| Processing for Highly Efficient AlGaN/GaN Emitters |
09-Sep-2009 |
14 pages |
| Authors:
Ilesanmi Adesida; ILLINOIS UNIV AT URBANA-CHAMAPAIGN
|
 | The fabrication of high-quality ohmic contacts on n- and p-type (Al,In)GaN is essential for improving the performance of optoelectronic devices, such as blue light emitting diodes, metal-semiconductor field effect transistors, HEMTs, and laser diodes. In particular, to realize solid-state UV emitters for chembioagent detection and general lighting, the formation of reliable ohmic contact systems for both n- and p-AlGaN with relatively high Al contents are indispensable. In conjunction with efforts ... |
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| Galvanic Corrosion Study on SS Cartridge Design |
05-Feb-2009 |
24 pages |
| Authors:
Daniel P Schmidt; ARMY RESEARCH DEVELOPMENT AND ENGINEERING COMMAND ABERDEEN PROVING GROUND MD
|
| BACKGROUND: Lightweight Cartridge for Small Arms program at Picatinny -- Designing/developing stainless steel cartridge case -- For structural support inserting Al plug * Galvanic corrosion -- Dissimilar metals that are in electrical contact while immersed in a solution electrolyte * 3 main galvanic couples of concern. OBJECTIVE: To investigate the galvanic interaction between the materials used in the new ammunition design under aggressive conditions to determine if there will be ... |
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| Galvanic Corrosion Study on Stainless Steel Cartridge Design |
Nov-2008 |
38 pages |
| Authors:
Daniel P Schmidt; Donald R Skelton; Michelle E Malham; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER PICATINNY ARSENAL NJ MUNITIONS ENGINEERING TECHNOLOGY CENTER
|
| A new ammunition design incorporates stainless steel as the cartridge case, a copper alloy bullet jacket, and an aluminum plug insert for structural support. The dissimilar materials in the new design will be physically connected (electrical contact) and may be exposed to environments that result in an electrolyte connection. Therefore, a study on the possible galvanic corrosion issues of the new ammunition design was conducted. Several different representative galvanic couples ... |
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| Long Life Durability of Electrodes of Electrical Resistance Change Method for Damage Monitoring of CFRP Composite Structures |
01-Mar-2008 |
16 pages |
| Authors:
Akira Todoroki; TOKYO INST OF TECH (JAPAN) DEPT OF MECHANICAL ENGINEERING
|
| Investigated the applicability of the electrical resistance change method through experiments of CFRP laminates [16-18]. Instead of using two or four electrodes, this research adopted multiple electrodes mounted on the surface of the target structure to identify delamination location and dimension. Orthotropic electric conductivity was also measured experimentally for three types of fiber volume fractions, and the paper revealed that electric conductivity in thickness direction of CFRP was approximately one ... |
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| Friction and Wear Sciences for a Highly Durable Railgun Weapon |
OCT 2007 |
63 pages |
| Authors:
S. Satapathy; C. Persad; TEXAS UNIV AT AUSTIN INST FOR ADVANCED TECHNOLOGY
|
| The interior ballistics of multi-shot electromagnetic launchers are more complex than that of conventional propellant guns. To be effective, a weapon must be able to fire thousands of rounds without refurbishment. New approaches are needed to understand the friction and wear sciences that influence the life of the railgun bore. A coordinated series of experimental measurements and analytical frameworks are required in order to produce a robust method of predicting ... |
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| Microscale Self-Assembled Electrical Contacts |
SEP 2007 |
38 pages |
| Authors:
Christopher J. Morris; ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
|
| Self-assembly, or the spontaneous organization of parts into larger structures via energy minimization, is an attractive solution to overcome packaging and integration challenges. Capillary forces from a molten alloy can be used to both bond microscale components and make electrical connections between them in a self-assembly process. This report presents a systematic study of a number of metal alloys and self-assembly media with the aim of reducing the metal contact ... |
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| High-Frequency Muzzle Voltage Measurements |
AUG 2007 |
9 pages |
| Authors:
S. Levinson; F. Stefani; TEXAS UNIV AT AUSTIN INST FOR ADVANCED TECHNOLOGY
|
| The muzzle voltage in solid-armature railguns is an important diagnostic because it can provide information about the state of the rail-armature interface. Sudden jumps in the muzzle voltage can indicate that an armature has made a transition from low voltage to arcing contact. However, in many tests, the muzzle voltage increases gradually, and the onset of transition as indicated by the muzzle voltage is ambiguous. This report describes research aimed ... |
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| Fabrication of a Lateral Polarity GaN MESFET: An Exploratory Study |
27-Jun-2007 |
16 pages |
| Authors:
Zlatko Sitar; Ramon Collazo; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| This report describes exploratory studies in the fabrication of the GaN LPH structures and their application in the fabrication of a depletion-mode metal semiconductor field effect transistors (MESFETs). Exploiting LPH growth technology, and the difference in the electronic properties of the different type of domains, i.e. as grown N-polar domains are conductive and Ga-polar domains are insulating, laterally selective doped areas can be realized for improving contact resistance to the ... |
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| Ohmic Contacts for Technology for Frequency Agile Digitally Synthesized Transmitters |
21 MAY 2007 |
6 pages |
| Authors:
Suzanne E. Mohney; PENNSYLVANIA STATE UNIV UNIVERSITY PARK OFFICE OF SPONSORED PROGRAMS
|
| Ohmic contacts to InAs and InGaAs have been investigated with the objective of providing low contact resistance, good thermal stability, and process compatibility for scaling lnP-based heterojunction bipolar transistors to smaller sizes. For p-type InAs, the combination of modest contact resistance and good thermal stability at 250 0 C was achieved with metallizations that had thin Pd layers deposited first, fol lowed by W or Ti/Pt barrier layers, then Au. ... |
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| Implantation-Free 4H-SiC Bipolar Junction Transistors with Double Base Epi-layers |
14-May-2007 |
15 pages |
| Authors:
Jianhui Zhang; Petre Alexandrov; Terry Burke; Jian H Zhao; Xueqing Li; UNITED SILICON CARBIDE INC NEW BRUNSWICK NJ
|
| This paper reports the first 4H-SiC power bipolar junction transistor (BJT) which is completely free of ion implantation and hence is free of the implantation-induced crystal damages and high-temperature activation annealing-induced surface roughness. The BJT is designed to have double epitaxial p-type base layers with the top layer more heavily doped for direct Ohmic contact formation while at the same time supporting a robust single-step junction termination extension without the ... |
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| Development of High-Temperature, High-Power, High-Efficiency, High-Voltage Converters Using Silicon Carbide (SiC) Delivery Order 0003: SiC High Voltage Converters, N-Type Ohmic Contract Development for SiC Power Devices |
DEC 2006 |
13 pages |
| Authors:
Lin Cheng; Michael S. Mazzola; MISSISSIPPI STATE UNIV MISSISSIPPI STATE CENTER FOR ADVANCED SEMICONDUCTOR PROTOTYPING
|
| The durability and reliability of metal-semiconductor contacts are two of the main factors limiting the operational high-temperature limits of SiC electronic devices. To date, nickel (Ni) has been the most widely used metal for ohmic contacts to n-type SiC. The way to make smooth Ni-silicide ? SiC interfaces and silicide top surfaces is important for producing uniformly low contact resistances to achieve device operation at high-current levels without hot spot ... |
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| Pulsed Current Static Electrical Contact Experiment |
MAY 2006 |
11 pages |
| Authors:
Harry N. Jones; Jesse M. Neri; Craig N. Boyer; Khershed P. Cooper; Robert A. Meger; NAVAL RESEARCH LAB WASHINGTON DC
|
| Railguns involve both static and sliding electrical contacts, which must transmit the large transient electrical currents necessary to impart high forces onto a projectile for acceleration to hypervelocity. Static electrical contacts between metals initially take place through small asperities, or "a-spots", distributed over the contact area. The voltage developed across the interface is directly related to the contact temperature and pressure, the number of a-spots, the thermophysical and mechanical properties ... |
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| Contact Metallization and Packaging Technology Development for SiC Bipolar Junction Transistors, PiN Diodes, and Schottky Diodes Designed for Long-Term Operations at 350degreeC |
MAY 2006 |
111 pages |
| Authors:
J. R. Williams; R. W. Johnson; S. E. Mohney; S. -H. Ryu; AUBURN UNIV AL AUBURN RESEARCH INST
|
| This report describes the development of composite ohmic contact and packaging technologies for the wideband gap semiconductor silicon carbide (SiC) with demonstrations of these technologies using 4H-SiC JFETs (junction field effect transistors). The goal of this effort is protection against oxidation / inter-diffusion and stable operation in air at 350 degrees C for up to 10,000 hr. Ta-Si and Ru-Ta barrier layers have been developed and tested for composite contacts ... |
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| Tribology of Co-sputtered Nanocomposite Au/MoS2 Solid Lubricant Films Over a Wide Contact Stress Range |
15 JAN 2005 |
17 pages |
| Authors:
J. R. Lince; AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS
|
| Slip-ring assemblies for spacecraft, and other sliding electrical contacts, require low friction and wear, as well as low electrical resistance and noise. Most current slip-ring technologies (both solid- and liquid- lubricated) are over forty years old, and their robustness is often less than satisfactory. Newer technologies have been developed, but have also shown limitations in spacecraft applications. We are investigating alternate material technologies to address these issues, concentrating on sputter-deposition ... |
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| Formation of Porous Silicon Carbide and its Suitability as a Chemical and Temperature Detector |
19 AUG 2004 |
151 pages |
| Authors:
Tilghman L. Rittenhouse; ILLINOIS UNIV AT URBANA DEPT OF CHEMISTRY
|
| The need to sense chemical mixtures in a variety of hostile environments (such as high temperature caustic gases) continues to grow. However, silicon electrical devices are limited to relatively low temperatures (< 250 deg C). For this reason, wide bandgap materials such as silicon carbide have received increased attention. Current SiC sensors such as Schottky diodes composed of catalytic metals show deficiencies such as unacceptable drift in the signal. Alternative ... |
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| SiC MEMS For Harsh Environments |
DEC 2003 |
25 pages |
| Authors:
Kenneth C. Bradley; Scott L. Roberson; Donald R. Wiff; AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
|
| This document is the final technical report for the SiC MEMS for Harsh Environments in-house research program jointly coordinated between AFRL/ MNMF and AFRL/MLPS, and addresses the benefits of silicon carbide (SiC) as a material of choice for harsh environment applications, specifically at the scale of microelectromechanical systems (MEMS). The results from this program provide clear evidence of the benefit of SiC as a harsh environment (specifically high temperature) material ... |
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| Tri-Services Workshop on Process Induced Defects in Wide Bandgap Semiconductors |
AUG 2003 |
87 pages |
| Authors:
Shari J. Allwood; ALLWOOD AND ASSOCIATES INC MENTOR OH
|
| Meeting program, abstracts, and attendee roster for Tri-Services Workshop on Process Inducted Defects in Wide Bandgap Semiconductors held in Grants Pass, OR, on August 17-21, 2003. Sponsored by the Air Force Office of Scientific Research; U.S. Army Research Office; and Office of Naval Research. |
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| Deep Ultraviolet Laser Diode for UV-Resonance Enhanced Raman Identification of Biological Agents |
01 JUN 2003 |
64 pages |
| Authors:
W. Hug; T. Moustakas; R. Treece; J. Smith; A. Bhattacharyya; PHOTON SYSTEMS COVINA CA
|
| This proposal addresses the need for deep UV semiconductor lasers for use in UV resonance enhanced Raman spectroscopic identification of biological agents. The proposed approach avoids the problems of p-doping and ohmic contacts by using subminiature direct electron injection excitation of an InAlGaN heterostructure. We have demonstrated strong stimulated emission at 274nm using this approach with measured linewidth reduction from 16nm to 4nm and five orders of magnitude non-linear increase ... |
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| Tribology of Composite Au-MoS2 Films at Varying Contact Stresses |
01 JUN 2003 |
20 pages |
| Authors:
J. R. Lince; AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS
|
| Solid-lubricant coatings for sliding electrical contact applications like slip-ring assemblies have very different requirements from typical applications like ball bearings and cutting tools: they have significantly lower contact stresses and sliding speeds. We are optimizing the performance of sputter-deposited nanocomposite Au-MoS2 films for such low con tact stress applications. Higher contact stress pin-on-disk tests (S(sub m) = 730 MPa) showed that low Au-MoS2 films (i.e., 22 to 38 at% Au) ... |
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| Contacts to AlGaN for UV Detectors |
31 MAR 2003 |
30 pages |
| Authors:
Suzanne E. Mohney; PENNSYLVANIA STATE UNIV UNIVERSITY PARK OFFICE OF SPONSORED PROGRAMS
|
| Electrical contacts to AlGaN were investigated at The Pennsylvania State University. |
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| Barrel Wear Reduction in Rail Guns: An Investigation of Silver Paste Liquid-Metal Interface |
DEC 2002 |
62 pages |
| Authors:
Michael W. Smith Jr; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This thesis tests the effects a commercial silver paste has on the damage at the projectile-rail interface of a 4" long rail gun test section. Projectiles (0.635 x 0.635 x 0.953 cm) were pushed through the rail test section at 34 plus or minus 19 m/s, while average current densities of 18 - 32 kA/cm2 was passed through the projectile - rail interface material. The specific objective is to examine ... |
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| Processing Technologies for Al(x)Ga(1-x)N Photodetector Arrays |
OCT 2002 |
92 pages |
| Authors:
Ilesanmi Adesida; ILLINOIS UNIV CHAMPAIGN GRANTS AND CONTRACTS ADMINISTRATION
|
| Processing technologies for Al(x)Ga(1-x)N have been developed. Inductively-coupled-plasma reactive ion etching (ICP-RIE) is shown to be capable of etching AlGaN materials at high etch rates and high anisotropy Plasma-induced damage in n-GaN is shown to depend mainly on the ion energy to which samples are exposed during ICP-RIE The damage can be annealed at 700 degrees C with samples recovering to their unetched states. Photoelectrochemical etching of n-GaN is shown ... |
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| Rail Erosion and Projectile Diagnostics for an Electro-Magnetic Gun |
JUN 2002 |
65 pages |
| Authors:
William E. Culpeper; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Rail guns will not be introduced to the Navy until there is a means of limiting rail erosion. Erosion occurs when a sliding contact loses electrical contact with the rails. Research for this thesis was centered on combating the rail erosion problem and developing a way to record the voltage drop across the rails of the Naval Post Graduate School's 4-inch Electro-Magnetic Gun. A laser was also added to the ... |
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| InP/GaAsSb/InP Double Heterojunction Bipolar Transistors |
2002 |
9 pages |
| Authors:
C. R. Bolgnesi; M. W. Dvorak; S. P. Watkins; SIMON FRASER UNIV BURNABY (BRITISH COLUMBIA)
|
| InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) are some of the fastest bipolar transistors ever fabricated, with current gain cutoff and maximum oscillation frequencies simultaneously exceeding 300 GHz while maintaining breakdown voltages BV(sub ceo> 6V I. InP/GaAsSb/InP DHBTs are particularly appealing because excellent device figures of merit are achievable with relatively simple structures involving abrupt junctions and uniform doping levels and compositions. This is a tremendous manufacturability advantage and the reason ... |
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| Inversion Channel MOSFETs in 3C-SiC on Silicon |
2002 |
7 pages |
| Authors:
Jianwei Wan; M. A. Capano; M. R. Melloch; James A. Cooper Jr.; PURDUE UNIV LAFAYETTE IN SCHOOL OF ELECTRICAL AND COMPUTER ENGINERING
|
| As a substrate material, single crystal SiC wafers are commercially available in diameters up to 75 mm, whereas silicon wafers a?e available in diameters of 200-300 mm. SiC wafers remain quite expensive compared to silicon, and contain%troublesome densities of micropipes that limit the yield of large devices. In the past, several groups have attempted to circumvent these problems by fabricating devices in 3C-SiC films grown epitaxially on silicon substrates, with ... |
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| Novel NI-Based Ohmic Contacts To a-SiC for High Temperature and High Power Device Applications |
2002 |
10 pages |
| Authors:
M. W. Cole; J. D. Demaree; C. W. Hubbard; M. C. Wood; M. H. Ervin; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| Novel Pt/Ti/WSi/Ni composite ohmic contacts to n-SiC were investigated as a function of annealing temperatures up to 1000 C. The onset of ohmic behavior occurred after annealing at 900 C. Annealing at temperatures between 950 and 1000 C yielded excellent ohmic behavior. At these temperatures the contact-SiC interface was smooth, defect free and characterized by a narrow Ni2Si reaction region. The annealed contacts possessed smooth surface morphologies and exhibited minimal ... |
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| Environmentally Compliant Corrosion Resistant, & Electrically Conductive Inorganic Coatings for Aluminum Alloys |
31 AUG 2001 |
352 pages |
| Authors:
S. R. Taylor; R. B. Leggat; E. Pehovaz; R. G. Buchheit; W. Zhang; VIRGINIA UNIV CHARLOTTESVILLE OFFICE OF SPONSORED PROGRAMS
|
| The objective of this project was to develop an environmentally compliant conversion coating for use on aerospace aluminum alloys (e.g., AA2024- T3). This conversion coating was to replace the current chromate conversion coating processes in both mode of application (bath or spray applied in the depot) and function (stand alone corrosion protection, adhesion to organic layers, self-healing, and low electrical contact resistance). Hydrotalcite (HT) was developed within this program as ... |
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| A Method of Making Electron Emitters |
31 JUL 2001 |
26 pages |
| Authors:
Pehr Pehrsson; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A method for fabricating an electron emitter is provided. This emitter structure may be used to form individual emitters or arrays of emitters. The method is comprised of implanting energetic ions into a diamond lattice to form cones or other continuous regions of damaged diamond. These regions are more electrically conducting than the surrounding diamond lattice, and have locally sharp tips at or near the point of entry of the ... |
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| Vanadium Oxide - Carbon Nanotube Composite Electrodes for Use in Secondary Lithium Batteries |
25 JUN 2001 |
29 pages |
| Authors:
Jeffrey S. Sakamoto; Bruce Dunn; CALIFORNIA UNIV LOS ANGELES DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Single-wall carbon nanotubes were used to form the electronically conducting network in lithium intercalation electrodes that incorporated vanadium oxide aerogels as the active material. Sol-gel methods were developed which integrated the nanotubes with V2O5 aerogel synthesis. The similarities in morphology and dimensional scale for the nanotubes and V2O5 ribbons enabled excellent electrical contact to be made between the two phases without seriously affecting the aerogel nanostructure. Intimate contact was established ... |
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| Configuration Management of the L96 and L97 Grenades |
19 FEB 2001 |
17 pages |
| Authors:
Philip E. Quantick; DEFENCE EVALUATION AND RESEARCH AGENCY PORTON DOWN (UNITED KINGDOM)
|
| The L96 and L97 anti-riot grenades were developed and tested by DERA Porton Down, in a joint UK/US collaborative programme. The grenades are now in- service with US Army and UK MOD. Follow-on contracts were placed with DERA by the US and UK authorities for the provision of Design Authority activities and to develop a new electrical clip assembly for the grenades. |
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| Microcontacts to High-Tc Superconductors: A Study of the Crossover from an Andreev Reflection to a Tunnel-Junction Character |
NOV 2000 |
6 pages |
| Authors:
Aharon Kapitulnik; STANFORD UNIV CA EDWARD L GINZTON LAB OF PHYSICS
|
| While the initial goal of the proposal was to concentrate on the study of point contact dots to HTSC. our initial measurements showed that surface preparation and impurities will be a major factor in determining the results, especially if we want to study the crossover from Andreev to tunneling behavior. We therefore launched a thorough study of the effects of single impurities and surface modifications on the tunneling spectra in ... |
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| Nonequilibrium Growth of GaN/Si(1-x-y)Ge(x)C(y)/Silicon-on-Insulator |
05 AUG 2000 |
27 pages |
| Authors:
Wilson Ho; CORNELL UNIV ITHACA NY
|
| The objectives of this project lies in the growth, characterization, optimization, and fabrication of wide band gap semiconductor thin films and structures. The emphasis lies in the integration of wide band gap semiconductors with silicon and the use of supersonic jet epitaxy to lower the growth temperature and to discover unique and novel applications of this growth technique. Research highlights include the successful growth of silicon ... |
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| Gallium Nitride Static Induction Power Transistors |
30 JUN 2000 |
21 pages |
| Authors:
Charles R. Eddy Jr.; Theodore D. Moustakas; BOSTON UNIV MA DEPT OF COMPUTER SCIENCE
|
| This report summarizes a one year program to investigate issues related to fabrication and performance of III-V nitride static induction power transistors. To understand vertical conduction mechanisms in this device a nearly ideal, vertical Schottky barrier diode was fabricated and analyzed. By applying the diffusion theory of Schottky barriers, a vertical mobility of ^950 sq cm/Vs was measured which, when compared to a lateral mobility ... |
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| Alternative Approaches to p-type Doping of GaN |
10 MAR 2000 |
6 pages |
| Authors:
Gary W. Wicks; ROCHESTER UNIV NY
|
| The problem being addressed: p-type doping of GaN. Conventional (column II) acceptors produce low hole concentrations. High hole concentrations are needed for low resistivity p-type material and p-type ohmic contacts. |
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| Dielectric Properties of Ordered and Disordered Particulates in Semiconductor Matrices |
14 DEC 1999 |
8 pages |
| Authors:
Michael R. Melloch; PURDUE RESEARCH FOUNDATION LAFAYETTE IN
|
| We have demonstrated a very unique application of LTG-GaAs for nanometer scale ohmic contacts to GaAs. We coat an LTG-GaAs layer with a self- assembled monolayer of xylyl diol, which serves as a metal/semiconductor interface layer. The xylyl diol molecules are 1.8 nm long and have a thiol group at each end to provide chemical bonding to the GaAs and to the gold clusters. The IV ... |
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| A Projectile for a Rectangular Barreled Rail Gun |
DEC 1999 |
98 pages |
| Authors:
Francisco M. Juanche; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The Physics Department at the Naval Postgraduate School is developing a concept to overcome the problems that keep present rail guns from being practical weapons. The rails must be replaced often if the rail gun operation is to be continuous. Replacing the rails in present rail gun configurations is time consuming. The Physics Department's design concept uses a rectangular barrel as part of the solution to the problem ... |
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| Polarized Optical Emission Due to Decay or Recombination of Spinpolarized Injected Carriers |
23 FEB 1999 |
|
| Authors:
Berend T. Jonker; DEPARTMENT OF THE NAVY WASHINGTON DC
|
 | A device for producing circularly polarized optical emission includes a light emitting semiconductor heterostructure, further including at least one semiconducting layer; a ferromagnetic contact having a magnetic moment, in electrical contact with a layer of the semiconductor heterostructure; and a contact electrically connected to a different region of the semiconductor heterostructure. This light emitting semiconductor heterostructure may be a light emitting diode (LED), or some other structure. The ferromagnetic contact ... |
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| Theoretical and Experimental Approach to Developing Improved Electrical Contacts to GaN |
04 JAN 1999 |
33 pages |
| Authors:
Suzanne Mohney; PENNSYLVANIA STATE UNIV UNIVERSITY PARK
|
| The metallurgy and electrical performance of contacts to GaN were examined. Thermodynamic estimates coupled with experimental work revealed clear trends in the nature of the contact metallurgy depending upon the position of the metal in the periodic table. This information was then used to aid in the investigation and design of electrical contacts to GaN. Ohmic contacts to n-GaN, Schottky barriers to n-GaN, and ohmic contacts to p-GaN were fabricated ... |
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| Experiments to Measure Armature Wear, Part 1: Wear Measurements on the KJ202 Armature |
AUG 1998 |
93 pages |
| Authors:
F. Stefani; J. Parker; TEXAS UNIV AT AUSTIN INST FOR ADVANCED TECHNOLOGY
|
| One of the research objectives of the Hypervelocity Launch group during 1997 was to understand armature wear, with the eventual goal of developing a predictive model. To this end we conducted sixteen experiments to measure wear at various conditions. This report describes the first ten experiments which directly measured wear in a typical "C-shaped" railgun armature. Section 2 of the report describes the objectives and our state of understanding at ... |
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| Design and Characterization of Mis Transsistors from III-V semiconductors |
MAR 1998 |
23 pages |
| Authors:
Hadis Morkoc; ILLINOIS UNIV CHAMPAIGN
|
| An ammonia based growth scheme was developed to achieve large growth rates and high quality III-N materials. The benefits of isomorphic substrates were pointed out followed by the demonstration of GaN growth on ZnO substrates. The band discontinuities were determined. recognizing the strong piezoelectric effect. Other developments include: low resistance ohmic contacts. highly ideal shottlu barriers. large power density MODFETs, optically pumped stimulated emission ... |
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| Defects and Impurities in 4H- and 6H-SiC Homoepitaxial Layers: Identification, Origin, Effect on Properties of Ohmic Contacts and Insulating Layers and Reduction |
DEC 1997 |
24 pages |
| Authors:
R. F. Davis; M. O. Aboelfotoh; B. J. Baliga; R. J. Nemanich; NORTH CAROLINA STATE UNIV AT RALEIGH
|
| A hot wall chemical vapor deposition system has been constructed to deposit thin films of 4H- and 6H-SiC and AlN. The design incorporates a separate load lock from which the growth chamber and a RHEED chamber are attached. Operation awaits the completion of the laboratory upfitting to address the safety requirements necessary to use silane. MOS capacitors were fabricated on 6H- and 4H-SiC with an average effective charge density of ... |
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| GaN Based Structures for NEA by MBE and Investigation of Nitrogen Species and Precursors for Optimum Layer Properties |
DEC 97 |
14 pages |
| Authors:
Hadis Morkoc; ILLINOIS UNIV AT URBANA COORDINATED SCIENCE LAB
|
| We have obtained: ohmic contacts with resistivities below 10(exp -7) Ohm sq cm to n type (GaN which are stable at 500 deg C, Pt Schottky barriers with nearly a unity ideality factor which appear stable at operation temperatures of about 500 deg C, AlGaN/GaN MODFETs on sapphire substrates with 1.5 micron gate length exhibiting extrinsic transconductances of about 220 mS/ mm, drain currents of about 600 mA/mm and breakdown ... |
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| A Triboscopic Investigation of the Wear and Friction of MoS2 in a Reciprocating Sliding Contact |
08 OCT 1997 |
26 pages |
| Authors:
K. J. Wahl; M. Belin; I. L. Singer; NAVAL RESEARCH LAB WASHINGTON DC
|
| Reciprocating sliding tests with ball-on-flat geometry were performed on a duplex coating at low speeds in moist air (RH=60%). The coating, 55 nm MoS2 on 35 nm of TiN, was deposited by ion-beam assisted deposition onto a steel substrate. Friction coefficient (micro) and electrical contact resistance (Rc) measurements were recorded at ~2micrometers intervals along the track; these spatially resolved measurements were compared to the more commonly presented cycle-averaged values. The ... |
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| Electroluminescent Device in Silicon on Sapphire |
26 AUG 1997 |
|
| Authors:
Wadad B. Dubbelday; Randy L. Shimabukuro; Stephen D. Russell; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| Electroluminescent devices are formed on a transparent sapphire substrate as follows. Crystalline silicon is formed on the sapphire substrate and patterned into a mesa. An electrode of, for example, titanium silicide, is formed in the silicon around the mesa, and an electrically insulating layer is formed over the electrode. The crystalline silicon is exposed on the mesa, and a porous silicon layer is formed on the crystalline silicon. An electrode ... |
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| Defects and Impurities in 4H- and 6H-SiC Homoepitaxial Layers: Identification, Origin, Effect on Properties of Ohmic Contacts and Insulating Layers and Reduction |
MAR 97 |
33 pages |
| Authors:
R. F. Davis; M. O. Aboelfotoh; B. J. Baliga; R. J. Nemanich; R. S. Busby; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Exposure of the 6H-SiC(000l) sub Si surface to atomic H selectively removed Si and converted the (3x3) surface to a (1x1) surface as determined from the results of X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and temperature programmed desorption (TPD). Reduction and loss of the Si 2p XPS peak from the (3x3) surface were observed. A three-step oxide growth process is being developed. The ... |
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| Photonic Technology Development for Densely-Interconnected Neural Networks |
27 FEB 97 |
27 pages |
| Authors:
B. K. Jenkins; Anupam Madhukar; Armand R. Tanguay Jr; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF ELECTRICAL ENGINEERING AND MATERIALS SCIENCE
|
| Progress on the grant, 'Photonic Technology Development for Densely Interconnected Neural Networks', is described. Substantial progress has been made in the following areas. Artificial neural network models (or implementation using photonics have been developed and analyzed. Radial basis function neural networks for analog nonparametric density function estimation and pattern recognition, and multilayer backward error propagation neural networks both for implementation on photonic hardware, have been characterized. Emphasis has been on ... |
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| Effect of Repair on the Electromagnetic Shielding Properties of Composite Materials |
JAN 97 |
|
| Authors:
C. L. Gardner; R. Apps; A. J. Russell; DEFENCE RESEARCH ESTABLISHMENT OTTAWA (ONTARIO)
|
| Composite materials are increasingly being used for the construction of aircraft because of their superior physical properties. Maintenance of adequate electromagnetic (EM) shielding inside the aircraft is often a concern because of the increasing use of sensitive avionics. Degradation of EM shielding provided by the skin of the aircraft during repair can be of particular concern. In this report, we present results of measurements that we have made to examine ... |
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| Defects and Impurities in 4H- and 6H-SiC Homoepitaxial Layers: Identification, Origin, Effect on Properties of Ohmic Contacts and Insulating Layers and Reduction |
31 DEC 96 |
42 pages |
| Authors:
R. F. Davis; M. O. Aboelfotoh; B. J. Baliga; R. J. Nemanich; S. W. King; NORTH CAROLINA STATE UNIV AT RALEIGH
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| A dry ex situ cleaning sequence, superior to conventional wet chemical processing, and based on UV/O3 oxidation and exposure to the vapor of a 10:1 buffered HF solution for removal of non-carbidic C and silicon oxide, respectively, has been demonstrated via XPS analysis for (0001)Si 6H-SiC surfaces. Exposure to UV/O3 resulted in a broad Si-O Si 2p peak at 102.4 eV and a shift in the non-carbidic Cls peak from ... |
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| AlGaN Channel Transistors for Power Management and Distribution |
30 DEC 96 |
36 pages |
| Authors:
James M. VanHove; SVT ASSOCIATES INC EDEN PRAIRIE MN
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| Contained within is the Final report of a Phase I SBIR program to develop AIGaN channel junction field effect transistors (JFET). The report summarizes our work to design, deposit, and fabricate JFETS using molecular beam epitaxy growth AIGaN. Nitride growth is described using a RF atomic nitrogen plasma source. Processing steps needed to fabricate the device such as ohmic source-drain contacts, reactive ion etching, gate formation, and air bride fabrication ... |
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| Interface Properties of Wide Bandgap Semiconductor Structures |
DEC 96 |
102 pages |
| Authors:
R. F. Davis; S. Bedair; J. Bernholc; R. J. Nemanich; Z. Sitar; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| Doping of GaN was achieved with doping levels of 5E16 - 3E18 /sq cm. Growth of GaN in H2 and N2 was accomplished with the two main differences being stronger PL intensity and slower growth rate for the films grown in N2. Biaxial strains resulting from mismatches in thermal expansion coefficients and lattice parameters in 22 GaN films grown on AlN buffer layers previously deposited on vicinal and on-axis 6H-SiC(000 ... |
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