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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Thermal design analysis for SuperTruck II lithium-titanate battery pack

Here, this paper presents a systematic thermal management analysis for a new lithium-titanate-oxide battery pack to be installed in a SuperTruck II, Class 8 hybrid truck. The authors investigate the feasibility of mounting the battery pack inside the vehicle and air-cooling it with fans supplying conditioned air from the cabin. Moreover, the cells within each module are to be immersed in a heat-transfer fluid to improve temperature homogeneity. A multi-stage thermal analysis is performed to ensure adequate thermal regulation of the battery under the proposed design, considering installation and operational constraints. The authors perform thermal and electrical characterization tests on a single cell. Results inform the development of computational fluid dynamics models of the cells, modules, and pack. Module-level analysis shows that the cell temperatures can be maintained below their upper operational limit of 55 °C with module wall-to-air heat transfer coefficients between 10 and 20 Wm -2 K -1 . Pack-level analysis of distinct configurations determines effective airflow paths for adequate heat transfer and delivers a final battery pack design that achieves sufficient cooling and temperature uniformity. A reduced-order electrothermal model is developed to rapidly predict the transient battery performance and to develop a temperature control strategy.

25 ENERGY STORAGE↗
DOE OSTI2024

Demonstrating the β-Ga 2 O 3 Schottky diodes for alpha radiation detection

Schottky barrier diodes were fabricated on (001) monoclinic β-Ga 2 O 3 wafers with low doped epitaxial layers of 7.0 × 10 15 cm −3 . Circular Ni Schottky contacts with area 2 mm 2 were deposited by electron beam evaporation. Devices were characterized electrically by performing forward and reverse current-voltage sweeps with a range of −100 V–2 V, as well as capacitance-voltage sweeps to −30 V. The breakdown voltage was also determined to be −180 V for the devices. Experiments measuring the electrical response from incident X-ray radiation was performed. A response time to X-ray radiation of less than 1 s was recorded and a decay time of approximately 2 s after removing X-ray source, which primarily attribute to X-ray switching on and off time. Energy spectra of alpha particles from a 0.9 μCi 241 Am button source was collected at various voltage biases using devices with the lowest measured leakage current while reverse biased. The total count rate was observed to increase linearly with increasing device bias. In conclusion, the peak channel number was observed to increase with increasing bias with the best resolution of 9.5% at −100 V reverse bias.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Anion diffusion in two-dimensional halide perovskites

Commercialization of halide perovskites in the semiconductor industry is hindered by their short-term stability. The instability of perovskites is closely interlinked with ionic diffusion. Historically, attempts to study diffusion in 2D perovskites mostly utilized electrical characterizations, but these characterizations pose a challenge in deconvoluting the impact of device architecture, interlayers, and ionic species. In this Perspective, we focus our attention on simple optical characterizations employed in the literature to investigate halide diffusion in 2D perovskites using lateral and vertical heterostructure platforms. We review the various synthesis techniques used for fabrication of halide perovskite heterostructures and discuss the qualitative and quantitative diffusion studies performed using these platforms. We discuss the numerical methods used to validate and supplement the experimental halide diffusion kinetics. Finally, we highlight the need to conduct further research on the impact of device operating conditions, lattice structure, and vacancy concentration on halide diffusion. Through this Perspective, we aim to emphasize the need of developing a comprehensive understanding of halide diffusion in perovskites for their successful deployment in optoelectronics.

36 MATERIALS SCIENCE↗
DOE OSTI2023

All-epitaxial resonant cavity enhanced long-wave infrared detectors for focal plane arrays

Here, we demonstrate a monolithic all-epitaxial resonant-cavity architecture for long-wave infrared photodetectors with substrate-side illumination. An nBn detector with an ultra-thin (t ≈ 350 nm) absorber layer is integrated into a leaky resonant cavity, formed using semitransparent highly doped (n⁺⁺) epitaxial layers, and aligned to the anti-node of the cavity’s standing wave. The devices are characterized electrically and optically and demonstrate an external quantum efficiency of 25% at T ¼ 180 K in an architecture compatible with focal plane array configurations.

42 ENGINEERING↗
DOE OSTI2025

Field-dependent carrier transport in implanted isolation region of GaN lateral power devices

Among GaN lateral power devices, with proper E-field management, the breakdown occurs in the device isolation region rather than the active region. In this paper, we investigate field-dependent carrier transport in the isolation structures. Isolation test structures with variations in buffer doping, un-intentionally doped (UID) GaN thickness, and implantation conditions were fabricated. Electrical characterization was performed over a wide range of voltage and temperature. With varying UID GaN thickness and buffer doping, the leakage current and breakdown characteristics remain the same for a specific implantation condition, indicating that the leakage conduction and breakdown are governed by the implanted GaN region. Analysis of the temperature-dependent I–V reveals that carrier transport in the implanted GaN can be well explained by hopping conduction, involving three distinctive regions of operation depending on the E-field. At low E-field, carrier transport is ohmic, consistent with variable range hopping, driven by thermal activation. At medium E-field, a field enhanced thermally activated hopping is observed, following σ ∼ σ(T)exp(E). At high E-field, activation-less hopping is visible, following σ ∼ exp(−1/E), which occurs above a critical E-field limited by localization length.

Sadek, Mansura (ORCID:0000000322588338)↗
DOE OSTI2025

Aging studies on chemical vapor deposition and mechanically exfoliated molybdenum disulfide flakes heated in ambient air

The structural integrity of atomically thin two-dimensional molybdenum disulfide (MoS 2 ) is crucial for high-temperature applications, including nanoelectronics and optoelectronics. This study explores the structural stability and electrical performance, under extended thermal exposure in air, of MoS 2 flakes synthesized via chemical vapor deposition (CVD) and mechanical exfoliation. The MoS 2 flakes, both CVD-grown and mechanically exfoliated, were subjected to heating at 200 °C with a relative humidity of 60(±5)% for a prolonged period and investigated with atomic force microscopy and Raman spectroscopy. This study shows that CVD-grown flakes developed noticeable cracks after prolonged heating, whereas mechanically exfoliated flakes mostly retained their structural integrity. Also, both types of flakes showed a decrease in layer thickness and lateral size over time, with mechanically exfoliated flakes exhibiting a comparatively smaller reduction in substrate coverage area. In addition, MoS 2 -based two-terminal devices were subjected to heating at 150 °C for approximately 1100 h, and their electrical characterization revealed a steady rise in current during constant voltage (5 V) conditions. This study enhances our understanding of MoS 2 stability and provides guidance for improving the reliability of MoS 2 -based devices in high-temperature electronic applications.

2D materials↗
DOE OSTI2023

Electrical performances of pre-production staves for the ATLAS ITk Strip Detector Upgrade

The ATLAS experiment is currently preparing for an upgrade of the inner tracking detector for the High-Luminosity LHC. The new tracker, ITk, employs an all-silicon detector with outer strip layers. The building block of the ITk strip barrel is the stave which consists of a low-mass support structure hosting the common electrical, optical and cooling services as well as 28 silicon modules. In this contribution, we outline the challenging aspects of the stave pre-production testing phase at Brookhaven National Laboratory. Here, the electrical characterization of these staves, hosting the final design of all ASICs, will be discussed in detail.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Production and testing of the powerboard for ATLAS ITk Strip barrel modules

The upgrade of the ATLAS ITk strips detector for HL-LHC will employ a custom PCB (powerboard) for on-module DC-DC conversion, HV switching, and monitoring. Production of about 14100 of such PCBs with high reliability is a big challenge. In this paper we will present the production procedure and quality control (QC) testing system for the powerboards to be installed on ITk Strip barrel modules. During production, about 150 powerboards will be produced every week. Each powerboard will need to pass QC tests before they are assembled to module. The QC tests include thermal cycling between -35 °C and 40 °C, soak test (continuous running of DC-DC converter at high load at 20 °C), and basic functionality and characterization electrical tests of the low voltage (LV), high voltage (HV), and monitoring functions of the powerboard. A custom QC test system is described, which is based on a reusable PCB (active board) with all testing circuits, a one-time powerboard carrier card, and a Z-turn SoC board which hosts and runs the testing program. The production procedure and QC test system has been tested with 400 powerboards during pre-production, and the system has been proven ready for production with the desired testing program, speed, safety, and cost. Performance and typical failures of powerboards observed during the QC test of pre-production powerboards is also presented.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Fluxbranes, generalized symmetries, and Verlinde’s metastable monopole

The stringy realization of generalized symmetry operators involves wrapping “branes at infinity”. We argue that in the case of continuous (as opposed to discrete) symmetries, the appropriate objects are fluxbranes. We use this perspective to revisit the phase structure of Verlinde’s monopole, a proposed particle satisfies the Bogomol’nyi-Prasad-Sommerfield (BPS) condition when gravity is decoupled, but is non-BPS and metastable when gravity is switched on. Geometrically, this monopole is obtained from branes wrapped on locally stable but globally trivial cycles of a compactification geometry. The fluxbrane picture allows us to characterize electric (respectively magnetic) confinement (respectively screening) in the 4D theory as a result of monopole decay. In the presence of the fluxbrane, this decay also creates lower-dimensional fluxbranes, which in the field theory is interpreted as the creation of an additional topological field theory sector. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2025

High-Intensity UV Exposure for the Rapid Screening of Silicon Photovoltaic Architectures

Advanced Si photovoltaic architectures incorporate different materials and processing pathways that influence degradation modes. Ultraviolet-induced degradation (UVID) is an understudied degradation mode for advanced cell architectures and is of increasing concern to industry due to growing adoption of UV-transparent encapsulation and bifacial technologies. In order to adopt new and evolving technologies confidently, novel component materials and processing techniques must be evaluated and designed for long-term stability, in addition to the conventional design focus on efficiency. In this work, a study protocol framework is presented for the rapid screening of unencapsulated devices against UVID. Unencapsulated passivated emitter rear contact (PERC) and tunnel oxide passivated contact (TOPCon) devices were aged under different UV irradiance intensities and measured via conventional nondestructive electrical characterization methods to assess performance degradation. Based on the results, protocol efficacy and recommendations for further study are discussed. As a result, this work is part of a broader effort to develop rapid screening processes that cut across architectures and exposure conditions to aid module manufacturers in vetting new materials choices for long-term stability.

Accelerated exposure↗
DOE OSTI2021

Sonic Lift-off of GaAs-based Solar Cells with Reduced Surface Facets

Spalling has been proposed as a promising kerfless technique for slicing thin wafers and devices, enhancing the wafer yield from an ingot by reducing kerf-losses and enabling substrate reuse for the case of costly devices. The main challenge of spalling is to control the roughness and thickness variation of the spalled wafers that can be as high as 100% of the wafer thickness. Here, we have shown previously that the thickness variations are largely influenced by the interaction of the crack front with its own reflected waves. Herein we show that through Sonic Lift-off we can offer a modification to standard spalling technologies that minimizes the interaction of reflected waves with the crack front during lift-off of GaAs(100)-based solar cells. We show that the average surface facets amplitude can be reduced by 96% while obtaining a high quality bulk with no discernible residual strain as measured by PL. The resulting spalling depth can easily be tuned from 100 µm to less than 15µm. The electrical characterization of the Sonic lift-off cell shows no degradation of the VOC and a power conversion within 99% relative of a non-spalled baseline.

42 ENGINEERING↗
DOE OSTI2022

Harvesting Wave Energy to Power Acoustic Transmitters Using Triboelectric Nanogenerator

Wave energy has the largest reserves and widest distribution among blue energy sources. However, the conversion and utilization of ocean wave energy are challenging. In this work, we developed a contact-separation mode triboelectric nanogenerator (TENG) with a simple structure for harvesting wave energy and powering marine sensors and transmitters and performed detailed electrical characterization under controlled laboratory conditions. A prototype power management circuit (PMC) was implemented to improve the output performance of the TENG. The output from the PMC could charge up a storage capacitor for powering sensors and electronics. Eventually, the TENG was integrated within a water-proof enclosure and tested using a custom-built wave simulator to evaluate the device performance in a more representative scenario. The device sustainably powered up an array of 27 LEDs and was able to charge up a capacitor up to 1.8 V for driving an acoustic transmitter. The results demonstrate that TENG technology shows great promise in harvesting low-frequency ocean wave energy.

Yang, Yang↗
DOE OSTI2023

Harmonic Signals Dataset

The Harmonic Signals Dataset (HSD) consists of one-dimensional time series data collected from current sensors with a goal of providing data for research and development of Non-Intrusive Load Monitoring (NILM) with high sample rate (800kHz) sensors. NILM seeks to detect and characterize electrical equipment operating within a facility by sensing changes in electrical current on the building power system associated with the equipment. To provide data with a known ground truth, but with the realism of a signal introduced within a building facility, a series of known ground truth signals were injected as voltage into the power system of a building and measurements of the signals at multiple locations across the building power system were made with electrical current sensors.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2025

2 kV Al 0.64 Ga 0.36 N-channel high electron mobility transistors with passivation and field plates

Abstract High voltage (∼2 kV) Al 0.64 Ga 0.36 N-channel high electron mobility transistors were fabricated with an on-resistance of ∼75 Ω. mm (∼21 mΩ. cm 2 ). Two field plates of variable dimensions were utilized to optimize the breakdown voltage. The breakdown voltage reached >3 kV (tool limit) before passivation however it reduced to ∼2 kV after Si 3 N 4 surface passivation and field plate deposition. The breakdown voltage and on-resistance demonstrated a strong linear correlation in a scattered plot of ∼50 measured transistors. The fabricated transistors were electrically characterized and benchmarked against the state-of-the-art high-voltage (> 1 kV) Al-rich (>40%) AlGaN-channel transistors in breakdown voltage and on-resistance, indicating significant progress.

Alam, Md Tahmidul (ORCID:000900086556839X)↗
DOE OSTI2025

Fabrication of 4H-SiC Low Gain Avalanche Detectors (LGADs)

Low gain avalanche detectors (LGADs) offer high temporal resolution for high energy particle detection, which is critical for next generation experiments in hadron colliders. While silicon LGADs (Si-LGADs) have rapidly matured in the last decade, research into silicon carbide (SiC) LGADs has only recently begun. By accounting for fundamental differences in material properties and fabrication processes, we present a prototype device design and process flow for 4H-SiC LGADs with etch-based isolation. Critical steps of the process flow and their results are discussed, including plasma etching, passivation, and the formation of low resistivity contacts. Electrical characterization (I-V, C-V) shows sufficient depletion of the device structure to demonstrate low-gain charge carrier multiplication.

High Energy Physics↗
NASA NTRS1974

Basic memory module

Construction and electrical characterization of the 4096 x 2-bit Basic Memory Module (BMM) are reported for the Space Ultrareliable Modular Computer (SUMC) program. The module uses four 2K x 1-bit N-channel FET, random access memory chips, called array chips, and two sense amplifier chips, mounted and interconnected on a ceramic substrate. Four 5% tolerance power supplies are required. At the Module, the address, chip select, and array select lines require a 0-8.5 V MOS signal level. The data output, read-strobe, and write-enable lines operate at TTl levels. Although the module is organized as 4096 x 2 bits, it can be used in a 8196 x 1-bit application with appropriate external connections. A 4096 x 1-bit organization can be obtained by depopulating chips.

Tietze, F. C.↗
NASA NTRS1977

Silicon ribbon growth by a capillary action shaping technique

Substantial improvements in ribbon surface quality are achieved with a higher melt meniscus than that attainable with the film-fed (EFG) growth technique. A capillary action shaping method is described in which meniscus shaping for the desired ribbon geometry occurs at the vertex of a wettable die. As ribbon growth depletes the melt meniscus, capillary action supplies replacement material. Topics discussed cover experimental apparatus and growth procedures; die materials investigations, fabrication and evaluation; process development for 25 mm, 38 mm, 50 mm and 100 mm silicon ribbons; and long grain direct solidification of silicon. Methods for the structural and electrical characterization of cast silicon ribbons are assessed as well as silicon ribbon technology for the 1978 to 1986 period.

Schwuttke, G. H.↗
NASA NTRS1976

Single crystal and polycrystalline GaAs solar cells using AMOS technology

A description is given of current technology for fabricating single AMOS (antireflection-coated metal oxide semiconductor) solar cells, with attention given to thermal, plasma, and anodic oxidation, native oxide stripping, and X-ray photoelectron spectroscopy results. Some preliminary results are presented on the chemistry and electrical characterization of such cells, and the characteristics of cells fabricated on sliced polycrystalline GaAs wafers are examined. Consideration is also given to the recrystallization of evaporated Ge films for use as low-cost substrates for polycrystalline GaAs solar cells.

Stirn, R. J.↗