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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Intrinsic property of defective β-Ga 2 O 3 to self-heal under ionizing irradiation

Damage evolution and phase stability in defective β-Ga 2 O 3 and an irradiation-converted γ-Ga 2 O 3 layer have been studied under ionizing irradiation at 300 K. By exploring athermal nonequilibrium processes in β-Ga 2 O 3 , we succeed in identifying a self-healing mechanism that enables recovery pre-existing damage, characterized by a recovery cross-section of ~0.17 nm 2 . Remarkably, this study further demonstrates that the crystallinity of the irradiation-converted γ-Ga 2 O 3 layer improves under ionizing irradiation. More importantly, X-ray diffraction analysis reveals that the highly-strained 𝛾 -phase transforms into a highly-crystalline structure without film disintegration, contrasting to that reported for isochronal annealing at 1000 K. The inelastic thermal spike calculations provide insights into the important effects of energy transfer to electrons in reordering the local atomic arrangement of both defective β- Ga 2 O 3 and 𝛾-Ga 2 O 3 . This behavior suggests a pathway for low-temperature crystallization, offering a promising strategy for fabricating ultrahigh-speed non-volatile memory devices.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Growth and characterization of high-quality Zr doped AlN epilayers

AlN stands out for its remarkable figures of merit for electronic and photonic devices, attributed to its ultrawide bandgap of ∼6.1 eV and an exceptionally high critical field of ∼15 MV/cm. More recently, zirconium (Zr) doped AlN (AlN:Zr) has also been identified as a promising material platform for the exploration of solid-state qubits for quantum information and technology, high performance piezoelectric acoustic wave resonators, and optically triggered ultrafast power switching devices facilitated by optically activating Zr related impurities. Despite the significant potential, the ability for producing AlN:Zr epitaxial structures has yet to be established. In this study, we have achieved AlN:Zr epilayers with a high Zr doping level [NZr] of up to 1020 cm−3 using industrial standard metal-organic chemical vapor deposition growth technique. High crystalline quality of AlN:Zr was confirmed by x-ray diffraction, revealing a narrow full width at half maximum of the (002) rocking curve at 216 arcsec for 1.8 μm thick epilayers deposited on sapphire at [NZr]=1020 cm−3. Zr doping was observed to slightly increase the c-lattice constant to 4.992 Å for AlN:Zr (at [NZr]=1020 cm−3) compared to 4.980 Å for undoped AlN. X-ray photoelectron spectroscopy measurement results verified the substitution of Zr at the Al site (ZrAl). The formation of (ZrAl–VN) complexes, which are predicted to possess all the desired properties required by quantum qubits, was confirmed through optical absorption studies. The realization of high-quality AlN:Zr epilayers significantly broadens the scope of technologically significant device applications for AlN.

36 MATERIALS SCIENCE↗
DOE OSTI2023

PacWave Anchoring and Mooring Study

PacWave, with its location in some of the most energetic waters in the nation and a buildout to support grid-connected devices, is poised to become a leader in field testing of wave energy converters (WECs) at high technology readiness levels. As part of the device deployment and testing protocols at PacWave, the client is responsible for providing all mooring system components, since there are currently no mooring system components specified for PacWave. NREL and PNNL have been tasked with conducting a preliminary analysis of permanent or temporary mooring systems at the PacWave South site. Previous work for this task included a global trade study of mooring systems used for WECs, and a site characterization of PacWave South. This current report will use the results of the previous studies to inform the design of various mooring systems to be installed at PacWave, which will allow cost analyses to be performed to compare the costs of acquisition of these mooring systems and the costs of mooring systems designed specifically for clients' devices.

16 TIDAL AND WAVE POWER↗
DOE OSTI2020

High voltage MOSFET devices and methods of making the devices

A SiC MOSFET device having low specific on resistance is described. The device has N+, P-well and JFET regions extended in one direction (Y-direction) and P+ and source contacts extended in an orthogonal direction (X-direction). The polysilicon gate of the device covers the JFET region and is terminated over the P-well region to minimize electric field at the polysilicon gate edge. In use, current flows vertically from the drain contact at the bottom of the structure into the JFET region and then laterally in the X direction through the accumulation region and through the MOSFET channels into the adjacent N+ region. The current flowing out of the channel then flows along the N+ region in the Y-direction and is collected by the source contacts and the final metal. Methods of making the device are also described.

42 ENGINEERING↗
DOE OSTI2020

Surge-Energy and Overvoltage Ruggedness of P-Gate GaN HEMTs

An essential ruggedness of power devices is the capability of safely withstanding the surge energy. The surge ruggedness of the GaN high-electron-mobility transistor (HEMT), a power transistor with no or minimal avalanche capability, has not been fully understood. This article unveils the comprehensive physics associated with the surge-energy withstand process and the failure mechanisms of p-gate GaN HEMTs. Two commercial p-gate GaN HEMTs with Ohmic- and Schottky-type gate contacts are studied. Two circuits are developed to study the device surge ruggedness: an unclamped inductive switching circuit is first used to identify the withstand dynamics and failure mechanisms, and a clamped inductive switching circuit with a controllable parasitic inductance is then designed to mimic the surge energy in converter-like switching events. The p-gate GaN HEMT is found to withstand the surge energy through a resonant energy transfer between the device capacitance and the load/parasitic inductance rather than a resistive energy dissipation as occurred in the avalanche. If the device resonant voltage goes below zero, the device reversely turns on and the inductor is discharged. The device failure occurs at the transient of peak resonant voltage and is limited by the device overvoltage capability rather than the surge energy, dV/dt , or overvoltage duration. Almost no energy is dissipated in the resonant withstand process and the device failure is dominated by an electric field rather than a thermal runaway. Furthermore, these results provide critical understandings on the ruggedness of GaN HEMTs and important references for their qualifications and applications.

42 ENGINEERING↗
DOE OSTI2021

Controllable Reset Behavior in Domain Wall–Magnetic Tunnel Junction Artificial Neurons for Task-Adaptable Computation

Neuromorphic computing with spintronic devices has been of interest due to the limitations of CMOS-driven von Neumann computing. Domain wall–magnetic tunnel junction (DW-MTJ) devices have been shown to be able to intrinsically capture biological neuron behavior. Edgy-relaxed behavior, where a frequently firing neuron experiences a lower action potential threshold, may provide additional artificial neuronal functionality when executing repeated tasks. In this letter, we demonstrate that this behavior can be implemented in DW-MTJ artificial neurons via three alternative mechanisms: shape anisotropy, magnetic field, and current-driven soft reset. Using micromagnetics and analytical device modeling to classify the Optdigits handwritten digit dataset, we show that edgy-relaxed behavior improves both classification accuracy and classification rate for ordered datasets while sacrificing little to no accuracy for a randomized dataset. This letter establishes methods by which artificial spintronic neurons can be flexibly adapted to datasets.

42 ENGINEERING↗
DOE OSTI2023

Design of Electrostatic Aberration Correctors for Scanning Transmission Electron Microscopy

Abstract In a scanning transmission electron microscope (STEM), producing a high-resolution image generally requires an electron beam focused to the smallest point possible. However, the magnetic lenses used to focus the beam are unavoidably imperfect, introducing aberrations that limit resolution. Modern STEMs overcome this by using hardware aberration correctors comprised of many multipole elements, but these devices are complex, expensive, and can be difficult to tune. We demonstrate a design for an electrostatic phase plate that can act as an aberration corrector. The corrector is comprised of annular segments, each of which is an independent two-terminal device that can apply a constant or ramped phase shift to a portion of the electron beam. We show the improvement in image resolution using an electrostatic corrector. Engineering criteria impose that much of the beam within the probe-forming aperture be blocked by support bars, leading to large probe tails for the corrected probe that sample the specimen beyond the central lobe. We also show how this device can be used to create other STEM beam profiles such as vortex beams and probes with a high degree of phase diversity, which improve information transfer in ptychographic reconstructions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Developing affordable and efficient heating devices for enhanced live cell imaging in confocal microscopy

Temperature control is crucial for live cell imaging, particularly in studies involving plant responses to high ambient temperatures and thermal stress. This study presents the design, development, and testing of two cost-effective heating devices tailored for confocal microscopy applications: an aluminum heat plate and a wireless mini-heater. The aluminum heat plate, engineered to integrate seamlessly with the standard 160 mm × 110 mm microscope stage, supports temperatures up to 36°C, suitable for studies in the range of non-stressful warm temperatures (e.g., 25-27°C forArabidopsis thaliana) and moderate heat stress (e.g., 30-36°C forA. thaliana). We also developed a wireless mini-heater that offers rapid, precise heating directly at the sample slide, with a temperature increase rate over 30 times faster than the heat plate. The wireless heater effectively maintained target temperatures up to 50°C, ideal for investigating severe heat stress and heat shock responses in plants. Both devices performed well in controlled studies, including the real-time analysis of heat shock protein accumulation and stress granule formation inA. thaliana. Our designs are effective and affordable, with total construction costs lower than $300. This accessibility makes them particularly valuable for small laboratories with limited funding. Future improvements could include enhanced heat uniformity, humidity control to mitigate evaporation, and more robust thermal management to minimize focus drift during extended imaging sessions. These modifications would further solidify the utility of our heating devices in live cell imaging, offering researchers reliable, budget-friendly tools for exploring plant thermal biology.

Plant Sciences↗
DOE OSTI2022

Spin injection by spin–charge coupling in proximity induced magnetic graphene

Abstract Within the field of spintronics major efforts are directed towards developing applications for spin-based transport devices made fully out of two-dimensional materials. In this work we present an experimental realization of a spin-valve device where the generation of the spin signal is exclusively attributed to the spin-dependent conductivity of the magnetic graphene resulting from the proximity of an interlayer antiferromagnet, chromium sulfide bromide (CrSBr). We clearly demonstrate that the usage of the conventional air-sensitive 3D magnetic contacts can be fully avoided when graphene/CrSBr heterostructures are employed. Moreover, apart from providing exceptionally long spin relaxation length, the usage of graphene for both generation and transport of the spin allows to automatically avoid the conductivity mismatch between the source and the channel circuits that has to be considered when using conventional low-resistive contacts. Our results address a necessary step in the engineering of spintronic circuitry out of layered materials and precede further developments in the area of complex spin-logic devices. Moreover, we introduce a fabrication procedure where we designed and implemented a recipe for the preparation of electrodes via a damage-free technique that offers an immediate advantage in the fields of air-sensitive and delicate organic materials.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Big Adaptive Rotor Phase I (Final Report)

The Big Adaptive Rotor (BAR) project was initiate by DOE in 2018 with the goal of identifying novel technologies that can enable large (>100m) blades for low specific power (SP) turbines. Five distinct tasks were completed to achieve this goal: 1. Assess trends, impacts, and value of low-SP turbines, 2. Wind turbine blade cost reduction roadmap study, 3. Research and Development (R&D) opportunity screening, 4. Detailed design and analysis, and 5. Low-cost carbon fiber. These tasks were completed by the national lab team consisting of Sandia National Laboratories (SNL), the National Renewable Energy Laboratory (NREL), and Lawrence Berkeley National Laboratory (LBNL). The objective of Task 1 was to assess the historical trends of low-SP of onshore deployments, and to assess the impact and value of low-SP turbines. Analysis under this task showed that there is significant value for low-SP turbines, especially in markets where there is a higher saturation of wind energy on the grid. This has to do with the fact that low-SP turbines have increased capacity factors, and can contribute more reliable energy to the grid, even in lower wind conditions. This bodes well as higher renewable scenarios are likely in the coming years. Task 2 was a detailed analysis on the logistical challenges of deploying very large (>100m) onshore blade. This work was completed by experts at DNV-GL. The report looked at various ways to get around the current transportation constraints which are estimated to be around 75m in length. The report concluded that there are viable solutions to this issue including: segmented blades (which the industry is already pursuing), lighter than air (LTA) transportation, on-site manufacturing, and controlled bending of blades on rail. The final option was recommended for further analysis and study by DOE and the national labs because keeping a single piece blade reduces manufacturing and operations and maintenance (O&M) costs. Task 3 focused on identifying novel concepts that are capable of enabling a cost effective 5MW 206m rotor for onshore deployment. The findings from the first two tasks were considered in the analysis, in that the concepts identified must be able to overcome the transportation logistics challenges. Around 20 concepts were identified and evaluated by experts within the industry. Additionally, science and engineering challenges were identified for each concept. Based on these evaluations six concepts were deemed the most impactful and were selected for further analysis in Task 4. The concepts were: highly flexible rail transportable blades, downwind rotors, distributed aerodynamic control (DAC) devices, inflatable blade, bi-wing blade, and 4/5 bladed rotors. Task 4 conducted detailed design, optimization, and analysis on the selected BAR concepts. A modeling gaps analysis was conducted, and modeling improvements were implemented that allowed for the study and design of the novel concepts. The BAR team established a set of baseline designs by which to compare the selected designs through a technoeconomic analysis. It was found that the highly flexible rail transportable blade, the downwind rotor, and the DAC devices have the most promise to deliver the BAR targets. A Phase II for BAR has been proposed to further mature these concepts and address the open science and engineering challenges identified in Task 3. Task 5 conducted research on optimized carbon fiber materials that were used throughout the BAR Phase I project. Overall, the BAR project has identified low-SP turbines as important to continued LCOE reductions for onshore turbines. Furthermore, the project has identified viable solutions to the technical and logistical challenges to realizing these goals. The most promising technologies that were identified in Phase I of the project will be further matured and de-risked in Phase II of the BAR project.

17 WIND ENERGY↗
DOE OSTI2026

Probing the Nanoscale Excitonic Landscape and Confinement of Excitons in Gated Monolayer Semiconductors

Engineering and probing excitonic properties at the nanoscale remains a central challenge in quantum photonics and optoelectronics. While exciton confinement via electrical control and strain engineering has been demonstrated in 2D semiconductors, substantial nanoscale heterogeneity limits the scalability of 2D quantum photonic device architectures. Here, in this work, we use cathodoluminescence spectroscopy to probe the excitonic landscape of monolayer WS 2 under electrostatic gating. Exploiting the high spatial resolution of the converged electron beam, we resolve a homojunction arising between gated and ungated regions. Moreover, we reveal an exciton confinement channel arising from an unconventional doping mechanism driven by the interplay between the electron beam and the applied gate fields. These findings offer new insights into the optoelectronic behavior of monolayer semiconductors under the combined influence of electron-beam excitation and electrostatic gating. Our approach provides a pathway for exciton manipulation at the nanoscale and opens opportunities for controlling quantum-confined exciton transport in 2D materials.

2D materials↗
DOE OSTI2024

3D‐Mapping and Manipulation of Photocurrent in an Optoelectronic Diamond Device

Abstract Establishing connections between material impurities and charge transport properties in emerging electronic and quantum materials, such as wide‐bandgap semiconductors, demands new diagnostic methods tailored to these unique systems. Many such materials host optically‐active defect centers which offer a powerful in situ characterization system, but one that typically relies on the weak spin‐electric field coupling to measure electronic phenomena. In this work, charge‐state sensitive optical microscopy is combined with photoelectric detection of an array of nitrogen‐vacancy (NV) centers to directly image the flow of charge carriers inside a diamond optoelectronic device, in 3D and with temporal resolution. Optical control is used to change the charge state of background impurities inside the diamond on‐demand, resulting in drastically different current flow such as filamentary channels nucleating from specific, defective regions of the device. Conducting channels that control carrier flow, key steps toward optically reconfigurable, wide‐bandgap optoelectronics are then engineered using light. This work might be extended to probe other wide‐bandgap semiconductors (SiC, GaN) relevant to present and emerging electronic and quantum technologies.

Wood, Alexander A.↗
DOE OSTI2024

Atomistic Probing of Defect-Engineered 2H-MoTe 2 Monolayers

Point defects dictate various physical, chemical, and optoelectronic properties of two-dimensional (2D) materials, and therefore, a rudimentary understanding of the formation and spatial distribution of point defects is a key to advancement in 2D material-based nanotechnology. In this work, we performed the demonstration to directly probe the point defects in 2H-MoTe 2 monolayers that are tactically exposed to (i) 200 °C-vacuum-annealing and (ii) 532 nm-laser-illumination; and accordingly, we utilize a deep learning algorithm to classify and quantify the generated point defects. We discovered that tellurium-related defects are mainly generated in both 2H-MoTe 2 samples; but interestingly, 200 °C-vacuum-annealing and 532 nm-laser-illumination modulate a strong n-type and strong p-type 2H-MoTe 2 , respectively. While 200 °C-vacuum-annealing generates tellurium vacancies or tellurium adatoms, 532 nm-laser-illumination prompts oxygen atoms to be adsorbed/chemisorbed at tellurium vacancies, giving rise to the p-type characteristic. This work significantly advances the current understanding of point defect engineering in 2H-MoTe 2 monolayers and other 2D materials, which is critical for developing nanoscale devices with desired functionality.

2H-MoTe 2↗
DOE OSTI2020

Multi-objective Optimization Paradigm for Toroidal Inductors with Spatially Tuned Permeability

Spatially tuning core permeability of an electromagnetic device enables superior performance. A permeability profile can be heuristically selected to improve the flux distribution in a device with a given geometry, but in order to fully leverage the capacity of spatial dependent permeability engineering, the geometry and the permeability should be optimized simultaneously. The work herein presented sets forth a multi-physics design optimization paradigm that includes the permeability profile tuning in the context of an inductor design. This approach enables the determination of Pareto optimal fronts consisting of a set of optimal solutions against competing objectives (e.g. mass and loss) under imposed constraints. To this end, analytical solutions of the heat transfer and electromagnetic formulations are derived for toroidal inductors. The software implemented in Matlab 2018b is available online as an attachment to this paper.

42 ENGINEERING↗
DOE OSTI2020

Ultimate Suppression of Thermal Transport in Amorphous Silicon Nitride by Phononic Nanostructure.

Engineering the thermal conductivity of amorphous materials is highly essential for the thermal management of future electronic devices. Here, we demonstrate the impact of ultrafine nanostructuring on the thermal conductivity reduction of amorphous silicon nitride (a-Si3N4) thin films, in which the thermal transport is inherently impeded by the atomic disorders. Ultrafine nanostructuring with feature sizes below 20 nm allows us to fully suppress contribution of the propagating vibrational modes (propagons), leaving only the diffusive vibrational modes (diffusons) to contribute to thermal transport in a-Si3N4. A combination of the phonon-gas kinetics model and the Allen-Feldmann theory reproduced the measured results without any fitting parameters. The thermal conductivity reduction was explained as extremely strong diffusive boundary scattering of both propagons and diffusIons. These findings give rise to substantial tunability of thermal conductivity of amorphous materials, which enables us to provide better thermal solutions in microelectronic devices.

Tambo, Naoki↗
DOE OSTI2021

SSP Personality Programmer

The Personality Programmer software is used as means for entities to configure, deploy, and redeploy SSP devices. SAND2020-14337 O Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Hunt, TannerR.↗
DOE OSTI2023

High Efficiency Multijunction Devices: Solar Cells, Thermophotovoltaics, LEDs

High-efficiency III-V multijunction solar cells require multiple alloys with optimal bandgaps and excellent material quality. However, many useful alloys are lattice-mismatched to available substrates, and require strain-engineering tricks to enable efficient use. To this extent, we have developed low-dislocation density metamorphic material and optically-thick stress-balanced superlattices, enabling access to a wide variety of III-V alloys. Combined with transparent tunnel junctions, these components allow optimizing multijunction devices for a variety of applications. We have designed multijunction cells for the G173G-terrestrial and AM0-space spectra with record 39.5% and 34.2% efficiency, respectively, and also thermophotovoltaic cells for blackbody spectra that reach over 40% TPV-efficiency. Finally, using these PV components, we demonstrate a multijunction LED with high quantum efficiency.

high-efficiency↗