Browsing by Subject "Nanotechnology"
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Item Adder and multiplier design and analysis in quantum-dot cellular automata(2006) Cho, Heumpil; Swartzlander, Earl E., Jr.Quantum-dot cellular automata (QCA) is an emerging nanotechnology for electronic circuits. Its advantages such as faster speed, smaller size, and lower power consumption are very attractive. The fundamental device, a quantum-dot cell, can be used to make gates, wires, and memories. As such it is the basic building block of nanotechnology circuits. While the physical nature of the nanoscale materials is complicated, the circuit designer can concentrate on the logical and structural design, so the design effort is reduced. Because of its novelty, the current literature shows only simple circuit structures. This research broadens the QCA circuit designs with larger circuits, explores the characteristics of QCA circuit designs, and shows analysis based on those design results. This dissertation proposes three kinds of adder designs in QCA from the conventional adder design approaches. Ripple carry adders, carry lookahead adders, and conditional sum adders are designed for optimization with QCA technology and simulated with several different operand sizes. Using the newly discovered knowledge of the QCA circuit characteristics, new designs for serial adders and multipliers are presented, which are the carry flow adder and the serial multiplier. The carry flow adder design is compared with the previous three adder designs. From the filter design methodology, the carry shift multiplication and the carry delay multiplication algorithms are proposed. The serial multipliers are implemented with both algorithms. The final designs are compared according to the complexity, area, and delay.Item Alkali impurities on quantum thin films : adsorption, electron scattering, and impurity-induced nano-structure formation in the quantum regime(2008-12) Khajetoorians, Alexander Ako, 1980-; Shih, Chih-kangFor thin epitaxial metal films, when the thickness is on the order of the Fermi wavelength, [lambda subscript F], quantum confinement can dramatically alter the physical properties of the film. These so-called Quantum Size Effects (QSE) can dramatically alter the morphology of thin films by an intricate interplay between kinetics and surface energy driven thermodynamics. These effects lead to rich growth-related phenomena in Pb(111) films grown on semiconductor substrates such as Si(111). For example, QSE can drive flat film formation when growth is dominated by surface energy oscillations. This is rather surprising for Pb/Si systems because of a rather high lattice mismatch. However, these films are not defect free, but rather show common occurrences of three defect types. Low Temperature Scanning Tunneling Microscopy (LT-STM) was utilized to characterize these defects on the atomic scale. Furthermore, these defects create modulations in the electron density resulting in fluctuations in QWS near defect sites. Another topic of recent interest is how QSE affect adsorption of as well as how adsorbates modify QSE for these Pb films. In this thesis, LT-STM and first principles calculations were utilized to study Cs adsorbates on Pb film surfaces, defects, and step edges. Cs adsorption is intricately related to the electronic structure of the surface, especially the defect sites which can act as surface traps. These Cs adsorbates, which are assumed to be ionized, enhance elastic surface scattering of empty-state electrons. This results in observable wave interference patterns near Cs impurities. Furthermore, Cs adsorbates, by an overall step energy reduction, can promote QSE-related nanostructures, which are otherwise too weak when kinetic effects cannot be ignored. This enhancement of "quantum stability" is driven by favorable Cs step binding and can be explained within the contexts of Density Functional Theory (DFT).Item Automated Morphology Analysis of Nanoparticles(2012-10-19) Park, ChiwooThe functional properties of nanoparticles highly depend on the surface morphology of the particles, so precise measurements of a particle's morphology enable reliable characterizing of the nanoparticle's properties. Obtaining the measurements requires image analysis of electron microscopic pictures of nanoparticles. Today's labor-intensive image analysis of electron micrographs of nanoparticles is a significant bottleneck for efficient material characterization. The objective of this dissertation is to develop automated morphology analysis methods. Morphology analysis is comprised of three tasks: separate individual particles from an agglomerate of overlapping nano-objects (image segmentation); infer the particle's missing contours (shape inference); and ultimately, classify the particles by shape based on their complete contours (shape classification). Two approaches are proposed in this dissertation: the divide-and-conquer approach and the convex shape analysis approach. The divide-and-conquer approach solves each task separately, taking less than one minute to complete the required analysis, even for the largest-sized micrograph. However, its separating capability of particle overlaps is limited, meaning that it is able to split only touching particles. The convex shape analysis approach solves shape inference and classification simultaneously for better accuracy, but it requires more computation time, ten minutes for the biggest-sized electron micrograph. However, with a little sacrifice of time efficiency, the second approach achieves far superior separation than the divide-and-conquer approach, and it handles the chain-linked structure of particle overlaps well. The capabilities of the two proposed methods cannot be substituted by generic image processing and bio-imaging methods. This is due to the unique features that the electron microscopic pictures of nanoparticles have, including special particle overlap structures, and large number of particles to be processed. The application of the proposed methods to real electron microscopic pictures showed that the two proposed methods were more capable of extracting the morphology information than the state-of-the-art methods. When nanoparticles do not have many overlaps, the divide-and-conquer approach performed adequately. When nanoparticles have many overlaps, forming chain-linked clusters, the convex shape analysis approach performed much better than the state-of-the-art alternatives in bio-imaging. The author believes that the capabilities of the proposed methods expedite the morphology characterization process of nanoparticles. The author further conjectures that the technical generality of the proposed methods could even be a competent alternative to the current methods analyzing general overlapping convex-shaped objects other than nanoparticles.Item Biopharmaceutical classification and development of limonene-based self-nanoemulsified capsule dosage form of coenzyme Q10(Texas Tech University, 2004-05) Palamakula, AnithaCoenzyme QIO (CoQ) is a challenging micronutrient for oral formulation due to its low aqueous solubility and bioavailability. The present dissertation deals with a systematic approach to classify CoQ biopharmaceutically according to FDA biopharmaceutical classification system (BCS), and to develop a self-nanoemulsified capsule dosage form (SNCDF) with chiral limonenes. We have hypothesized that the oral bioavailability of CoQ may be enhanced by limonene based SNCDF. In vitro transport studies using Caco-2 cells and solubility studies indicated that CoQ is moderately permeable and has low solubility. However, CoQ exhibits substantial solubility in limonenes. The permeability of CoQ across isolated rat GI segments revealed regional differences with maximum absorption through duodenum. Based on these results, a limonene based self-nanoemulsified formulation of CoQ was prepared and evaluated by in vitro and in vivo methods. Dissolution studies in water have shown CoQ release of > 90% within 5 minutes. Thermal analysis showed no significant change in CoQ endotherm. FT-IR and X-ray diffraction studies revealed the preservation of CoQ structure, indicating no interactions. Particle size, turbidity and zeta potential measurements have indicated that R-(+)-limonene provided superior self-nanoemulsified formulation of CoQ when compared with S-(-)-limonene. A three-factor, three-level optimization design was used to evaluate the effect of critical process variables on the drug release characteristics. Mathematical relationships, contour plots and response surface methodology were employed with constrained optimization to predict levels of factors that provide maximum drug release. The predicted and observed responses were in good agreement. The long term stability of the formulation was ascertained by subjecting to various temperature and humidity conditions for 6 months. The results indicated no significant effect on turbidity, particle size, zeta potential, DSC, FT-IR and total drug release at room temperature. The in vivo performance of CoQ limonene based SNCDF and eutectic based self-nanoemulsified drug delivery systems (SNEDDS) was evaluated by assessing the pharmacokinetic parameters, Tmax, Cmax, and AUC in rats. The oral bioavailability of SNCDF and SNEDDS was found to increase by 650% and 730% respectively when compared with CoQ powder (control). Preliminary assessment in human volunteers indicated increased tendency of rate and extent and metabolism of nanoemulsified preparations as compared to control.Item Colloidal nanocrystals with near-infrared optical properties : synthesis, characterization, and applications(2011-12) Panthani, Matthew George; Korgel, Brian Allan, 1969-; Dodabalapur, Ananth; Chelikowsky, James; Mullins, C. Buddie; Manthiram, ArumugamColloidal nanocrystals with optical properties in the near-infrared (NIR) are of interest for many applications such as photovoltaic (PV) energy conversion, bioimaging, and therapeutics. For PVs and other electronic devices, challenges in using colloidal nanomaterials often deal with the surfaces. Because of the high surface-to-volume ratio of small nanocrystals, surfaces and interfaces play an enhanced role in the properties of nanocrystal films and devices. Organic ligand-capped CuInSe2 (CIS) and Cu(InXGa1-X)Se2 (CIGS) nanocrystals were synthesized and used as the absorber layer in prototype solar cells. By fabricating devices from spray-coated CuInSe nanocrystals under ambient conditions, solar-to-electric power conversion efficiencies as high as 3.1% were achieved. Many treatments of the nanocrystal films were explored. Although some treatments increased the conductivity of the nanocrystal films, the best devices were from untreated CIS films. By modifying the reaction chemistry, quantum-confined CuInSeXS2-X (CISS) nanocrystals were produced. The potential of the CISS nanocrystals for targeted bioimaging was demonstrated via oral delivery to mice and imaging of nanocrystal fluorescence. The size-dependent photoluminescence of Si nanocrystals was measured. Si nanocrystals supported on graphene were characterized by conventional transmission electron microscopy and spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM). Enhanced imaging contrast and resolution was achieved by using Cs-corrected STEM with a graphene support. In addition, clear imaging of defects and the organic-inorganic interface was enabled by utilizing this technique.Item Combustion behavior of nano-composite aluminum iron oxide(Texas Tech University, 2004-05) Plantier, KeithBum rates of nano-scale aluminum (Al) powders mixed with iron oxide (Fe2O3) were measured as a function of Fe2O3 synthesis technique and fuel/oxidizer composition. Three reactant synthesis techniques were examined; two focused on sol-gel processing of nano-scale Fe2O3 particles and the third utilized commercially available nano-scale Fe203 powder. Nano-scale aluminum particles (52.7 nm in diameter) were combined with each oxidizer in various proportions. One goal was to determine the equivalence ratio corresponding to the maximum bum rate. The bum rates of five different nanocomposites of Al/Fe203 were compared. Flame propagation was studied by igniting low density mixtures and taking data photographically with a high-speed camera. Both open and confined burning was examined. Results indicated that the bum rate was a strong function of the stoichiometry of the mixture. An Equivalence ratio of 1.4 provides an optimum bum rate regardless of oxidizer synthesis technique. The magnitude of the bum rate is also a strong function of the oxidizer synthesis technique. Oxidizers processed using the sol-gel technology originally contained impurities which retarded the bum rates. When the same oxidizers were annealed at high temperatures, the new heat-treated oxidizer showed a dramatic improvement, with bum rates on the order of 900 m/s. The results of this work ultimately optimized the sol-gel synthesis process for preparing thermites.Item Conjugated dithiols as model systems for molecular electronics: assembly, structure, and electrical response(2008-05) Kraptchetov, Dmitri A., 1982-; Loo, Yueh-Lin, 1974-; Sanchez, Isaac C., 1941-Molecular assemblies are promising candidates for nano-scale electronics due to their chemical and structural versatility. The successful fabrication of assembly-based nano-scale electronics, where molecular assemblies comprise the electrically-active components, requires the ability to reliably form molecular assemblies and the ability to 'wire them into electrical junctions. This dissertation focuses on the processing-structure relationships of model conjugated dithiols, the formation of electrical junctions with these molecular assemblies, and the characterization of these junctions. Biphenyldithiol (BPDT), terphenyldithiol (TPDT), and quaterphenyldithiol (QPDT) are assembled in solution from their thioacetyl precursors which are converted in-situ to thiolates using NH4OH. We elucidated how the type of substrate, the solvent quality, and the concentrations of NH4OH and the thioacetyl precursors affect the final structures of these assemblies. BPDT molecular assemblies are disordered on both gold (Au) and gallium arsenide (GaAs) at all conditions explored. TPDT and QPDT adopt the most upright molecular orientations on both Au and GaAs when the assembly is carried out from EtOH-rich solutions at low NH4OH and high precursor concentrations. At these conditions, the assembly formation process is dominated by the adsorption of thioacetylterminated molecules. When the assembly is carried with high NH4OH and low precursor concentrations, adsorption is dominated by thiolates; TPDT and QPDT are disordered on Au and GaAs. None of the molecules adsorb significantly on GaAs from THF. The presence of S-Au bonds at the molecular assembly -- top Au contact interface was directly probed by x-ray photoelectron spectroscopy. Depositing Au electrodes on QPDT assemblies by nTP in dichloroethane results in the reproducible formation of S-Au bonds at the molecule-Au interface. Finally, we measured the electrical response of the model conjugated molecular assemblies on GaAs through direct contact with galinstan. The current densities scale inversely with the tunneling distance, which is determined by factors including the length of the conjugated molecule and the molecular orientation of the assembly. We also examined the electrical response of GaAs--QPDT--Au junctions in which the Au electrodes were transferred using an elastomeric stamps. The electrical characteristics of these junctions were independent of orientation of the molecules and the presence of SAu bonds at the charge transfer nterface. Hydrocarbon contamination on the Au electrodes left by the elastomeric stamp during transfer masked any electrical response from QPDT. It is therefore crucial to ensure the pristine quality of the electrical contact in order to reliably measure the electrical response of the molecular assembly. The fabrication and testing of assembly-based electrical junctions is challenging in terms of both controlling the assembly structures and measuring their electrical response. Careful attention must therefore be paid to each aspect of molecular assemblybased junction formation and characterization.Item Control strategies and motion planning for nanopositioning applications with multi-axis magnetic-levitation instruments(Texas A&M University, 2007-09-17) Shakir, HuzefaThis dissertation is the first attempt to demonstrate the use of magnetic-levitation (maglev) positioners for commercial applications requiring nanopositioning. The key objectives of this research were to devise the control strategies and motion planning to overcome the inherent technical challenges of the maglev systems, and test them on the developed maglev systems to demonstrate their capabilities as the next-generation nanopositioners. Two maglev positioners based on novel actuation schemes and capable of generating all the six-axis motions with a single levitated platen were used in this research. These light-weight single-moving platens have very simple and compact structures, which give them an edge over most of the prevailing nanopositioning technologies and allow them to be used as a cluster tool for a variety of applications. The six-axis motion is generated using minimum number of actuators and sensors. The two positioners operate with a repeatable position resolution of better than 3 nm at the control bandwidth of 110 Hz. In particular, the Y-stage has extended travel range of 5 mm ???? 5 mm. They can carry a payload of as much as 0.3 kg and retain the regulated position under abruptly and continuously varying load conditions. This research comprised analytical design and development, followed by experimental verification and validation. Preliminary analysis and testing included open-loop stabilization and rigorous set-point change and load-change testing to demonstrate the precision-positioning and load-carrying capabilities of the maglev positioners. Decentralized single-input-single-output (SISO) proportional-integral-derivative (PID) control was designed for this analysis. The effect of actuator nonlinearities were reduced through actuator characterization and nonlinear feedback linearization to allow consistent performance over the large travel range. Closed-loop system identification and order-reduction algorithm were developed in order to analyze and model the plant behavior accurately, and to reduce the effect of unmodeled plant dynamics and inaccuracies in the assembly. Coupling among the axes and subsequent undesired motions and crosstalk of disturbances was reduced by employing multivariable optimal linear-quadratic regulator (LQR). Finally, application-specific nanoscale path planning strategies and multiscale control were devised to meet the specified conflicting time-domain performance specifications. All the developed methodologies and algorithms were implemented, individually as well as collectively, for experimental verification. Some of these applications included nanoscale lithography, patterning, fabrication, manipulation, and scanning. With the developed control strategies and motion planning techniques, the two maglev positioners are ready to be used for the targeted applications.Item Controlled assembly of biodegradable gold nanoclusters for in vivo imaging(2015-12) Stover, Robert John; Johnston, Keith P., 1955-; Truskett, Thomas M; Fan, Donglei; Korgel, Brian; Sokolov, KonstantinGold nanoparticles are of interest in biomedical imaging applications due to their inert nature and ability to exhibit surface plasmon resonance. These phenomena can result in high near-infrared extinction (NIR) due to asymmetry or close interparticle spacings within gold structures, making these materials ideal for photoacoustic imaging. Using this imaging modality, these materials allow for high contrast compared to the body’s tissues which exhibit a transparent “window” between 700-1100 nm, making them perfect for early cancer detection. However many gold structures designed for this application fail to achieve high NIR-absorbance at the <5 nm sizes which are required for efficient kidney clearance. Therefore, we designed a system which assembles ~4 nm primary gold particles into closely-spaced clusters of controlled size using a biodegradable, weakly adsorbing polymer and balance of colloidal attractive and repulsive forces. Thus, when the polymer degrades in acidic environments – such as within cells – the residual charge on the primary particles leads to dissociation of the clusters back to renal-clearable constituents. Since proteins in the blood and cells can increase the diameter of the primary particles above the 5 nm threshold, nanoparticle surfaces were designed to have a mixture of charged and zwitterionic molecules to limit protein interactions through buried charges and increased particle hydration. Strongly-bound, zwitterionic thiol-containing ligands were also investigated to resist the intracellular exchange of biomolecules which could compromise the clearable nature of the particles. These decorated nanoparticles were then assembled into clusters through one of two methods which varied either gold and polymer concentrations through evaporation, or particle charge via electrolyte addition prior to quenching by dilution in DI water. Once assembled, clusters assembled with polymer showed dissociation behavior after incubation in pH 5 acidic solutions to mimic the cellular pH environment. In other cases, sintering of the gold nanoparticle clusters prevented such dissociation. This thesis demonstrates the ability to not only create biocompatible nanoparticle surfaces, but to establish control size control over nanocluster assemblies which are capable of being used as NIR contrast agents.Item Controlling infrared radiation with subwavelength metamaterials and silicon carbide(2011-05) Neuner, Burton Hamilton; Shvets, G.; Fink, Manfred; Florin, Ernst-Ludwig; Yao, Zhen; Zhang, XiaojingThe control and manipulation of infrared (IR) radiation beyond the capabilities of natural materials using silicon carbide (SiC), metamaterials, or a combination thereof, is presented. Control is first demonstrated using SiC, a polar crystal that exhibits a dielectric permittivity less than zero in the mid-IR range, through the excitation of tightly confined surface phonon-polaritons (SPPs), thus enabling a multitude of applications not possible with conventional dielectrics. Optimal, or critical coupling to SPPs is explored in SiC films through Otto-configuration attenuated total reflection. One practical application based on Otto-coupled SPPs is presented: IR refractive index sensing is shown for three pL-scale fluid analytes. It is then demonstrated that when two SiC films are brought to a few-micron separation, IR radiation can excite surface modes that possess phase velocities near the speed of light, a property required for efficient table-top particle accelerators. Metamaterials are engineered with subwavelength structure and possess optical properties not found in nature. Two such metamaterials will be introduced: metal films perforated with arrays of rectangular holes display the ability to control IR light polarization through spoof surface plasmon excitation, and metal/dielectric multilayers patterned with subwavelength-pitch corrugations display frequency-tunable, wide-angle, perfect IR absorption. Two experiments, which have implications in polarization control and thermal emission, combine the benefits of SiC with those of metamaterials: extraordinary optical transmission and absorption are observed in SiC hole arrays, and the design of individual SiC antennas permits the control of the bulk metamaterial responses of impedance and absorption/emission. Finally, a new optical beamline based on Fourier transform IR spectroscopy was designed, built, characterized, and implemented, serving as the major experimental objective of this dissertation. The novel beamline, which confines radiation to a 200-micron diameter and enables angle-dependent IR spectroscopy, was verified using multiple metamaterial structures.Item Design of parallel multipliers and dividers in quantum-dot cellular automata(2011-05) Kim, Seong-Wan; Swartzlander, Earl E.; Ambler, Anthony P.; Driga, Mircea D.; Gouda, Mohamed G.; Touba, Nur A.; Schulte, Michael J.; Bickerstaff, K'Andrea C.Conventional CMOS (the current dominant technology for VLSI) implemented with ever smaller transistors is expected to encounter serious problems in the near future with the need for difficult fabrication technologies. The most important problem is heat generation. The desire for device density, power dissipation and performance improvement necessitates new technologies that will provide innovative solutions to integration and computations. Nanotechnology, especially Quantum-dot Cellular Automata (QCA) provides new possibilities for computing owing to its unique properties. Numerous nanoelectronic devices are being investigated and many experimental devices have been developed. Thus, high level circuit design is needed to keep pace with changing physical studies. The circuit design aspects of QCA have not been studied much because of its novelty. Arithmetic units, especially multipliers and dividers play an important role in the design of digital processors and application specific systems. Therefore, designs for parallel multipliers and dividers are presented using this technology. Optimal design of parallel multipliers for Quantum-Dot Cellular Automata is explored in this dissertation. As a main basic element to build multipliers, adders are implemented and compared their performances with previous adders. And two different layout schemes that single layer and multi-layer wire crossings are compared and analyzed. This dissertation proposes three kinds of multipliers. Wallace and Dadda parallel multipliers, quasi-modular multipliers, and array multipliers are designed and simulated with several different operand sizes. Also array multipliers that are well suited in QCA are constructed and formed by a regular lattice of identical functional units so that the structure is conformable to QCA technology without extra wire delay. All these designs are constructed using coplanar layouts and compared with other QCA multipliers. The delay, area and complexity are compared for several different operand sizes. This research also studies divider designs for quantum-dot cellular automata. A digit recurrence restoring binary divider is a conventional design that serves as a baseline. By using controlled full subtractor cell units, a relatively simple and efficient implementation is realized. The Goldschmidt divider using the new architecture (data tag method) to control the various elements of the divider is compared for the performance.Item An efficient solution procedure for simulating phonon transport in multiscale multimaterial systems(2013-05) Loy, James Madigan; Murthy, JayathiOver the last two decades, advanced fabrication techniques have enabled the fabrication of materials and devices at sub-micron length scales. For heat conduction, the conventional Fourier model for predicting energy transport has been shown to yield erroneous results on such length scales. In semiconductors and dielectrics, energy transport occurs through phonons, which are quanta of lattice vibrations. When phase coherence effects can be ignored, phonon transport may be modeled using the semi-classical phonon Boltzmann transport equation (BTE). The objective of this thesis is to develop an efficient computational method to solve the BTE, both for single-material and multi-material systems, where transport across heterogeneous interfaces is expected to play a critical role. The resulting solver will find application in the design of microelectronic circuits and thermoelectric devices. The primary source of computational difficulties in solving the phonon BTE lies in the scattering term, which redistributes phonon energies in wave-vector space. In its complete form, the scattering term is non-linear, and is non-zero only when energy and momentum conservation rules are satisfied. To reduce complexity, scattering interactions are often approximated by the single mode relaxation time (SMRT) approximation, which couples different phonon groups to each other through a thermal bath at the equilibrium temperature. The most common methods for solving the BTE in the SMRT approximation employ sequential solution techniques which solve for the spatial distribution of the phonon energy of each phonon group one after another. Coupling between phonons is treated explicitly and updated after all phonon groups have been solved individually. When the domain length is small compared to the phonon mean free path, corresponding to a high Knudsen number ([mathematical equation]), this sequential procedure works well. At low Knudsen number, however, this procedure suffers long convergence times because the coupling between phonon groups is very strong for an explicit treatment of coupling to suffice. In problems of practical interest, such as silicon-based microelectronics, for example, phonon groups have a very large spread in mean free paths, resulting in a combination of high and low Knudsen number; in these problems, it is virtually impossible to obtain solutions using sequential solution techniques. In this thesis, a new computational procedure for solving the non-gray phonon BTE under the SMRT approximation is developed. This procedure, called the coupled ordinates method (COMET), is shown to achieve significant solution acceleration over the sequential solution technique for a wide range of Knudsen numbers. Its success lies in treating phonon-phonon coupling implicitly through a direct solution of all equations in wave vector space at a particular spatial location. To increase coupling in the spatial domain, this procedure is embedded as a relaxation sweep in a geometric multigrid. Due to the heavy computational load at each spatial location, COMET exhibits excellent scaling on parallel platforms using domain decomposition. On serial platforms, COMET is shown to achieve accelerations of 60 times over the sequential procedure for Kn<1.0 for gray phonon transport problems, and accelerations of 233 times for non-gray problems. COMET is then extended to include phonon transport across heterogeneous material interfaces using the diffuse mismatch model (DMM). Here, coupling between phonon groups occurs because of reflection and transmission. Efficient algorithms, based on heuristics, are developed for interface agglomeration in creating coarse multigrid levels. COMET is tested for phonon transport problems with multiple interfaces and shown to outperform the sequential technique. Finally, the utility of COMET is demonstrated by simulating phonon transport in a nanoparticle composite of silicon and germanium. A realistic geometry constructed from x-ray CT scans is employed. This composite is typical of those which are used to reduce lattice thermal conductivity in thermoelectric materials. The effective thermal conductivity of the composite is computed for two different domain sizes over a range of temperatures. It is found that for low temperatures, the thermal conductivity increases with temperature because interface scattering dominates, and is insensitive to temperature; the increase of thermal conductivity is primarily a result of the increase in phonon population with temperature consistent with Bose-Einstein statistics. At higher temperatures, Umklapp scattering begins to take over, causing a peak in thermal conductivity and a subsequent decrease with temperature. However, unlike bulk materials, the peak is shallow, consistent with the strong role of interface scattering. The interaction of phonon mean free path with the particulate length scale is examined. The results also suggest that materials with very dissimilar cutoff frequencies would yield a thermal conductivity which is closest to the lowest possible value for the given geometry.Item Experimental demonstration of new optical properties in hybrid nanostructures(2015-12) Hartsfield, Thomas Murray; Li, Elaine; Bengtson, Roger; Shih, Chih-Kang; Sitz, Greg; Wang, ZhengIn this dissertation, I present experimental investigation of the optical properties of nanoscale systems composed of both metallic and semiconductor components. Metallic nanostructures may act as resonant cavities for conduction electrons, allowing drastic electromagnetic field enhancement and the concentration of these surface plasmon field modes into tiny volumes. Semiconductor quantum dot emitters demonstrate desirable and broadly tunable optical properties due to the quantized nature of their internal electron states. When paired together, the absorption, emission, optical gain, and internal energy decay pathways of the quantum dot as well as the scattering of the cavity may be strongly modified. This work focuses on the optical properties of two such model hybrid nanostructure systems. Of the many studies of plasmonic cavities, relatively few investigate the influence of a quantum dot on the scattering of the plasmonic cavity itself. The main experimental challenge lies in the difficulty of placing an absorber or emitter at the desired position: the very virtue of the small mode volume of a plasmonic cavity demands precise spatial emitter placement. We will study the simplest plasmonic cavity, a single metal nanoparticle and a single quantum dot. We assembled a hybrid nanostructure using a nanomanipulation “nano-golfing” technique and demonstrated for the first time that the state of a single quantum dot can resonantly control the scattering of a vastly larger plasmonic cavity, manifested as a Fano resonance. A device of this design could potentially be used as a photon source capable of outputting photons of classical or quantum statistics on demand. We then turn to the optical properties of the emitter element of a hybrid nanostructure. We measured the ability of an atomically smooth Ag film to influence the optical properties of a quantum dot. This novel system has been shown to produce more uniform emitter-plasmon coupling and a greater product of excitation and radiative decay rates than possible with traditional systems relying upon rough metal films. Applications utilizing coupling between metallic films and quantum emitters could see benefit from high quality atomically smooth films as demonstrated by our studies.Item Exploring scaling limits and computational paradigms for next generation embedded systems(2009-12) Zykov, Andrey V.; De Veciana, GustavoIt is widely recognized that device and interconnect fabrics at the nanoscale will be characterized by a higher density of permanent defects and increased susceptibility to transient faults. This appears to be intrinsic to nanoscale regimes and fundamentally limits the eventual benefits of the increased device density, i.e., the overheads associated with achieving fault-tolerance may counter the benefits of increased device density -- density-reliability tradeoff. At the same time, as devices scale down one can expect a higher proportion of area to be associated with interconnection, i.e., area is wire dominated. In this work we theoretically explore density-reliability tradeoffs in wire dominated integrated systems. We derive an area scaling model based on simple assumptions capturing the salient features of hierarchical design for high performance systems, along with first order assumptions on reliability, wire area, and wire length across hierarchical levels. We then evaluate overheads associated with using basic fault-tolerance techniques at different levels of the design hierarchy. This, albeit simplified model, allows us to tackle several interesting theoretical questions: (1) When does it make sense to use smaller less reliable devices? (2) At what scale of the design hierarchy should fault tolerance be applied in high performance integrated systems? In the second part of this thesis we explore perturbation-based computational models as a promising choice for implementing next generation ubiquitous information technology on unreliable nanotechnologies. We show the inherent robustness of such computational models to high defect densities and performance uncertainty which, when combined with low manufacturing precision requirements, makes them particularly suitable for emerging nanoelectronics. We propose a hybrid eNano-CMOS perturbation-based computing platform relying on a new style of configurability that exploits the computational model's unique form of unstructured redundancy. We consider the practicality and scalability of perturbation-based computational models by developing and assessing initial foundations for engineering such systems. Specifically, new design and decomposition principles exploiting task specific contextual and temporal scales are proposed and shown to substantially reduce complexity for several benchmark tasks. Our results provide strong evidence for the relevance and potential of this class of computational models when targeted at emerging unreliable nanoelectronics.Item Inhaled mycophenolate mofetil formulations for the prevention of lung allograft rejection(2012-08) Dugas, Helene Laurence; Williams, Robert O., 1956-; Cui, Zhengrong; McConville, Jason T.; McGinity, James W.; Peters, Jay I.The use of lung transplantation, a life saving intervention, has been increasing over the last thirty years with a disappointing median survival of only 4.8 years. Despite the progress made in immunosuppressive therapies, allograft rejection following transplantation is the leading cause of death. As part of the immunosuppressive therapy, mycophenolate mofetil (MMF), the ester prodrug of mycophenolic acid (MPA) has proven its efficacy among heart, liver, kidney as well as lung transplanted patients. However, due to its rapid excretion, high daily doses are necessary and lead to serious side effects, forcing the patient to stop and change their course of treatment. Administration of drugs to the lungs is known to minimize local and systemic side effects by employing a lower amount of drug, to increase patient compliance and to improve the efficacy of the treatment. Therefore, developing novel MMF formulations for targeted delivery to the lungs will broaden the therapeutic options against lung transplant rejection. Within the framework of this dissertation, the development of an inhaled formulation of MMF was investigated. MMF must be metabolized by carboxylesterases to become active and its metabolism suffers from high inter- and intra-patient variability. The first objective of this dissertation was to investigate the occurrence of MMF hydrolysis in the lung. The second objective was to study the in vivo deposition,metabolism and distribution in rats, of an inhaled micron-size MMF suspension in comparison to inhaled IV Cellcept® and oral Cellcept®, the currently marketed products. According to the in vitro results, MMF is metabolized in human lung cells by carboxylesterases. The in vivo results showed an incomplete metabolism of MMF when delivered as a suspension due to the limited dissolution of the drug in the lungs. Following inhalation, the MMF suspension achieved higher and more prolonged concentration of the total drug in the lungs and lymphoid tissues as compared to the inhaled IV Cellcept®. The pulmonary delivery of the MMF suspension was able to achieve similar levels of drug in the lungs, higher levels in the lymphoid tissues and significantly lower levels in the systemic circulation when compared to the levels obtained from the oral gavage of oral Cellcept®. Ultimately, this dissertation demonstrated that the administration of micron-size MMF suspension offers a great potential for pulmonary administration.Item Integration of nanotechnology in a STEM based high school curriculum through the investigation of wetting properties of nano-imprinted and silanized surfaces(2014-08) Negley, Maria Blanco; Sreenivasan, S. V.; Crawford, Richard H.Nanotechnology is an emerging field of engineering. Awareness needs to be fostered in the K-12 education system in order to sustain its expansion. As a current Algebra 1 teacher, I participated in the NASCENT research program to further my education in nanotechnology and find ways to integrate this content and practices in my Science Technology Engineering and Math (STEM) based Algebra 1 curriculum. During the research, I learned about surface tension of solids and liquids and its effects on materials' wetting properties. After completing the research program, I created a 2-week long project where students will replicate my experiences during this research. The purpose of this report is to investigate the need for the integration of nanotechnology in STEM classes and find ways to turn my research experience into real-world learning opportunities for my students.Item Intelligent nanoscale hydrogels for the oral delivery of hydrophobic therapeutics(2015-05) Puranik, Amey Shreekant; Peppas, Nicholas A., 1948-; Contreras , Lydia; Sanchez , Isaac; Stachowiak , Jeanne; Yeh, Hsin-ChihIn this work, novel oral drug delivery formulations were developed for the administration of hydrophobic therapeutics, with the overarching goal of improving their solubility and permeability in the gastrointestinal tract. We have developed a set of four nanoscale hydrogels, formulated by incorporating different hydrophobic monomer components, and screen them for optimal physicochemical properties, drug loading and release, and ability to modulate intestinal permeability and P-glycoprotein related drug efflux. Here, we employ an evolved paradigm of in vitro tests to gauge the potential of these novel nanoscale carriers for the specific application of improving oral solubility and permeability of poorly water-soluble and less permeable therapeutics. All the responsive nanoscale hydrogels are capable of undergoing a transition in size in response to change in pH. We capitalize on the interplay between the incorporated hydrophobic monomer choices and screened resulting physicochemical properties to determine an optimal nanoscale formulation. Depending upon the selection of the hydrophobic monomer, the sizes of the nanoparticles vary widely from 120 nm to about 500 nm at pH 7.4. We also evaluate cytocompatibility of the nanoparticle formulations in vitro in the presence of an intestinal epithelial cell mode to find that all formulations are reasonably cytocompatible. Subsequently, we discuss some of the key findings and results of characterization studies that validate the success of achieving desired molecular architecture and physicochemical properties of the formulation. We then confirm the capacity of the nanocarrier to be able to load and release hydrophobic therapeutics in gastrointestinally relevant environments. Further, the ability of the nanocarriers to transport the hydrophobic therapeutic doxorubicin is determined by evaluating permeability of doxorubicin with intestinal epithelial cell monolayers. Furthermore, demonstrate functional abilities desired from a therapeutically relevant, oral delivery system is tested. Specifically, to overcome problems associated with P-glycoprotein related efflux and reduced drug permeability in the small intestine, we evaluated the ability of the nanoformulation to achieve therapeutic success in relevant and characteristic in vitro cancer cell lines. Finally, we make concluding remarks on the ability of the nanoparticles to function as improved formulations of hydrophobic therapeutics capable of performing and achieving the end-goal of delivering hydrophobic therapeutics orally for the treatment of cancer.Item Laser micro/nano scale processing of glass and silicon(2006) Theppakuttai Komaraswamy, Senthil Prakash; Chen, ShaochenItem Laser micro/nano scale processing of glass and silicon(2006-05) Theppakuttai Komaraswamy, Senthil Prakash, 1977-; Chen, ShaochenThe revolutionary progress in semiconductor, communication, and information industries based on electronic and photonic technologies demands for the development and enhancement of new laser processes to support micro and nanotechnologies. This dissertation is aimed at exploring the use of lasers for micro and nano scale processing of glass and silicon, the most commonly used materials in the IC industry. The objective of the dissertation is two fold: a) use lasers for locally micro bonding glass and silicon wafers, and b) use lasers for nanopatterning glass and silicon substrates by circumventing the diffraction limit of light. In the first part of the thesis, glass and silicon wafers are bonded locally in microscale by a pulsed Nd:YAG laser. Glass is transparent to the wavelength used and hence the laser beam passes through the glass wafer and is absorbed by silicon. As a result, silicon is melted and upon resolidification bonding is realized between the two substrates. The transient melting and resolidification of the substrates is studied experimentally and compared to the simulation results of a finite element numerical model. The bonded areas are studied in detail using a scanning electron microscope and a chemical analysis is done to understand the bonding mechanism. In the second part of the thesis, nanopatterns are created on glass and silicon substrates by circumventing the diffraction limit of light. The nanofeatures are created by irradiating silica and gold nanospheres deposited on a substrate. In case of silica spheres, features approximately half the diameter of the sphere were obtained by utilizing the optical field enhancement around the spheres. In case of gold spheres, features as small as 40 nm were realized by the excitation of coherent resonant electron plasma oscillations. The effect of sphere size, laser wavelength, polarization, incident angle, and energy were studied experimentally. Finally, these experimental results are compared with the numerical results from a multidimensional, heat transfer model.Item Magnetic field enhancement of Coulomb blockade conductance oscillations in metal-metal oxide double barrier tunnel devices fabricated using atomic force microscope nanolithography(2005) Wiemeri, Jeffrey Charles; Shih, Chih-Kang
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