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High-Precision Micropipette Thermal Sensor for Measurement of Thermal Conductivity of Carbon Nanotubes Thin Film

Description: The thesis describes novel glass micropipette thermal sensor fabricated in cost-effective manner and thermal conductivity measurement of carbon nanotubes (CNT) thin film using the developed sensor. Various micrometer-sized sensors, which range from 2 µm to 30 µm, were produced and tested. The capability of the sensor in measuring thermal fluctuation at micro level with an estimated resolution of ±0.002oC is demonstrated. The sensitivity of sensors was recorded from 3.34 to 8.86 µV/oC, which is independent of tip size and dependent on the coating of Nickel. The detailed experimental setup for thermal conductivity measurement of CNT film is discussed and 73.418 W/moC was determined as the thermal conductivity of the CNT film at room temperature.
Date: August 2011
Creator: Shrestha, Ramesh
Partner: UNT Libraries

Dislocation Dynamics Simulations of Plasticity in Cu Thin Films

Description: Strong size effects in plastic deformation of thin films have been experimentally observed, indicating non-traditional deformation mechanisms. These observations require improved understanding of the behavior of dislocation in small size materials, as they are the primary plastic deformation carrier. Dislocation dynamics (DD) is a computational method that is capable of directly simulating the motion and interaction of dislocations in crystalline materials. This provides a convenient approach to study micro plasticity in thin films. While two-dimensional dislocation dynamics simulation in thin film proved that the size effect fits Hall-Petch equation very well, there are issues related to three-dimensional size effects. In this work, three-dimensional dislocation dynamics simulations are used to study model cooper thin film deformation. Grain boundary is modeled as impenetrable obstacle to dislocation motion in this work. Both tension and cyclic loadings are applied and a wide range of size and geometry of thin films are studied. The results not only compare well with experimentally observed size effects on thin film strength, but also provide many details on dislocation processes in thin films, which could greatly help formulate new mechanisms of dislocation-based plasticity.
Date: August 2013
Creator: Wu, Han
Partner: UNT Libraries

Understanding Size Effect in Cleavage Cracking in Thin Materials

Description: In a specially designed tensile fracture experiment on bicrysal thin films, it was discovered that the fracture toughness of a thin film is not a material constant; rather, as the film becomes thinner it decreases much faster than the prediction of conventional theory. A detailed analysis revealed that this is caused by the mismatch of crystalline structures and, more importantly, with an appropriate crystalline orientation distribution the decrease may be suppressed. This result shed light on the fundamentals of crystal behaviors in pressurized matters. It also provides a promising solution to minimize unexpected failures in nano/micro-electromechanical systems, and therefore is of immense technological importance.
Date: February 22, 2013
Creator: Qiao, Yu
Partner: UNT Libraries Government Documents Department

Materials properties of ruthenium and ruthenium oxides thin films for advanced electronic applications.

Description: Ruthenium and ruthenium dioxide thin films have shown great promise in various applications, such as thick film resistors, buffer layers for yttrium barium copper oxide (YBCO) superconducting thin films, and as electrodes in ferroelectric memories. Other potential applications in Si based complementary metal oxide semiconductor (CMOS) devices are currently being studied. The search for alternative metal-based gate electrodes as a replacement of poly-Si gates has intensified during the last few years. Metal gates are required to maintain scaling and performance of future CMOS devices. Ru based materials have many desirable properties and are good gate electrode candidates for future metal-oxide-semiconductor (MOS) device applications. Moreover, Ru and RuO2 are promising candidates as diffusion barriers for copper interconnects. In this thesis, the thermal stability and interfacial diffusion and reaction of both Ru and RuO2 thin films on HfO2 gate dielectrics were investigated using Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). An overview of Ru and RuO2/HfO2 interface integrity issues will be presented. In addition, the effects of C ion modification of RuO2 thin films on the physico-chemical and electrical properties are evaluated.
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Date: May 2006
Creator: Lim, ChangDuk
Partner: UNT Libraries

Theory and experimental study of surfactant effects on epitaxial growth of compound semiconductors.

Description: The work discussed in this report was supported by a Campus Fellowship LDRD. The report contains three papers that were published by the fellowship recipient and these papers form the bulk of his dissertation. They are reproduced here to satisfy LDRD reporting requirements.
Date: February 1, 2004
Creator: Wixom, Ryan R. (University of Utah, Salt Lake City, UT)
Partner: UNT Libraries Government Documents Department

Solar Power Generation Development

Description: This project centered on creating a solar cell prototype enabling significant reductions in module cost and increases in module efficiency. Low cost was addressed by using plentiful organic materials that only comprise 16% of the total module cost, and by leveraging building integrated PV concepts that reduce the cost of key module components to zero. High efficiency was addressed by implementing multiband organic PV, low cost spectral splitting, and possibly integrating photovoltaic and photothermal mechanisms. This research has contributed to the design of multiband organic PV, and the sealing of organic PV cells. If one assumes that the aggregate multiband efficiency can reach 12%, projected cost would be $0.97/W. If the sealing technology enables 10 to 20 year lifetimes, the LCOE will match that of domestic coal. The final report describes progress towards these goals.
Date: October 28, 2011
Creator: Jr., Robert L. Johnson & Carver, Gary E.
Partner: UNT Libraries Government Documents Department

Low Cost Thin Film Building-Integrated Photovoltaic Systems

Description: The goal of the program is to develop 'LOW COST THIN FILM BUILDING-INTEGRATED PV SYSTEMS'. Major focus was on developing low cost solution for the commercial BIPV and rooftop PV market and meet DOE LCOE goal for the commercial market segment of 9-12 cents/kWh for 2010 and 6-8 cents/kWh for 2015. We achieved the 2010 goal and were on track to achieve the 2015 goal. The program consists of five major tasks: (1) modules; (2) inverters and BOS; (3) systems engineering and integration; (4) deployment; and (5) project management and TPP collaborative activities. We successfully crossed all stage gates and surpassed all milestones. We proudly achieved world record stable efficiencies in small area cells (12.56% for 1cm2) and large area encapsulated modules (11.3% for 800 cm2) using a triple-junction amorphous silicon/nanocrystalline silicon/nanocrystalline silicon structure, confirmed by the National Renewable Energy Laboratory. We collaborated with two inverter companies, Solectria and PV Powered, and significantly reduced inverter cost. We collaborated with three universities (Syracuse University, University of Oregon, and Colorado School of Mines) and National Renewable Energy Laboratory, and improved understanding on nanocrystalline material properties and light trapping techniques. We jointly published 50 technical papers in peer-reviewed journals and International Conference Proceedings. We installed two 75kW roof-top systems, one in Florida and another in New Jersey demonstrating innovative designs. The systems performed satisfactorily meeting/exceeding estimated kWh/kW performance. The 50/50 cost shared program was a great success and received excellent comments from DOE Manager and Technical Monitor in the Final Review.
Date: May 25, 2012
Creator: Guha, Dr. Subhendu & Yang, Dr. Jeff
Partner: UNT Libraries Government Documents Department

Thin-Film Reliability Trends Toward Improved Stability: Preprint

Description: Long-term, stable performance of photovoltaic (PV) modules will be increasingly important to their successful penetration of the power grid. This paper summarizes more than 150 thin-film and more than 1700 silicon PV degradation rates (Rd) quoted in publications for locations worldwide. Partitioning the literature results by technology and date of installation statistical analysis shows an improvement in degradation rate especially for thin-film technologies in the last decade. A CIGS array deployed at NREL for more than 5 years that appears to be stable supports the literature trends. Indoor and outdoor data indicate undetectable change in performance (0.2+/-0.2 %/yr). One module shows signs of slight degradation from what appears to be an initial manufacturing defect, however it has not affected the overall system performance.
Date: July 1, 2011
Creator: Jordan, D. C. & Kurtz, S. R.
Partner: UNT Libraries Government Documents Department

Overcoming Degradation in Organic Photovoltaics: Illuminating the Role of Fullerene Functionalization: Preprint

Description: Photobleaching rates are investigated for thin films of poly(3-hexylthiophene) (P3HT) blends employing either an indene-C60 bisadduct (ICBA) or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the electron acceptor. Relative to the bisindene, PCBM significantly enhances resistance to photobleaching of the P3HT donor polymer. We tentatively attribute a decrease in the charge transfer rate as the mechanism responsible for the more rapid photobleaching in the sample containing the bisindene adduct. In order to elucidate the influence of the photobleaching rate on the initial performance of unencapsulated devices, we also monitored the time-dependent behavior for P3HT:fullerene inverted devices. Under conditions of constant illumination, we observe essentially identical behavior in device performance parameters regardless of the energy levels of the electron acceptor. We conclude that over the time frame measured for these devices, the primary degradation mechanism of the active layer is independent of the electron acceptor, despite the enhanced tolerance to photobleaching it may impart to the donor material.
Date: July 1, 2011
Creator: Lloyd, M. T.; Garcia, A.; Berry, J. J.; Reese, M. O.; Ginley, D. S. & Olson, D. C.
Partner: UNT Libraries Government Documents Department

Characterization of Field Exposed Thin Film Modules: Preprint

Description: Test arrays of thin film modules have been deployed at the Solar Energy Centre near New Delhi, India since 2002-2003. Performances of these arrays were reported by O.S. Sastry [1]. This paper reports on NREL efforts to support SEC by performing detailed characterization of selected modules from the array. Modules were selected to demonstrate both average and worst case power loss over the 8 years of outdoor exposure. The modules characterized included CdTe, CIS and three different types of a-Si. All but one of the a-Si types were glass-glass construction. None of the modules had edge seals. Detailed results of these tests are presented along with our conclusions about the causes of the power loss for each technology.
Date: June 1, 2012
Creator: Wohlgemuth, J. H.; Sastry, O. S.; Stokes, A.; Singh, Y. K. & Kumar, M.
Partner: UNT Libraries Government Documents Department

Development of Advanced Polymeric Reflector for CSP Applications - Final Report

Description: This project attempted to deposit extremely thick and dense protective barrier onto a mirror film stack with a PET substrate. The target thickness was very high for thin film products; particularly since large areas and long production lengths of film are needed to make the final product economic. The technical investigations in this project centered on maintaining a quality barrier (i.e. dense film) while evaporating alumina with a high deposition rate onto a low cost PET substrate. The project found that the proposed configuration, particularly direct ion bombardment, provides too narrow a solution space to effectively and economically produce the ASRM attempted. The initial project goals were met when depositing on a limited width and at a modest rate. However, expanding to wide deposition at aggressive deposition rates did not produce consistent film quality. Economic viability drives the process to maximize deposition rate. The current system configuration has a limiting upper rate threshold that does not appear economically viable. For future work, alternate approaches seem needed to address the challenges encountered in the scale-up phase of this project.
Date: March 28, 2013
Creator: Treglio, Richard T.; Boyle, Keith, A & Henderson, Hildie
Partner: UNT Libraries Government Documents Department

Development of an efficient large-aperture high damage-threshold sol-gel diffraction grating.

Description: In order to develop the next generation of high peak intensity lasers, new grating technology providing higher damage thresholds and large apertures is required. The current assumption is that this technical innovation will be multilayer dielectric gratings, wherein the uppermost layer of a thin film mirror is etched to create the desired binary phase grating. A variant of this is explored with the upper grating layer being a lower density gelatin-based volume phase grating in either sol-gel or dichromated gelatin. One key benefit is the elimination of the etching step.
Date: March 1, 2005
Creator: Ashley, Carol S.; Rambo, Patrick K.; Schwarz, Jens; Dunphy, Darren Robert; Branson, Eric D.; Smith, Ian Craig et al.
Partner: UNT Libraries Government Documents Department

Texture Control in Cerium Oxide Films (Poster)

Description: The conclusions are: (1) Texture control is possible in cerium oxide by epitaxial growth or adjusting the substrate angle; (2) Biaxial (111) texture emerges with inclined angle depositions on glass; and (3) Biaxial (200) texture emerges by epitaxial growth on YSZ.
Date: May 1, 2006
Creator: van Hest, M. F. A. M.; Leenheer, A. J.; Perkins, J. D.; Teplin, C. W. & Ginley, D. S.
Partner: UNT Libraries Government Documents Department

The NSLS-II Multilayer Laue Lens Deposition System

Description: The NSLS-II[1] program has a requirement for an unprecedented level of x-ray nanofocusing and has selected the wedged multilayer Laue lens[2,3] (MLL) as the optic of choice to meet this goal. In order to fabricate the MLL a deposition system is required that is capable of depositing depth-graded and laterally-graded multilayers with precise thickness control over many thousands of layers, with total film growth in one run up to 100m thick or greater. This machine design expounds on the positive features of a rotary deposition system[4] constructed previously for MLLs and will contain multiple stationary, horizontally-oriented magnetron sources where a transport will move a substrate back and forth in a linear fashion over shaped apertures at well-defined velocities to affect a multilayer coating.
Date: August 2, 2009
Creator: Conley, R.; Bouet, N.; Biancarosa, J.; Shen, Q.; Boas, L.; Feraca, J. et al.
Partner: UNT Libraries Government Documents Department

Optical Switching in VO2 films by below-gap excitation

Description: We study the photo-induced insulator-metal transition in VO2, correlating threshold and dynamic evolution with excitation wavelength. In high-quality single crystal samples, we find that switching can only be induced with photon energies above the 670-meV gap. This contrasts with the case of polycrystalline films, where formation of the metallic state can also be triggered with photon energies as low as 180 meV, well below the bandgap. Perfection of this process may be conducive to novel schemes for optical switches, limiters and detectors, operating at room temperature in the mid-IR.
Date: March 14, 2008
Creator: Dipartimento di Fisica, Universita?di Brescia, Italy
Partner: UNT Libraries Government Documents Department

Development of novel boron-based multilayer thin-film. Semi-annual report for December 15, 1998 to June 15, 1999

Description: In the past six months, this project was focused on more fundamental studies of the coating properties. The properties of each individual coating TiB{sub 2}, TiBC as well as the alternating TiB{sub 2}/TiBC laminates were studied. These properties include residual stress, surface morphology and topography, adhesion and wear rate. The coatings were deposited using dc magnetron reactive sputtering process. Deposition of the films was carried out in a production-scale, three-chamber-in-line coating system, consisting of a load-lock chamber, and two deposition chambers. The substrates were cleaned and mounted on a rack before going into the chamber. A computerized conveyor system transported the rack into the load-lock chamber, where the pressure was pumped down to around 2E-5 torr. The substrates were then preheated by an infrared heater to about 100 C. After preheating, the substrates were transported into the first deposition chamber through a gate valve. The base pressure of the deposition chambers is 2E-6 torr. A layer of Ti was deposited on the substrates using two 5 inch x 20 inch Ti targets in the first deposition chamber as the adhesion layer. The substrates were then transported to the second deposition chamber for the TiB{sub 2} and Ti-B-C-N depositions. In the second deposition chamber, two 5 inch x 20 inch TiB{sub 2} targets were mounted on both sides. For the TiB{sub 2} deposition, argon was introduced into the chamber. For the Ti-B-C-N deposition, acetylene and nitrogen were introduced into the chamber through four gas distribution manifolds to insure the uniformity. The partial pressure of the reactive gases were controlled by a PID control loop. Substrate bias is one of the key deposition parameters. Bias voltages ranged from 40 to 300V. Current density is around 2 mA/cm{sup 2}. The deposition rate is about 1.5 {micro}m/hr. All the test coatings, used for thickness ...
Date: August 2, 1999
Creator: Nieh, Simon
Partner: UNT Libraries Government Documents Department

Stable Nanocrystalline Au Film Structures for Sliding Electrical Contacts

Description: Hard gold thin films and coatings are widely used in electronics as an effective material to reduce the friction and wear of relatively less expensive electrically conductive materials while simultaneously seeking to provide oxidation resistance and stable sliding electrical contact resistance (ECR). The main focus of this dissertation was to synthesize nanocrystalline Au films with grain structures capable of remaining stable during thermal exposure and under sliding electrical contact stress and the passing of electrical current. Here we have utilized a physical vapor deposition (PVD) technique, electron beam evaporation, to synthesize Au films modified by ion implantation and codeposited ZnO hardened Au nanocomposites. Simultaneous friction and ECR experiments of low fluence (< 1x10^17 cm^-2) He and Ar ion implanted Au films showed reduction in friction coefficients from ~1.5 to ~0.5 and specific wear rates from ~4x10^-3 to ~6x10^-5 mm^3/N·m versus as-deposited Au films without significant change in sliding ECR (~16 mΩ). Subsurface microstructural changes of He implanted films due to tribological stress were analyzed via site-specific cross-sectional transmission electron microscopy (TEM) and revealed the formation of nanocrystalline grains for low energy (22.5 keV) implantation conditions as well as the growth and redistribution of cavities. Nanoindentation hardness results revealed an increase from 0.84 GPa for as-deposited Au to ~1.77 GPa for Au uniformly implanted with 1 at% He. These strength increases are correlated with an Orowan hardening mechanism that increases proportionally to (He concentration)1/3. Au-ZnO nanocomposite films in the oxide dilute regime (< 5 vol% ZnO) were investigated for low temperature aging stability in friction and ECR. Annealing at 250 °C for 24 hours Au-(2 vol%)ZnO retained a friction coefficient comparable to commercial Ni hardened Au of ~ 0.3 and sliding ECR values of ~35 mΩ. Nanoindentation hardness increases of these films (~2.6 GPa for 5 vol% ZnO) are correlated to ...
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Date: May 2016
Creator: Mogonye, Jon-Erik
Partner: UNT Libraries

ENHANCED GROWTH RATE AND SILANE UTILIZATION IN AMORPHOUS SILICON AND NANOCRYSTALLINE-SILICON SOLAR CELL DEPOSITION VIA GAS PHASE ADDITIVES

Description: Air Products set out to investigate the impact of additives on the deposition rate of both µCSi and αSi-H films. One criterion for additives was that they could be used in conventional PECVD processing, which would require sufficient vapor pressure to deliver material to the process chamber at the required flow rates. The flow rate required would depend on the size of the substrate onto which silicon films were being deposited, potentially ranging from 200 mm diameter wafers to the 5.7 m2 glass substrates used in GEN 8.5 flat-panel display tools. In choosing higher-order silanes, both disilane and trisilane had sufficient vapor pressure to withdraw gas at the required flow rates of up to 120 sccm. This report presents results obtained from testing at Air Products’ electronic technology laboratories, located in Allentown, PA, which focused on developing processes on a commercial IC reactor using silane and mixtures of silane plus additives. These processes were deployed to compare deposition rates and film properties with and without additives, with a goal of maximizing the deposition rate while maintaining or improving film properties.
Date: August 31, 2012
Creator: Ridgeway, R.G.; Hegedus, S.S. & Podraza, N.J.
Partner: UNT Libraries Government Documents Department

Outdoor Performance of a Thin-Film Gallium-Arsenide Photovoltaic Module

Description: We deployed a 855 cm2 thin-film, single-junction gallium arsenide (GaAs) photovoltaic (PV) module outdoors. Due to its fundamentally different cell technology compared to silicon (Si), the module responds differently to outdoor conditions. On average during the test, the GaAs module produced more power when its temperature was higher. We show that its maximum-power temperature coefficient, while actually negative, is several times smaller in magnitude than that of a Si module used for comparison. The positive correlation of power with temperature in GaAs is due to temperature-correlated changes in the incident spectrum. We show that a simple correction based on precipitable water vapor (PWV) brings the photocurrent temperature coefficient into agreement with that measured by other methods and predicted by theory. The low operating temperature and small temperature coefficient of GaAs give it an energy production advantage in warm weather.
Date: June 1, 2013
Creator: Silverman, T. J.; Deceglie, M. G.; Marion, B.; Cowley, S.; Kayes, B. & Kurtz, S.
Partner: UNT Libraries Government Documents Department

Group 3: Humidity, Temperature and Voltage (Presentation)

Description: This is a summary of the work of Group 3 of the International PV QA Task Force. Group 3 is chartered to develop accelerated stress tests that can be used as comparative predictors of module lifetime versus stresses associated with humidity, temperature and voltage.
Date: September 1, 2013
Creator: Wohlgemuth, J.
Partner: UNT Libraries Government Documents Department

A NOVEL LOW THERMAL BUDGET THIN-FILM POLYSILICON FABRICATION PROCESS FOR LARGE-AREA, HIGH-THROUGHPUT SOLAR CELL PRODUCTION

Description: A novel thin-film poly-Si fabrication process has been demonstrated. This low thermal budget process transforms the single- and multi-layer amorphous silicon thin films into a poly-Si structure in one simple step over a pulsed rapid thermal annealing process with the enhancement of an ultrathin Ni layer. The complete poly-Si solar cell was fabricated in a short period of time without deteriorating the underneath glass substrate. The unique vertical crystallization process including the mechanism is discussed. Influences of the dopant type and process parameters on crystal structure will be revealed. The poly-Si film structure has been proved using TEM, XRD, Raman, and XPS methods. The poly-Si solar cell structure and the performance have been examined. In principle, the new process is potentially applicable to produce large-area thin-film poly-Si solar cells at a high throughput and low cost. A critical issue in this process is to prevent the excessive dopant diffusion during crystallization. Process parameters and the cell structure have to be optimized to achieve the production goal.
Date: August 15, 2010
Creator: Kuo, Yue
Partner: UNT Libraries Government Documents Department

Evaluation of a Thin-Film Sea Water Distillation Unit for Marine and Shore Base Application

Description: Report issued by the Office of Saline Water over studies conducted on a thin film sea water distillation unit. As stated in the summary, "a General Electric Thin Film Sea Water Distillation Unit designed for marine application has been evaluated. The results demonstrate the feasibility of the thin film process for this application. The technology made available by this work provides criteria for the design of compact equipment" (p. 1). This report includes tables, illustrations, and photographs.
Date: October 1961
Creator: General Electric Company
Partner: UNT Libraries Government Documents Department

Thin Film Photovoltaics

Description: The motivation to develop thin film technologies dates back to the inception of photovoltaics. It is an idea based on achieving truly low-cost photovoltaics appropriate for mass production and energy significant markets. The key to the idea is the use of pennies worth of active materials. Since sunlight carries relatively little energy in comparison with combustion-based energy sources, photovoltaic (PV) modules must be cheap to produce energy that can be competitive. Thin films are presumed to be the answer to that low-cost requirement. But how cheap do they have to be? The following is an oversimplified analysis that allows some insight into this question.
Date: November 19, 1998
Creator: Zweibel, K.
Partner: UNT Libraries Government Documents Department