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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
581

Barium Strontium Titanate films for tunable microwave and acoustic wave applications

Gurumurthy, Venkataramanan 01 June 2007 (has links)
The composition-dependent Curie temperature and bias-dependant dielectric permittivity of Barium Strontium Titanate (BST) makes it very attractive for tunable application in the RF/Microwave regime. In this research work, the performance of BST varactors fabricated on the conventional Pt/Ti/SiO2/Si bottom electrode stack were compared with those fabricated using chemical vapor deposited Nanocrystalline Diamond (NCD) as the diffusion barrier layer instead of SiO2. The varactors fabricated on NCD films displayed much better symmetry in capacitance-voltage behavior and better overall quality factors than varactors fabricated on SiO2. The improvement in performance can be attributed to existence of stable interfaces in the devices fabricated on NCD which reduced the bottom electrode losses at high frequencies. The SiO2 based BST varactors on the other hand displayed better reliability and breakdown fields. The main purpose of this research work is to develop a robust Metal Insulator Metal (MIM) structure to achieve better all round performance of BST varactors. In the second part of this research work, the prospect of developing diamond based layered Surface Acoustic Wave (SAW) devices using Ba0.8Sr0.2TiO3 as the piezoelectric layer is investigated. Structural characterization of BST thin films deposited on Si/NCD/Pt and Si/SiO2/Ti/Pt stack were performed using X-Ray Diffraction (XRD) and Atomic Force Microscopy (AFM). Cross-sectional studies on the two stacks were performed using Scanning Electron Microscopy (SEM). X-Ray Mapping (XRM) was then done to ascertain the quality of the interfaces and to check for interdiffusion between layers. MIM structures in the Coplanar Waveguide (CPW) configuration were fabricated using conventional lithography and etching techniques for high frequency measurements. The performance of the fabricated varactors was characterized from 100 MHz to 1 GHz. For the SAW application, structural characterization of Ba0.8Sr0.2TiO3 on Chemical Vapor Deposited (CVD) diamond was done and the deposition procedure was optimized to obtain thick BST films. SAW bandpass filters and resonators were designed wherein the device geometry was varied over a wide range in order to characterize the variation in device performance with geometry. Finally interdigital capacitor structures were fabricated and used for conducting Curie temperature measurements on the deposited BST films in order to determine the operation range of the deposited BST films.
582

Thermal analyses of hydrophilic polymers used in nanocomposites and biocompatible coatings

Mohomed, Kadine 01 June 2006 (has links)
ABSRACT: This research focuses on two hydrophilic polymers that form hydrogels when they sorb water: Poly(2-hydroxyethyl methacrylate) (PHEMA) and Poly(2,3-dihydroxypropyl methacrylate) (PDHPMA). Present work in the field obviated the need to properly characterize the thermal and dielectric properties of these materials.The dielectric permittivity, e', and the loss factor, e", of dry poly(2-hydroxyethyl methacrylate) and poly(2,3-dihydroxypropyl methacrylate) were measured using a dielectric analyzer in the frequency range of 0.1Hz to 100 kHz and between the temperature range of -150 °C to 275°C. The dielectric response of the sub-Tg gamma transition of PHEMA has been widely studied before but little to no DEA data above 50°C is present in the literature. This study is the first to present the full range dielectric spectrum of PHEMA, PDHPMA and their random copolymers up to and above the glass transition region. The electric modulus formalism and several mathematical proofs were used to reveal the gamma, beta, alpha and conductivity relaxations. Dielectric analysis gives insight into the network structure of the polymer; it has been shown through thermal analyses that as the DHPMA content increased in HEMA-DHPMA copolymers the polymer matrix increased in available free volume and facilitated the movement of ions in its matrix. This is of significance as we then investigated the feasibility of using PHEMA, PDHPMA and their random copolymers as materials for a biocompatible coating for an implantable glucose sensor. The biocompatibility of hydrogels can be attributed to the low interfacial tension with biological fluids, high gas permeability, high diffusion of low molecular weight compounds, and reduced mechanical and frictional irritation to surrounding tissue. Once the biocompatibility of the hydrogels was established, the task to coat the polyurethane (PU)/epoxy coated metal glucose sensor was addressed. Plasma polymerization was found to be the most feasible technique for the application of the biocompatible hydrogel as a coating on the implantable glucose sensor. It has also been shown that thermal analysis techniques provide a mode of investigation that can be used to investigate the interfacial interactions of a novel hydroxylated, self-assembled nanoparticle with two functionally different polymers, poly(2-dihydroxyethyl methacrylate) and poly(methyl methacrylate).
583

A study on the calibration and accuracy of the one-step TDR method

Runkles, Brian David 01 June 2006 (has links)
Traditional in-situ soil compaction monitoring methods are often limited in their application, thus quality control of compacted fills and roadway embankments remains a challenging problem. As a result, new methods are being developed to more accurately measure in-situ compaction parameters. Time domain reflectometry (TDR) is one such method. Several advances have been made over the past few years to further the use of TDR technology in water content and density measurement of compacted fill. The one-step method relies on the measurement of the apparent dielectric constant in conjunction with the bulk electrical conductivity, and correlates them through two soil-specific constants, f and g. The two measurements, together with other soil specific constants, are then used to back calculate the water content and density in a single step. However, questions remain regarding the accuracy and bias of TDR measurements in relation to other "established" in-situ procedures such as the nuclear gage and speedy moisture. Results from an experimental program to obtain calibration constants for typical sands used in roadway construction are presented. A number of side-by-side tests are performed to compare the measurements obtained using the TDR one-step method to those obtained form other methods. Conducting such side-by-side tests is a critical step in the progress and eventual widespread usage of the one-step method. In addition, all the results are compared against an independent measurement of the in-place density from a slurry-replacement method. The objective of the independent measurement is to provide a baseline for accurate and unbiased evaluation of TDR and other technologies.
584

Parameter extraction and characterization of transmission line interconnects based on high frequency measurement

Kim, Jooyong 28 August 2008 (has links)
Not available / text
585

Scalable Genome Engineering in Electrowetting on Dielectric Digital Microfluidic Systems

Madison, Andrew Caldwell January 2015 (has links)
<p>Electrowetting-on-dielectric (EWD) digital microfluidics is a droplet-based fluid handling technology capable of radically accelerating the pace of genome engineering research. EWD-based laboratory-on-chip (LoC) platforms demonstrate excellent performance in automating labor-intensive laboratory protocols at ever smaller scales. Until now, there has not been an effective means of gene transfer demonstrated in EWD microfluidic platforms. This thesis describes the theoretical and experimental approaches developed in the demonstration of an EWD-enabled electrotransfer device. Standard microfabrication methods were employed in the integration of electroporation (EP) and EWD device architectures. These devices enabled the droplet-based bulk transformation of E. coli with plasmid and oligo DNA. Peak on-chip transformation efficiencies for the EP/EWD device rivaled that of comparable benchtop protocols. Additionally, ultrasound induced in-droplet microstreaming was developed as a means of improving on-chip electroporation. The advent of electroporation in an EWD platform offers synthetic biologists a reconfigurable, programmable, and scalable fluid handling platform capable of automating next-generation genome engineering methods. This capability will drive the discovery and production of exotic biomaterials by providing the instrumentation necessary for rapidly generating ultra-rich genomic diversity at arbitrary volumetric scales.</p> / Dissertation
586

Magneto-dielectric material characterization and RF antenna design

Han, Kyuhwan 21 September 2015 (has links)
A novel material characterization method for magneto-dielectric composite material was proposed. MD materials have been reported as providing new opportunities for effective antenna size reduction in many studies. Since MD materials have to be realized through material synthesis, an accurate measurement method is required to extract them. The proposed method, cavity perturbation technique using substrate integrated waveguide cavity resonator, has been demonstrated through theories, simulations and measurement that it can be used to extract both electric and magnetic properties of the MD composite material effectively. MD materials using cobalt-fluoropolymer have been synthesized and material design guidelines for antenna applications are also provided. The benefits of using MD materials on antenna miniaturization was also demonstrated by comparing the performance of an antenna on MD material to other antennae on high dielectric constant materials and FR-4 material. Through simulations and measurements, the MD material is a promising solution for next generation smartphone or wearable type applications.
587

Dielectric tensor of monoclinic Ga2O3 single crystals in the spectral range 0.5–8.5 eV

Sturm, Chris, Furthmüller, Jürgen, Bechstedt, Friedhelm, Schmidt-Grund, Rüdiger, Grundmann, Marius 20 November 2015 (has links) (PDF)
The dielectric tensor of Ga2O3 in the monoclinic (β) phasewas determined by generalized spectroscopic ellipsometry in a wide spectral range from 0.5 eV to 8.5 eV as well as by density functional theory calculations combined with many-body perturbation theory including quasiparticle and excitonic effects. The dielectric tensors obtained by both methods are in excellent agreement with each other and the observed transitions in the dielectric function are assigned to the corresponding valence bands. It is shown that the off-diagonal element of the dielectric tensor reaches values up to |εxz| ≈ 0.30 and cannot be neglected. Even in the transparent spectral range where it is quite small (|εxz| < 0.02) it causes a rotation of the dielectric axes around the symmetry axis of up to 20◦.
588

Development of interdigitated capacitor sensors for direct and wireless measurements of the dielectric properties of liquids

Kim, Jun Wan 18 March 2011 (has links)
The miniaturization of chemical and biological sensors has received considerable attention in recent years for medical diagnostics, environmental monitoring, pharmaceutical screening, military applications, etc. One interesting area of development in microfluidic system is detecting dielectric properties of MUT (Material Under Test) using IDC (Interdigital Capacitor) electrodes. The IDC chemical sensor has been investigated by many researchers because they are cheap to manufacture and can be easily integrated with other sensing components and signal processing electronics. This dissertation presents the design, fabrication, and testing of an IDC (interdigital capacitor) electrode sensor for a fluid property monitoring component that can be integrated into a microfluidic system. One practical point of this research is the analytical evaluation of the interdigital electrode capacitance for the detection of conductivity and permittivity of the aqueous solutions, which is not apparently analyzed in other chemical sensor applications. In addition, a new noble methodology of remotely accessing the IDC sensor by wireless inductive coupling similar to EAS (Electronic Article Surveillance) tags is presented. / text
589

Process development, material analysis, and electrical characterization of ultra thin hafnium silicate films for alternative gate dielectric application

Gopalan, Sundararaman 21 April 2011 (has links)
Not available / text
590

Effects of moisture on the breakdown strength and lifetime of low permittivity dielectric for nanometer scale interconnects

Choi, Soo Young, doctor of materials science and engineering 13 June 2011 (has links)
Advanced integrated circuit (IC) technology has implemented new materials for necessary and timely performance improvements. New materials are now required at both the front-end-of-line (FEoL) and back-end-of-line (BEoL) of the device because simple dimensional scaling with standard materials has come with performance costs that negate dimensional scaling performance improvements. At the FEoL, high-[kappa]/metal gate processes are being developed to reduce gate oxide leakage. At the BEoL, Cu-based metallization and low-[kappa] dielectric materials have been developed to reduce BEoL contribution to RC-propagation delay. Cu-based metallization has required change in integration strategy, which has led to concerns about new material reliability performance. Furthermore, continuing pressure to improve device performance requires that a new, more advanced low-[kappa] dielectric be used, which are mechanically and electrically inferior. These performance demands and greater reliability concerns must be balanced. This kind of balance requires that better understanding of the extrinsic threats to device reliability be understood and is the general area of interest for this work. In particular, this study examines the extent of degradation found in low-[kappa] dielectric when it is exposed to ambient moisture and the potential impact of this degradation on intrinsic reliability performance under electrical stress. The integration method is described for low-[kappa] dielectric processing so that potential damages during process can be explained. Local damages can allow moisture incorporation at the expense of additional dielectric performance and reliability degradation. The molecular form of moisture incorporation into low-[kappa] dielectric and potential process methods to reduce moisture incorporation are also discussed. The electrical reliability performance is shown using interdigitated structures through voltage ramped dielectric breakdown study of inter-metal dielectric (IMD). Clear evidence of dielectric degradation is found after extreme moisture incorporation. Moisture penetration impact is also examined on the long-term reliability of integrated low-[kappa] dielectric using time-dependent dielectric breakdown (TDDB). Results show a dramatic change in the observed field acceleration parameter through moisture exposure that is not easily explained in a standard way according to proposed dielectric breakdown models for low-[kappa] dielectrics. A simple modification of the thermochemical [Epsilon]-model is proposed to explain the results. / text

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