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Title: REDISTRIBUTION OF MANGANESE ION IMPLANTED IN SILICON.
Creator: Shunmugavelu, Arun, An, Linan, University of Central Florida
Abstract / Description: Ion implantation and the subsequent redistribution of manganese atoms in Czochralski Silicon (Cz-Si) and Floating Zone Silicon (Fz-Si) due to thermal annealing between 300 C and 1000 C is studied using Secondary Ion Mass Spectroscopy. The samples ion implanted at 340 C showed multiple peak formation above 900 C. This was not observed for the samples ion implanted at room temperature. Cz-Si and Fz-Si showed similar redistribution profiles.
Date Issued: 2007
Identifier: CFE0001909, ucf:47477
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001909

Title: Characterization, Morphology, Oxidation, and Recession of Silicon Nanowires Grown by Electroless Process.
Creator: Mertens, Robert, Sundaram, Kalpathy, Yuan, Jiann-Shiun, Chow, Louis, Wahid, Parveen, Blair, Richard, University of Central Florida
Abstract / Description: This dissertation presents heretofore undiscovered properties of Silicon Nanowires (SiNWs) grown by electroless process and presents mathematical solutions to the special problems of the oxidation and diffusion of dopants for SiNWs. Also presented here is a mathematical description of morphology of oxidized SiNWs. This dissertation is comprised of several discussions relating to SiNWs growth, oxidation, morphology and doping.In here is presented work derived from a long-term study of SiNWs....
Show moreThis dissertation presents heretofore undiscovered properties of Silicon Nanowires (SiNWs) grown by electroless process and presents mathematical solutions to the special problems of the oxidation and diffusion of dopants for SiNWs. Also presented here is a mathematical description of morphology of oxidized SiNWs. This dissertation is comprised of several discussions relating to SiNWs growth, oxidation, morphology and doping.In here is presented work derived from a long-term study of SiNWs. Several important aspects of SiNWs were investigated and the results published in journals and conference papers. The recession of SiNWs was heretofore unreported by other research groups. In our investigations, this began as a question, (")How far into the substrate does the etching process go when this method is used to make SiNWs?(") Our investigations showed that recession did take place, was controllable and that a number of variables were responsible. The growth mechanism of SiNWs grown by electroless process is discussed at length. The relation of exposed area to volume of solution is shown, derived from experimentation. A relation of Silver used to Si removed is presented, derived from experimentation. The agglomeration of SiNWs grown by the electroless process is presented.The oxidation of SiNWs is a subject of interest to many groups, although most other groups work with SiNWs grown by the VLS process, which is more difficult, time-consuming and expensive to do. The oxidation of planar Silicon (Si) is still a subject of study, even today, after many years of working with and refining our formulae, because of the changing needs of this science and industry. SiNWs oxidation formulae are more complicated than those for planar Si, partly because of their morphology and partly because of their scale. While planar Si only presents one orientation for oxidation, SiNWs present a range of orientations, usually everything between (<)100(>) and (<)110(>) ( the (<)111(>) orientation is usually not presented during oxidation). This complicates the post-oxidation morphology to the extent that, subsequent to oxidation, SiNWs are more rectangular than cylindrical in shape. After etching to remove an oxidation layer from the SiNWs, the rectangular shape shifts 90(&)deg; in orientation.In traditional oxidation, the Deal-Grove formulae are used, but when the oxidation must take place in very small layers, such as with nanoscale devices, the Massoud formulae have to be used. However, even with Massoud, these formulae are not as good because of the morphology. Deal-Grove and Massoud formulae are intended for use with planar Si. We present some formulae that show the change in shape of SiNWs during oxidation, due to their morphology.The diffusion of dopants in SiNWs is a subject few research groups have taken up. Most of the groups who have, use SiNWs grown by the VLS method to make measurements and report findings. In order to measure the diffusion of dopants in SiNWs, a controllable diameter is needed. There are a number of ways to measure diffusion in SiNWs, but none of the ones used so far apply well to SiNWs grown by electroless process. Usually these groups present some mathematical formulae to predict diffusion in SiNWs, but these seem to lack mathematical rigor. Diffusion is a process that is best understood using Fick's Laws, which are applied to the problem of SiNWs in this dissertation.Diffusion is a science with a long history, going back at least 150 years. There are many formulae that can be used in the most common diffusion processes, but the processes involved with the diffusion of dopants in SiNWs is more complex than the simple diffusion processes that are fairly well-understood. Diffusion doping of SiNWs is a multiphase process that is more complex, first because it is multiphase and second because the second step involves a multiplicity of diffusing elements, plus oxidation, which brings on the problems of moving boundaries.In this dissertation, we present solutions to these problems, and the two-step diffusion process for SiNWs.
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Date Issued: 2012
Identifier: CFE0004412, ucf:49366
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004412

Title: INFRARED SURFACE PLASMON POLARITONS ON SEMICONDUCTOR, SEMIMETAL AND CONDUCTING POLYMER.
Creator: Shahzad, Monas, Peale, Robert, Heinrich, Helge, Coffey, Kevin, Diaz, Diego, University of Central Florida
Abstract / Description: Conductors with IR (infrared) plasma frequencies are potentially useful hosts of surface plasmon polaritons (SPPs) with subwavelength mode confinement for sensing applications. The underlying aim of this work is to identify such conductors that also have sharp SPP excitation resonances for biosensor applications at infrared (3-11 ?m) wavelengths, where biological analytes are strongly differentiated by their IR absorption spectra. In this work, various materials were investigated such as a...
Show moreConductors with IR (infrared) plasma frequencies are potentially useful hosts of surface plasmon polaritons (SPPs) with subwavelength mode confinement for sensing applications. The underlying aim of this work is to identify such conductors that also have sharp SPP excitation resonances for biosensor applications at infrared (3-11 ?m) wavelengths, where biological analytes are strongly differentiated by their IR absorption spectra. In this work, various materials were investigated such as a heavily doped semiconductor, a semimetal, a conducting polymer and its composite.Heavily doped silicon was investigated by tuning its plasma frequency to the infrared region by heavily doping. The measured complex permittivity spectra for p-type silicon with a carrier concentration of 6 (&)#215; 1019 and 6 (&)#215; 1020 cm-3 show that these materials support SPPs beyond 11 and 6 ?m wavelengths, respectively. SPP generation was observed in angular reflection spectra of doped-silicon gratings. Photon-to-plasmon coupling resonances, a necessary condition for sensing, were demonstrated near 10 ?m wavelength for the heaviest doped, and the observed resonances were confirmed theoretically using analytic calculations. The permittivity spectra were also used to calculate SPP mode heights above the silicon surface and SPP propagation lengths. Reasonable merit criteria applied to these quantities suggest that only the heaviest doped material has sensor potential, and then mainly within the wavelength range of 6 to 10 ?m. The semimetal bismuth (Bi) has an infrared plasmon frequency less than the infrared plasma frequency of noble metals such as gold and silver, which is one order of magnitude lower than their plasma frequencies. The excitation of IR surface plasmons on Bi lamellar gratings in the wavelength range of 3.4 (&)#181;m to 10.6 (&)#181;m was observed. Distinct SPP resonances were observed although the usual condition for bound SPP is not satisfied in this wavelength range because the real part of the permittivity is positive. The excitation of these resonances agrees theoretically with the electromagnetic surface waves called surface polaritons (SPs). The measured permittivity spectra were used to calculate the SP mode heights above the bismuth surface and SP propagation length, which satisfied our criteria for sensors.A conducting polymer and its composite with graphite were also investigated since their plasma frequency may lie in the infrared region. Polyaniline was chemically synthesized and doped with various acids to prepare its salt form. A composite material of polyaniline with colloidal and nano-graphite was also prepared. Optical constants were measured in the long wave infrared region (LWIR) and were used to calculate SPP propagation length and penetration depth. SPP resonance spectra were calculated and suggested that polyaniline and its composite can be used as a host with sufficient mode confinement for IR sensor application.
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Date Issued: 2012
Identifier: CFE0004598, ucf:49215
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004598

Title: Design and characterization of system level electrostatic discharge (ESD) protection solutions.
Creator: Xi, Yunfeng, Liou, Juin, Yuan, Jiann-Shiun, Sundaram, Kalpathy, Jin, Yier, Salcedo, Javier, University of Central Florida
Abstract / Description: Electrostatic Discharges (ESD) are one of the main reliability threats in modern electronics. Design, implementation, and characterization of ESD and transient protection of these modern electronics are increasingly challenging due to the process, packaging and cost constraints. Growing communication between 'objects' to be sensed and controlled remotely is creating opportunities for greater integration with computer systems, resulting in improved efficiency, accuracy and economic benefits...
Show moreElectrostatic Discharges (ESD) are one of the main reliability threats in modern electronics. Design, implementation, and characterization of ESD and transient protection of these modern electronics are increasingly challenging due to the process, packaging and cost constraints. Growing communication between 'objects' to be sensed and controlled remotely is creating opportunities for greater integration with computer systems, resulting in improved efficiency, accuracy and economic benefits across existing and emerging network infrastructures. This tendency is driving an expansion in data communication as well as industrial applications environment. To keep up with the interconnectivity expansion, the industry requires new devices to support more effectively high speed signals processing over long distances and be able to reliably operate in harsh and noisy environments. Electrical over-stress transients caused by ESD or switching of inductive loads can corrupt data transmission and damage bus transceivers unless effective measures are taken to address the impact of such high energy transient stress conditions. Today's industry specifications for integrated circuits require 1kV HBM on all pins, but selected pins with direct contact to the external environment must comply with levels as high as 8kV for IEC 61000-4-2 and ISO 10605 standards. The rapid evolution of the handheld and mobile device market segment, dramatic increase of electronic content in automotive products, and substantial progress in industrial and medical applications created a new need for on-chip protection against system level ESD stresses. This PhD work investigates the impact of system-level type of ESD stress on components. Firstly, correlation factors between different ESD pulse types for different BEOL metal line topologies have been studied to support system level on-chip ESD design. The component level (HMM, HBM and TLP on wafer) and system level (IEC gun contact on package) ESD stresses were correlated followed by extraction of correlation factors between the IEC/HMM and TLP, as well as the HBM and TLP supported by analytical approximation. The major conclusions were verified using the thermal coupled mixed-mode simulations analysis. Secondly, operation of NLDMOS-SCR devices under the HMM and IEC air gap electrostatic discharge (ESD) stresses has been studied based on both the pulsed measurements and mixed-mode simulations. Under the IEC air gap testing, the devices are found to suffer the non-uniform multi-finger turn-on behavior and hence a relatively low passing level, while both the IEC contact and HMM stresses do not give rise to such an adversary effect and result in a considerably higher passing level. It is further shown that the non-uniform multi-finger turn-on effect depends on the stress pulse rise time. Such a dependency has also been examined and verified using the transmission line pulsing (TLP) technique with rise times ranging from 10 to 40ns. In the last section, a new silicon-controlled rectifier (SCR) fabricated in a 30 V mixed-signal CDMOS (CMOS/DMOS) technology is presented. This device allows for robust EMI (electromagnetic interference) and ESD (electrostatic discharge) protection solution for high speed industrial interface applications operating in variable voltage swing range from -7V to +12V. This new SCR has reduced overshoot voltage and leakage current when electrically stressed under different pulse widths and temperatures. Analysis of the device physics is complemented via numerical TCAD mixed-mode simulations. A 200 x 200 (&)#181;m2 device designed in an annular configuration achieved (>) (&)#177; 8 kV IEC robustness by handling (>) (&)#177; 20 Amp of TLP current while clamping the voltage to (&)#177;3V within 2-nsec.
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Date Issued: 2016
Identifier: CFE0006199, ucf:51113
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006199

Title: Advanced Metrology and Diagnostic Loss Analytics for Crystalline Silicon Photovoltaics.
Creator: Schneller, Eric, Schoenfeld, Winston, Thomas, Jayan, Fenton, James, Coffey, Kevin, Sundaram, Kalpathy, University of Central Florida
Abstract / Description: Characterization plays a key role in developing a comprehensive understanding of the structure and performance of photovoltaic devices. High quality characterization methods enable researchers to assess material choices and processing steps, ultimately giving way to improved device performance and reduced manufacturing costs. In this work, several aspects of advanced metrology for crystalline silicon photovoltaic are investigated including in-line applications for manufacturing, off-line...
Show moreCharacterization plays a key role in developing a comprehensive understanding of the structure and performance of photovoltaic devices. High quality characterization methods enable researchers to assess material choices and processing steps, ultimately giving way to improved device performance and reduced manufacturing costs. In this work, several aspects of advanced metrology for crystalline silicon photovoltaic are investigated including in-line applications for manufacturing, off-line applications for research and development, and module/system level applications to evaluate long-term reliability. A frame work was developed to assess the cost and potential value of metrology within a manufacturing line. This framework has been published to an on-line calculator in an effort to provide the solar industry with an intuitive and transparent method of evaluating the economics of in-line metrology. One important use of metrology is in evaluating spatial non-uniformities, as localized defects in large area solar cells often reduce overall device performance. Techniques that probe spatial uniformity were explored and analysis algorithms were developed that provide insights regarding process non-uniformity and its impact on device performance. Finally, a comprehensive suite of module level characterization was developed to accurately evaluate performance and identify degradation mechanisms in field deployed photovoltaic modules. For each of these applications, case-studies were used to demonstrate the value of these techniques and to highlight potential use cases.
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Date Issued: 2016
Identifier: CFE0006499, ucf:51386
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006499

Title: Nonlinear integrated photonics on silicon and gallium arsenide substrates.
Creator: Ma, Jichi, Fathpour, Sasan, Hagan, David, Li, Guifang, Peale, Robert, University of Central Florida
Abstract / Description: Silicon photonics is nowadays a mature technology and is on the verge of becoming a blossoming industry. Silicon photonics has also been pursued as a platform for integrated nonlinear optics based on Raman and Kerr effects. In recent years, more futuristic directions have been pursued by various groups. For instance, the realm of silicon photonics has been expanded beyond the well-established near-infrared wavelengths and into the mid-infrared (3 (-) 5 (&)#181;m). In this wavelength range,...
Show moreSilicon photonics is nowadays a mature technology and is on the verge of becoming a blossoming industry. Silicon photonics has also been pursued as a platform for integrated nonlinear optics based on Raman and Kerr effects. In recent years, more futuristic directions have been pursued by various groups. For instance, the realm of silicon photonics has been expanded beyond the well-established near-infrared wavelengths and into the mid-infrared (3 (-) 5 (&)#181;m). In this wavelength range, the omnipresent hurdle of nonlinear silicon photonics in the telecommunication band, i.e., nonlinear losses due to two-photon absorption, is inherently nonexistent. With the lack of efficient light-emission capability and second-order optical nonlinearity in silicon, heterogeneous integration with other material systems has been another direction pursued. Finally, several approaches have been proposed and demonstrated to address the energy efficiency of silicon photonic devices in the near-infrared wavelength range. In this dissertation, theoretical and experimental works are conducted to extend applications of integrated photonics into mid-infrared wavelengths based on silicon, demonstrate heterogeneous integration of tantalum pentoxide and lithium niobate photonics on silicon substrates, and study two-photon photovoltaic effect in gallium arsenide and plasmonic-enhanced structures.Specifically, performance and noise properties of nonlinear silicon photonic devices, such as Raman lasers and optical parametric amplifiers, based on novel and reliable waveguide technologies are studied. Both near-infrared and mid-infrared nonlinear silicon devices have been studied for comparison. Novel tantalum-pentoxide- and lithium-niobate-on-silicon platforms are developed for compact microring resonators and Mach-Zehnder modulators. Third- and second-harmonic generations are theoretical studied based on these two platforms, respectively. Also, the two-photon photovoltaic effect is studied in gallium arsenide waveguides for the first time. The effect, which was first demonstrated in silicon, is the nonlinear equivalent of the photovoltaic effect of solar cells and offers a viable solution for achieving energy-efficient photonic devices. The measured power efficiency achieved in gallium arsenide is higher than that in silicon and even higher efficiency is theoretically predicted with optimized designs. Finally, plasmonic-enhanced photovoltaic power converters, based on the two-photon photovoltaic effect in silicon using subwavelength apertures in metallic films, are proposed and theoretically studied.
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Date Issued: 2014
Identifier: CFE0005373, ucf:50441
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005373

Title: LASER METALLIZATION AND DOPING FOR SILICON CARBIDE DIODE FABRICATION AND ENDOTAXY.
Creator: Tian, Zhaoxu, Kar, Aravinda, University of Central Florida
Abstract / Description: Silicon carbide is a promising semiconductor material for high voltage, high frequency and high temperature devices due to its wide bandgap, high breakdown electric field strength, highly saturated drift velocity of electrons and outstanding thermal conductivity. With the aim of overcoming some challenges in metallization and doping during the fabrication of silicon carbide devices, a novel laser-based process is provided to direct metallize the surface of silicon carbide without metal...
Show moreSilicon carbide is a promising semiconductor material for high voltage, high frequency and high temperature devices due to its wide bandgap, high breakdown electric field strength, highly saturated drift velocity of electrons and outstanding thermal conductivity. With the aim of overcoming some challenges in metallization and doping during the fabrication of silicon carbide devices, a novel laser-based process is provided to direct metallize the surface of silicon carbide without metal deposition and dope in silicon carbide without high temperature annealing, as an alternative to the conventional ion implantation, and find applications of this laser direct write metallization and doping technique on the fabrication of diodes, endotaxial layer and embedded optical structures on silicon carbide wafers. Mathematical models have been presented for the temperature distributions in the wafer during laser irradiation to optimize laser process parameters and understand the doping and metallization mechanisms in laser irradiation process. Laser irradiation of silicon carbide in a dopant-containing ambient allows to simultaneously heating the silicon carbide surface without melting and incorporating dopant atoms into the silicon carbide lattice. The process that dopant atoms diffuse into the bulk silicon carbide by laser-induced solid phase diffusion (LISPD) can be explained by considering the laser enhanced substitutional and interstitial diffusion mechanisms. Nitrogen and Trimethyaluminum (TMA) are used as dopants to produce n-type and p-type doped silicon carbide, respectively. Two laser doping methods, i.e., internal heating doping and surface heating doping are presented in this dissertation. Deep (800 nm doped junction for internal heating doping) and shallow (200 nm and 450 nm doped junction for surface heating doping) can be fabricated by different doping methods. Two distinct diffusion regions, near-surface and far-surface regions, were identified in the dopant concentration profiles, indicating different diffusion mechanisms in these two regions. The effective diffusion coefficients of nitrogen and aluminum were determined for both regions by fitting the diffusion equation to the measured concentration profiles. The calculated diffusivities are at least 6 orders of magnitude higher than the typical values for nitrogen and aluminum, which indicate that laser doping process enhances the diffusion of dopants in silicon carbide significantly. No amorphization was observed in laser-doped samples eliminating the need for high temperature annealing. Laser direct metallization can be realized on the surface of silicon carbide by generating metal-like conductive phases due to the decomposition of silicon carbide. The ohmic property of the laser direct metallized electrodes can be dramatically improved by fabricating such electrodes on laser heavily doped SiC substrate. This laser-induced solid phase diffusion technique has been utilized to fabricate endolayers in n-type 6H-SiC substrates by carbon incorporation. X-ray energy dispersive spectroscopic analysis shows that the thickness of endolayer is about 100 nm. High resolution transmission electron microscopic images indicate that the laser endotaxy process maintains the crystalline integrity of the substrate without any amorphization. Rutherford backscattering studies also show no amorphization and evident lattice disorder occur during this laser solid phase diffusion process. The resistivity of the endolayer formed in a 1.55 omega•cm silicon carbide wafer segment was found to be 1.1E5 omega•cm which is sufficient for device fabrication and isolation. Annealing at 1000 oC for 10 min to remove hydrogen resulted in a resistivity of 9.4E4 omega•cm. Prototype silicon carbide PIN diodes have been fabricated by doping the endolayer and parent silicon carbide epilayer with aluminum using this laser-induced solid phase diffusion technique to create p-regions on the top surfaces of the substrates. Laser direct metallized contacts were also fabricated on selected PIN diodes to show the effectiveness of these contacts. The results show that the PIN diode fabricated on a 30 nm thick endolayer can block 18 V, and the breakdown voltages and the forward voltages drop at 100 A/cm2 of the diodes fabricated on 4H-SiC with homoepilayer are 420 ~ 500 V and 12.5 ~ 20 V, respectively. The laser direct metallization and doping technique can also be used to synthesize embedded optical structures, which can increase 40% reflectivity compared to the parent wafer, showing potential for the creation of optical, electro-optical, opto-electrical, sensor devices and other integrated structures that are stable in high temperature, high-pressure, corrosive environments and deep space applications.
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Date Issued: 2006
Identifier: CFE0001061, ucf:46803
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001061

Title: Classification of Silicone-Based Personal and Condom Lubricants Using DART-TOFMS.
Creator: Harvey, Lauren, Bridge, Candice, Sigman, Michael, Campiglia, Andres, Yestrebsky, Cherie, University of Central Florida
Abstract / Description: Sexual lubricants are used to enable sexual encounters. There are different types of sexual lubricants such as water-based, oil-based, and silicone-based. They come pre-applied to condoms and separately in bottles as personal lubricants. Although sexual lubricants are intended for consensual use, they are also unfortunately used during the commission of sexual assaults. The analysis of sexual lubricants facilitates sexual assault investigations. With the increased usage of condoms in sexual...
Show moreSexual lubricants are used to enable sexual encounters. There are different types of sexual lubricants such as water-based, oil-based, and silicone-based. They come pre-applied to condoms and separately in bottles as personal lubricants. Although sexual lubricants are intended for consensual use, they are also unfortunately used during the commission of sexual assaults. The analysis of sexual lubricants facilitates sexual assault investigations. With the increased usage of condoms in sexual assault cases, the potential of collected DNA evidence in each case is reduced. In the absence of biological evidence, the presence of sexual lubricants after a sexual assault can provide an additional link between a suspect and the crime scene and/or victim. Having the ability to compare known and unknown sexual lubricants may be the only actionable information available for investigators. Current lubricant analysis only classifies samples into lubricant types based on the major component such as glycerol, petrolatum, and polydimethylsiloxane for water-based, oil-based, and silicone-based lubricants respectively. Differentiation within major types has not been explored. Previously, protocols have been developed to detect and categorize personal lubricants using Fourier transform infrared (FTIR) spectroscopy, gas chromatography-mass spectrometry (GC-MS), liquid chromatography mass spectrometry (LC-MS), and pyrolysis GC-MS. FTIR is routinely used as a screening tool to detect peaks of the major lubricant components and the mass spectrometry (MS) techniques are commonly used to confirm the presence of some of the major components, excluding PDMS.This thesis focused on the differentiation of silicone-based personal and condom lubricants because it is a common type of lubricant due to its ability to reduce friction for a longer period of time. Fifty-six (56) silicone personal and condom lubricants were analyzed to identify unique characteristics that can be used to determine individual sub-classes and test those sub-classes. Direct analysis in real time-time of flight mass spectrometry (DART-TOFMS) was utilized because minor and unique molecular ions that could be attributed to different sub-groups can easily be distinguished from the major sample peaks. This is primarily based on the direct mass spectrometry design of the instrumentation that can differentiate minor components from major components that might not be observed using traditional chromatographic separation. The DART source creates molecular ions for individual components in mixed samples under atmospheric conditions in either positive or negative mode. The TOF-MS, which is capable of high resolution and accurate mass analysis, allows more accurate and precise detection of molecular component ions. Additionally, no sample preparation is required to analyze neat samples, which minimizes potential contamination issues. Attenuated total reflectance-FTIR (ATR-FIR) was used to analyze the training set personal lubricants to compare previous methods of analysis to the newly developed DART-TOFMS method of analysis.Principle component analysis (PCA) and cluster analysis were used to identify potential sub-groups and subsequently a classification scheme. Linear discriminant analysis was utilized to conduct leave one out cross validation and to categorize test samples. Eight sub-groups were developed based on the presence and/or absence of PDMS and minor component peaks observed.A classification scheme was developed using the eight sub-groups identified through PCA and cluster analysis. This classification scheme was tested using LDA to classify blind samples. One group includes a scented personal lubricant. Another group includes flavored condom lubricants. The other groups were developed based on the relative intensity of PDMS peaks and minor component peaks. Variation of the intensity of PDMS peaks between and within samples of different lot numbers causes some misclassification of samples. This classification scheme also doesn't take into account real-world factors such as dilution and biodegradation. Although further research is required to create a more stable classification scheme, the identified sub-groups are a good foundation for the creation of a lubricant database and finalized classification scheme.
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Date Issued: 2016
Identifier: CFE0006459, ucf:51415
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006459

Title: Study of Surface Passivation Behavior of Crystalline Silicon Solar Cells.
Creator: Ali, Haider, Schoenfeld, Winston, Coffey, Kevin, Gaume, Romain, Thomas, Jayan, Chanda, Debashis, University of Central Florida
Abstract / Description: To achieve efficiencies approaching the theoretical limit of 29.4% for industrially manufactured solar cells based on crystalline silicon, it is essential to have very low surface recombination velocities at both the front and rear surfaces of the silicon substrate. Typically, the substrate surfaces feature contacted and uncontacted regions, and recombination should be limited for both to maximize the energy conversion efficiency.Uncontacted silicon surfaces are often passivated by the...
Show moreTo achieve efficiencies approaching the theoretical limit of 29.4% for industrially manufactured solar cells based on crystalline silicon, it is essential to have very low surface recombination velocities at both the front and rear surfaces of the silicon substrate. Typically, the substrate surfaces feature contacted and uncontacted regions, and recombination should be limited for both to maximize the energy conversion efficiency.Uncontacted silicon surfaces are often passivated by the deposition of silicon nitride (SiNx) or an aluminum oxide film with SiNx as capping layer (Al2O3/SiNx stack). Further, proper surface preparation and cleaning of Si wafers prior to deposition also plays an important role in minimizing surface recombination. In the present work, the effect of various cleans based on different combinations of HCl, HF, HNO3, and ozonated deionized water (DIO3) on surface passivation quality of boron-diffused and undiffused {100} n-type Cz Si wafers was studied. It was observed that for SiNx passivated Si, carrier lifetime was strongly influenced by cleaning variations and that a DIO3-last treatment resulted in higher lifetimes. Moreover, DIO3+HF+HCl?HF?DIO3 and HNO3?HF?HNO3 cleans emerged as potential low-cost alternatives to HCl/HF clean in the photovoltaics industry.Transmission electron microscopy (TEM) studies were carried out to get insight into the origin of variation in carrier lifetimes for different cleans. Changes in the surface cleans used were not found to have a significant impact on Al2O3/SiNx passivation stacks.ivHowever, an oxide-last cleaning step prior to deposition of SiNx passivation layers was found to create a 1-2 nm SiOx tunnel layer resulting in excellent carrier lifetimes.For contacted regions, low surface recombination can be achieved using passivated carrier selective contacts, which not only passivate the silicon surface and improve the open circuit voltage, but are also carrier selective. This means they only allow the majority carrier to be transported to the metal contacts, limiting recombination by reducing the number of minority carriers. Typically, carrier selectivity is achieved using a thin metal oxide layer, such as titanium oxide (TiO2) for electron-selective contacts and molybdenum oxide (MoOx) for hole-selective contacts. This is normally coupled with a very thin passivation layer (e.g., a-Si:H, SiOx) between the silicon wafer and the contact.In the present work, TiO2-based electron-selective passivated rear contacts were investigated for n-type c-Si solar cells. A low efficiency of 9.8% was obtained for cells featuring a-Si:H/TiO2 rear contact, which can be attributed to rapid degradation of surface passivation of a-Si:H upon FGA at 350(&)deg;C due to hydrogen evolution leading to generation of defect states which increases recombination and hence a much lower Voc of 365 mV is obtained. On the other hand, 21.6% efficiency for cells featuring SiO2/TiO2 rear contact is due to excellent passivation of SiO2/TiO2 stack upon FGA anneal, which can be attributed to the presence of 1-2 nm SiO2 layer whose passivation performance improves upon FGA at 350(&)deg;C whereas presence of large number of oxygen vacancies in TiO2-x reduces rear contact resistivity.vLikewise, MoOx-based contacts were investigated as hole-selective front contacts for an n-type cell with a boron-doped emitter. It has been previously reported that cell efficiencies up to 22.5% have been achieved with silicon heterojunction solar cells featuring a front contact wherein MoOx is inserted between a-Si:H(i) and hydrogenated indium oxide (IO:H). However, device performance and FF degrades upon annealing beyond 130(&)deg;C. In this work, contact resistivity measurements by TLM technique in combination with TEM studies revealed that degradation of device performance is due to oxygen diffusion into MoOx upon annealing in air which reduces concentration of oxygen vacancies in MoOx and increases contact resistivity. The increase in contact resistivity reduces FF resulting in deterioration of device performance.
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Date Issued: 2017
Identifier: CFE0006554, ucf:51351
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006554

Title: Silicon photonic devices for optical delay lines and mid infrared applications.
Creator: Khan, Saeed, Fathpour, Sasan, Likamwa, Patrick, Gong, Xun, Delfyett, Peter, Schoenfeld, Winston, University of Central Florida
Abstract / Description: Silicon photonics has been a rapidly growing subfield of integrated optics and optoelectronic in the last decade and is currently considered a mature technology. The main thrust behind the growth is its compatibility with the mature and low-cost microelectronic integrated circuits fabrication process. In recent years, several active and passive photonic devices and circuits have been demonstrated on silicon. Optical delay lines are among important silicon photonic devices, which are essential...
Show moreSilicon photonics has been a rapidly growing subfield of integrated optics and optoelectronic in the last decade and is currently considered a mature technology. The main thrust behind the growth is its compatibility with the mature and low-cost microelectronic integrated circuits fabrication process. In recent years, several active and passive photonic devices and circuits have been demonstrated on silicon. Optical delay lines are among important silicon photonic devices, which are essential for a variety of photonic system applications including optical beam-forming for controlling phased-array antennas, optical communication and networking systems and optical coherence tomography. In this thesis, several types of delay lines based on apodized grating waveguides are proposed and demonstrated. Simulation and experimental results suggest that these novel devices can provide high optical delay and tunability at very high bit rate. While most of silicon photonics research has focused in the near-infrared wavelengths, extending the operating wavelength range of the technology into in the 3(-)5 (&)#181;m, or the mid-wave infrared regime, is a more recent field of research. A key challenge has been that the standard silicon-on-insulator waveguides are not suitable for the mid-infrared, since the material loss of the buried oxide layer becomes substantially high. Here, the silicon-on-sapphire waveguide technology, which can extend silicon's operating wavelength range up to 4.4 (&)#181;m, is investigated. Furthermore, silicon-on-nitride waveguides, boasting a wide transparent range of 1.2(-)6.7 ?m, are demonstrated and characterized for the first time at both mid-infrared (3.39 ?m) and near-infrared (1.55 ?m) wavelengths.
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Date Issued: 2013
Identifier: CFE0005014, ucf:49996
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005014

Title: The Effect of Morphology on Reflectance in Silicon Nanowires Grown by Electroless Etching.
Creator: Velez, Victor, Sundaram, Kalpathy, Kapoor, Vikram, Yuan, Jiann-Shiun, Abdolvand, Reza, Kar, Aravinda, University of Central Florida
Abstract / Description: The strong light trapping properties of Silicon Nanowires have attracted much interest in the past few years for the conversion of sun energy into conventional electricity. Studies have been completed for many researchers to reduce the cost of fabrication and reflectance of solar light in these nanostructures to make a cheaper and more efficient solar cell technology by using less equipment for fabrication and employing different materials and solution concentrations. Silver, a conducting and...
Show moreThe strong light trapping properties of Silicon Nanowires have attracted much interest in the past few years for the conversion of sun energy into conventional electricity. Studies have been completed for many researchers to reduce the cost of fabrication and reflectance of solar light in these nanostructures to make a cheaper and more efficient solar cell technology by using less equipment for fabrication and employing different materials and solution concentrations. Silver, a conducting and stable metal is used these days as a precursor to react with silicon and then form the nanowires. Its adequate selection of solution concentration for a size of silicon substrate and the treatment for post-cleaning of silver dendrites make it a viable method among the others. It is an aim of this research to obtain significant low reflectance across the visible solar light range. Detailed concentration, fabrication and reflectance studies is carried out on silicon wafer in order to expand knowledge and understanding.In this study, electroless etching technique has been used as the growth mechanism of SiNWs at room temperature. Optimum ratios of solution concentration and duration for different sizes of exposed area to grow tall silicon nanowires derived from experimentation are presented. Surface imaging of the structures and dimension of length and diameter have been determined by Scanner Electron Microscopy (SEM) and the reflectance in the optical range in silicon nanowires has been make using UV-Visible Spectrophotometer.
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Date Issued: 2017
Identifier: CFE0006815, ucf:51807
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006815

Title: SILICON CARBIDE AND AGILE OPTICS BASED SENSORS FOR POWER PLANT GAS TURBINES, LASER BEAM ANALYSIS AND BIOMEDICINE.
Creator: Sheikh, Mumtaz, Riza, Nabeel, University of Central Florida
Abstract / Description: Proposed are novel sensors for extreme environment power plants, laser beam analysis and biomedicine. A hybrid wireless-wired extreme environment temperature sensor using a thick single-crystal Silicon Carbide (SiC) chip embedded inside a sintered SiC probe design is investigated and experimentally demonstrated. The sensor probe employs the SiC chip as a Fabry-Perot (FP) interferometer to measure the change in refractive index and thickness of SiC with temperature. A novel temperature sensing...
Show moreProposed are novel sensors for extreme environment power plants, laser beam analysis and biomedicine. A hybrid wireless-wired extreme environment temperature sensor using a thick single-crystal Silicon Carbide (SiC) chip embedded inside a sintered SiC probe design is investigated and experimentally demonstrated. The sensor probe employs the SiC chip as a Fabry-Perot (FP) interferometer to measure the change in refractive index and thickness of SiC with temperature. A novel temperature sensing method that combines wavelength-tuned signal processing for coarse measurements and classical FP etalon peak shift for fine measurements is proposed and demonstrated. This method gives direct unambiguous temperature measurements with a high temperature resolution over a wide temperature range. An alternative method using blackbody radiation from a SiC chip in a two-color pyrometer configuration for coarse temperature measurement and classical FP laser interferometry via the same chip for fine temperature measurement is also proposed and demonstrated. The sensor design is successfully deployed in an industrial test rig environment with gas temperatures exceeding 1200 C. This sensor is proposed as an alternate to all-electrical thermocouples that are susceptible to severe reliability and lifetime issues in such extreme environments. A few components non-contact thickness measurement system for optical quality semi-transparent samples such as Silicon (Si) and 6H SiC optical chips such as the one used in the design of this sensor is proposed and demonstrated. The proposed system is self-calibrating and ensures a true thickness measurement by taking into account material dispersion in the wavelength band of operation. For the first time, a 100% repeatable all-digital electronically-controlled pinhole laser beam profiling system using a Texas Instruments (TI) Digital Micro-mirror Device (DMD) commonly used in projectors is experimentally demonstrated using a unique liquid crystal image generation system with non-invasive qualities. Also proposed and demonstrated is the first motion-free electronically-controlled beam propagation analyzer system using a TI DMD and a variable focus liquid lens. The system can be used to find all the parameters of a laser beam including minimum waist size, minimum waist location and the beam propagation parameter M2. Given the all-digital nature of DMD-based profiling and all-analog motion-free nature of the Electronically Controlled Variable Focus Lens (ECVFL) beam focus control, the proposed analyzer versus prior-art promises better repeatability, speed and reliability. For the first time, Three Dimensional (3-D) imaging is demonstrated using an electronically controlled Liquid Crystal (LC) optical lens to accomplish a no-moving parts depth section scanning in a modified commercial 3-D confocal microscope. The proposed microscopy system within aberration limits has the potential to eliminate the sample or objective motion-caused mechanical forces that can distort the original sample structure and lead to imaging errors. A signal processing method for realizing high resolution three dimensional (3-D) optical imaging using diffraction limited low resolution optical signals is also proposed.
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Date Issued: 2009
Identifier: CFE0002922, ucf:47995
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002922

Title: LASER ENHANCED DOPING FOR SILICON CARBIDE WHITE LIGHTEMITTING DIODES.
Creator: Bet, Sachin, Kar, Aravinda, University of Central Florida
Abstract / Description: This work establishes a solid foundation for the use of indirect band gap semiconductors for light emitting application and presents the work on development of white light emitting diodes (LEDs) in silicon carbide (SiC). Novel laser doping has been utilized to fabricate white light emitting diodes in 6H-SiC (n-type N) and 4H-SiC (p-type Al) wafers. The emission of different colors to ultimately generate white light is tailored on the basis of donor acceptor pair (DAP) recombination mechanism...
Show moreThis work establishes a solid foundation for the use of indirect band gap semiconductors for light emitting application and presents the work on development of white light emitting diodes (LEDs) in silicon carbide (SiC). Novel laser doping has been utilized to fabricate white light emitting diodes in 6H-SiC (n-type N) and 4H-SiC (p-type Al) wafers. The emission of different colors to ultimately generate white light is tailored on the basis of donor acceptor pair (DAP) recombination mechanism for luminescence. A Q-switched Nd:YAG pulse laser (1064 nm wavelength) was used to carry out the doping experiments. The p and n regions of the white SiC LED were fabricated by laser doping an n-type 6H-SiC and p-type 4H-SiC wafer substrates with respective dopants. Cr, B and Al were used as p-type dopants (acceptors) while N and Se were used as n-type dopants (donors). Deep and shallow donor and acceptor impurity level states formed by these dopants tailor the color properties for pure white light emission. The electromagnetic field of lasers and non-equilibrium doping conditions enable laser doping of SiC with increased dopant diffusivity and enhanced solid solubility. A thermal model is utilized to determine the laser doping parameters for temperature distribution at various depths of the wafer and a diffusion model is presented including the effects of Fick's diffusion, laser electromagnetic field and thermal stresses due to localized laser heating on the mass flux of dopant atoms. The dopant diffusivity is calculated as a function of temperature at different depths of the wafer based on measured dopant concentration profile. The maximum diffusivities achieved in this study are 4.6110-10 cm2/s at 2898 K and 6.9210-12 cm2/s at 3046 K for Cr in 6H-SiC and 4H-SiC respectively. Secondary ion mass spectrometric (SIMS) analysis showed the concentration profile of Cr in SiC having a penetration depth ranging from 80 nm in p-type 4H-SiC to 1.5 m in n-type 6H-SiC substrates respectively. The SIMS data revealed enhanced solid solubility (2.291019 cm-3 in 6H-SiC and 1.421919 cm-3 in 4H-SiC) beyond the equilibrium limit (31017 cm-3 in 6H-SiC above 2500 C) for Cr in SiC. It also revealed similar effects for Al and N. The roughness, surface chemistry and crystalline integrity of the doped sample were examined by optical interferometer, energy dispersive X-ray spectrometry (EDS) and transmission electron microscopy (TEM) respectively. Inspite of the larger atomic size of Cr compared to Si and C, the non-equilibrium conditions during laser doping allow effective incorporation of dopant atoms into the SiC lattice without causing any damage to the surface or crystal lattice. Deep Level Transient Spectroscopy (DLTS) confirmed the deep level acceptor state of Cr with activation energies of Ev+0.80 eV in 4H-SiC and Ev+0.45 eV in 6H-SiC. The Hall Effect measurements showed the hole concentration to be 1.981019 cm-3 which is almost twice the average Cr concentration (11019 cm-3) obtained from the SIMS data. These data confirmed that almost all of the Cr atoms were completely activated to the double acceptor state by the laser doping process without requiring any subsequent annealing step. Electroluminescence studies showed blue (460-498 nm), blue-green (500-520 nm) green (521-575 nm), and orange (650-690 nm) wavelengths due to radiative recombination transitions between donor-acceptors pairs of N-Al, N-B, N-Cr and Cr-Al respectively, while a prominent violet (408 nm) wavelength was observed due to transitions from the nitrogen level to the valence band level. The red (698-738 nm) luminescence was mainly due to metastable mid-bandgap states, however under high injection current it was due to the quantum mechanical phenomenon pertaining to band broadening and overlapping. This RGB combination produced a broadband white light spectrum extending from 380 to 900 nm. The color space tri-stimulus values for 4H-SiC doped with Cr and N were X = 0.3322, Y = 0.3320 and Z = 0.3358 as per 1931 CIE (International Commission on Illumination) corresponding to a color rendering index of 96.56 and the color temperature of 5510 K. And for 6H-SiC n-type doped with Cr and Al, the color space tri-stimulus values are X = 0.3322, Y = 0.3320 and Z = 0.3358. The CCT was 5338 K, which is very close to the incandescent lamp (or black body) and lies between bright midday sun (5200 K) and average daylight (5500 K) while CRI was 98.32. Similar white LED's were also fabricated using Cr, Al, Se as one set of dopants and B, Al, N as another.
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Date Issued: 2008
Identifier: CFE0002362, ucf:47808
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002362

Title: Thin-film Lithium Niobate Photonics for Electro-optics, Nonlinear Optics, and Quantum Optics on Silicon.
Creator: Rao, Ashutosh, Fathpour, Sasan, Delfyett, Peter, Li, Guifang, Thomas, Jayan, University of Central Florida
Abstract / Description: Ion-sliced thin-film lithium niobate (LN) compact waveguide technology has facilitated the resurgence of integrated photonics based on lithium niobate. These thin-film LN waveguides offer over an order of magnitude improvement in optical confinement, and about two orders of magnitude reduction in waveguide bending radius, compared to conventional LN waveguides. Harnessing the improved confinement, a variety of miniaturized and efficient photonic devices are demonstrated in this work. First,...
Show moreIon-sliced thin-film lithium niobate (LN) compact waveguide technology has facilitated the resurgence of integrated photonics based on lithium niobate. These thin-film LN waveguides offer over an order of magnitude improvement in optical confinement, and about two orders of magnitude reduction in waveguide bending radius, compared to conventional LN waveguides. Harnessing the improved confinement, a variety of miniaturized and efficient photonic devices are demonstrated in this work. First, two types of compact electrooptic modulators are presented (-) microring modulators, and Mach-Zehnder modulators. Next, two distinct approaches to nonlinear optical frequency converters are implemented (-) periodically poled lithium niobate, and mode shape modulation (grating assisted quasi-phase matching). Following this, stochastic variations are added to the mode shape modulation approach to demonstrate random quasi-phase matching. Afterward, broadband photon-pair generation is demonstrated in the miniaturized periodically poled lithium niobate, and spectral correlations of the biphoton spectrum are reported. Finally, extensions of the aforementioned results suitable for future work are discussed.
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Date Issued: 2018
Identifier: CFE0007085, ucf:52013
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007085

Title: Room Temperature Operation of Quantum Cascade Lasers Monolithically Integrated Onto a Lattice-Mismatched Substrate.
Creator: Go, Rowel, Lyakh, Arkadiy, Delfyett, Peter, Likamwa, Patrick, Wu, Shintson, University of Central Florida
Abstract / Description: The experimental results of a 40-stage indium phosphide (InP) based quantum cascade laser (QCL) grown on a lattice-mismatched gallium arsenide (GaAs) substrate with metamorphic buffer (M-buffer) will be discussed. The QCL's strain-balanced active region was composed of Al0.78In0.22As/In0.73Ga0.27As and an 8 (&)#181;m-thick all-InP waveguide. Since the M-buffer was insulating, the wafer was processed into ridge-waveguide chips with lateral current injection scheme. Laser chips with high...
Show moreThe experimental results of a 40-stage indium phosphide (InP) based quantum cascade laser (QCL) grown on a lattice-mismatched gallium arsenide (GaAs) substrate with metamorphic buffer (M-buffer) will be discussed. The QCL's strain-balanced active region was composed of Al0.78In0.22As/In0.73Ga0.27As and an 8 (&)#181;m-thick all-InP waveguide. Since the M-buffer was insulating, the wafer was processed into ridge-waveguide chips with lateral current injection scheme. Laser chips with high reflection (HR) coating delivered total peak power in excess of 200 mW at cryogenic temperature (78 K), and lasing was observed up to 230 K. Partial HR coating was then utilized on the front facet to extend lasing range up to 303 K. After 200 minutes of preliminary reliability testing at maximum power, no sign of performance degradation was observed. Initial results of InP-based QCL on germanium-coated silicon substrate with M-buffer will also be covered in this work.
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Date Issued: 2018
Identifier: CFE0007568, ucf:52564
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007568

Title: Performance optimization of lateral-mode thin-film piezoelectric-on-substrate resonant systems.
Creator: Fatemi, Hedy, Abdolvand, Reza, Sundaram, Kalpathy, Malocha, Donald, Gong, Xun, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: The main focus of this dissertation is to characterize and improve the performance of thin-film piezoelectric-on-substrate (TPoS) lateral-mode resonators and filters. TPoS is a class of piezoelectric MEMS devices which benefits from the high coupling coefficient of the piezoelectric transduction mechanism while taking advantage of superior acoustic properties of a substrate. The use of lateral-mode TPoS designs allows for fabrication of dispersed-frequency filters on a single substrate, thus...
Show moreThe main focus of this dissertation is to characterize and improve the performance of thin-film piezoelectric-on-substrate (TPoS) lateral-mode resonators and filters. TPoS is a class of piezoelectric MEMS devices which benefits from the high coupling coefficient of the piezoelectric transduction mechanism while taking advantage of superior acoustic properties of a substrate. The use of lateral-mode TPoS designs allows for fabrication of dispersed-frequency filters on a single substrate, thus significantly reducing the size and manufacturing cost of devices. TPoS filters also offer a lower temperature coefficient of frequency, and better power handling capability compared to rival technologies all in a very small footprint.Design and fabrication process of the TPoS devices is discussed. Both silicon and diamond substrates are utilized for fabrication of TPoS devices and results are compared. Specifically, the superior acoustic properties of nanocrystalline diamond in scaling the frequency and energy density of the resonators is highlighted in comparison with silicon. The performance of TPoS devices in a variety of applications is reported. These applications include lateral-mode TPoS filters with record low IL values (as low as 2dB) and fractional bandwidth up to 1%, impedance transformers, very low phase noise oscillators, and passive wireless temperature sensors.
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Date Issued: 2015
Identifier: CFE0005945, ucf:50805
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005945

Title: Assessment of Tattoo and Silicone Wounds in Terms of Time of Treatment and Perceived Treatment Quality.
Creator: Pettitt, M, Karwowski, Waldemar, Shumaker, Randall, Cendan, Juan, Sottilare, Robert, University of Central Florida
Abstract / Description: At the point of injury, critical medical tasks include locating and identifying an injury as well as applying the appropriate initial care. Over the past decade, to increase the fidelity of wound representation and ultimately the quality of medical care, a considerable amount of research and development has occurred to improve simulated wounds during training, primarily at the point of injury. As material and techniques mature and as more relevant data is collected on tissue properties,...
Show moreAt the point of injury, critical medical tasks include locating and identifying an injury as well as applying the appropriate initial care. Over the past decade, to increase the fidelity of wound representation and ultimately the quality of medical care, a considerable amount of research and development has occurred to improve simulated wounds during training, primarily at the point of injury. As material and techniques mature and as more relevant data is collected on tissue properties, examining what fidelity is required for training at the point of injury is crucial. The main objective of this effort was to assess a three dimensional silicone wound versus a two dimensional tattoo wound for training and to examine differences in user perceptions and treatment time. This was accomplished with a test population of 158 City of Orlando Fire Department First Responders which were randomly assigned to each group (three dimensional silicone wound group versus a two dimensional tattoo wound group). The data analyses incorporated the use of non-parametric statistics (Mann-Whitney U Test) to compare the differences between the two groups on depth perception, sense of urgency, immersion, and time on task. Other factors that were examined included the costs for the average tattoo wound and silicone wound as well as the number of uses before the synthetic wound is visibly damaged. The data results indicated that at the point of injury, there were relatively few statistically significant differences in the survey data or time on task between the silicone and tattoo wounds. Additionally, the cost analysis revealed that the silicone wound is significantly more expensive than the tattoo wound. Supporting the military and civilian first responder communities, the results of this study provides statistically reliable data on the use of trauma tattoos as a tool for mastering point of injury treatment during training exercises.
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Date Issued: 2017
Identifier: CFE0006904, ucf:51733
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006904

Title: Light Trapping in Thin Film Crystalline Silicon Solar Cells.
Creator: Boroumand Azad, Javaneh, Chanda, Debashis, Peale, Robert, Del Barco, Enrique, Flitsiyan, Elena, Schoenfeld, Winston, University of Central Florida
Abstract / Description: This dissertation presents numerical and experimental studies of a unified light trapping approach that is extremely important for all practical solar cells. A 2D hexagonal Bravais lattice diffractive pattern is studied in conjunction with the verification of the reflection mechanisms of single and double layer anti-reflective coatings in the broad range of wavelength 400 nm - 1100 nm. By varying thickness and conformity, we obtained the optimal parameters which minimize the broadband...
Show moreThis dissertation presents numerical and experimental studies of a unified light trapping approach that is extremely important for all practical solar cells. A 2D hexagonal Bravais lattice diffractive pattern is studied in conjunction with the verification of the reflection mechanisms of single and double layer anti-reflective coatings in the broad range of wavelength 400 nm - 1100 nm. By varying thickness and conformity, we obtained the optimal parameters which minimize the broadband reflection from the nanostructured crystalline silicon surface over a wide range of angle 0(&)deg;-65(&)deg;. While the analytical design of broadband, angle independent anti-reflection coatings on nanostructured surfaces remains a scientific challenge, numerical optimization proves a viable alternative, paving the path towards practical implementation of the light trapping solar cells. A 3 (&)#181;m thick light trapping solar cell is modeled in order to predict and maximize combined electron-photon harvesting in ultrathin crystalline silicon solar cells. It is shown that the higher charge carrier generation and collection in this design compensates the absorption and recombination losses and ultimately results in an increase in energy conversion efficiency. Further, 20 (&)#181;m and 100 (&)#181;m thick functional solar cells with the light trapping scheme are studied. The efficiency improvement is observed numerically and experimentally due to photon absorption enhancement in the light trapping cells with respect to a bare cell of same thickness.
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Date Issued: 2017
Identifier: CFE0006936, ucf:51654
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006936

Title: DESIGN, CHARACTERIZATION AND COMPACT MODELING OF NOVEL SILICON CONTROLLED RECTIFIER (SCR)-BASED DEVICES FOR ELECTROSTATIC DISCHARGE (ESD) PROTECTION APPLICATIONS IN INTEGRATED CIRCUITS.
Creator: Lou, Lifang, Liou, Juin J., University of Central Florida
Abstract / Description: Electrostatic Discharge (ESD), an event of a sudden transfer of electrons between two bodies at different potentials, happens commonly throughout nature. When such even occurs on integrated circuits (ICs), ICs will be damaged and failures result. As the evolution of semiconductor technologies, increasing usage of automated equipments and the emerging of more and more complex circuit applications, ICs are more sensitive to ESD strikes. Main ESD events occurring in semiconductor industry have...
Show moreElectrostatic Discharge (ESD), an event of a sudden transfer of electrons between two bodies at different potentials, happens commonly throughout nature. When such even occurs on integrated circuits (ICs), ICs will be damaged and failures result. As the evolution of semiconductor technologies, increasing usage of automated equipments and the emerging of more and more complex circuit applications, ICs are more sensitive to ESD strikes. Main ESD events occurring in semiconductor industry have been standardized as human body model (HBM), machine model (MM), charged device model (CDM) and international electrotechnical commission model (IEC) for control, monitor and test. In additional to the environmental control of ESD events during manufacturing, shipping and assembly, incorporating on-chip ESD protection circuits inside ICs is another effective solution to reduce the ESD-induced damage. This dissertation presents design, characterization, integration and compact modeling of novel silicon controlled rectifier (SCR)-based devices for on-chip ESD protection. The SCR-based device with a snapback characteristic has long been used to form a VSS-based protection scheme for on-chip ESD protection over a broad rang of technologies because of its low on-resistance, high failure current and the best area efficiency. The ESD design window of the snapback device is defined by the maximum power supply voltage as the low edge and the minimum internal circuitry breakdown voltage as the high edge. The downscaling of semiconductor technology keeps on squeezing the design window of on-chip ESD protection. For the submicron process and below, the turn-on voltage and sustain voltage of ESD protection cell should be lower than 10 V and higher than 5 V, respectively, to avoid core circuit damages and latch-up issue. This presents a big challenge to device/circuit engineers. Meanwhile, the high voltage technologies push the design window to another tough range whose sustain voltage, 45 V for instance, is hard for most snapback ESD devices to reach. Based on the in-depth elaborating on the principle of SCR-based devices, this dissertation first presents a novel unassisted, low trigger- and high holding-voltage SCR (uSCR) which can fit into the aforesaid ESD design window without involving any extra assistant circuitry to realize an area-efficient on-chip ESD protection for low voltage applications. The on-chip integration case is studied to verify the protection effectiveness of the design. Subsequently, this dissertation illustrate the development of a new high holding current SCR (HHC-SCR) device for high voltage ESD protection with increasing the sustain current, not the sustain voltage, of the SCR device to the latchup-immune level to avoid sacrificing the ESD protection robustness of the device. The ESD protection cells have been designed either by using technology computer aided design (TCAD) tools or through trial-and-error iterations, which is cost- or time-consuming or both. Also, the interaction of ESD protection cells and core circuits need to be identified and minimized at pre-silicon stage. It is highly desired to design and evaluate the ESD protection cell using simulation program with integrated circuit emphasis (SPICE)-like circuit simulation by employing compact models in circuit simulators. And the compact model also need to predict the response of ESD protection cells to very fast transient ESD events such as CDM event since it is a major ESD failure mode. The compact model for SCR-based device is not widely available. This dissertation develops a macromodeling approach to build a comprehensive SCR compact model for CDM ESD simulation of complete I/O circuit. This modeling approach offers simplicity, wide availability and compatibility with most commercial simulators by taking advantage of using the advanced BJT model, Vertical Bipolar Inter-Company (VBIC) model. SPICE Gummel-Poon (SGP) model has served the ICs industry well for over 20 years while it is not sufficiently accurate when using SGP model to build a compact model for ESD protection SCR. This dissertation seeks to compare the difference of SCR compact model built by using VBIC and conventional SGP in order to point out the important features of VBIC model for building an accurate and easy-CAD implement SCR model and explain why from device physics and model theory perspectives.
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Date Issued: 2008
Identifier: CFE0002374, ucf:47788
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002374

Title: Precision Metrology of Laser Plasmas in the XUV Band.
Creator: Szilagyi, John, Richardson, Martin, Sundaram, Kalpathy, Abdolvand, Reza, Baudelet, Matthieu, Shivamoggi, Bhimsen, University of Central Florida
Abstract / Description: The XUV band, a region of light spanning the wavelength range of 5 - 200 nm, is located between the Ultraviolet and X-ray regions of the electromagnetic spectrum. It is further divided into a 100 - 200 nm region called the Vacuum Ultraviolet (VUV), and a 5 (-) 100 nm region called the Extreme Ultraviolet (EUV). Applications of this light have been slow to develop due to the lack of suitable sources, efficient optics, and sensitive detectors. Recently, many industries such as the semiconductor...
Show moreThe XUV band, a region of light spanning the wavelength range of 5 - 200 nm, is located between the Ultraviolet and X-ray regions of the electromagnetic spectrum. It is further divided into a 100 - 200 nm region called the Vacuum Ultraviolet (VUV), and a 5 (-) 100 nm region called the Extreme Ultraviolet (EUV). Applications of this light have been slow to develop due to the lack of suitable sources, efficient optics, and sensitive detectors. Recently, many industries such as the semiconductor manufacturing industry, medical surgery, micromachining, microscopy, and spectroscopy have begun to benefit from the short wavelengths and the high photon energies of this light. At present, the semiconductor chip industry is the primary reason for the investment in, and development of, XUV sources, optics, and detectors. The demand for high power EUV light sources at 13.5 nm wavelength is driven by the development of the next generation of semiconductor lithography tools. The development of these tools enables the continued reduction in size, and the increase in transistor density of semiconductor devices on a single chip. Further development and investigation of laser produced plasma EUV light sources is necessary to increase the average optical power and reliability. This will lead to an increase in the speed of EUV lithographic processes, which are necessary for future generations of advanced chip design, and high volume semiconductor manufacturing. Micromachining, lithography, and microscopy benefit from improvements in resolution due to the shorter wavelengths of light in the VUV band. In order to provide adequate illumination for these applications, sources are required which are brighter and have higher average power. Laser produced plasma (LPP) VUV light sources are used extensively for lithography and defect detection in semiconductor manufacturing. Reductions in the wavelength and increases in the average power will increase the rate and yield of chip manufacture, as well as reduce the costs of semiconductor manufacture.The work presented in this thesis, describes the development of two laser plasma source facilities in the Laser Plasma Laboratory at UCF, which were designed to investigate EUV and VUV laser plasma sources. The HP-EUV-Facility was developed to optimize and demonstrate a high power 13.5 nm EUV LPP source. This facility provides high resolution spectroscopy across 10.5 - 20 nm, and absolute energy measurement of 13.5 nm +/- 2% in 2? sr. The VUV-MS-Facility was developed to investigate VUV emission characteristics of laser plasmas of various target geometries and chemistries. This facility provides absolute calibrated emission spectra for the 124 - 250 nm wavelength range, in addition to, at wavelength plasma imaging. Calibrated emission spectra, in-band power, and conversion efficiency are presented in this work for gas targets of Argon, Krypton, and Xenon and solid targets of Silicon, Copper, Molybdenum, Indium, Tantalum, Tin, and Zinc, across the laser intensity range of 8.0x10^6 (-) 3.2x10^12 W/cm2.
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Date Issued: 2017
Identifier: CFE0006805, ucf:51793
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006805

silicon (4)	+ -
Silicon (3)	+ -
Silicon Carbide (3)	+ -
Diffusion (2)	+ -
Electrostatic Discharge (2)	+ -

Integrated photonics (2)	+ -
nonlinear optics (2)	+ -
silicon photonics (2)	+ -
simulation (2)	+ -
Anti-reflective Coating (1)	+ -
Au-In (1)	+ -
Black silicon (1)	+ -
CEB (1)	+ -
Characterization (1)	+ -
Charged Device Mode (1)	+ -
Charged Device Model (CDM) (1)	+ -
Classification (1)	+ -
Combustion (1)	+ -
Combustion in Porous Media (1)	+ -
Compact Modeling (1)	+ -
Condoms (1)	+ -
Conducting polymers (1)	+ -
Confocal Microscopy (1)	+ -
DART-TOFMS (1)	+ -
DLTS (1)	+ -
Diamond (1)	+ -
Die-Attach (1)	+ -
Dirac semimetal (1)	+ -
EGR (1)	+ -
EUV (1)	+ -

University of Central Florida (26)	+ -
Sundaram, Kalpathy (8)	+ -
Yuan, Jiann-Shiun (5)	+ -
Peale, Robert (4)	+ -
Schoenfeld, Winston (4)	+ -

Abdolvand, Reza (3)	+ -
Coffey, Kevin (3)	+ -
Delfyett, Peter (3)	+ -
Fathpour, Sasan (3)	+ -
Kar, Aravinda (3)	+ -
Thomas, Jayan (3)	+ -
Chanda, Debashis (2)	+ -
Chow, Louis (2)	+ -
Del Barco, Enrique (2)	+ -
Gong, Xun (2)	+ -
Li, Guifang (2)	+ -
Likamwa, Patrick (2)	+ -
Liou, Juin (2)	+ -
Shen, Zheng (2)	+ -
Ali, Haider (1)	+ -
An, Linan (1)	+ -
Baudelet, Matthieu (1)	+ -
Bet, Sachin (1)	+ -
Blair, Richard (1)	+ -
Boroumand Azad, Javaneh (1)	+ -
Boyd, Christopher (1)	+ -
Bridge, Candice (1)	+ -
Campiglia, Andres (1)	+ -
Cendan, Juan (1)	+ -
Chen, Quanfang (1)	+ -

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