers implement composites in their cars. The high material, testing and development costs, much like the aerospace industry, have been prohibitive to widespread use of these materials but progress is being made in overcoming those challenges. The "trace" method, while initially intended for quasi-isotropic, aerospace grade carbon-fiber laminates, still yields reasonable, and correctable, results for types of laminates as well such as with woven fabrics and thermoplastic matrices, much of which are being used in these early stages of automotive composite development. Despite the varying use of materials, the "trace" method could potentially boost automotive composites in a similar way to the aerospace industry by reducing testing time and costs and perhaps even playing a role in establishing emerging simulations of these materials.
Date Created
2016-05
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From Pedometers to Giving Sight to the Blind: Market Research for Wearable Electronics

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Description
How can we change what it means to be a human? Products can be used that will allow for near-instantaneous communication with one’s friends and family wherever they are: and the newest devices do not have to be even carried

How can we change what it means to be a human? Products can be used that will allow for near-instantaneous communication with one’s friends and family wherever they are: and the newest devices do not have to be even carried around, as they can be worn instead. Wearable electronics are quickly becoming very popular, with 232.0 million wearable devices sold in 2015. This report provides an overview of current and developing wearable devices, investigates the characteristics of the average buyer for these different types of devices. Finally, marketing strategies are suggested. This work was completed in conjunction with a capstone project with Intel, where three objectives were achieved: First, a universal strain tester that could strain samples cyclically in a manner similar to the body was designed. This equipment was especially designed to be flexible in the testing conditions it could be exposed to, so samples could be tested at elevated temperatures or even underwater. Next, dogbone shaped samples for the testing of Young’s Modulus and elongation to failure were produced, and the cut quality of laser, water-jet, and die-cutting was compared in order to select the most defect-free method for reliable testing. Polydimethylsiloxane (PDMS) is a fantastic candidate material for wearable electronics, however there is some discrepancies in the literature—such as from Eleni et. al—about the impact of ultraviolet radiation on the mechanical properties. By conducting accelerated aging tests simulating up to five years exposure to the sun, it was determined that ultraviolet-induced cross-linking of the polymer chains does occur, leading to severe embrittlement (strain to failure reduced from 3.27 to 0.06 in some cases, reduction to approximately 0.21 on average). As simulated tests of possible usage conditions required strains of at least 0.50-0.70, a variety of solutions were suggested to reduce this embrittlement. This project can lead to standardization of wearables electronics testing methods for more reliable predictions about the device behavior, whether that device is a simple pedometer or something that allows the visually impaired to “see”, such as Toyota’s Blaid.
Date Created
2016-05
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INTEL ATOM'S TRANSITION TO THE MOBILE DEVICES CPU MARKET

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Description
The semiconductor industry looks to constantly improve the efficiency of research and development in order to reduce costs and time to market. One such method was designed in order to decrease time spent inducing warpage in integrated circuits in an

The semiconductor industry looks to constantly improve the efficiency of research and development in order to reduce costs and time to market. One such method was designed in order to decrease time spent inducing warpage in integrated circuits in an Intel research process. Intel's Atom product line seeks to compete with ARM architecture by entering the mobile devices CPU market. Due to the fundamental differences between the Atom's Bonnell architecture and the ARM architecture, the Intel Atom product line must utilize such improved research and development methods. Until power consumption is drastically lowered while maintaining processing speed, the Atom product line will not be able to effectively break into the mobile devices CPU market.
Date Created
2013-05
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Characterization of Novel Thin-Films and Structures for Integrated Circuit and Photovoltaic Applications

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Description
Thin films have been widely used in various applications. This research focuses on the characterization of novel thin films in the integrated circuits and photovoltaic techniques. The ion implanted layer in silicon can be treated as ion implanted thin film,

Thin films have been widely used in various applications. This research focuses on the characterization of novel thin films in the integrated circuits and photovoltaic techniques. The ion implanted layer in silicon can be treated as ion implanted thin film, which plays an essential role in the integrated circuits fabrication. Novel rapid annealing methods, i.e. microwave annealing and laser annealing, are conducted to activate ion dopants and repair the damages, and then are compared with the conventional rapid thermal annealing (RTA). In terms of As+ and P+ implanted Si, the electrical and structural characterization confirms that the microwave and laser annealing can achieve more efficient dopant activation and recrystallization than conventional RTA. The efficient dopant activation in microwave annealing is attributed to ion hopping under microwave field, while the liquid phase growth in laser annealing provides its efficient dopant activation. The characterization of dopants diffusion shows no visible diffusion after microwave annealing, some extent of end range of diffusion after RTA, and significant dopant diffusion after laser annealing.

For photovoltaic applications, an indium-free novel three-layer thin-film structure (transparent composited electrode (TCE)) is demonstrated as a promising transparent conductive electrode for solar cells. The characterization of TCE mainly focuses on its optical and electrical properties. Transfer matrix method for optical transmittance calculation is validated and proved to be a desirable method for predicting transmittance of TCE containing continuous metal layer, and can estimate the trend of transmittance as the layer thickness changes. TiO2/Ag/TiO2 (TAgT) electrode for organic solar cells (OSCs) is then designed using numerical simulation and shows much higher Haacke figure of merit than indium tin oxide (ITO). In addition, TAgT based OSC shows better performance than ITO based OSC when compatible hole transfer layer is employed. The electrical and structural characterization of hole transfer layers (HTLs) in OSCs reveals MoO3 is the compatible HTL for TAgT anode. In the end, the reactive ink printed Ag film for solar cell contact application is studied by characterizing its electromigration lifetime. A percolative model is proposed and validated for predicting the resistivity and lifetime of printed Ag thin films containing porous structure.
Date Created
2017
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