Search NASA⌕ Search

SEARCH · Search NASA

Results for “GERMANIUM”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

The development of a segmented N-type germanium detector, and its application to astronomical gamma-ray spectroscopy

Extensive calculations and simulations have shown that the instrumental background in a coaxial germanium photon detector flown at balloon altitudes or in space, can be substantially reduced by segmenting the outer contact. The contact is divided into horizontal strips around the side of the detector, giving it many characteristics similar to that of a stack of planar detectors. By choosing different segment coincidence requirements in different energy ranges, one can obtain a factor of approx. 2 increase in sensitivity to spectral lines between 40 keV and 1 MeV, compared with an unsegmented detector. The reverse electrode configuration (using n-type germanium), with the p contact outside, is preferred for this application due to its thin dead layer and resistance to radiation damage in space. A small two segment n type detector is being developed to serve as a prototype for larger multisegment devices. Results of this development effort and of detector tests are presented. Previously announced in STAR as N84-13039

Gehrels, N.↗
NASA NTRS1985

Extension of long wavelength response by modulation doping in extrinsic germanium infrared detectors

A new concept for infrared detectors based on multilayer epitaxy and modulation doping has been investigated. This permits a high doping concentration and lower excitation energy in the photodetecting layer as is necessary for longer wavelength response, without incurring the detrimental effects of increased dark current and noise as would be the case with conventional detector designs. Germanium photodetectors using conventional materials and designs have a long wavelength cutoff in the infrared at 138 microns, which can only be extended through the inconvenient application of mechanical stress or magnetic fields. As a result of this approach which was arrived at from theoretical considerations and subsequently demonstrated experimentally, the long wavelength cutoff for germanium extrinsic detectors was extended beyond 200 microns, as determined by direct infrared optical measurements.

Hadek, V.↗
NASA NTRS1986

Microstructures of niobium-germanium alloys processed in inert gas in the 100 meter drop tube

The 100 meter drop tube at NASA's Marshall Space Flight Center has been used for a series of experiments with niobium-germanium alloys. These experiments were conducted with electromagnetic levitation melting in a 200 torr helium environment. Liquid alloys experienced large degrees of undercooling prior to solidification in the drop tube. Several interesting metastable structures were observed. However, the recalescence event prevented extended solid solubility of germanium in the A-15 beta phase. Liquids of eutectic composition were found to undercool in the presence of solid alpha and solid Nb5Ge3.

Bayuzick, R. J.↗
NASA NTRS1991

Plasma-deposited germanium nitride gate insulators for indium phosphide metal-insulator-semiconductor field-effect transistors

Plasma-deposited germanium nitride was investigated for the first time as a possible gate insulator for InP compound semiconductor metal-insulator-semiconductor FET (MISFET) technology. The germanium nitride films were successfully deposited in a capacitively coupled parallel plate reactor at 13.56 MHz operation using GeH4/N2/NH3 and GeH4/N2 mixtures as reactant gases. The former process produced better quality films with enhanced uniformity, increased deposition rates, and increased resistivity. The breakdown field strength of the films was greater than 10 to the 6th V/cm. Auger electron spectroscopy did not indicate significant chemical composition differences between the two processes. For MISFETs with 2-micron channel lengths fabricated on InP, the device transconductance and threshold voltage for the GeH4/N2/NH3 process were 17 mS/mm and -3.6 V, respectively. The drain-source breakdown voltages were greater than 10 V.

Johnson, Gregory A.↗
NASA NTRS1992

Variable-Temperature Cryostat For Radiation-Damage Testing Of Germanium Detectors

Variable-temperature cryostats developed to study radiation damage to, and annealing of, germanium gamma-ray detectors. Two styles: one accommodates large single detector and one accommodates two medium-sized detectors. New cryostats allow complete testing of large-volume germanium gamma-ray detectors without breaking cryostat vacuum and removing detectors for annealing.

Floyd, Samuel R.↗
NASA NTRS1993

Germanium Resistance Thermometer For Subkelvin Temperatures

Improved germanium resistance thermometer measures temperatures as small as 0.01 K accurately. Design provides large area for electrical connections (to reduce electrical gradients and increase sensitivity to changes in temperatures) and large heat sink (to minimize resistance heating). Gold pads on top and bottom of germanium crystal distribute electrical current and flow of heat nearly uniformly across crystal. Less expensive than magnetic thermometers or superconducting quantum interference devices (SQUID's) otherwise used.

Castles, Stephen H.↗
NASA NTRS1995

Growth rates and interface shapes in germanium and lead tin telluride observed in-situ, real-time in vertical Bridgman furnaces

Using the advanced technology developed to visualize the melt-solid interface in low Prandtl number materials, crystal growth rates and interface shapes have been measured in germanium and lead tin telluride semiconductors grown in vertical Bridgman furnaces. The experimental importance of using in-situ, real time observations to determine interface shapes, to measure crystal growth rates, and to improve furnace and ampoule designs is demonstrated. The interface shapes observed in-situ, in real-time were verified by quenching and mechanically induced interface demarcation, and they were also confirmed using machined models to ascertain the absence of geometric distortions. Interface shapes depended upon the interface position in the furnace insulation zone, varied with the nature of the crystal being grown, and were dependent on the extent of transition zones at the ends of the ampoule. Actual growth rates varied significantly from the constant translation rate in response to the thermophysical properties of the crystal and its melt and the thermal conditions existing in the furnace at the interface. In the elemental semiconductor germanium the observed rates of crystal growth exceeded the imposed translation rate, but in the compound semiconductor lead tin telluride the observed rates of growth were less than the translation rate. Finally, the extent of ampoule thermal loading influenced the interface positions, the shapes, and the growth rates.

Barber, P. G.↗
NASA NTRS1968

The Use of Large Lithium-Drifted, Germanium Diodes for Gamma-Ray Spectral Measurements at Balloon Altitudes

A series of balloon-borne experiments has been initiated at the Oak Ridge National Laboratory (ORNL) in cooperation with the Space Sciences Laboratory of the NASA G. C. Marshall Space Flight Center to determine the feasibility of using large (greater than 20 cc) lithium-drifted, germanium diodes to investigate the spectrum of atmospheric gamma rays (60 keV < E < 1.5 MeV) at altitudes corresponding to a few grams per cm (sup 2) residual atmosphere. The results of these measurements will also provide a basis for designing an appropriate shield for a multi-diode, highly directional gamma-ray spectrometer for use in astrophysical measurements. Two flights were accomplished during 1967 using the same two diodes and basic instrument package. Both flights were launched at the NCAR Scientific Balloon Flight Base, Palestine, Texas, and attained a float altitude of 117, 000 ft. The measured atmospheric gamma-ray spectrum shows at least one distinct line at 511 keV (annihilation radiation) superimposed on a continuous distribution of gamma rays attributable to both energy-degraded gamma rays and brems-strahlung photons. A second diode, encased in a passive shield of plastic and lead, shows the expected lines resulting from both neutron inelastic scattering and capture in the germanium. Data acquisition was accomplished on an event-by-event basis through the use of 512-channel, on-board ADC and word-generator circuits and a ground-based, on-line telemetry decoder. The decoder makes it possible to store the data in the memory of a modified pulse-height analyzer simultaneously with storage on magnetic tape. This provides a real-time visual observation of the data as it is accumulated and greatly facilitates preflight calibrations.

Chapman, G. T.↗
NASA NTRS2003

Reduction of Defects in Germanium-Silicon

Crystals grown without contact with a container have far superior quality to otherwise similar crystals grown in direct contact with a container. In addition to float-zone processing, detached- Bridgman growth is a promising tool to improve crystal quality, without the limitations of float zoning or the defects introduced by normal Bridgman growth. Goals of this project include the development of the detached Bridgman process to be reproducible and well understood and to quantitatively compare the defect and impurity levels in crystals grown by these three methods. Germanium (Ge) and germanium-silicon (Ge-Si) alloys are being used. At MSFC, we are responsible for the detached Bridgman experiments intended to differentiate among proposed mechanisms of detachment, and to confirm or refine our understanding of detachment. Because the contact angle is critical to determining the conditions for detachment, the sessile drop method was used to measure the contact angles as a function of temperature and composition for a large number of substrates made of potential ampoule materials. Growth experiments have used pyrolytic boron nitride (pBN) and fused silica ampoules with the majority of the detached results occurring predictably in the pBN. Etch pit density (EPD) measurements of normal and detached Bridgman-grown Ge samples show a two order of magnitude improvement in the detached-grown samples. The nature and extent of detachment is determined by using profilometry in conjunction with optical and electron microscopy. The stability of detachment has been analyzed, and an empirical model for the conditions necessary to achieve sufficient stability to maintain detached growth for extended periods has been developed. We have investigated the effects on detachment of ampoule material, pressure difference above and below the melt, and Si concentration; samples that are nearly completely detached can be grown repeatedly in pBN. Current work is concentrated on developing a method to make in situ pressure measurements in the growth ampoules.

Source record↗
NASA NTRS2008

Silicon germanium semiconductive alloy and method of fabricating same

A silicon germanium (SiGe) semiconductive alloy is grown on a substrate of single crystalline Al.sub.2O.sub.3. A {111} crystal plane of a cubic diamond structure SiGe is grown on the substrate's {0001} C-plane such that a <110> orientation of the cubic diamond structure SiGe is aligned with a <1,0,-1,0> orientation of the {0001} C-plane. A lattice match between the substrate and the SiGe is achieved by using a SiGe composition that is 0.7223 atomic percent silicon and 0.2777 atomic percent germanium.

Park, Yeonjoon↗
NASA NTRS2009

Performance of the THS4302 and the Class V Radiation-Tolerant THS4304-SP Silicon Germanium Wideband Amplifiers at Extreme Temperatures

This report discusses the performance of silicon germanium, wideband gain amplifiers under extreme temperatures. The investigated devices include Texas Instruments THS4304-SP and THS4302 amplifiers. Both chips are manufactured using the BiCom3 process based on silicon germanium technology along with silicon-on-insulator (SOI) buried oxide layers. The THS4304-SP device was chosen because it is a Class V radiation-tolerant (150 kRad, TID silicon), voltage-feedback operational amplifier designed for use in high-speed analog signal applications and is very desirable for NASA missions. It operates with a single 5 V power supply [1]. It comes in a 10-pin ceramic flatpack package, and it provides balanced inputs, low offset voltage and offset current, and high common mode rejection ratio. The fixed-gain THS4302 chip, which comes in a 16-pin leadless package, offers high bandwidth, high slew rate, low noise, and low distortion [2]. Such features have made the amplifier useful in a number of applications such as wideband signal processing, wireless transceivers, intermediate frequency (IF) amplifier, analog-to-digital converter (ADC) preamplifier, digital-to-analog converter (DAC) output buffer, measurement instrumentation, and medical and industrial imaging.

Patterson, Richard L.↗
NASA NTRS2015

Crystal Growth of Germanium-Silicon Alloys on the ISS

A series of Ge(1-x)Si(x) crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. The experiments are part of the investigation "Influence of Containment on the Growth of Silicon-Germanium" (ICESAGE). The primary objective of the research is to determine the influence of containment on the processing-induced defects and impurity incorporation in germanium-silicon alloy crystals. A comparison will be made between crystals grown by the normal and "detached" Bridgman methods and the ground-based float zone technique. Crystals grown without being in contact with a container have superior quality to otherwise similar crystals grown in direct contact with a container, especially with respect to impurity incorporation, formation of dislocations, and residual stress in crystals. "Detached" or "dewetted" Bridgman growth is similar to regular Bridgman growth in that most of the melt is in contact with the crucible wall, but the crystal is separated from the wall by a small gap, typically of the order of 10-100 microns. Long duration reduced gravity is essential to test the proposed theory of detached growth. Detached growth requires the establishment of a meniscus between the crystal and the ampoule wall. This meniscus can exist over a much larger range of processing parameters in microgravity and the meniscus is more stable under microgravity conditions. The plans for the flight experiments will be described.

Volz, M. P.↗
NASA NTRS2018

The Contrast in Outgassing of Germanium Between Shergottites and Nakhlites

Final Paper and not the abstract is attached. Introduction: Germanium is generally thought to follow Si in its geochemical behavior, but little data has existed to rigorously understand the behavior of Ge in the Martian mantle. Germanium is known to be more siderophile than Si, and its partitioning into the martian core has been studied by. Typical abundances in igneous martian meteorites range from 0.5-3 ppm, a larger range than what is observed in terrestrial basalts (1.5 +/- 0.1 ppm). In situ measurements by the MER and MSL rovers have revealed a surprisingly large range in Ge abundances in surface rocks (30-650 ppm), but many igneous rocks and soils are shown to have greater than 30 ppm Ge (the detection limit of the APXS). Recently, reported that shergottite minerals showed a depletion of Ge with increasing fractionation, while nakhlites and chassignites exhibited Ge behavior compatible with closed system igneous differentiation. They interpreted their observations as tentatively indicating volcanic outgassing of Ge from shergottites (but not from nakhlite-chassignites) with recondensation of the Ge vapor into soils and breccias. Recent experimental studies show that Ge is significantly volatile from magmas. In this study, we followed up on those results by analyzing minerals in five nakhlites and five shergottites by laser ablation ICP-MS (LA-ICP-MS). See Attached

Yang, S.↗
DOE OSTI2022

Temperature-dependent charge barrier height of amorphous germanium contact detector

The exploration of germanium (Ge) detectors with amorphous Ge (a-Ge) contacts has drawn attention to the searches for rare-event physics such as dark matter and neutrinoless double-beta decay. The charge barrier height (CBH) of the a-Ge contacts deposited on the detector surface is crucial to suppress the leakage current of the detector in order to achieve a low-energy detection threshold and high-energy resolution. The temperature-dependent CBH of a-Ge contacts for three Ge detectors is analyzed to study the bulk leakage current (BLC) characteristics. The detectors were fabricated at the University of South Dakota using homegrown crystals. The CBH is determined from the BLC when the detectors are operated in the reverse bias mode with a guard-ring structure, which separates the BLC from the surface leakage current (SLC). Here the results show that CBH is temperature dependent. The direct relation of the CBH variation to temperature is related to the barrier inhomogeneities created on the interface of a-Ge and crystalline Ge. The inhomogeneities that occur at the interface were analyzed using the Gaussian distribution model for three detectors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Revealing a Pathway for Low-Temperature Recrystallization in Germanium

Thermally activated annealing in semiconductors faces inherent limitations, such as dopant diffusion. Here, a nonthermal pathway is demonstrated for a complete structural restoration in predamaged germanium via ionization-induced recovery. By combining experiments and modeling, this study reveals that the energy transfer of only 2.4 keV nm −1 from incident ions to target electrons can effectively annihilate pre-existing defects and restore the original crystalline structure at room temperature. Moreover, it is revealed that the irradiation-induced crystalline-to-amorphous (c/a) transformation in Ge is reversible, a phenomenon previously considered unattainable without additional thermal energy imposed during irradiation. For partially damaged Ge, the overall damage fraction decreases exponentially with increasing fluence. Surprisingly, the recovery process in preamorphized Ge starts with defect recovery outside the amorphous layer and a shrinkage of the amorphous thickness. After this initial stage, the remaining damage decreases slowly with increasing fluence, but full restoration of the pristine state is not achieved. These differences in recovery are interpreted in the framework of structural differences in the initial defective layers that affect recovery kinetics. This study provides new insights on reversing the c/a transformation in Ge using highly-ionizing irradiation and has broad implications across materials science, radiation damage mitigation, and fabrication of Ge-based devices.

athermal recovery↗
DOE OSTI2023

Germanium(II) Dithiolene Complexes

The 1 : 2 reaction of the imidazole-based dithiolate (2) with GeCl 2 • dioxane in THF/TMEDA gives 3, a TMEDA-complexed dithiolene-based germylene. Compound 3 is converted to monothiolate-complexed (5) and N-heterocyclic carbene-complexed (7) germanium(II) dithiolene complexes via Lewis base ligand exchange. A bis-dithiolene-based germylene (8), involving a 3c–4e S-Ge-S bond, has also been synthesized through controlled hydrolysis of 7. The bonding nature of 3, 5, and 8 was investigated by both experimental and theoretical methods.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Characterizing hole trap production due to proton irradiation in germanium cross-strip detectors

We present an investigation into the effects of high-energy proton damage on charge trapping in germanium cross-strip detectors with the goal of accomplishing three important measurements. First, we calibrated and characterized the spectral resolution of a spare COSI-balloon detector in order to determine the effects of intrinsic trapping, finding that electron trapping due to impurities dominates over hole trapping in the undamaged detector. Second, we performed two rounds of proton irradiation of the detector in order to quantify, for the first time, the rate at which charge traps are produced by proton irradiation. We find that the product of the hole trap density and cross-sectional area, [nσ] h , follows a linear relationship with the proton fluence, F p , with a slope of (5.4 ± 0.4) x 10 -11 cm/p + . Third, by utilizing our measurements of physical trapping parameters, we performed calibrations which corrected for the effects of trapping and mitigated degradation to the spectral resolution of the detector.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Impacts of Mode Mixity on Controlled Spalling of (100)-Oriented Germanium

Controlled spalling is a technology to prepare single-crystal thin films of semiconductors by fracture with a subsurface crack propagating nearly parallel to the substrate surface. Practical applications require uniform thickness and a smooth surface across the whole film. Both wafer-scale and patterned-stressor-defined small-area spalling of germanium substrates are conducted experimentally and numerically. River line features are observed on spalled surfaces close to lateral edges of the spall, regardless of the spall direction and the size of the spalled area. Three-dimensional finite element method modeling shows the river lines are caused by mixed mode I?+?III loading near the lateral edges of spall and predicts a spall depth variation near the lateral edges of spall due to mixed mode I?+?II loading. The absolute range of river lines increases with lateral size of spall, while the relative range of river lines decreases, consistent with variations in mode mixity.

36 MATERIALS SCIENCE↗