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Air Force Institute of Technology

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Articles 31 - 57 of 57

Full-Text Articles in Electronic Devices and Semiconductor Manufacturing

Micro-Scale Flapping Wings For The Advancement Of Flying Mems, Nicholas R. Coleman Mar 2009

Micro-Scale Flapping Wings For The Advancement Of Flying Mems, Nicholas R. Coleman

Theses and Dissertations

This research effort presents conceptual micro scale air vehicles whose total dimensions are less than one millimeter. The initial effort was to advance the understanding of micro aerial vehicles at sub-millimeter dimensions by fabricating and testing micro scale flapping wings. Fabrication was accomplished using a surface micromachining process called PolyMUMPs™. Both rigid mechanical structures and biomimetic devices were designed and fabricated as part of this effort. The rigid mechanical structures focused on out of plane deflections with solid connections and assembling a multiple hinge wing structure through the aid of residual stress. These devices were actuated by double hot arm …

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A Mems Multi-Cantilever Variable Capacitor On Metamaterial, Luke A. Rederus Feb 2009

A Mems Multi-Cantilever Variable Capacitor On Metamaterial, Luke A. Rederus

Theses and Dissertations

Negative refractive index materials are an example of metamaterials that are becoming increasingly popular. Research into these metamaterials could possibly be the first steps toward bending electromagnetic radiation (i.e., microwaves, light, etc.) around an object or person. Split ring resonators (SRR) are classified as metamaterials that create an artificial magnetic response from materials with no inherent magnetic properties. Once fabricated, an SRR has a specific resonant frequency due to its permanent geometry. This research introduces a new concept of using a variable capacitive micro- electro-mechanical system (MEMS) device located at the gap of an SRR to mechanically alter the capacitance …

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Sensitivity Analysis Of Algan/Gan Hemts To Process Variation, Adam J. Liddle Mar 2008

Sensitivity Analysis Of Algan/Gan Hemts To Process Variation, Adam J. Liddle

Theses and Dissertations

A sensitivity analysis of AlGaN/GaN HEMT performance on material and process variations was performed. Aluminum mole fraction, barrier thickness, and gate length were varied ± 5% over nominal values to determine how sensitive simulated device performance was to changes in these 3 parameters. Simulated data was generated with the Synopsys TCAD software suite using a physics-based HEMT model. To validate model performance, simulated data was correlated with experimental data, which consisted of wafer epilayer characterization data as well as DC and small-signal RF device performance data from 1-26 GHz. Trends were observed in the experimental data due to variations in …

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Performance Comparison Of Pb(Zr0.52Ti0.48)O3-Only And Pb(Zr0.52Ti0.48)O3-On-Silicon Resonators, Hengky Chandrahalim, Sunil A. Bhave, Ronald G. Polcawich, Jeff Pulskamp, Dan Judy, Roger Kaul, Madan Dubey Jan 2008

Performance Comparison Of Pb(Zr0.52Ti0.48)O3-Only And Pb(Zr0.52Ti0.48)O3-On-Silicon Resonators, Hengky Chandrahalim, Sunil A. Bhave, Ronald G. Polcawich, Jeff Pulskamp, Dan Judy, Roger Kaul, Madan Dubey

Faculty Publications

This paper provides a quantitative comparison and explores the design space of lead zirconium titanate (PZT)–only and PZT-on-silicon length-extensional mode resonators for incorporation into radio frequency microelectromechanical system filters and oscillators. We experimentally measured the correlation of motional impedance (RX) and quality factor (Q) with the resonators’ silicon layer thickness (tSi). For identical lateral dimensions and PZT-layer thicknesses (tPZT), the PZT-on-silicon resonator has higher resonant frequency (fC), higher Q (5100 versus 140), lower RX (51 Ω versus 205 Ω), and better linearity [third-order input intercept …

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Piezo-Electrochemical Transducer Effect (Pect) Intercalated Graphite Micro-Electromechanical Actuators, Glen A. Kading Nov 2007

Piezo-Electrochemical Transducer Effect (Pect) Intercalated Graphite Micro-Electromechanical Actuators, Glen A. Kading

Theses and Dissertations

The purpose of this research is to investigate the Piezo-Electrochemical Transducer (PECT) effect in intercalated graphite as a possible mechanism of actuation for micro-electromechanical systems (MEMS). This dissertation presents the results of research into the PECT effect in H2SO4-intercalated graphitized carbon fibers, including both electrical and mechanical characteristics of this effect. PECT fibers achieve up to 1.7% strain at 1.4 V of applied potential. In contrast, the piezoelectric material polyvinylidene difluoride (PVDF) generates only 0.01% strain and polysilicon thermal expansion between 0.02 and 0.06% strain depending on the thermal conductivity of the particular polysilicon that the actuators are fabricated in. …

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Hybrid Micro-Electro-Mechanical Tunable Filter, Edward M. Ochoa Sep 2007

Hybrid Micro-Electro-Mechanical Tunable Filter, Edward M. Ochoa

Theses and Dissertations

While advantages such as good thermal stability and processing-chemical compatibilities exist for common monolithic-integrated micro-electro-mechanically tunable filters (MEM-TF) and MEM-tunable vertical cavity surface emitting lasers (MT-VCSEL), they often require full processing to determine device characteristics. Alternatively, the MEM actuators and the optical parts may be fabricated separately, then subsequently bonded. This "hybrid approach" potentially increases design flexibility. Since hybrid techniques allow integration of heterogeneous material systems, "best of breed" compound optoelectronic devices may be customized to enable materials groups to be optimized for tasks they are best suited. Thus, as a first step toward a hybrid (AlxGa1- …

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Radio Frequency Mems Switch Contact Metal Selection, Ronald A. Coutu Jr., Paul E. Kladitis, Robert L. Crane, Kevin D. Leedy Jun 2007

Radio Frequency Mems Switch Contact Metal Selection, Ronald A. Coutu Jr., Paul E. Kladitis, Robert L. Crane, Kevin D. Leedy

AFIT Patents

A method for selecting metal alloys as the electric contact materials for microelectromechanical systems (MEMS) metal contact switches. This method includes a review of alloy experience, consideration of equilibrium binary alloy phase diagrams, obtaining thin film material properties and, based on a suitable model, predicting contact electrical resistance performance. After determination of a candidate alloy material, MEMS switches are conceptualized, fabricated and tested to validate the alloy selection methodology. Minimum average contact resistance values of 1.17 and 1.87 ohms are achieved for micro-switches with gold (Au) and gold-platinum (Au-(6.3 at %)Pt) alloy contacts. In addition, `hot-switched` life cycle test results …

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Investigation Of Gate Current In Neutron Irradiated AlXGa1-XN/Gan Heterogeneous Field Effect Transistors Using Voltage And Temperature Dependence, Thomas E. Gray Mar 2007

Investigation Of Gate Current In Neutron Irradiated AlXGa1-XN/Gan Heterogeneous Field Effect Transistors Using Voltage And Temperature Dependence, Thomas E. Gray

Theses and Dissertations

The gate current of Al27Ga73N/GaN heterogeneous field effect transistors (HFETs) is investigated using current-voltage (IV) and current-temperature (IT) measurement demonstrating that trap assisted tunneling (TAT) is the primary current mechanism. A thermionic trap assisted tunneling (TTT) model is used with variables of Schottky barrier height, trap energy, donor density and trap density. This results in a sigma of 1.38x10-8 A for IT data measured between 85K and 290K and for IV data measured between 0.0 V and -4.0 V. High energy (>0.5 MeV) neutron irradiation confirms an increase of gate current with fluence. An …

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Air Gap Error Compensation For Coaxial Transmission Line Method Of Electromagnetic Material Characterization, Ronald G. Fehlen Mar 2006

Air Gap Error Compensation For Coaxial Transmission Line Method Of Electromagnetic Material Characterization, Ronald G. Fehlen

Theses and Dissertations

This research analyzes material characterization measurements from 50 Mhz to 3.05 GHz where an axially symmetric air gap exists between the sample material and the inner or outer conductor. Higher order fields are excited by the air gap and are accounted for through modal analysis methods. A root search minimizes the difference between the calculated scattering parameters from the modal method and the experimentally measured scattering parameters. The root is the permittivity and permeability of the material. This method is tested with a non-magnetic material and a heavily loaded magnetic material. An error analysis based on dimension measurement uncertainty is …

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Computational Modeling Of The Dielectric Barrier Discharge (Dbd) Device For Aeronautical Applications, Christopher S. Charles Mar 2006

Computational Modeling Of The Dielectric Barrier Discharge (Dbd) Device For Aeronautical Applications, Christopher S. Charles

Theses and Dissertations

Dielectric Barrier Discharge (DBD) type devices, when used as plasma actuators, have shown significant promise for use in many aeronautical applications. Experimentally, DBD actuator devices have been shown to induce motion in initially still air, and to cause re-attachment of air flow over a wing surface at a high angle of attack. This thesis explores the numerical simulation of the DBD device in both a lD and 2D environment. Using well established fluid equation techniques, along with the appropriate approximations for the regime under which these devices will be operating, computational results for various conditions and geometries are explored. In …

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High-Temperature Ferromagnetism In Transition Metal Implanted Wide-Bandgap Semiconductors, Jeremy A. Raley Jun 2005

High-Temperature Ferromagnetism In Transition Metal Implanted Wide-Bandgap Semiconductors, Jeremy A. Raley

Theses and Dissertations

Material with both semiconductor and magnetic properties, which is commonly called a dilute magnetic semiconductor (DMS), will prove most useful in the fabrication of spintronic devices. In order to produce a DMS at above room temperature, transition metals (TMs) were implanted into host semiconductors of p-GaN, Al0.35Ga0.65N, or ZnO. Magnetic hysteresis measurements using a superconducting quantum interference device (SQUID) magnetometer show that some of the material combinations clearly exhibit ferromagnetism above room temperature. The most promising materials for creating spintronic devices using ion implantation are p-GaN:Mn, Al0.35Ga0.65N:Cr, and Fe-implanted ZnO nanotips on …

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Using Multiple Mems Imus To Form A Distributed Inertial Measurement Unit, Ryan D. Hanson Mar 2005

Using Multiple Mems Imus To Form A Distributed Inertial Measurement Unit, Ryan D. Hanson

Theses and Dissertations

MEMS IMUs are readily available in quantity and have extraordinary advantages over conventional IMUs in size, weight, cost, and power consumption. However, the poor performance of MEMS IMUs limits their use in more demanding military applications. It is desired to use multiple distributed MEMS IMUs to simulate the performance of a single, more costly IMU, using the theory behind Gyro-Free IMUs. A Gyro-Free IMU (GF-IMU) uses a configuration of accelerometers only to measure the three accelerations and three angular rotations of a rigid body in 3-D space. Theoretically, almost any configuration of six distributed accelerometers yields sufficient measurements to solve …

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Deviation Of Time-Resolved Luminescence Dynamics In Mwir Semiconductor Materials From Carrier Recombination Theory Predictions, Peter M. Johnson Mar 2004

Deviation Of Time-Resolved Luminescence Dynamics In Mwir Semiconductor Materials From Carrier Recombination Theory Predictions, Peter M. Johnson

Theses and Dissertations

Time resolved luminescence spectroscopy was used to characterize luminescence decay curves for a bulk InAs sample and an InAsSb type-I quantum-well sample over the first 3ns following excitation. The luminescence decay curves were then converted to carrier densities and used to find recombination coefficients that provided the least-squared-error solution of the rate equation describing carrier recombination. Recombination coefficients describing Shockley Read-Hall (ASRH) radiative (Brad) and Auger (CAug) recombination were determined at two different temperatures and four excitation powers, then analyzed for consistency and physical significance. For all of the resulting least …

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Stress Analysis Of Silicon Carbide Microeletromechanical Systems Using Raman Spectroscopy, Stanley J. Ness Mar 2003

Stress Analysis Of Silicon Carbide Microeletromechanical Systems Using Raman Spectroscopy, Stanley J. Ness

Theses and Dissertations

During the fabrication of Micro-Electro-Mechanical Systems (MEMS), residual stress is often induced in the thin films that are deposited to create these systems. These stresses can cause the device to fail due to buckling, curling, or fracture. Government and industry are looking for ways to characterize the stress during the deposition of thin films in order to reduce or eliminate device failure. Micro-Raman spectroscopy has been successfully used to analyze poly-silicon MEMS devices made with the Multi-User MEMS Process (MUMPS trade name). Micro-Raman spectroscopy was selected because it is nondestructive, fast and has the potential for in situ stress monitoring. …

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Quantum Mechanical Calculations Of Monoxides Of Silicon Carbide Molecules, John W. Roberts Jr. Mar 2003

Quantum Mechanical Calculations Of Monoxides Of Silicon Carbide Molecules, John W. Roberts Jr.

Theses and Dissertations

Modern semiconductor devices are principally made using the element silicon. In recent years, silicon carbide (SiC), with its wide band-gap, high thermal conductivity, and radiation resistance, has shown prospects as a semiconductor material for use in high temperature and radiation environments such as jet engines and satellites. A limiting factor in the performance of many SiC semiconductor components is the presence of lattice defects formed at oxide dielectric junctions during processing. Recent theoretical work has used small quantum mechanical systems embedded in larger molecular mechanics structures to attempt to better understand SiC surfaces and bulk materials and their oxidation. This …

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Total Dose Effects Of Ionizing And Non-Ionizing Radiation On Piezoresistive Pressure Transducer Chips, Samuel J. Willmon Mar 2003

Total Dose Effects Of Ionizing And Non-Ionizing Radiation On Piezoresistive Pressure Transducer Chips, Samuel J. Willmon

Theses and Dissertations

The effects of ionizing and non ionizing radiation on the resistivity of silicon based, piezoresistive bulk micro-machined chips from pressure transducers were examined. Standard current-voltage (I-V) measurements were taken in-situ and post-irradiation during isothermal annealing at room temperature. One group of chips was irradiated to a maximum total gamma dose of lMrad(Si) in the 11,000 Ci (60) Co gamma cell at Ohio State University. The second group of chips was irradiated at the Ohio State University Research Reactor facility to a maximum total neutron dose of 4 Mrad(Si) using beam port Hi. The resistivity was shown to decrease during gamma …

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Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley Mar 2002

Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley

Theses and Dissertations

This thesis studies selective etching techniques for the development of AlxGa1-xAs micro-opto-electro-mechanical systems (MOEMS). New MEMS technology based on materials such as AlxGa1-xAs enables the development of micro-systems with embedded active micro-optical devices. Tunable micro-lasers and optical switching based on MOEMS technology will improve future wavelength division multiplexing (WDM) systems. WDM vastly increases the speed of military communications and sensor data processing. From my designs, structures are prepared by molecular beam epitaxy. I design a mask set for studies of crystal plane selectivity. I perform a series of experiments on the selective …

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Design And Fabrication Of Micro-Electro-Mechanical Structures For Tunable Micro-Optical Devices, Michael C. Harvey Mar 2002

Design And Fabrication Of Micro-Electro-Mechanical Structures For Tunable Micro-Optical Devices, Michael C. Harvey

Theses and Dissertations

Tunable micro-optical devices are expected to be vital for future military optical communication systems. In this research I seek to optimize the design of a microelectromechanical (MEM) structure integrated with a III-V semiconductor micro-optical device. The resonant frequency of an integrated optical device, consisting of a Fabry-Perot etalon or vertical cavity surface emitting laser (VCSEL), may be tuned by applying an actuation voltage to the MEM Flexure, thereby altering the device's optical cavity length. From my analysis I demonstrate tunable devices compatible with conventional silicon 5V integrated circuit technology. My design for a Fabry-Perot etalon has a theoretical tuning range …

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Investigation Of Ge2Te2Sb5 Chalcogenide Thin Film For Use As An Analog Memory, Travis F. Blake Mar 2000

Investigation Of Ge2Te2Sb5 Chalcogenide Thin Film For Use As An Analog Memory, Travis F. Blake

Theses and Dissertations

This work investigates the feasibility of using Ge2Te2Sb5 chalcogenide films for analog memory. Thick film chalcogenide memory devices provided by Ovonyx, Inc. are characterized to determine how well the devices meet the repeatability, stability and predictability criteria needed to accurately store analog data values. Chalcogenide memory devices take advantage of the phase-shifting nature of chalcogenide materials to store the analog data as a resistance level. An automated test system was developed to characterize the material and the prototype devices with the goal to determine the 1) non-destructive readability of the device at different resistance values; …

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Development And Packaging Of Microsystems Using Foundry Services, Jeffrey T. Butler Jun 1998

Development And Packaging Of Microsystems Using Foundry Services, Jeffrey T. Butler

Theses and Dissertations

Micro-electro-mechanical systems (MEMS) are a new and rapidly growing field of research. Several advances to the MEMS state of the art were achieved through design and characterization of novel devices. Empirical and theoretical model of polysilicon thermal actuators were developed to understand their behavior. The most extensive investigation of the Multi-User MEMS Processes (MUMPs) polysilicon resistivity was also performed. The first published value for the thermal coefficient of resistivity (TCR) of the MUMPs Poly 1 layer was determined as 1.25 x 10(exp -3)/K. The sheet resistance of the MUMPs polysilicon layers was found to be dependent on linewidth due to …

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Nlo Waveguide "And" Switch And Method Therefor, John J. Kester, Iyad A. Dajani, Peter M. Ranon, Thomas G. Alley Sep 1996

Nlo Waveguide "And" Switch And Method Therefor, John J. Kester, Iyad A. Dajani, Peter M. Ranon, Thomas G. Alley

AFIT Patents

Method and apparatus are provided for NLO switching by first providing a phase-matched SHG grating which outputs a reinforced SHG beam only when two input beams of frequency (ω) are present in two modes of such wg. The so encoded NLO switch is operated by directing at least two input pulsed laser beams of frequency (ω) into the two modes of the wg to generate a reinforced pulsed output SHG beam and output same from the wg in an NLO switching process. The two input beams desirably have a separate pulse train and the spatial and temporal overlap of the …

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Design, Fabrication, Processing, And Testing Of Micro-Electro-Mechanical Chemical Sensors, Brian S. Freeman Dec 1995

Design, Fabrication, Processing, And Testing Of Micro-Electro-Mechanical Chemical Sensors, Brian S. Freeman

Theses and Dissertations

Chemical microsensors are a new field integrating chemical thin film technology with solid-state fabrication techniques to make devices capable of detecting chemicals in the environment. This thesis evaluated commercially available fabrication processes and numerous sensor designs for working chemical sensors. The commercial processes used were MUMPS for surface micromachined devices and MOSIS for bulk micromachined devices. Overall, eight fabrication runs and 29 different designs were made. Of these designs, two were shown to work effectively. Other designs failed due to fabrication problems and design errors that caused release problems. One design that worked was a surface micromachined chemoresistor with interdigitated …

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Ohmic Contact To Ion Implanted Gallium Arsenide Antimonide For Application To Indium Aluminum Arsenide-Gallium Arsenide Antimonide Heterostructure Insulated-Gate Field Effect Transistors, Kenneth G. Merkel Ii Jul 1995

Ohmic Contact To Ion Implanted Gallium Arsenide Antimonide For Application To Indium Aluminum Arsenide-Gallium Arsenide Antimonide Heterostructure Insulated-Gate Field Effect Transistors, Kenneth G. Merkel Ii

Theses and Dissertations

The p-channel In0.52Al0.48As-GaAs1-xSbx heterostructure insulated-gate field effect transistor (p-HIGFET) is a candidate for complementary integrated circuits due to superior cutoff characteristics and low gate leakage current. Advancement of the In0.52Al0.48As-GaAs1-xSbx p-HIGFET requires improved source-drain design. Five main tasks were accomplished to achieve this goal. First, thermal limits of the In0.52Al0.48As-GaAs0.51Sb0.49 HIGFET were investigated. Second, the temperature dependence of band gap and impurity energies were determined for beryllium doped In0.52Al0.48. Third, high acceptor concentrations were obtained …

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Total Ionizing Dose Effects In Mosfet Devices At 77 K, Kevin J. Daul Dec 1994

Total Ionizing Dose Effects In Mosfet Devices At 77 K, Kevin J. Daul

Theses and Dissertations

Total ionizing dose effects on thermal oxide and reoxidized nitrided oxide (RNO) MOSFET devices at 77 K were studied. The MOSFETs were immersed in liquid nitrogen and irradiated, using a 60Co source, up to 1 Mrad(Si) at a dose rate of 107 rads(Si)-sec. Drain current-gate voltage characteristics were obtained and used to determine threshold voltage and transconductance. At 77 K the subthreshold slopes indicated no observed buildup of interface states in any of the transistors. Furthermore, all transistors experienced very little change in the transconductance. Typical negative shifts in threshold voltage as dose increased were observed in all of …

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Model Of A Single Impurity In A Wide Bandgap Semiconductor Describing Electric Field Screening, Anthony N. Dills Dec 1994

Model Of A Single Impurity In A Wide Bandgap Semiconductor Describing Electric Field Screening, Anthony N. Dills

Theses and Dissertations

A mathematical model of the influence on electric field screening arising from a single impurity in a wide bandgap semiconductor has been numerically investigated and compared with analytically derived solutions. The parameter set chosen to perform the comparison of analytical solution and numerical solution is based upon a bismuth silicate crystal. Both the analytical calculations and the numerical calculations are an attempt to mathematically model the internal electric field within a semiconductor. Two types of impurities were looked at: a single donor level and a single trap impurity level. In general, after an abrupt application of a voltage across the …

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Photoluminescence Spectroscopy Of 4h- And 6h-Sic, William A. Davis Dec 1994

Photoluminescence Spectroscopy Of 4h- And 6h-Sic, William A. Davis

Theses and Dissertations

Typical undoped bulk grown SiC shows n- or p-type conductivity due to residual impurities such as nitrogen, boron, or aluminum. In order to produce high resistivity material, vanadium can be used as a compensating dopant. Since vanadium is an amphoteric dopant in SiC, it produces either a donor state, VSi4+(3d1) → VSi5+(3d0), or an acceptor state, VSi4+(3d1) → VSi3+(3d2). Thus, vanadium doping can compensate both n- and p-type conductivity. In this work, vanadium doped and undoped 4H- and 6H-SiC grown …

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Design, Fabrication, Modeling, And Optical Characterization Of Organic Polymer Nonlinear Directional Couplers, John N. Berry Dec 1994

Design, Fabrication, Modeling, And Optical Characterization Of Organic Polymer Nonlinear Directional Couplers, John N. Berry

Theses and Dissertations

This research was an investigation into the suitability of a recently developed polymer, polyphenylene, as a material for integrated optical circuits (IOCs). Polymers show great promise in the area of IOCs because of material processing advantages, compatibility with most existing integrated circuit technology, and relatively strong nonlinear optical characteristics. This thesis contains an overview of: dielectric waveguides, linear and nonlinear directional coupler theory; various models useful in the design and analysis of optical waveguides; the fabrication of three different waveguide designs; the experimental apparatus and procedure used to optically characterize the waveguides; and the experimental results of the characterization. Waveguiding …

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