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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

A high resolution semiconductor detector for applications in space

Nuclear radiation detectors with volumes of approximately 1 cu cm was fabricated from single crystals of germanium-silicon alloy containing as much as 20 weight percent germanium. The properties of these detectors were investigated and will be discussed. Tests reveal that the gamma ray photoelectric peak efficiency of an alloy detector with only 12 weight percent germanium is approximately 4 times that of a silicon detector of equal volume. The room temperature roomure appears to be a good possibility. Storage for long periods at room temperature does not seem to adversely affect these devices. The results of preliminary radiation damage experiments suggest that the alloy detectors possess a radiation damage resistance far greater than that of silicon.

Alexander, P.↗
NASA NTRS1976

Construction of prototypes of a new class of infrared detectors

A class of infrared detectors is proposed and experimental results are presented for a prototype device. The material used is LaF3, an ionic conductor with a capacitance that varies exponentially with temperature. The detectivity of a prototype detector is estimated from measured signal voltages and incident power, and a Johnson noise voltage calculated from the measured resistance. For the parameters characterizing this device the estimated detectivity is consistent with a theoretical prediction. The theory further predicts an optimum detectivity for much thinner devices than the prototypes.

Sher, A.↗
NASA NTRS1976

LaF3 infrared detector

A class of infrared detectors is proposed, and experimental results are presented for a prototype device. The material used is LaF3, an ionic conductor with a capacitance that varies exponentially with temperature. The detectivity of a prototype detector is estimated from measured signal voltages and incident power, and a Johnson noise voltage is calculated from the measured resistance. At a modulation frequency of 20 Hz, the estimated detectivity is about 2 million cm/sq root Hz/W. For the parameters characterizing this device, the estimated detectivity is consistent with a theoretical prediction. The theory further predicts an optimum detectivity of about 1 billion cm/sq root Hz/W for much thinner devices than the prototypes.

Sher, A.↗
NASA NTRS1990

A new thermal sensor for X-ray microcalorimetry

A concept for a detector is introduced which exploits the significant temperature dependence of the dielectric constant in ferroelectric materials. The concept permits the use of a microcalorimeter without the resistive sensors which are associated with heat dissipation and increased Johnson noise in the electronic conversion circuit. General calorimeter features are listed, and the concepts related to dielectric calorimeters are discussed in terms of operational and detection advantages. The use of the device is delineated both theoretically and experimentally with the results of an operational dielectric material. The mixed-crystal quantum ferroelectric is employed and detects 6 MeV alpha particles while operating at 1.2 K in the first detection conducted. The temperature dependence of the dielectric constant in the materials allows for the elimination of resistive sensors in microcalorimeters, thereby improving the ultimate sensitivity of the instrument.

Silver, Eric↗
NASA NTRS2012

Process for Patterning Indium for Bump Bonding

An innovation was created for the Cosmology Large Angular Scale Surveyor for integration of low-temperature detector chips with a silicon backshort and a silicon photonic choke through flipchip bonding. Indium bumps are typically patterned using liftoff processes, which require thick resist. In some applications, it is necessary to locate the bumps close to high-aspect-ratio structures such as wafer through-holes. In those cases, liftoff processes are challenging, and require complicated and time-consuming spray coating technology if the high-aspect-ratio structures are delineated prior to the indium bump process. Alternatively, processing the indium bumps first is limited by compatibility of the indium with subsequent processing. The present invention allows for locating bumps arbitrarily close to multiple-level high-aspect-ratio structures, and for indium bumps to be formed without liftoff resist. The process uses the poor step coverage of indium deposited on a silicon wafer that has been previously etched to delineate the location of the indium bumps. The silicon pattern can be processed through standard lithography prior to adding the high-aspect-ratio structures. Typically, high-aspectratio structures require a thick resist layer so this layer can easily cover the silicon topography. For multiple levels of topography, the silicon can be easily conformally coated through standard processes. A blanket layer of indium is then deposited onto the full wafer; bump bonding only occurs at the high points of the topography.

Denis, Kevin↗
NASA NTRSDate not supplied

Detached Melt and Vapor Growth of InI in SUBSA hardware

Indium iodide (InI) single crystals, grown by the Bridgman process, have shown a significant promise as room temperature detector material for X-rays and γ-rays due to the large, close to ideal, bandgap of Eg = 2 eV, and high electrical resistivity. Yet the transport properties of the charge and the detector performance remain inadequate. The Bridgman growth of semiconductor crystals in microgravity have typically resulted in partial dewetting and Marangoni convection, which disturbed the diffusion-controlled growth and produced nonuniform dopant distribution. However, unconfined or partially confined solidification drastically reduced the number of stress-induced defects compared to the confined growth in crucibles on Earth.The goal of the present investigation was to explore melt growth of a heavy metal halide in microgravity, focusing on dewetting, in order to improve the crystalline perfection, i.e., to reduce the number of stress-related defects. InI was chosen because it is non-toxic and has a low melting point of only 365 C (~150 C below the melting point of InSb, used in the SUBSA experiments in 2002). Furthermore, InI melts and evaporates congruently, making it suitable for both growth by directional solidification and growth from the vapor phase. In preparation for the flight experiments, ground-based experiments were conducted in the SUBSA ground unit, consisting of 4 melt growth and 2 vapor growth experiments. The crystals were grown by a gradient freeze method by lowering the setpoint of the furnace. The transparent section of the SUBSA furnace did not allow observations of the solid-liquid interface. Contrary to our expectations, the possible occurrence of dewetting during growth could not be observed. We will present i) the ampoule design and preparation, ii) the experiments conducted in the SUBSA ground unit, iii) the images obtained during the microgravity experiments and iv) the results of the characterization of the grown crystals and detector fabrication.

Crystal Growth↗
NASA NTRS1993

Synthesis, Properties, and Applications Of Boron Nitride

Report describes synthesis, properties, and applications of boron nitride. Especially in thin-film form. Boron nitride films useful as masks in x-ray lithography; as layers for passivation of high-speed microelectronic circuits; insulating films; hard, wear-resistant, protective films for optical components; lubricants; and radiation detectors. Present status of single-crystal growth of boron nitride indicates promising candidate for use in high-temperature semiconductor electronics.

Pouch, John J.↗
NASA NTRS2019

Vapor Growth of Indium Monoiodide

Indium (I) iodide, InI, is part of a group of heavy metal iodides that can be used as room temperature radiation detectors. Other examples are HgI2, PbI2, BiI3, or TlPbI3. InI has several advantages, such as low toxicity, no solid phase transition (such as in HgI2), and no tendency to form polytypes (PbI2, BiI3 ). All binary iodides have layered structures and are quite soft, but InI is also the mechanically most stable compound of the binary compounds. Table 1 shows the main properties of InI in comparison with the other iodides and the most common room temperature radiation detector material, (Cd, Zn)Te. InI is typically grown by the unseeded Bridgman method using a nucleation tip, but Czochralski (CZ) growth has also been demonstrated. The resulting crystals have been used successfully for radiation detection, but both resistivity and mobility are usually well below theoretically predicted values. Physical vapor transport (PVT), although much slower than melt growth, is an alternative method and has been used to grow e.g. HgI2, PbI2, BiI3, CdTe. PVT growth should eliminate or reduce inclusions and impurities since it is based on sublimation, reduce intrinsic defects due to the lower growth temperature, and reduce dislocation densities due to reduced thermal and mechanical stress. As an example, PVT-grown CdTe showed a much improved structural quality compared to Bridgman- or THM-grown material.

Cröll, Arne↗
NASA NTRS1984

Monolithic silicon bolometers

A new type of bolometer detector for the millimeter and submillimeter spectral range is described. The bolometer is constructed of silicon using integrated circuit fabrication techniques. Ion implantation is used to give controlled resistance vs temperature properties as well as extremely low 1/f noise contacts. The devices have been tested between 4.2 and 0.3 K. The best electrical NEP measured is 4 x 10 to the -16th W/Hz to the 1/2 at 0.35 K between 1- and 10-Hz modulation frequency. This device had a detecting area of 0.25 sq cm and a time constant of 20 msec at a bath temperature of 0.35 K.

Downey, P. M.↗
NASA NTRS1960

Emittance Measurements at the Langley Chemical Physics Laboratory

Total hemispherical emittance measurements are made routinely for materials which may be heated by electrical resistance methods over the temperature range of 600 degrees to 2,000 F by using a black-body reference method. This employs a conical black body and a thermopile detector with a calcium fluoride lens. Emittance is obtained by measuring the radiant flux from the specimen strip and comparing it with the flux from an equal area of the black-body cone at the same temperature. The temperature measurements are made by use of thermocouples. It is planned to extend the temperature range of this type of measurement to temperatures above 2,000 F. Another technique has been investigated for measuring emittance of materials not amenable to electrical heating or thermocouple attachment. This method uses a black-body-cavity furnace similar to that used in reference 5 to measure emittance of transparent materials such as glass. The method employs a heated black-body cavity in which the semicircular specimen is allowed to come to the equilibrium temperature of the cavity and then is rotated in front of a water-cooled viewing port where a sensitive thermistor detector alternately views the specimen surface and the black-body cavity. The ratio of the two readings gives the specimen emittance directly, for the temperature of the black body. The detector output is recorded on a fast Brown self-balancing potentiometer. The furnace is provided with a water-cooled blackened shutter which may be inserted behind the specimen to eliminate any transmitted black-body radiation if the specimen is transparent. This apparatus is capable of measuring total normal emittance over the temperature range of 1,000 degrees to 2,000 F. Preliminary data for boron nitride specimens of two thicknesses are shown where total normal emittance is plotted against temperature for two experimental conditions: (1) black-body radiation incident on the back of the specimen and (2) no black-body radiation incident on the back of the specimen (that is, with a watercooled shutter behind the specimen). The data appear to indicate a slight transparency for the thin specimen and emittances of from 0.7 to 0.8 over the temperature range.

Lewis, B. W.↗
NASA NTRS1994

Low-Heat-Leak Electrical Leads For Cryogenic Systems

Electrical leads offering high electrical conductivity and low thermal conductivity developed for use in connecting electronic devices inside cryogenic systems to power supplies, signal-processing circuits, and other circuitry located in nearby warmer surroundings. Strip of superconductive leads on ceramic substrate, similar to ribbon cable, connects infrared detectors at temperature of liquid helium with warmer circuitry. Electrical leads bridging thermal gradient at boundary of cryogenic system designed both to minimize conduction of heat from surroundings through leads into system and to minimize resistive heating caused by electrical currents flowing in leads.

Wise, Stephanie A.↗
NASA NTRS2016

The Design, Implementation, and Performance of the Astro-H SXS Calorimeter Array and Anti-Coincidence Detector

The calorimeter array of the JAXA Astro-H (renamed Hitomi) Soft X-ray Spectrometer (SXS) was designed to provide unprecedented spectral resolution of spatially extended cosmic x-ray sources and of all cosmic x-ray sources in the Fe-K band around 6 keV, enabling essential plasma diagnostics. The SXS has a square array of 36 microcalorimeters at the focal plane. These calorimeters consist of ion-implanted silicon thermistors and HgTe thermalizing x-ray absorbers. These devices have demonstrated a resolution of better than 4.5 eV at 6 keV when operated at a heat-sink temperature of 50 mK. We will discuss the basic physical parameters of this array, including the array layout, thermal conductance of the link to the heat sink, resistance function, absorber details, and means of attaching the absorber to the thermistor-bearing element. We will also present the thermal characterization of the whole array, including thermal conductance and crosstalk measurements and the results of pulsing the frame temperature via alpha particles, heat pulses, and the environmental background. A silicon ionization detector is located behind the calorimeter array and serves to reject events due to cosmic rays. We will briefly describe this anti-coincidence detector and its performance.

x-ray calorimeter↗
NASA NTRS2001

Development of Low-Noise High Value Chromium Silicide Resistors for Cryogenic Detector Applications

Extremely high sensitivity detectors, such as silicon bolometers are required in many NASA missions for detection of photons from the x-ray to the far infrared regions. Typically, these detectors are cooled to well below the liquid helium (LHe) temperature (4.2 K) to achieve the maximum detection performance. As photoconductors, they are generally operated with a load resistor and a pre-set bias voltage, which is then coupled to the input gate of a source-follower Field Effect Transistor (FET) circuit. It is imperative that the detector system signal to noise performance be limited by the noise of the detector and not by the noise of the external components. The load resistor value is selected to optimize the detector performance. These two criteria tend to be contradictory in that these detectors require load resistors in the hundreds of megaohms, which leads to a higher Johnson noise. Additionally, the physical size of the resistor must be small for device integration as required by such missions as the NASA High Resolution Airborne Wide-Band Camera (HAWC) instrument and the Submillimeter High Angular Resolution Camera (SHARC) for the Caltech Submillimeter Observatory (CSO). We have designed, fabricated and characterized thin film resistors using a CrSi/TiW/Al metal system on optical quality quartz substrates. The resistor values range from 100 megaohms to over 650 megaohms and are Johnson noise limited at LHe temperatures. The resistor film is sputtered with a sheet resistance ranging from 300 ohms to 1600 ohms and the processing sequence developed for these devices allows for chemically fine tuning the sheet resistance in-situ. The wafer fabrication process was of sufficiently high yield (>80%) providing clusters of good resistors for integrated multiple detector channels, a very important feature in the assembly of these two instruments.

Jhabvala, Murzy↗
NASA NTRS2018

Design, Implementation, and Performance of the Astro-H SXS Calorimeter Array and Anticoincidence Detector

The calorimeter array of the JAXA Astro-H (renamed Hitomi) soft x-ray spectrometer (SXS) was designed to provide unprecedented spectral resolution of spatially extended cosmic x-ray sources and of all cosmic x-ray sources in the Fe-K band around 6 keV, enabling essential plasma diagnostics. The SXS had a square array of 36 x-ray calorimeters at the focal plane. These calorimeters consisted of ion-implanted silicon thermistors and HgTe thermalizing x-ray absorbers. These devices demonstrated a resolution of better than 4.5 eV at 6 keV when operated at a heat-sink temperature of 50 mK. We will discuss the basic physical parameters of this array, including the array layout, thermal conductance of the link to the heat sink, resistance function, absorber details, and means of attaching the absorber to the thermistor-bearing element. We will also present the thermal characterization of the whole array, including thermal conductance and crosstalk measurements and the results of pulsing the frame temperature via alpha particles, heat pulses, and the environmental background. A silicon ionization detector was located behind the calorimeter array and served to reject events due to cosmic rays. We will briefly describe this anticoincidence detector and its performance.

Kilbourne, Caroline A.↗
NASA NTRS1996

Gas Sensor Test Chip

The use of organic polymers to detect gasses has been known for several years to be an effective means for gas detection via conductivity changes. These chemoresistors offer significant advantages over other gas detectors in that they operate near room temperature and thus can be used in compact, low-power applications.

organic polymers sheet resistance conduction aniso↗
NASA NTRS2011

Implications of Weak-Link Behavior on the Performance of Mo/Au Bilayer Transition-Edge Sensors

Understanding the physical properties of the superconducting-to-normal transition is fundamental for optimizing the design and performance of transition-edge sensors (TESs). Recent critical current measurements of Mol Au bilayer test structures show that they act as weak superconducting links, exhibiting oscillatory, Fraunhofer-like behavior with applied magnetic field. In this paper we investigate the implications of this behavior for TES X-ray detectors, under operational bias conditions. These devices include normal metal features used for absorber attachment and unexplained noise suppression, which result in modifications to the previously reported critical current behavior. We present measurements of the logarithmic resistance sensitivity with temperature, a, and current, b, as a function of applied magnetic field and bias point within the resistive transition. Results show that these important device parameters exhibit similar oscillatory behavior with applied magnetic field, which in turn affects the signal responsivity and noise, and hence the energy resolution. These results show the significance of the critical current in determining the performance of TESs and hold promise to improve future.

Smith, Stephen J.↗
NASA NTRS2006

Carbon-Nanotube Schottky Diodes

Schottky diodes based on semiconducting single-walled carbon nanotubes are being developed as essential components of the next generation of submillimeter-wave sensors and sources. Initial performance predictions have shown that the performance characteristics of these devices can exceed those of the state-of-the-art solid-state Schottky diodes that have been the components of choice for room-temperature submillimeter-wave sensors for more than 50 years. For state-of-the-art Schottky diodes used as detectors at frequencies above a few hundred gigahertz, the inherent parasitic capacitances associated with their semiconductor junction areas and the resistances associated with low electron mobilities limit achievable sensitivity. The performance of such a detector falls off approximately exponentially with frequency above 500 GHz. Moreover, when used as frequency multipliers for generating signals, state-of-the-art solid-state Schottky diodes exhibit extremely low efficiencies, generally putting out only micro-watts of power at frequencies up to 1.5 THz. The shortcomings of the state-of-the-art solid-state Schottky diodes can be overcome by exploiting the unique electronic properties of semiconducting carbon nanotubes. A single-walled carbon nanotube can be metallic or semiconducting, depending on its chirality, and exhibits high electron mobility (recently reported to be approx.= 2x10(exp 5)sq cm/V-s) and low parasitic capacitance. Because of the narrowness of nanotubes, Schottky diodes based on carbon nanotubes have ultra-small junction areas (of the order of a few square nanometers) and consequent junction capacitances of the order of 10(exp -18) F, which translates to cutoff frequency >5 THz. Because the turn-on power levels of these devices are very low (of the order of nano-watts), the input power levels needed for pumping local oscillators containing these devices should be lower than those needed for local oscillators containing state-of-the-art solid-state Schottky diodes.

Manohara, Harish↗
NASA NTRS2009

NASA Tech Briefs, July 2009

Topics covered include: Dual Cryogenic Capacitive Density Sensor; Hail Monitor Sensor; Miniature Six-Axis Load Sensor for Robotic Fingertip; Improved Blackbody Temperature Sensors for a Vacuum Furnace; Wrap-Around Out-the-Window Sensor Fusion System; Wide-Range Temperature Sensors with High-Level Pulse Train Output; Terminal Descent Sensor Simulation; A Robust Mechanical Sensing System for Unmanned Sea Surface Vehicles; Additive for Low-Temperature Operation of Li-(CF)n Cells; Li/CFx Cells Optimized for Low-Temperature Operation; Number Codes Readable by Magnetic-Field-Response Recorders; Determining Locations by Use of Networks of Passive Beacons; Superconducting Hot-Electron Submillimeter-Wave Detector; Large-Aperture Membrane Active Phased-Array Antennas; Optical Injection Locking of a VCSEL in an OEO; Measuring Multiple Resistances Using Single-Point Excitation; Improved-Bandwidth Transimpedance Amplifier; Inter-Symbol Guard Time for Synchronizing Optical PPM; Novel Materials Containing Single-Wall Carbon Nanotubes Wrapped in Polymer Molecules; Light-Curing Adhesive Repair Tapes; Thin-Film Solid Oxide Fuel Cells; Zinc Alloys for the Fabrication of Semiconductor Devices; Small, Lightweight, Collapsible Glove Box; Radial Halbach Magnetic Bearings; Aerial Deployment and Inflation System for Mars Helium Balloons; Steel Primer Chamber Assemblies for Dual Initiated Pyrovalves; Voice Coil Percussive Mechanism Concept for Hammer Drill; Inherently Ducted Propfans and Bi-Props; Silicon Nanowire Growth at Chosen Positions and Orientations; Detecting Airborne Mercury by Use of Gold Nanowires; Detecting Airborne Mercury by Use of Palladium Chloride; Micro Electron MicroProbe and Sample Analyzer; Nanowire Electron Scattering Spectroscopy; Electron-Spin Filters Would Offer Spin Polarization Greater than 1; Subcritical-Water Extraction of Organics from Solid Matrices; A Model for Predicting Thermoelectric Properties of Bi2Te3; Integrated Miniature Arrays of Optical Biomolecule Detectors; A Software Rejuvenation Framework for Distributed Computing; Kurtosis Approach to Solution of a Nonlinear ICA Problem; Robust Software Architecture for Robots; R4SA for Controlling Robots; Bio-Inspired Neural Model for Learning Dynamic Models; Evolutionary Computing Methods for Spectral Retrieval; Monitoring Disasters by Use of Instrumented Robotic Aircraft; Complexity for Survival of Living Systems; Using Drained Spacecraft Propellant Tanks for Habitation; Connecting Node; and Electrolytes for Low-Temperature Operation of Li-CFx Cells.

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