The work presented in this thesis shows how tunneling spectroscopy techniques can be applied to metallic nanoparticles to obtain useful information about fundamental physical processes in nanoscopic length scales. At low temperatures, the discrete character of the energy spectrum of these particles, allows the study of spin-polarized current via resolved "electron-in-a-box" energy levels. In samples consisting of two ferromagnetic electrodes tunnel coupled to single aluminum nanoparticles, spin accumulation mechanisms are responsible for the observed spin-polarized current. The observed effect of an applied perpendicular magnetic field, relative to the magnetization orientation of the electrodes, indicates the suppression of spin precession in such small particles. More generally, in the presence of an external non-collinear magnetic field, it is the local field "felt" by the particle that determines the character of the tunnel current. This effect is also observed in the case where only one of the electrodes is ferromagnetic. In contrast to the non-magnetic case, ferromagnetic nanoparticles exhibit a much more complex energy spectrum, which cannot be accounted for, using the simple free-electron picture. It will be shown that interactions between quasi-particle excitations due to sequential electron tunneling and spin excitations in the particle are likely to play an important role in the observed temperature/voltage dependence of magnetic hysteresis loops.

<p>The aim of this diploma work is to improve selectivity and sensitivity in DNA-chips by utilizing fluorescence resonance energy transfer (FRET) between conjugated polyelectrolytes (CPEs) and fluorophores.</p><p>Leclerc and co-workers have presented successful results from studies of super FRET between fluorophore tagged DNA and a CPE during hybridisation of the double strand. Orwar and co-workers have constructed a DNA-chip using standard photo lithography creating a pattern of the hydrophobic photoresist SU-8 and cholesterol tagged DNA (chol-DNA). This diploma work will combine and modify these two ideas to fabricate a improved DNA-chip.</p><p>Immobilizing of DNA onto surface has been done by using soft lithography. Hydrophobic pattern arises from the poly(dimethylsiloxane) (PDMS) stamp. The hydrophobic pattern will attract chol-DNA that is adsorbed to the chip. Different sets of fluorophores are covalently bound to the DNA and adding CPEs to the complex will make FRET occur between CPE and bound fluorophore.</p><p>We will here show that the specificity in DNA hybridization by using PDMS patterning was high. FRET clearly occurred, especially with the CPEs as donor to the fluorophore Cy5. The intensity of FRET was higher when the fluorophore and the CPE were conjugated to the same DNA strand. The largest difference in FRET intensity between double stranded and single stranded complexes was observed with the CPE tPOMT. Super FRET has been observed but not yet fully proved. The FRET efficiency was lower with the fluorophore Alexa350 as donor compared to the Cy5/CPE complex. Most of the energy transferred from Alexa350 was extinguished by quenching.</p>

Title from PDF of title page. / Document formatted into pages; contains 73 pages. / Thesis (M.S.E.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The goals of this research project were the design and construction of a carbon nanotube (CNT) reactor based on the plasma enhanced chemical vapor deposition (PECVD) principle and the development of a method for directed assembly of CNTs by catalyst patterning. PECVD was selected as the growth method due to the requirement of a catalyst for the growth process, thereby facilitating directed assembly and controlled diameter CNT growth at well-defined locations. The reactor was built in accord with horizontal flow design using standard ultra high vacuum components. The controllable parameters of the reactor include sample temperature, DC plasma intensity, chamber pressure, gas flow ratios, and total gas flow. The most favorable parameters for growing CNTs of well defined length, diameter, and separation were obtained by initially using parameter values obtained from literature, then optimized by changing a parameter and noting the effect on CNT growth. / ABSTRACT: Catalyst patterns for the directed assembly of CNTs were prepared by electron-beam lithography (EBL). Experiments were performed that demonstrated the feasibility of using lithographic methods to achieve directed assembly of carbon nanotubes for the manufacture of CNT devices. Experiments focusing on growth interruption and regrowth of CNTs were conducted to investigate methods of introducing tailored branching points into carbon nanotubes during the growth process. These experiments clearly demonstrate that growth interruption increases the occurrence of CNT branching. An analysis of the relationships between CNT diameter, branching points, and the number of growth steps was conducted. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Polymeric waveguide-on-flex has the potential to replace complex and costly light-turning devices in optoelectronic applications. As light signals are propagated and confined through the definition of core-cladding interface, the light guiding structure is required to adhere well and ensure long term interfacial stability. This thesis addresses the gap that has emerged in the fundamental material issues such as the polymeric optical waveguide materials deposited on the flexible substrates. In addition, this thesis investigates the feasibility of a new approach using electrostatic-induced lithography in micro-patterning of polymer, in optical waveguide fabrication. Plasma treatment is applied to enhance interfacial adhesion between flex substrates and optical cladding layers. The modified flex surfaces of polyimide KaptonHNTM and liquid crystal polymer VecstarTM materials are characterised. In addition, sonochemical surface treatment is evaluated on these flexible substrates. ToF-SIMS depth profiling has confirmed the interface reaction mechanisms where it has shown that plasma treatment increases the interfacial interpenetration. The larger interfacial width increases the possible entanglement mechanism between the polymer chains. These results, together with the double cantilever beam testing, indicate the strengthening of the polymeric interface upon plasma treatment, which is essential for long term optical and mechanical stability of waveguide-on-flex applications. A new method of micro-pattering of polymer material has been adopted for fabricating multimode waveguide-on-flex. The method, using an electrostatic-induced lithography, is developed to produce 50 μm x 50 μm arrays of polysiloxane LightlinkTM waveguide on flex. This thesis looks at various process recipes of the technique and reports the pattern formation of polymeric optical core. By adjusting the spin-coated liquid core thickness, pre-bake condition, UV exposure and applied voltage, the aspect ratio and profile of the optical core microstructure can be varied. As the electrostatic pressure overcoming the surface tension of spin-coated waveguide material induces the optical core formation, the core structure is smooth, making it ideal for low scattering loss waveguide. The propagation loss of fabricated waveguide is measured at 1.97 dB/cm at 850 nm wavelength. The result shows that the use of electrostatic-induced lithography in optical polymer is a promising approach for low cost and low temperature (<150 °C) processing at back end optical-electrical integrated circuitry assembly.

This thesis discusses two patterning techniques: Step and Flash Imprint Lithography, a nanoimprint technique, and patterning thin films utilizing electrohydrodynamic instabilities. Step and Flash Imprint Lithography, SFIL, is promising alternative approach to photolithography. SFIL replicates the relief pattern of a template in a photocurable liquid that has been dispensed on a substrate. The pattern is then crosslinked when the photocurable liquid is exposed to UV light through the template. In order to study the volume change in the created features upon exposure, a stochastic mesoscale model was formulated. This model allows the study of the possibility of defects forming, from under cured etch barrier, or particle contamination of the template. The results showed large defects should not occur regularly until the minimum feature size is below 3 nanometers. The mesoscale model proved to computationally intensive to simulate features of engineering interest. A base multiscale model was formulated to simulate the effects of the densification of the photocurable liquid as well as the effects of the polymerization on the feature integrity. The multiscale model combines a continuum model (compressible Mooney-Rivlin) coupled to the mesoscale code using the Arlequin method. The multiscale model lays the framework that may be adapted to the study of other SFIL processes like template release. Patterning thin films utilizing electrohydrodynamic instabilities allows for the creation of periodic arrays of pillar like features. These pillars form due to the electric field destabilizing the thin film. Prior work has focused on utilizing polymeric films heated above their glass transition temperatures. In order to decrease the process time in the pillar formation process, work was done to study photocurable systems. The systems which proved favorable to the pillar creation process were the thiol-ene system as well as the maleimide systems. Further work was done on controlling the packing and ordering of the formed pillar arrays by using patterned templates. The result of these studies is that control was only able to be achieved to the third generation of pillars formed due to the inability to fully control the gap over the entire active area. / text

We report the design and fabrication of a micro-mechanical oscillator for use in extremely small force detection experiments such as transverse force measurements of a moving vortex and Nuclear Magnetic Resonance Force Microscopy (NMRFM). We study the basic physics of the double torsional mechanical oscillator, and pursue double torsional oscillators with small spring constants, high resonance frequencies, and high quality factors. Using a series of semiconductor manufacturing techniques, especially using the electron-beam lithography technique, we successfully micro-fabricate double torsional mechanical oscillators from silicon-on-insulator wafers. We conduct characterization experiments to extract important parameters of a mechanical oscillator, including the resonance frequencies, spring constants, and quality factors. We focus on the four typical resonance modes of these oscillators, and then compare the force detection sensitivity of each mode. Eventually we apply these force sensitive oscillators to gold micro-mass measurements, and achieve very small mass detection. In the future we are going to continue to micro-fabricate thinner oscillators to reduce the spring constants, and improve the quality factors by designing more suitable geometric shapes and by pursuing annealing studies. Thus, we might be able to achieve single nuclear spin measurements using NMRFM. / text

The Bio J-FIL process has been demonstrated to be a viable method for manufacturing nanoscale, polymeric drug carriers. The process allows for precise control of the size and shape of the drug carriers. While the original process is sufficient for research scale projects, reliability issues have prevented it from being scalable to levels that could potentially be used for mass-production of the drug carriers. In this thesis, a detailed root cause analysis has been conducted to determine the cause of the reliability issues limiting the Bio JFIL process. A series of experiments with varying substrate and imprint fluid combinations were conducted to pinpoint the cause of imprint failure in the Bio J-FIL process. Upon determining the cause of failure, an alternative imprint process was investigated that sought to increase the variety of materials used in the process by utilizing an intermediary layer. This process is referred to in this thesis as the Bio JFIL-I process. The results using Bio JFIL-I indicated increased reliability over the standard Bio J-FIL process. Further refinement of the Bio JFIL-I process could also address additional issues with the Bio J-FIL process unrelated to process reliability. The Bio JFIL-I approach presented in this thesis is complementary to other approaches that have been recently pursued in the literature which are discussed in the thesis. / text

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In 1960's Gordon Moore predicted that the increase in the number of components in integrated circuits would exponentially decrease the relative manufacturing cost per component with time. The semiconductor industry has managed to keep that pace for nearly 45 years and one of the main contributors to this phenomenal improvement in technology is advancement in the field of lithography. However, the technical challenges ahead are severe and the future roadmap laid by the International Technology Roadmap for Semiconductors looks mostly red (i.e. no solution has been found to specific problem). There are efforts in the industry and academia directed toward development of newer, alternative lithographic techniques. Step and Flash Imprint Lithography (SFIL) has recently emerged as one of the most promising alternatives, capable of producing high resolution patterns. While it has numerous advantages over conventional photolithography, several engineering challenges must be overcome to eliminate defects due to the nature of contact imprinting if SFIL is to be a viable alternative technique for manufacturing tomorrow's integrated circuits. The complete filling of template features is vital in order for the SFIL imprint process to truly replicate the template features. The feature filling phenomena for SFIL was analyzed by studying diffusion of a gas, entrapped in the features, through liquid imprint resist. A simulation of the dynamics of feature filling for different pattern configurations and process conditions during the SFIL imprint step is presented. Simulations show that initial filling is pressure-controlled and very rapid; while the rest of the feature filling is diffusion-controlled, but fast enough that diffusion of entrapped gas is not a cause for non-filling of features. A theory describing pinning of an air-liquid interface at the feature edge of a template during the SFIL imprint step was developed, which shows that pinning is the main cause of non-filling of features. Pinning occurs when the pressure at the air-liquid interface reaches the pressure of the bulk liquid. At this condition, there is no pressure gradient or driving force to move the liquid and fill the feature. The effect of several parameters on pinning was examined. A SFIL process window was established and template modifications are proposed that minimize the pinning at the feature edge while still preventing any extrusion along the mesa (pattern containing area on the template) edge. Part of semiconductor manufacturing community believes that optical lithography has the capability to drive this industry further and is committed to the continuous improvement of current optical patterning approaches. Some of the major challenges with shrinking critical dimensions (CDs) in coming years are the control of line-edge roughness (LER) and other related defects. The current CDs are such that the presence or absence of even a single polymer molecule can have a considerable impact on LER. Therefore molecular level understanding of each step in the patterning process is required. Computer simulations are a cost-effective approach to explore the huge process space. Mesoscale modeling is one promising approach to simulations because it captures the stochastic phenomena at a molecular level within reasonable computational time. The modeling and simulation of the post-exposure bake (PEB) and the photoresist dissolution steps are presented. The new simulator enables efficient exploration of the statistical excursions that lead to LER and the formation of insoluble residues during the dissolution process. The relative contributions of the PEB and the dissolution step to the LER have also been examined in the low/high frequency domain. The simulations were also used to assess the commonly proposed measures to reduce LER. The goal of the work was to achieve quantification of the effect of changes in resist composition, developer concentration, and process variables on LER and the associated defectivity. / text

In the recent years threaded run-to-run (RtR) control algorithms have experienced drawbacks under certain circumstances, one such trait is when applied to high-mix of products such as in Application Specific Integrated Circuits (ASIC) foundries. The variations in the process are a function of the product being manufactured as well as the tool being used. The presence of semiconductor layers increases the number of times the lithography process must be repeated. Successive layers having different patterns must be exposed using different reticles/masks in order to maximize tool utilizations. The objectives of this research are to develop a set of methodologies for evaluation and extension of threaded control applied to overlay. This project defines methods to quantify the efficacy of threaded controls, finds the drawbacks of threaded control under production of high mix of semiconductors and suggests extensions and alternatives to improve threaded control. To evaluate the performance of threaded control, extensive simulations were performed in MATLAB. The effects of noise, disturbances, sampling and delays on the control and estimation performance of threaded controller were studied through these simulations. Based on the results obtained, several ideas to extend threaded control by reducing overall number of threads, by improving thread definitions and combination have been introduced. A unique idea of sampling the measurements dynamically based on the estimation accuracy is also presented. Future work includes implementing the extensions to threaded control suggested in this work in real production data and comparing the results without the use of those methods. Future work also includes building new alternatives to threaded control. / text