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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Evidence for sulphur implantation in Europa's UV absorption band

The UV spectral characteristics of the Galilean satellites are investigated (using data from the International Ultraviolet Explorer (IUE) spacecraft) as a function of the orbital position, large-scale areal variability, and temporal dynamics. The discovery of an absorption feature at 280 nm in Europa's reflection spectrum is reported and observations show that the absorption is strongest on the trailing hemisphere (central longitude 270 degrees). The feature resembles SO2 and seems to result from S-O bond formation between deeply implanted sulphur atoms and the adjacent damaged water-ice-lattice. The sulphur supposedly comes from energetic (hundreds of keV) sulphur ions that are present in the Jovian magnetosphere. An appropriate equilibrium condition can be found to match the observed spectral data if sputtering erosion occurs at no greater than approximately 20 meters per one billion years.

Lane, A. L.↗
NASA NTRS1982

Low-Noise Implantable Electrode

New implantable electrocardiogram electrode much less sensitive than previous designs to spurious biological potentials. Designed in novel "pocket" configuration, new electrode is intended as sensor for radiotelemetry of biological parameters in experiments on unrestrained subjects. Electrode is esentially squashed cylinder that admits body fluid into interior. Cylinder and electrical lead are made of stainless steel. Spot welding and crimping are used for assembly, rather than soldering.

Lund, G. F.↗
NASA NTRS1983

Implantable Drug Dispenser

Drugs such as insulin are injected as needed directly into bloodstream by compact implantable dispensing unit. Two vapor cavities produce opposing forces on drug-chamber diaphragm. Heaters in cavities allow control of direction and rate of motion of bellows. Dispensing capsule fitted with coil so batteries can be recharged by induction.

Collins, E. R. J.↗
NASA NTRS1981

Fabrication and high temperature characteristics of ion-implanted GaAs bipolar transistors and ring-oscillators

Ion implantation techniques that permit the reproducible fabrication of bipolar GaAs integrated circuits are studied. A 15 stage ring oscillator and discrete transistor were characterized between 25 and 400 C. The current gain of the transistor was found to increase slightly with temperature. The diode leakage currents increase with an activation energy of approximately 1 eV and dominate the transistor leakage current 1 sub CEO above 200 C. Present devices fail catastrophically at about 400 C because of Au-metallization.

Doerbeck, F. H.↗
NASA NTRS1982

Implantable telemetry for small animals

A series of totally implantable telemetry devices for use in measuring deep body parameters in small animals were developed. Under a collaborative agreement with NASA, several of these systems; the continuous wave Doppler ultrasonic flowmeter, the multichannel telemetry system, and the inductively-powered dual channel cardiac pacer were evaluated in a series of ten mongrel dogs (15 to 20 kg.). These systems were used to measure ascending aortic and coronary blood flow, aortic pressure, and subcutaneous EKG.

Source record↗
NASA NTRS1982

Implantable electrical device

A fully implantable and self contained device is disclosed composed of a flexible electrode array for surrounding damaged nerves and a signal generator for driving the electrode array with periodic electrical impulses of nanoampere magnitude to induce regeneration of the damaged nerves.

Jhabvala, M. D.↗
NASA NTRS1982

Non-mass-analyzed ion implantation from a solid phosphorus source

A phosphorus ion beam, extracted from a Freeman ion source charged with elemental phosphorus, has been investigated for use in solar cell fabrication. Mass spectroscopy of the beam indicates the absence of both minority-carrier lifetime degrading impurities and hydrogen. The ion beam, without mass analysis, was used for ion implantation of solar cells, and performance for all cells was found to be equivalent to mass-analyzed controls.

Spitzer, M. B.↗
NASA NTRS1984

Less-Costly Ion Implantation of Solar Cells

Experiments point way toward more relaxed controls over ion-implanation dosage and uniformity in solar-cell fabrication. Data indicate cell performance, measured by output current density at fixed voltage, virtually same whether implant is particular ion species or broad-beam mixture of several species.

Fitzgerald, D. J.↗
NASA NTRS1984

Radiation damage and defect behavior in ion-implanted, lithium counterdoped silicon solar cells

Boron doped silicon n+p solar cells were counterdoped with lithium by ion implantation and the resuitant n+p cells irradiated by 1 MeV electrons. The function of fluence and a Deep Level Transient Spectroscopy (DLTS) was studied to correlate defect behavior with cell performance. It was found that the lithium counterdoped cells exhibited significantly increased radiation resistance when compared to boron doped control cells. It is concluded that the annealing behavior is controlled by dissociation and recombination of defects. The DLTS studies show that counterdoping with lithium eliminates at least three deep level defects and results in three new defects. It is speculated that the increased radiation resistance of the counterdoped cells is due primarily to the interaction of lithium with oxygen, single vacanies and divacancies and that the lithium-oxygen interaction is the most effective in contributing to the increased radiation resistance.

Weinberg, I.↗
NASA NTRS1986

'On-line' analyses of simulated solar wind implantations of terrestrial analogs of lunar materials

In connection with the establishment of a lunar base, it would be necessary to provide water, and the feasibility to obtain water from solar wind (SW) implanted lunar soils has been considered. In this context, a project involving the examination of materials under conditions of simulated SW irradiation has been initiated. A description is presented of initial results on oligoclase, ilmenite, and simulated lunar glass (SLG). Attention is given to the reaction chamber, the target materials, the saturation concentrations, aspects of water release, depth profiles, thermal release, effects from helium-3 preimplants, mechanisms of possible water release related to direct emission and thermal release, and lunar soil components enriched in trapped SW hydrogen. It is found that ilmenite stores about twice as much deuterium as the other target materials. However, it is unknown whether the small enrichment factor will be sufficient to make the material a potential source of lunar water.

Blanford, G. E.↗
NASA NTRS1986

Deep levels in as-grown and Si-implanted In(0.2)Ga(0.8)As-GaAs strained-layer superlattice optical guiding structures

Trap levels in about 2-micron In(0.2)Ga(0.8)As(94 A)/GaAs(25 A) strained-layer superlattices, suitable for optical waveguides, have been identified and characterized by deep-level transient spectroscopy and optical deep-level transient spectroscopy measurements. Several dominant electron and hole traps with concentrations of approximately 10 to the 14th/cu cm, and thermal ionization energies Delta-E(T) varying from 0.20 to 0.75 eV have been detected. Except for a 0.20-eV electron trap, which might be present in the In(0.2)Ga(0.8)As well regions, all the other traps have characteristics similar to those identified in molecular-beam epitaxial GaAs. Of these, a 0.42-eV hole trap is believed to originate from Cu impurities, and the others are probably related to native defects. Upon Si implantation and halogen lamp annealing, new deep centers are created. These are electron traps with Delta-E(T) = 0.81 eV and hole traps with Delta-E(T) = 0.46 eV. Traps occurring at room temperature may present limitations for optical devices.

Dhar, S.↗
NASA NTRS1985

Large-area high-efficiency ion-implanted cells and flat-plate modules

This paper reports the development of a flat-plate module based on highly efficient ion-implanted silicon solar cells. The cells are 53 sq cm in area and have exhibited AM 1.5 efficiencies of over 18 percent. The use of back surface reflectors to reduce module operating temperature is discussed. A comparison of various approaches to cell design is made, and module test data for these designs are presented. Module efficiency of 14 percent (25 C) is reported.

Spitzer, M. B.↗
NASA NTRS1986

30 GHz monolithic balanced mixers using an ion-implanted FET-compatible 3-inch GaAs wafer process technology

An all ion-implanted Schottky barrier mixer diode which has a cutoff frequency greater than 1000 GHz has been developed. This new device is planar and FET-compatible and employs a projection lithography 3-inch wafer process. A Ka-band monolithic balanced mixer based on this device has been designed, fabricated and tested. A conversion loss of 8 dB has been measured with a LO drive of 10 dBm at 30 GHz.

Bauhahn, P.↗
NASA NTRS1988

Implanted Blood-Pressure-Measuring Device

Arterial pressure compared with ambient bodily-fluid pressure. Implanted apparatus, capable of measuring blood pressure of patient, includes differential-pressure transducer connected to pressure sensor positioned in major artery. Electrical signal is function of differential pressure between blood-pressure sensor and reference-pressure sensor transmitted through skin of patient to recorder or indicator.

Fischell, Robert E.↗
NASA NTRS1988

Optical waveguides in oxygen-implanted buried-oxide silicon-on-insulator structures

An analysis is made of the waveguiding properties of the oxygen-implanted, buried-oxide, silicon-on-insulator structures currently being developed for use in microelectronics. It is found that in spite of the fact that the buried-oxide layer is only a few tenths of a micrometer thick, the single-crystal overlayer can support TEo guided-wave propagation, at subbandgap wavelengths, with losses due to substrate radiation leakage at or below the benchmark level of 1 dB/cm.

Kurdi, B. N.↗
NASA NTRS1989

DBR laser with nondynamic plasma grating formed by focused ion beam implanted dopants

A static plasma grating has been demonstrated experimentally (Wu et al., 1988) in a large-optical-cavity focused-ion-beam-distributed-Bragg-reflector (FIB-DBR) GaAlAs/GaAs laser diode. The grating is formed by implanting stripes of dopants with a focused ion beam. The dopants ionize to form periodic fluctuations in the carrier concentration which, through the Kramers-Kronig relations, form an index grating. A model of the grating strength for optimizaton of the laser design is developed and presented. The computed results show that the coupling coefficient k can be increased by more than an order of magnitude over the 15/cm experimentally. Therefore, FIB-DBR or FIB-distributed-feedback (DFB) lasers with performance comparable to that of conventional DBR (or DFB) lasers can be expected.

Boenke, Myra M.↗
NASA NTRS1990

Surface and implantation effects on p-n junctions

The contribution of the graded region of implanted p-n junctions is analyzed using an exponential profile. Though previously neglected, it was recently shown that this contribution to the saturation current of HgCdTe diodes is significant. Assuming a dominant Auger recombination, an analytical solution to the continuity equation is obtained. An expression for the current generation by the graded region is presented for both ohmic and reflecting boundary conditions. A revised condition for a wide region is derived. When the region is narrow, the current differs drastically from that of the zero-gradient case. The effects of the junction depth and the substrate and surface concentrations on the current are investigated. It is shown that the reverse current does not saturate.

Schacham, Samuel E.↗
NASA NTRS1992

A model for the trap-assisted tunneling mechanism in diffused n-p and implanted n(+)-p HgCdTe photodiodes

A theoretical model for the trap-assisted tunneling process in diffused n-on-p and implanted n(+)-on-p HgCdTe photodiodes is presented. The model describes the traps and the trap characteristics: concentration, energy level, and capture cross sections. We have observed that the above two types of diodes differ in the voltage dependence of the trap-assisted tunneling current and dynamic resistance. Our model takes this difference into account and offers an explanation of the phenomenon. The good fit between measured and calculated DC characteristics of the photodiodes (for medium and high reverse bias and for temperatures from 65 to 140 K) supports the validity of the model.

Rosenfeld, David↗