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At least 1,783 records · Page 99
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on ScMnGe by Materials Project

ScMnGe crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Sc is bonded in a 5-coordinate geometry to five Ge atoms. There are one shorter (2.74 Å) and four longer (2.77 Å) Sc–Ge bond lengths. Mn is bonded to four Ge atoms to form a mixture of distorted edge and corner-sharing MnGe4 tetrahedra. There are two shorter (2.46 Å) and two longer (2.61 Å) Mn–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to three equivalent Sc and six equivalent Mn atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to six equivalent Sc and three equivalent Mn atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg5Ge by Materials Project

Mg5Ge crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are five inequivalent Mg sites. In the first Mg site, Mg is bonded to eight Mg and four equivalent Ge atoms to form distorted MgMg8Ge4 cuboctahedra that share corners with eighteen MgMg8Ge4 cuboctahedra, edges with six MgMg10Ge2 cuboctahedra, and faces with fourteen MgMg8Ge4 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.01–3.17 Å. All Mg–Ge bond lengths are 3.12 Å. In the second Mg site, Mg is bonded to ten Mg and two equivalent Ge atoms to form a mixture of distorted edge, corner, and face-sharing MgMg10Ge2 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.10–3.17 Å. Both Mg–Ge bond lengths are 3.09 Å. In the third Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.16–3.18 Å. In the fourth Mg site, Mg is bonded to six Mg and two equivalent Ge atoms to form distorted MgMg6Ge2 cuboctahedra that share corners with twelve MgMg10Ge2 cuboctahedra, edges with ten MgMg10Ge2 cuboctahedra, and faces with ten MgMg8Ge4 cuboctahedra. Both Mg–Ge bond lengths are 3.03 Å. In the fifth Mg site, Mg is bonded in a 12-coordinate geometry to six Mg and two equivalent Ge atoms. Both Mg–Ge bond lengths are 2.97 Å. Ge is bonded in a 10-coordinate geometry to ten Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge7O16 by Materials Project

Ge7O16 crystallizes in the cubic P-43m space group. The structure is three-dimensional. there are two inequivalent Ge sites. In the first Ge site, Ge is bonded to four equivalent O atoms to form corner-sharing GeO4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. All Ge–O bond lengths are 1.78 Å. In the second Ge site, Ge is bonded to six O atoms to form GeO6 octahedra that share corners with three equivalent GeO4 tetrahedra and edges with three equivalent GeO6 octahedra. There is three shorter (1.85 Å) and three longer (1.99 Å) Ge–O bond length. There are two inequivalent O sites. In the first O site, O is bonded in a distorted trigonal non-coplanar geometry to three equivalent Ge atoms. In the second O site, O is bonded in a bent 120 degrees geometry to two Ge atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YAgGe by Materials Project

YAgGe crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Y is bonded in a 11-coordinate geometry to six equivalent Ag and five Ge atoms. There are two shorter (3.20 Å) and four longer (3.35 Å) Y–Ag bond lengths. There are one shorter (2.99 Å) and four longer (3.02 Å) Y–Ge bond lengths. Ag is bonded in a 12-coordinate geometry to six equivalent Y, two equivalent Ag, and four Ge atoms. Both Ag–Ag bond lengths are 3.16 Å. There are two shorter (2.75 Å) and two longer (2.78 Å) Ag–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to three equivalent Y and six equivalent Ag atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to six equivalent Y and three equivalent Ag atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Fe3Ge2 by Materials Project

Fe3Ge2 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. there are two inequivalent Fe sites. In the first Fe site, Fe is bonded in a 11-coordinate geometry to five Fe and six Ge atoms. There are a spread of Fe–Fe bond distances ranging from 2.41–2.63 Å. There are three shorter (2.61 Å) and three longer (2.63 Å) Fe–Ge bond lengths. In the second Fe site, Fe is bonded to six equivalent Fe and five Ge atoms to form a mixture of distorted corner and face-sharing FeFe6Ge5 trigonal bipyramids. There are three shorter (2.31 Å) and two longer (2.46 Å) Fe–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 8-coordinate geometry to eight Fe atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to nine Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiDyGe by Materials Project

LiDyGe crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Li is bonded to four Ge atoms to form a mixture of distorted edge and corner-sharing LiGe4 tetrahedra. There are two shorter (2.70 Å) and two longer (2.77 Å) Li–Ge bond lengths. Dy is bonded in a 5-coordinate geometry to five Ge atoms. There are one shorter (2.97 Å) and four longer (3.01 Å) Dy–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to six equivalent Li and three equivalent Dy atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to three equivalent Li and six equivalent Dy atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ScGeRh by Materials Project

ScRhGe crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Sc is bonded in a 11-coordinate geometry to six equivalent Rh and five Ge atoms. There are two shorter (2.97 Å) and four longer (3.11 Å) Sc–Rh bond lengths. There are four shorter (2.79 Å) and one longer (2.81 Å) Sc–Ge bond lengths. Rh is bonded in a 12-coordinate geometry to six equivalent Sc, two equivalent Rh, and four Ge atoms. Both Rh–Rh bond lengths are 2.86 Å. There are two shorter (2.53 Å) and two longer (2.59 Å) Rh–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to six equivalent Sc and three equivalent Rh atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to three equivalent Sc and six equivalent Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba2Ge4Pd5 by Materials Project

Ba2Pd5Ge4 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. Ba is bonded in a 7-coordinate geometry to five Pd and two equivalent Ge atoms. There are a spread of Ba–Pd bond distances ranging from 3.30–3.51 Å. Both Ba–Ge bond lengths are 3.41 Å. There are three inequivalent Pd sites. In the first Pd site, Pd is bonded in a 6-coordinate geometry to two equivalent Ba and four equivalent Ge atoms. All Pd–Ge bond lengths are 2.61 Å. In the second Pd site, Pd is bonded in a 6-coordinate geometry to two equivalent Ba and four equivalent Ge atoms. There are two shorter (2.52 Å) and two longer (2.59 Å) Pd–Ge bond lengths. In the third Pd site, Pd is bonded in a 4-coordinate geometry to two equivalent Ba and four equivalent Ge atoms. There are two shorter (2.50 Å) and two longer (2.58 Å) Pd–Ge bond lengths. Ge is bonded in a 6-coordinate geometry to one Ba and five Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr2Al3Ge by Materials Project

Pr2Al3Ge is hexagonal omega structure-derived structured and crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. there are two inequivalent Pr sites. In the first Pr site, Pr is bonded to ten Al and two equivalent Ge atoms to form a mixture of face and edge-sharing PrAl10Ge2 cuboctahedra. There are four shorter (3.32 Å) and six longer (3.33 Å) Pr–Al bond lengths. Both Pr–Ge bond lengths are 3.32 Å. In the second Pr site, Pr is bonded to eight Al and four equivalent Ge atoms to form a mixture of face and edge-sharing PrAl8Ge4 cuboctahedra. There are two shorter (3.31 Å) and six longer (3.32 Å) Pr–Al bond lengths. All Pr–Ge bond lengths are 3.31 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 9-coordinate geometry to six Pr and three Al atoms. All Al–Al bond lengths are 2.52 Å. In the second Al site, Al is bonded in a distorted bent 120 degrees geometry to six Pr, one Al, and two equivalent Ge atoms. Both Al–Ge bond lengths are 2.52 Å. In the third Al site, Al is bonded in a distorted single-bond geometry to six Pr, two equivalent Al, and one Ge atom. The Al–Ge bond length is 2.50 Å. Ge is bonded in a distorted trigonal planar geometry to six Pr and three Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn2Co2SiGe by Materials Project

Mn2Co2GeSi crystallizes in the orthorhombic Pmc2_1 space group. The structure is three-dimensional. there are two inequivalent Mn sites. In the first Mn site, Mn is bonded in a 5-coordinate geometry to six Co, four equivalent Ge, and one Si atom. There are a spread of Mn–Co bond distances ranging from 2.70–2.85 Å. There are two shorter (2.56 Å) and two longer (2.60 Å) Mn–Ge bond lengths. The Mn–Si bond length is 2.52 Å. In the second Mn site, Mn is bonded in a 11-coordinate geometry to six Co, one Ge, and four equivalent Si atoms. There are a spread of Mn–Co bond distances ranging from 2.65–2.78 Å. The Mn–Ge bond length is 2.57 Å. There are two shorter (2.54 Å) and two longer (2.57 Å) Mn–Si bond lengths. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 12-coordinate geometry to six Mn, two equivalent Co, two equivalent Ge, and two equivalent Si atoms. Both Co–Co bond lengths are 2.74 Å. Both Co–Ge bond lengths are 2.32 Å. There are one shorter (2.25 Å) and one longer (2.26 Å) Co–Si bond lengths. In the second Co site, Co is bonded in a 12-coordinate geometry to six Mn, two equivalent Co, two equivalent Ge, and two equivalent Si atoms. There are one shorter (2.35 Å) and one longer (2.37 Å) Co–Ge bond lengths. Both Co–Si bond lengths are 2.26 Å. Ge is bonded in a 9-coordinate geometry to five Mn and four Co atoms. Si is bonded in a 9-coordinate geometry to five Mn and four Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba4Zn11Ge12 by Materials Project

Ba4Zn11Ge12 crystallizes in the cubic Pm-3n space group. The structure is three-dimensional. there are two inequivalent Ba sites. In the first Ba site, Ba is bonded in a 12-coordinate geometry to eight equivalent Ge atoms. All Ba–Ge bond lengths are 3.61 Å. In the second Ba site, Ba is bonded in a 8-coordinate geometry to eight equivalent Zn and twelve equivalent Ge atoms. All Ba–Zn bond lengths are 3.43 Å. All Ba–Ge bond lengths are 3.63 Å. There are two inequivalent Zn sites. In the first Zn site, Zn is bonded in a tetrahedral geometry to four equivalent Ge atoms. All Zn–Ge bond lengths are 2.51 Å. In the second Zn site, Zn is bonded in a 3-coordinate geometry to one Ba and three equivalent Ge atoms. All Zn–Ge bond lengths are 2.56 Å. Ge is bonded in a 3-coordinate geometry to three Ba and three Zn atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LuAgGe by Materials Project

LuAgGe crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Lu is bonded in a 11-coordinate geometry to six equivalent Ag and five Ge atoms. There are two shorter (3.14 Å) and four longer (3.30 Å) Lu–Ag bond lengths. There are one shorter (2.94 Å) and four longer (2.98 Å) Lu–Ge bond lengths. Ag is bonded in a 12-coordinate geometry to six equivalent Lu, two equivalent Ag, and four Ge atoms. Both Ag–Ag bond lengths are 3.13 Å. There are two shorter (2.69 Å) and two longer (2.74 Å) Ag–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to three equivalent Lu and six equivalent Ag atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to six equivalent Lu and three equivalent Ag atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Spinning the Facts against Genetically Engineered Foods?

A signaling game is developed in order to derive the equilibrium conditions under which special interest groups (SIGs) involved in the controversial debate over genetically engineered (GE) foods have the incentive to truthfully reveal their information or spin facts regarding the health impact of GE foods. Consumers can choose to inspect information provided by SIGs at a cost. The risk of spinning facts is much higher for pro-GE groups, because if it turns out that a certain GE food is unsafe, the penalty will be severe. However, anti-GE groups can still spin facts at low risk even if consumers choose to inspect. This helps explain why some pro-GE groups, particularly the biotech industry, tend to remain silent. Revealing information regarding the safety of GE foods could be counterproductive given pre-existing public skepticism. Consumers may not make “better” decisions with more information provided because more information increases their inspection costs. When it is costlier for consumers to inspect, it is more likely that anti-GE groups will continue to spin facts about the negative health impact of GE foods.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Uncooled GeSn MWIR Photodetectors Using Fully Relaxed Thin Triple‐Step Buffer

GeSn photodetectors monolithically grown on Ge virtual substrates demonstrate mid-wave infrared (MWIR) detection at room temperature. The lattice mismatch between GeSn and Ge causes dislocations and compressive strain, creating leakage pathways and unwanted indirect band transitions. Designed thin Ge 0.91 Sn 0.09 triple-step buffer layers of ≈175 nm total thickness reduce dislocations and enable full relaxation, showing 100% lattice relaxation and smooth surface roughness of 0.83 nm with shorter auto-correlation length in surface morphology compared to single-step buffers. Ge 1-x Sn x photodetectors (x = 0.09, 0.12, and 0.15) on triple-step buffers with n-i-p configurations achieve lattice strain relaxations of 99%, 88%, and 80%, respectively. Ge 0.91 Sn 0.09 and Ge 0.88 Sn 0.12 show gradual variation in auto-correlation amplitude, while Ge 0.85 Sn 0.15 shows an increase due to lattice mismatch. Shockley–Read–Hall recombination current dominates at low reverse bias due to mismatch-induced dislocations, while band-to-band tunneling current dominates at higher reverse bias due to narrowing bandgap under strong electric fields. Here, the photodetectors show extended spectral response with increasing Sn composition of i-GeSn active layer sandwiched by barriers. Ge 0.88 Sn 0.12 and Ge 0.85 Sn 0.15 exhibit extended wavelength cut-offs of 3.12 and 3.27 µm at room temperature, demonstrating significant potential for silicon-based MWIR applications.

GeSn↗
DOE OSTI2023

Dangling Bonds as Possible Contributors to Charge Noise in Silicon and Silicon–Germanium Quantum Dot Qubits

Spin qubits based on Si and Si 1–x Ge x quantum dot architectures exhibit among the best coherence times of competing quantum computing technologies, yet they still suffer from charge noise that limit their qubit gate fidelities. Identifying the origins of these charge fluctuations is therefore a critical step toward improving Si quantum-dot-based qubits. Here, we use hybrid functional calculations to investigate possible atomistic sources of charge noise, focusing on charge trapping at Si and Ge dangling bonds (DBs). We evaluate the role of global and local environment in the defect levels associated with DBs in Si, Ge, and Si 1–x Ge x alloys, and consider their trapping and excitation energies within the framework of configuration coordinate diagrams. We additionally consider the influence of strain and oxidation in charge-trapping energetics by analyzing Si and GeSi DBs in SiO 2 and strained Si layers in typical Si 1–x Ge x quantum dot heterostructures. Our results identify that Ge dangling bonds are more problematic charge-trapping centers both in typical Si 1–x Ge x alloys and associated oxidation layers, and they may be exacerbated by compositional inhomogeneities. In conclusion, these results suggest the importance of alloy homogeneity and possible passivation schemes for DBs in Si-based quantum dot qubits and are of general relevance to mitigating possible trap levels in other Si, Ge, and Si 1–x Ge x -based metal-oxide-semiconductor stacks and related devices.

36 MATERIALS SCIENCE↗
DOE OSTI2024

GeSn-on-GaAs with photoconductive carrier lifetime >400 ns: role of substrate orientation and atomistic simulation

Group IV GeSn quantum material finds application in electronics and silicon-compatible photonics. Synthesizing these materials with low defect density and high carrier lifetime is a potential challenge due to lattice mismatch induced defects and tin segregation at higher growth temperature. Recent advancements in the growth of these GeSn materials on Si, Ge, GaAs, and with substrate orientations, demonstrated different properties using epitaxial and chemical deposition methods. This article addresses the effect of GaAs substrate orientation and misorientation on the materials’ properties and carrier lifetimes in epitaxial Ge 0.94 Sn 0.06 layers. With starting GaAs substrates of (100)/2°, (100)/6°, (110) and (111)A orientations, Ge 0.94 Sn 0.06 epitaxial layers were grown with an intermediate Ge buffer layer by molecular beam epitaxy and analyzed by several analytical tools. X-ray analysis displayed good crystalline quality, and Raman spectroscopy measurements showed blue shifts in phonon wavenumber due to biaxial compressive strain in Ge 0.94 Sn 0.06 epilayers. Cross-sectional transmission electron microscopy analysis confirmed the defect-free heterointerface of Ge 0.94 Sn 0.06 /Ge/GaAs heterostructure. Minority carrier lifetimes of the unintentionally doped n-type Ge 0.94 Sn 0.06 epilayers displayed photoconductive carrier lifetimes of >400 ns on (100)/6°, 319 ns on (100)/2°, and 434 ns on (110) GaAs substrate at 1500 nm excitation wavelength. On the other hand, Ge 0.94 Sn 0.06 layer showed poor carrier lifetime on (111)A GaAs substrate. The observed differences in carrier lifetimes were correlated with the formation energy of the Ge on (100)/6° and (100)/2° GaAs heterointerface using Stillinger–Weber interatomic potential model-based atomistic simulation with different heterointerfacial bonding by Synopsys QuantumATK tool. Total energy computation of 6280-atom Ge/GaAs supercell on (100)/6° leads to lower formation energy than (100)/2°, making it more thermodynamically stable. Hence, the growth of the GeSn/III–V material system using misoriented (100) substrates that are more thermodynamically stable will enhance the performances of optoelectronic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Strain-Driven Evolution of Structural and Carrier Recombination Dynamics in Germanium

Strain engineering in group-IV semiconductors, in particular germanium (Ge), offers a promising route for advancing next-generation optoelectronic device performance. High minority carrier lifetime serves as a direct indicator of superior material quality and device efficiency. Several factors govern the minority carrier lifetime in both strained Ge and strained GeSn, such as strain level, epilayer thickness, defects, surface roughness, and Sn alloying. In this study, the impact of biaxial strain on effective minority carrier lifetimes of tensile-strained Ge (0% ..epsilon..-Ge/Al?As, 0.78% ..epsilon..-Ge/In0.115?Ga0.885?As, and 0.93% ..epsilon..-Ge/In0.16?Ga0.84?As) and compressively strained GeSn (-0.53% c-Ge0.97?Sn0.03/Al?As) epilayers, grown by molecular beam epitaxy, was experimentally investigated via the microwave-reflection photoconductive decay (..mu..-PCD) technique as a simultaneous function of thickness and strain. The structural and strain-relaxation properties were analyzed by high-resolution x-ray diffraction and Raman spectroscopy, while surface morphology analysis using atomic force microscopy provided insights into the surface roughness of strained Ge-based epilayers. Defect characterization by cross-section transmission electron microscopy revealed superior crystalline quality of ..epsilon..-Ge in one epilayer, while twin boundary formation was observed in the other. We investigated the carrier recombination dynamics in epitaxially strained Ge by extracting the bulk recombination lifetime and surface recombination velocity using the thickness-dependent minority carrier lifetime. High effective minority carrier lifetimes of approximately 60-340 ns were achieved at high strain levels with minimal dependence on the thickness of the strained Ge-based epilayers by means of the ..mu..-PCD technique. Minority carrier lifetimes in Ge-based epilayers exhibit a quadratic dependence on the biaxial strain, ranging from -0.88% (compressive) to +1.6% (tensile). The analysis of the carrier recombination dynamics in strained Ge-based heterostructures offers a pathway to designing group-IV based optoelectronic devices.

36 MATERIALS SCIENCE↗
NASA NTRS2015

Germanium Enrichments in Sedimentary Rocks in Gale Crater, Mars: Constraining the Timing of Alteration and Character of the Protolith

Rocks enriched in Ge have been discovered in Gale Crater, Mars, by the Alpha-particle X-ray spectrometer (APXS) on the Mars Science Lab (MSL) rover, Curiosity. The Ge concentrations in Gale Crater (commonly >50 ppm) are remarkably high in comparison to Earth, where Ge ranges from 0.5-4.0 ppm in igneous rocks and 0.2-3.3 ppm in siliciclastic sediment. Primary meteoritic input is not likely the source of high Ge because Ge/Ni in chondrites (approx.0.003) and irons (<0.04) is lower than in Gale rocks (0.08-0.2). Earth studies show Ge is a useful geochemical tracer because it is coherent with Si during magmatic processes and Ge/Si varies less than 20% in basalts. Ge and Si fractionate during soil/regolith weathering, with Ge preferentially sequestered in clays. Ge is also concentrated in Cu- and Zn-rich hydrothermal sulfide deposits and Fe- and Mnrich oxide deposits. Other fluid-mobile elements (K, Zn, Cl, Br, S) are also enriched at Gale and further constrain aqueous alteration processes. Here, we interpret the sediment alteration history and present a possible model for Ge enrichments at Gale involving fluid alteration of the protolith.

Berger, J. A.↗