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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


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

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

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

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


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


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

First Results with the Prototype Detectors of the Si/W ECAL

Description: Measurements on the prototype silicon sensors for use with an electromagnetic calorimeter with tungsten absorber are reported. The prototype sensors are based on a hexagonal geometry that optimally utilizes the space available on 6 inch silicon wafers. The sensors are segmented into approximately 750 5mm hexagonal pixels, which are connected to a bump-bonding array located at the center of the sensors. We report on those properties of the sensors that are important for linear collider applications including depletion voltage, stray capacitance and series resistance.
Date: July 12, 2005
Creator: Strom, D; Frey, R.; U., /Oregon; Breidenbach, M.; Deng, J.; Freytag, D. et al.
Partner: UNT Libraries Government Documents Department

Traceable Micro-Force Sensor for Instrumented Indentation Calibration

Description: Instrumented indentation testing (IIT), commonly referred to as nanoindentation when small forces are used, is a popular technique for determining the mechanical properties of small volumes of material. Sample preparation is relatively easy, usually requiring only that a smooth surface of the material to be tested be accessible to a contact probe, and instruments that combine sophisticated automation with straightforward user interfaces are available commercially from several manufacturers. In addition, documentary standards are now becoming available from both the International Standards Organization (ISO 14577) and ASTM International (E28 WK382) that define test methods and standard practices for IIT, and will allow the technique to be used to produce material property data that can be used in product specifications. These standards also define the required level of accuracy of the force data produced by IIT instruments, as well as methods to verify that accuracy. For forces below 10 mN, these requirements can be difficult to meet, particularly for instrument owners who need to verify the performance of their instrument as it is installed at their site. In this paper, we describe the development, performance and application of an SI-traceable force sensor system for potential use in the field calibration of commercial IIT instruments. The force sensor itself, based on an elastically deforming capacitance gauge, is small enough to mount in a commercial instrument as if it were a test specimen, and is used in conjunction with an ultra-high accuracy capacitance bridge. The sensor system is calibrated with NIST-traceable masses over the range 5.0 {micro}N through 5.0 mN. We will present data on its accuracy and precision, as well its potential application to the verification of force in commercial instrumented indentation instruments.
Date: April 2, 2007
Creator: Smith, D T; Shaw, G A; Seugling, R M; Xiang, D & Pratt, J R
Partner: UNT Libraries Government Documents Department

Early testing of a coarse/fine precision motion control system

Description: This abstract presents a brief overview of key components of a motion control stage for accurate nanometer level positioning for scanning specimens over an area measuring 50 mm x 50 mm. The completed system will utilize a short-range, third generation 6 degree-of-freedom fine motion control platform (4 microns, 160 micro-radians) carried by a long-range, two-axis x-y positioning system (50 mm x 50 mm). Motion of the controlled platform relative to a measurement frame will be measured using a heterodyne laser interferometer and capacitance sensing. The final stage will be mounted onto an isolation table in a vacuum chamber, itself on isolation supports mounted to a granite slab on bed rock and isolated from the main floor of the building. This whole system is housed in a temperature-controlled laboratory. It is envisaged that the current system will provide the ability to ''pick and place'' at nanometer levels and be used for long range scanning of specimens (including biological specimens), micro- /macroassembly, lithography and as a coordinate measuring machine (CMM). Furthermore, the system performance will be compared with other comparable systems at international locations such as, National Physical Laboratory (NPL) in the UK, Technical University of Eindhoven (TUE) in the Netherlands, Physikalisch-Technische Bundesanstalt (PTB) in Germany, and our own sub-atomic measuring machine (SAMM) [1, 2] at UNC-Charlotte. Critical requirements of the system are as follows: (1) Vacuum compatible to better than 20 mPa; (2) Range of 50 mm x 50 mm x 4 microns; (3) Maximum translation velocity of 5 mm {center_dot} s{sup -1}; (4) Sub-nanometer resolution; and (5) System accuracy of better than 10 nm.
Date: August 1, 2005
Creator: Buice, E. S.; Yang, H.; Smith, S. T.; Hocken, R. J.; Seugling, R. M.; Trumper, D. L. et al.
Partner: UNT Libraries Government Documents Department

Thermal Modeling Tool for a Spherical Capsule in a Sputtering Chamber

Description: It is known that a film's temperature during a sputtering process greatly influences its mechanical structure. Currently, there is no known tool to effectively model the temperature history of a sputtered film on a spherical capsule in a sputtering chamber. Therefore, a tool has been developed that allows for the prediction of this temperature history using a lumped capacitance approximation for the capsule. This tool has been developed as part of LLNL's Diablo II multi-mechanics code to allow for the coupling of the capsule mechanics with the finite element-based sputtering chamber mechanics. The tool incorporates three forms of heat transfer: contact heat transfer between the capsule and the walls, enclosure radiation among all surfaces, and adsorption of chamber gas on all surfaces. The physics of the system have been validated by determining less than 1% difference in simulated results of twelve test runs to values determined via analytical or finite difference approaches, and validation of eight further tests involving capsule motion provide confidence in the model.
Date: February 3, 2006
Creator: Wemhoff, A P
Partner: UNT Libraries Government Documents Department

Micro-system inertial sensing technology overview.

Description: The purpose of this report is to provide an overview of Micro-System technology as it applies to inertial sensing. Transduction methods are reviewed with capacitance and piezoresistive being the most often used in COTS Micro-electro-mechanical system (MEMS) inertial sensors. Optical transduction is the most recent transduction method having significant impact on improving sensor resolution. A few other methods are motioned which are in a R&D status to hopefully allow MEMS inertial sensors to become viable as a navigation grade sensor. The accelerometer, gyroscope and gravity gradiometer are the type of inertial sensors which are reviewed in this report. Their method of operation and a sampling of COTS sensors and grade are reviewed as well.
Date: February 1, 2009
Creator: Allen, James Joe
Partner: UNT Libraries Government Documents Department

Four-Plate Pick-Up Capacitance and Sensitivity Calculations

Description: The goal of calculations presented in this note is to find and maximize the sensitivity of a quadrupole pick-up currently being designed. The calculations are made using the CERN package Poisson. The range of electrode widths under consideration is:.006m < w < .03. Studies indicate that sensitivity is maximized in this range by the smallest width plate if the electronics contributes negligible capacitance. The plate size for which the sensitivity is optimized increases with increasing electronics capacitance. As well, 6cm and 8cm outer shells of both circular and square geometry are considered. An 8cm square quadrupole pickup yields the higher sensitivity.
Date: January 1, 1991
Creator: O'Day, S.
Partner: UNT Libraries Government Documents Department

Capacitance Flatness Gauge Prototype

Description: The DO calorimeter has within it thousands of large plates. Our ability to construct the detector depends on the flatness of these plates. The performance of the detector depends on the flatness of the plates after they are assembled into a module. It has been proposed that the flatness of the plates before and after assembly could be determined by measuring capacitance. This device demonstrates the viability of using capacitance to measure the flatness of individual plates. No attempt has been made to extrapolate the results to measuring the flatness of the plates once they are in a module.
Date: March 20, 1986
Creator: Pitas, A. & Angstadt, R.
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

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

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