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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Seeking & Evaluating Applications of SAWs (SEASAWs)

Surface Acoustic Wave sensors (SAWs) offer a battery less, wireless, passive, noninvasive, durable means of sensing which might be appealing to many fields in space technology. Developments in many aspects of SAWs including the miniaturization of associated hardware, improvements in interrogation and device fabrication / characterization allow for the use of SAWs in many aerospace settings where traditional sensors may have sufficed but SAWs might enhance. In order to place this technology in relevant environments, an inherent understanding of operation and capabilities must be understood. With the many possibilities of SAWs in their implementation, breaking down their tradeoffs and primary systems allows for their application.

Michael Szostak↗
NASA NTRS2021

A Nanoscale Vacuum Field Emission Gated Diode with an Umbrella Cathode

A nanoscale field emission vacuum channel gated diode structure is proposed and a tungsten cathode with an umbrella-like geometry and sharp vertical edge is fabricated. The edge of the suspended cathode becomes the field emission surface. Unlike in the traditional transistor with the gate typically located between the source and the drain, the bottom silicon plate becomes the gate here and the anode terminal is located between the umbrella cathode and the gate. The fabricated devices show excellent diode characteristics and the gated diode structure is attractive for extremely low gate leakage.

Vacuum field emission diode↗
NASA NTRSDate not supplied

Fine Optimization of TES Design for the X-IFU Instrument on ATHENA

The X-ray Integral Field Unit (X-IFU) instrument on the Advanced Telescope for High ENergy Astrophysics (ATHENA) is baselined to have 3168 transition-edge sensor (TES) microcalorimeter pixels. These pixels will be DC biased and readout using time division multiplexing. We recently reported a demonstration of the required pixel and readout performance in 252 pixels from a 1 kilo-pixel array (e.g. 2.16 eV resolution for 6.9 keV X-rays). Having achieved the required performance, the 50um square TES design in this demonstration array is considered the baseline pixel design for X-IFU. However, by making small adjustments to the TES design, we may be able to make small but consequential improvements to the instrument performance, while staying within the many constraints of the X-IFU requirements. In this presentation, we will show results from newly fabricated devices with subtle changes from the baseline TES design to further optimize the performance for X-IFU. We will discuss optimizing the TES sheet resistance, normal metal features, X-ray absorber attachment points, TES aspect ratio, and heat capacity. These minor design changes can have significant effects on thermo-electric time constants, thermal fluctuation noise, resistive transition shape and uniformity, and non-linearity of X-ray event pulses. In addition, full characterization of these new TES designs allows greater understanding of the relevant physics within the TES and gives routes for further optimization.

Nick Wakeham↗
NASA NTRS1993

Fabrication of micro-optical devices

We have fabricated a variety of micro-optic components including Fresnel and non-Frensel lenses, off-axis and dispersive lenses with binary stepped contours, and analog contours. Process details for all lens designs fabricated are given including multistep photolithography for binary fabrication and grayscale mask photolithography for analog fabrication. Reactive ion etching and ion beam milling are described for the binary fabrication process, while ion beam milling was used for the analog fabrication process. Examples of micro-optic components fabricated in both Si and CdTe substrates are given.

Anderson, W. W.↗
NASA NTRS2001

Thin-Film Organic-Based Solar Cells for Space Power

Recent advances in dye-sensitized and organic polymer solar cells have lead NASA to investigate the potential of these devices for space power generation. Dye-sensitaized solar cells were exposed to simulated low-earth orbit conditions and their performance evaluated. All cells were characterized under simulated air mass zero (AM0) illumination. Complete cells were exposed to pressures less than 1 x 10 (exp -7)torr for over a month, with no sign of sealant failure or electrolyte leakage. Cells from Solaronix SA were rapid thermal cycled under simulated low-earth orbit conditions. The cells were cycled 100 times from -80 C to 80 C, which is equivalent to 6 days in orbit. The best cell had a 4.6% loss in efficiency as a result of the thermal cycling. In a separate project, novel -Bridge-Donor-Bridge-Acceptor- (-BDBA-) type conjugated block copolymer systems have been synthesized and characterized by photoluminescence (PL). In comparison to pristine donor or acceptor, the PL emissions of final -B-D-B-A- block copolymer films were quenched over 99%. Effective and efficient photo induced electron transfer and charge separation occurs due to the interfaces of micro phase separated donor and acceptor blocks. The system is very promising for a variety high efficiency light harvesting applications. Under an SBIR contract, fullerene-doped polymer-based photovoltaic devices were fabricated and characterized. The best devices showed overall power efficiencies of approximately 0.14% under white light. Devices fabricated from 2% solids content solutions in chlorobenzene gave the best results. Presently, device lifetimes are too short to be practical for space applications.

Bailey, Sheila G.↗
NASA NTRS2002

Thin-film Organic-based Solar Cells for Space Power

Recent advances in dye-sensitized and organic polymer solar cells have lead NASA to investigate the potential of these devices for space power generation. Dye-sensitized solar cells were exposed to simulated low-earth orbit conditions and their performance evaluated. All cells were characterized under simulated air mass zero (AM0) illumination. Complete cells were exposed to pressures less than 1 x 10(exp -7) torr for over a month, with no sign of sealant failure or electrolyte leakage. Cells from Solaronix SA were rapid thermal cycled under simulated low-earth orbit conditions. The cells were cycled 100 times from -80 C to 80 C, which is equivalent to 6 days in orbit. The best cell had a 4.6 percent loss in efficiency as a result of the thermal cycling. In a separate project, novel -Bridge-Donor-Bridge- Acceptor- (-BDBA-) type conjugated block copolymer systems have been synthesized and characterized by photoluminescence (PL). In comparison to pristine donor or acceptor, the PL emissions of final -B-D-B-A- block copolymer films were quenched over 99 percent. Effective and efficient photo induced electron transfer and charge separation occurs due to the interfaces of micro phase separated donor and acceptor blocks. The system is very promising for a variety high efficiency light harvesting applications. Under an SBIR contract, fullerene-doped polymer-based photovoltaic devices were fabricated and characterized. The best devices showed overall power efficiencies of approx. 0.14 percent under white light. Devices fabricated from 2 percent solids content solutions in chlorobenzene gave the best results. Presently, device lifetimes are too short to be practical for space applications.

Bailey, Sheila G.↗
NASA NTRS1991

YBa2Cu3O(7-x)/Au/Nb device structures

Fabrication and testing of planar and edge geometry YBaCuO/Au/Nb superconductor/normal-metal/superconductor (SNS) device structures is described. Weak-link devices of this type serve as sensitive probes of the electrical quality of the YBaCuO/Au interface. The devices are fabricated using laser-ablated, in situ, c-axis-oriented YBaCuO thin films, with both annealed and unannealed YBaCuO/Au interfaces. The planar SNS structures are formed by sequential, in situ deposition of YBaCuO, Au, and Nb, followed by etching, planarization, and wiring electrode definition to produce junctions ranging from 5 to 20 micron on a side. Resulting RnA products are 1-10 x 10 to the -8th ohm-sq cm with critical current densities up to 5 kA/sq cm. For the edge geometry devices, the YBaCuO film edges are patterned using Ar ion milling, followed by a low energy ion cleaning step and in situ deposition of Au and Nb. Devices with areas in the 10 to the -7th to 10 to the -8th sq cm range have been fabricated with RnA products lower than 10 to the -8th ohm-sq cm and critical current densities up to 3kA/sq cm. Both types of devices show ac Josephson steps under microwave irradiation. The best results have been obtained with annealed YBaCuO/Au interfaces.

Hunt, B. D.↗
NASA NTRS2009

Zinc Alloys for the Fabrication of Semiconductor Devices

ZnBeO and ZnCdSeO alloys have been disclosed as materials for the improvement in performance, function, and capability of semiconductor devices. The alloys can be used alone or in combination to form active photonic layers that can emit over a range of wavelength values. Materials with both larger and smaller band gaps would allow for the fabrication of semiconductor heterostructures that have increased function in the ultraviolet (UV) region of the spectrum. ZnO is a wide band-gap material possessing good radiation-resistance properties. It is desirable to modify the energy band gap of ZnO to smaller values than that for ZnO and to larger values than that for ZnO for use in semiconductor devices. A material with band gap energy larger than that of ZnO would allow for the emission at shorter wavelengths for LED (light emitting diode) and LD (laser diode) devices, while a material with band gap energy smaller than that of ZnO would allow for emission at longer wavelengths for LED and LD devices. The amount of Be in the ZnBeO alloy system can be varied to increase the energy bandgap of ZnO to values larger than that of ZnO. The amount of Cd and Se in the ZnCdSeO alloy system can be varied to decrease the energy band gap of ZnO to values smaller than that of ZnO. Each alloy formed can be undoped or can be p-type doped using selected dopant elements, or can be n-type doped using selected dopant elements. The layers and structures formed with both the ZnBeO and ZnCdSeO semiconductor alloys - including undoped, p-type-doped, and n-type-doped types - can be used for fabricating photonic and electronic semiconductor devices for use in photonic and electronic applications. These devices can be used in LEDs, LDs, FETs (field effect transistors), PN junctions, PIN junctions, Schottky barrier diodes, UV detectors and transmitters, and transistors and transparent transistors. They also can be used in applications for lightemitting display, backlighting for displays, UV and visible transmitters and detectors, high-frequency radar, biomedical imaging, chemical compound identification, molecular identification and structure, gas sensors, imaging systems, and for the fundamental studies of atoms, molecules, gases, vapors, and solids.

Ryu, Yungryel↗
NASA NTRS2016

Photonic Integrated Circuit (PIC) Device Structures: Background, Fabrication Ecosystem, Relevance to Space Systems Applications, and Discussion of Related Radiation Effects

Electronic integrated circuits are considered one of the most significant technological advances of the 20th century, with demonstrated impact in their ability to incorporate successively higher numbers transistors and construct electronic devices onto a single CMOS chip. Photonic integrated circuits (PICs) exist as the optical analog to integrated circuits; however, in place of transistors, PICs consist of numerous scaled optical components, including such "building-block" structures as waveguides, MMIs, lasers, and optical ring resonators. The ability to construct electronic and photonic components on a single microsystems platform offers transformative potential for the development of technologies in fields including communications, biomedical device development, autonomous navigation, and chemical and atmospheric sensing. Developing on-chip systems that provide new avenues for integration and replacement of bulk optical and electro-optic components also reduces size, weight, power and cost (SWaP-C) limitations, which are important in the selection of instrumentation for specific flight projects. The number of applications currently emerging for complex photonics systems-particularly in data communications-warrants additional investigations when considering reliability for space systems development. This Body of Knowledge document seeks to provide an overview of existing integrated photonics architectures; the current state of design, development, and fabrication ecosystems in the United States and Europe; and potential space applications, with emphasis given to associated radiation effects and reliability.

Body of Knowledge (BOK)↗
NASA NTRS2005

Some Improvements in H-PDLCs

Some improvements have been made in the formulation of holographically formed polymer-dispersed liquid crystals (H-PDLCs) and in the fabrication of devices made from these materials, with resulting improvements in performance. H-PDLCs are essentially volume Bragg gratings. Devices made from H-PDLCs function as electrically switchable reflective filters. Heretofore, it has been necessary to apply undesirably high drive voltages in order to switch H-PDLC devices. Many scientific papers on H-PDLCs and on the potential utility of H-PDLC devices for display and telecommunication applications have been published. However, until now, little has been published about improving quality control in synthesis of H-PDLCs and fabrication of H-PDLC devices to minimize (1) spatial nonuniformities within individual devices, (2) nonuniformities among nominally identical devices, and (3) variations in performance among nominally identical devices. The improvements reported here are results of a research effort directed partly toward solving these quality-control problems and partly toward reducing switching voltages. The quality-control improvements include incorporation of a number of process controls to create a relatively robust process, such that the H-PDLC devices fabricated in this process are more nearly uniform than were those fabricated in a prior laboratory-type process. The improved process includes ultrasonic mixing, ultrasonic cleaning, the use of a micro dispensing technique, and the use of a bubble press.

Crawford, Gregory P.↗
NASA NTRS1975

Microelectronic fabrication of superconducting devices and circuits

It is expected that thin-film superconductors can be used as detectors or sources of infrared and microwave radiation, as magnetometers, as voltage standards, and for voltage and current measurements, for electronic signal processing, and in digital circuitry.

Kirschman, R. K.↗
NASA NTRS1985

GaAs Schottky barrier photo-responsive device and method of fabrication

A gallium arsenide photo-responsive device is provided with an intermediate, transparent layer of a refractory metal or alkaline earth metal forming a tenacious bond between a non-hydroscopic oxide layer and a noble metal Schottky barrier layer. The device has a gallium arsenide substrate with a predetermined type conductivity and a gallium arsenide epitaxial layer with the same type conductivity but a lower charge carrier concentration grown on the substrate. The oxide layer is formed to cover the epitaxial layer, and the transparent metal layer followed by the noble metal layer are deposited upon the oxide layer. An interdigitated ohmic contact is then formed upon the noble metal layer.

Alcorn, G. E.↗
NASA NTRS2003

Fabricating a hybrid imaging device

A hybrid detector or imager includes two substrates fabricated under incompatible processes. An array of detectors, such as charged-coupled devices, are formed on the first substrate using a CCD fabrication process, such as a buried channel or peristaltic process. One or more charge-converting amplifiers are formed on a second substrate using a CMOS fabrication process. The two substrates are then bonded together to form a hybrid detector.

Wadsworth, Mark↗
NASA NTRS1990

Method of fabricating germanium and gallium arsenide devices

A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium by either molecular beam epitaxy (MBE) or by metal-organic chemical vapor deposition (MOCVD). The method involves: depositing a layer of doped or undoped silicon dioxide on a germanium or gallium arsenide wafer or substrate, selectively removing the silicon dioxide layer to define one or more surface regions for a device to be fabricated thereon, growing a matched epitaxial layer of doped germanium or gallium arsenide of an appropriate thickness using MBE or MOCVD techniques on both the silicon dioxide layer and the defined one or more regions; and etching the silicon dioxide and the epitaxial material on top of the silicon dioxide to leave a matched epitaxial layer of germanium or gallium arsenide on the germanium or gallium arsenide substrate, respectively, and upon which a field effect device can thereafter be formed.

Jhabvala, Murzban↗
NASA NTRS2003

High density pixel array and laser micro-milling method for fabricating array

A pixel array device is fabricated by a laser micro-milling method under strict process control conditions. The device has an array of pixels bonded together with an adhesive filling the grooves between adjacent pixels. The array is fabricated by moving a substrate relative to a laser beam of predetermined intensity at a controlled, constant velocity along a predetermined path defining a set of grooves between adjacent pixels so that a predetermined laser flux per unit area is applied to the material, and repeating the movement for a plurality of passes of the laser beam until the grooves are ablated to a desired depth. The substrate is of an ultrasonic transducer material in one example for fabrication of a 2D ultrasonic phase array transducer. A substrate of phosphor material is used to fabricate an X-ray focal plane array detector.

Wiener-Avnear, Eliezer↗