114 Matching Results

Search Results

Advanced search parameters have been applied.

Capacitance and effective area of flush monopole probes.

Description: Approximate formulas are constructed and numerical simulations are carried out for electric field derivative probes that have the form of flush mounted monopoles. Effects such as rounded edges are included. A method is introduced to make results from two-dimensional conformal mapping analyses accurately apply to the three-dimensional axisymmetric probe geometry
Date: August 1, 2004
Creator: Warne, Larry Kevin; Johnson, William Arthur; Morris, Marvin E.; Basilio, Lorena I.; Lehr, Jane Marie & Higgins, Matthew B.
Partner: UNT Libraries Government Documents Department

Characterization of a fused silica capacitance standard

Description: An ovenized 10 pF standard capacitor was constructed by the National Institute of Standards and Technology (NIST). The dielectric material used as Wuprasil II grade fused silica. This report discusses a temperature coefficient analysis of the capacitor performed at the Primary Standards Laboratory (PSL) of Sandia National Laboratories (SNL). The effects of temperature change on dielectric loss will also be discussed.
Date: January 1, 1995
Creator: Daniel, M.G.
Partner: UNT Libraries Government Documents Department

Actively Biased p-Channel MOSFET Studied with Scanning Capacitance Microscopy

Description: Scanning capacitance microscopy (SCM) was used to study the cross section of an operating p-channel MOSFET. We discuss the novel test structure design and the modifications to the SCM hardware that enabled us to perform SCM while applying dc bias voltages to operate the device. The results are compared with device simulations performed with DAVINCI.
Date: September 22, 1999
Partner: UNT Libraries Government Documents Department

GaAs Self-Aligned JFETS with Carbon-Doped P+ Region

Description: Self-aligned JFETs with a carbon-doped p{sup +} region have been reported for the first time. For these JFETs, both the channel and p{sup +} region were grown by metal organic chemical vapor deposition (MOCVD) and are termed epitaxial JFETs in this study. The epitaxial JFETs were compared to ion implanted JFETs of similar channel doping and threshold voltage. Both JFETs were fabricated using the same self-aligned process for doping the source and drain regions of the JFET and for eliminating excess gate capacitance of conventional JFETs. The gate turn-on voltage for the epitaxial JFETs was 1.06 V, about 0.1 V higher than for the implanted JFETs. The reverse breakdown voltage was similar for both JFETs but the reverse gate leakage current of the epitaxial JFETs was 1-3 orders of magnitude less than the implanted JFETs. The epitaxial JFETs also showed higher transconductance and lower knee voltage than the implanted JFETs.
Date: February 15, 1999
Creator: Allerman, A.A.; Baca, A.G.; Chang, P.C. & Drummond, T.J.
Partner: UNT Libraries Government Documents Department

Lead zirconate titanate on base metal foils: An approach for embedded high-K passive components

Description: An approach for embedding high-K dielectric thin films into polymer packages has been developed. Pb{sub 0.85}La{sub 0.15}(Zr{sub 0.52}Ti{sub 0.48}){sub 0.96}O{sub 3} thin films were prepared by chemical solution deposition on 50 {micro}m thick Ni-coated Cu foils. Sputter deposited Ni top electrodes completed the all base-metal capacitor stack. After high temperature N{sub 2} crystallization anneals, the PLZT composition showed reduction resistance while the base-metal foils remained flexible. Capacitance density and Loss tangent values range between 300 and 400 nF/cm{sup 2} and 0.01 and 0.02 from 1 to 1,000 kHz respectively. These properties represent a 2 to 3 order of magnitude improvement over available embedded capacitor technologies for polymeric packages.
Date: January 26, 2000
Creator: Maria, J.-P.; Cheek, K.; Streiffer, S. K.; Kim, S.-H.; Dunn, G. & Kingon, A. I.
Partner: UNT Libraries Government Documents Department


Description: The 28 MHz accelerating system consists of a quarter wave cavity driven by an inductively coupled 100kW tetrode amplifer and 1kW solid state driver amplifer. 40dB of rf feedback closed around the cavity and amplifers reduces small perturbations within the loop by a factor of 100, and reduces the time required to shift the phase at transition by a factor of 10, limited by the saturation of the drive chain. The cavity is tuned over a 200kHz range by a mechanical tuner which varies the gap capacitance. Broadband HOM damping is provided by two orthogonal loop coupled high pass filters. Design parameters and commissioning results are presented.
Date: June 18, 2001
Partner: UNT Libraries Government Documents Department

Controller strategy for a 6 DOF piezoelectric translation stage

Description: A controller for the third generation, 6 degree-of-freedom (DOF) piezoelectric translation stage shown in Figure 1 is presented. This was tested by monitoring all six coordinate motions using an orthogonal array of six, high-resolution capacitance gages. The full 6 DOF matrix transformations and controller block diagrams for this system have been measured and the system operated under closed loop control. Results of early experiments to determine the 21 open loop response functions as well as preliminary results showing the closed loop response for the 3 linear translations are presented in this abstract. The ultimate goal of this project is to incorporate this 6 DOF stage within a long range X-Y scanning system for nanometer pick-and-place capability over an area of 50 x 50 mm. The control strategy and early results from this system will be presented.
Date: March 22, 2006
Creator: Buice, E S; Yang, H; Smith, S T; Hocken, R J; Trumper, D L; Otten, D et al.
Partner: UNT Libraries Government Documents Department

Correlations of Capacitance-Voltage Hysteresis with Thin-Film CdTe Solar Cell Performance During Accelerated Lifetime Testing

Description: In this paper we present the correlation of CdTe solar cell performance with capacitance-voltage hysteresis, defined presently as the difference in capacitance measured at zero-volt bias when collecting such data with different pre-measurement bias conditions. These correlations were obtained on CdTe cells stressed under conditions of 1-sun illumination, open-circuit bias, and an acceleration temperature of approximately 100 degrees C.
Date: March 1, 2011
Creator: Albin, D. & del Cueto, J.
Partner: UNT Libraries Government Documents Department

Role of Copper in the Performance of CdS/CdTe Solar Cells: Preprint

Description: The performance of CdS/CdTe solar cells made with evaporated Cu as a primary back contact was studied through current-voltage (JV) at different intensities, quantum efficiency (QE) under light and voltage bias, capacitance-voltage (CV), and drive-level capacitance profiling (DLCP) measurements. The results show that while modest amounts of Cu enhance cell performance, excessive amounts degrade device quality and reduce performance. The analysis is supported with numerical simulations to reproduce and explain some of the experimental results.
Date: May 1, 2006
Creator: Demtsu, S.; Albin, D. & Sites, J.
Partner: UNT Libraries Government Documents Department

Survey of Micromanometers

Description: This survey is concerned with instrumentation for measuring pressures from about 0.001 to 50mm of mercury (0.13 to 6650 Nm-2), described in publications during the years 1900-1968. U-tube micromanometers and diaphragm-capacitance gages are treated in considerable detail. Other instrumentation described includes gas column manometers; elastic element micromanometers with optical, inductance, resistance wire, strain gage, and vacuum tube transducers; piston gages; vane gages; and centrifugal micromanometers. The measurement of dynamic pressure, atmospheric pressure oscillations, low vapor pressure, and calibration techniques are discussed. Schematic diagrams of approximately 70 instruments are included. References to the sources of information and available performance data are given.
Date: 1970
Creator: Brombacher, W. G.
Partner: UNT Libraries Government Documents Department

A comparison of the electrochemical behavior of carbon aerogels and activated carbon fiber cloths

Description: Electrochemical capacitative behavior of carbon aerogels and commercial carbon fiber cloths was studied in 5M KOH, 3M sulfuric acid, and 0.5M tetrethylammonium tetrafluoroborate/propylene carbonate electrolytes. The resorcinol-formaldehyde based carbon aerogels with a range of denisty (0.2-0.85 g/cc) have open-cell structures with ultrafine pore sizes (5-50 nm), high surface area (400-700 m{sup 2}/g), and a solid matrix composed of interconnected particles or fibers with characteristic diameters of 10 nm. The commercial fiber cloths in the density range 0.2-04g/cc have high surface areas (1000-2500 m{sup 2}/g). The volumetric capacitances of high-density aerogels are shown to be comparable to or exceeding those from activated carbon fibers. Electrochemical behavior of these materials in various electrolytes is compared and related to their physical properties.
Date: May 10, 1996
Creator: Tran, T.D.; Alviso, C.T.; Hulsey, S.S.; Nielsen, J.K. & Pekala, R.W.
Partner: UNT Libraries Government Documents Department

Closed-field capacitive liquid level sensor

Description: A liquid level sensor based on a closed field circuit comprises a ring oscillator using a symmetrical array of plate units that creates a displacement current. The displacement current varies as a function of the proximity of a liquid to the plate units. The ring oscillator circuit produces an output signal with a frequency inversely proportional to the presence of a liquid. A continuous liquid level sensing device and a two point sensing device are both proposed sensing arrangements. A second set of plates may be located inside of the probe housing relative to the sensing plate units. The second set of plates prevent any interference between the sensing plate units.
Date: January 1, 1995
Creator: Kronberg, J.W.
Partner: UNT Libraries Government Documents Department

Novel integrated CMOS pixel structures for vertex detectors

Description: Novel CMOS active pixel structures for vertex detector applications have been designed and tested. The overriding goal of this work is to increase the signal to noise ratio of the sensors and readout circuits. A large-area native epitaxial silicon photogate was designed with the aim of increasing the charge collected per struck pixel and to reduce charge diffusion to neighboring pixels. The photogate then transfers the charge to a low capacitance readout node to maintain a high charge to voltage conversion gain. Two techniques for noise reduction are also presented. The first is a per-pixel kT/C noise reduction circuit that produces results similar to traditional correlated double sampling (CDS). It has the advantage of requiring only one read, as compared to two for CDS, and no external storage or subtraction is needed. The technique reduced input-referred temporal noise by a factor of 2.5, to 12.8 e{sup -}. Finally, a column-level active reset technique is explored that suppresses kT/C noise during pixel reset. In tests, noise was reduced by a factor of 7.6 times, to an estimated 5.1 e{sup -} input-referred noise. The technique also dramatically reduces fixed pattern (pedestal) noise, by up to a factor of 21 in our tests. The latter feature may possibly reduce pixel-by-pixel pedestal differences to levels low enough to permit sparse data scan without per-pixel offset corrections.
Date: October 29, 2003
Creator: Kleinfelder, Stuart; Bieser, Fred; Chen, Yandong; Gareus, Robin; Matis, Howard S.; Oldenburg, Markus et al.
Partner: UNT Libraries Government Documents Department

15.4% CuIn1-XGaXSe2-Based Photovoltaic Cells from Solution-Based Precursor Films

Description: We have fabricated 15.4%- and 12.4%-efficient CuIn1-XGaXSe2 (CIGS)-based photovoltaic devices from solution-based electrodeposition (ED) and electroless-deposition (EL) precursors. As-deposited precursors are Cu-rich CIGS. Additional In, Ga, and Se are added to the ED and EL precursor films by physical vapor deposition (PVD) to adjust the final film composition to CuIn1-XGaXSe2. The ED and EL device parameters are compared with those of a recent world record, an 18.8%-efficient PVD device. The tools used for comparison are current voltage, capacitance voltage, and spectral response characteristics.
Date: May 25, 1999
Creator: Bhattacharya, R. N.; Batchelor, W.; Contreras, M. A.; Noufi, R. N. (National Renewable Energy Laboratory); Hiltner, J. F. & Sites, J. R. (Department of Physics, Colorado State University)
Partner: UNT Libraries Government Documents Department


Description: Large accelerator main magnet system consists of hundreds, even thousands, of dipole magnets. They are linked together under selected configurations to provide highly uniform dipole fields when powered. Distributed capacitance, insulation resistance, coil resistance, magnet inductance, and coupling inductance of upper and lower pancakes make each magnet a complex network. When all dipole magnets are chained together in a circle, they become a coupled pair of very high order complex ladder networks. In this study, a network of more than thousand inductive, capacitive or resistive elements are used to model an actual system. The circuit is a large-scale network. Its equivalent polynomial form has several hundred degrees. Analysis of this high order circuit and simulation of the response of any or all components is often computationally infeasible. We present methods to use frequency decomposition approach to effectively simulate and analyze magnet configuration and power supply topologies.
Date: June 25, 2007
Creator: Zhang, W.; MARNERIS, I. & SANDBERG, J.
Partner: UNT Libraries Government Documents Department

Gamma Ray Imaging for Environmental Remediation (GRIER)

Description: Germanium detector systems with both high spectral resolution and good imaging capabilities to the problems of environmental remediation. Over the last year, much progress has been made. We have (1) developed and built amorphous-contact germanium detectors of increasing sophistication, (2) built and tested an array of four position sensitive germanium detectors, (3) demonstrated spectroscopy and imaging uses with 235U, and Results from this research were presented at the EMSP's first workshop in Chicago in 1998, at the SPIE Session in July 1999, and at the IEEE Nuclear Science Symposium in November 1998 and 1999. AMORPHOUS CONTACTS The goal of the amorphous contact effort was to extend the single element (pixel) amorphous technology developed by Luke et al. (1994) to double-sided orthogonal strip detectors. Amorphous contact provides multiple advantages over the current lithium contact technology. We have fabricated the first orthogonal strip detector with dimensions appropriate for field use. The detector has an active volume of 50 mm x 50 mm x 10 mm and has 25 x 25 strips (see Figure 1). It is currently undergoing tests. The resolution is {approx}12 keV FWHM, which is dominated by electronic noise. The noise was high because of the large capacitance and the non-optimal electronics used with the test cryostat.
Date: June 1, 2000
Creator: Johnson,W.N.; Phlips, B.F.; Kroeger, R.A.; Kurfess, J.D.; Phillips, G. & Luke, P.N.
Partner: UNT Libraries Government Documents Department

Investigation of defects in highly photosensitive germanosilicate thin films

Description: Germanosilicate glasses exhibit a significant photosensitive response which has been linked to the presence of oxygen-deficient germanium point defects in the glass structure. Based on this correlation, highly photosensitive thin films have been engineered which demonstrate the largest reported ultraviolet-induced refractive index perturbations (An) in an as-synthesized material. Our thin-film fabrication process avoids the use of hydrogen sensitizing treatments and, thus, yields stable films which retain their predisposition for large photosensitivity for over one year of storage. Understanding the nature of the defects in such films and their relationship to charge trapping and enhanced photosensitivity is of paramount importance in designing and optimizing the materials. Toward this end, our films have been studied using electron paramagnetic resonance (EPR), capacitance-voltage, and optical bleaching and absorption spectroscopies. We find experimental evidence suggesting a model in which a change in spin state and charge state of isolated paramagnetic neutral Ge dangling bonds form either diamagnetic positively or negatively charged Ge sites which are largely responsible for the charge trapping and photosensitivity in these thin films. We present experimental data and theoretical modeling to support our defect model and to show the relevance of the work.
Date: February 1, 1997
Creator: Simmons-Potter, K.; Potter, B.G. Jr. & Warren, W.L.
Partner: UNT Libraries Government Documents Department

Use of air gap structures to lower intralevel capacitance

Description: Interconnect delays, arising in part from intralevel capacitance, are one of the factors limiting the performance of advanced circuits. In addition, the problem of filling the spaces between neighboring metal lines with an insulator is becoming increasingly acute as aspect ratios increase. We address these problems simultaneously by intentionally creating an air gap between closely spaced metal lines. Undesirable topography is eliminated using a spin-on dielectric. We then cap the wafers with silicon dioxide and planarize using chemical mechanical polishing. Simple modeling of test structures predicts an equivalent dielectric constant of 1.9 on features similar to those expected for 0.25 micron technologies. Two level metal test structures fabricated in a 0.5 micron CMOS technology show that the process can be readily integrated with current standard CMOS processes. The potential problems of via misalignment, overall dielectric stack height, and the relative difficulty of ensuring void formation compared to that of ensuring a void-free fill are considered.
Date: March 1, 1997
Creator: Fleming, J.G. & Roherty-Osmun, E.
Partner: UNT Libraries Government Documents Department

Sandia Smart Anti-Islanding Project; Summer 2001: Task II Investigation of the Impact of Single-Phase Induction Machines in Islanded Loads: Summary of Results

Description: Islanding, the supply of energy to a disconnected portion of the grid, is a phenomenon that could result in personnel hazard, interfere with reclosure, or damage hardware. Considerable effort has been expended on the development of IEEE 929, a document that defines unacceptable islanding and a method for evaluating energy sources. The worst expected loads for an islanded inverter are defined in IEEE 929 as being composed of passive resistance, inductance, and capacitance. However, a controversy continues concerning the possibility that a capacitively compensated, single-phase induction motor with a very lightly damped mechanical load having a large rotational inertia would be a significantly more difficult load to shed during an island. This report documents the result of a study that shows such a motor is not a more severe case, simply a special case of the RLC network.
Date: May 1, 2002
Partner: UNT Libraries Government Documents Department

Final LDRD Report for the Project Entitled: Biosensors Based on the Electrical Impedance of Tethered Lipid Bilayers on Planar Electrodes

Description: Impedance based, planar chemical microsensors are the easiest sensors to integrate with electronics. The goal of this work is a several order of magnitude increase in the sensitivity of this sensor type. The basic idea is to mimic biological chemical sensors that rely on changes in ion transport across very thin organic membranes (supported Bilayer Membranes: sBLMs) for the sensing. To improve the durability of bilayers we show how they can be supported on planar metal electrodes. The large increase in sensitivity over polyelectrolytes will come from molecular recognition elements like antibodies that bind the analyte molecule. The molecular recognition sites can be tied to the lipid bilayer capacitor membrane and a number of mechanisms can be used to modulate the impedance of the lipid bilayers. These include coupled ion channels, pore modification and double layer capacitance modification by the analyte molecule. The planar geometry of our electrodes allows us to create arrays of sensors on the same chip, which we are calling the ''Lipid Chip''.
Date: February 1, 2003
Partner: UNT Libraries Government Documents Department

Fully Integrated Applications of Thin Films on Low Temperature Cofired Ceramic (LTCC)

Description: Thin film multilayers have previously been introduced on multilayer low temperature cofired ceramic (LTCC), as well as initial thin film capacitors on LTCC. The ruggedness of a multipurpose Ti-Cu-Pt-Au stack for connectivity and RF conductivity has continued to benefit fabrication and reliability in state of-the-art modules, while the capacitors have followed the traditional Metal-Insulator-Metal (MIM) style. The full integration of thin film passives with thin film connectivity traces is presented. Certain passives, such as capacitors, require specifically tailored and separately patterned thin film (multi-)layers, including a dielectric. Different capacitance values are achieved by variation of both the insulator layer thickness and the active area of the capacitor. Other passives, such as filters, require only the conductor - a single thin film multilayer. This can be patterned from the same connectivity thin film material (Ti-Cu-Pt-Au), or a specially tailored thin film material (e.g. Ti-Cu-Au) can be deposited. Both versions are described, including process and integration details. Examples are discussed, ranging from patterning for maximum tolerances, to space and performance-optimized designs. Cross-sectional issues associated with integration are also highlighted in the discussion.
Date: April 19, 2012
Creator: Wolf, Ambrose; Peterson, Ken; O'Keefe, Matt; Huebner, Wayne & Kuhn, Bill
Partner: UNT Libraries Government Documents Department


Description: A numerical technique has been developed to solve the three-dimensional potential distribution about a point source of current located in or on the surface of a half-space containing an arbitrary three-dimensional conductivity distribution. Self-adjoint difference equations are obtained for Poisson's equation using finite-difference approximations in conjunction with an elemental volume discretization of the lower half-space. Potential distribution at all points in the set defining the subsurface are simultaneously solved for multiple point sources of current. Accurate and stable solutions are obtained using full, banded, Cholesky decomposition of the capacitance matrix as well as the recently developed Incomplete Cholesky-Conjugate Gradient Iterative method. A comparison of the two- and three-dimensional simple block-shaped models, for the collinear dipole-dipole array, indicates substantially lower anomaly indices for inhomogeneities of finite strike-extent. In general, the strike-extents of inhomogeneities have to be approximately 10 times the dipole lengths before the response becomes two-dimensional. The saturation effect with increasing conductivity contrasts appears sooner for the three-dimensional conductive inhomogeneities than for corresponding models with infinite strike lengths. A downhole-to-surface configuration of electrodes produces diagnostic total field apparent resistivity maps for three-dimensional buried inhomogeneities. Experiments with various lateral and depth locations of the current pole indicate that mise a la masse surveys give the largest anomaly if a current pole is located asymmetrically and preferably near the top-surface of the buried conductor.
Date: October 1, 1977
Creator: Dey, Abhijit & Morrison, H. Frank
Partner: UNT Libraries Government Documents Department