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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Directly Linking Low-Angle Grain Boundary Misorientation to Device Functionality for GaAs Grown on Flexible Metal Substrates

A new growth method to make highly oriented GaAs thin films on flexible metal substrates has been developed, enabling roll-to-roll manufacturing of flexible semiconductor devices. The grains are oriented in the <001> direction with <1 degree misorientations between them, and they have a comparable mobility to single-crystalline GaAs at high doping concentrations. At the moment, the role of low-angle grain boundaries (LAGBs) on device performance is unknown. A series of electron backscatter diffraction (EBSD) and cathodoluminesence (CL) studies reveal that increased doping concentrations decrease the grain size and increase the LAGB misorientation. Cross-sectional scanning transmission electron microscopy (STEM) reveals the complex dislocation structures within LAGBs. Most importantly, a correlative EBSD/electron beam-induced current (EBIC) experiment reveals that LAGBs are carrier recombination centers and that the magnitude of recombination is dependent on the degree of misorientation. The presented results directly link increased LAGB misorientation to degraded device performance, and therefore, strategies to reduce LAGB misorientations and densities would improve highly oriented semiconductor devices.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Low Threshold Voltages Electrochemically Drive Gold Migration in Halide Perovskite Devices

The constituent ions of halide perovskite materials are mobile in the solid state and known to participate in reduction/oxidation reactions. Yet few parameters related to electrochemical processes occurring within devices have been carefully determined. Here, we characterize such reactions in model MAPbI3 perovskite devices, and we quantify threshold voltages for key reactions. Gold is oxidized and mobilized under nitrogen, in the dark, at the MAPbI3/Au interface at 0.8 V. When this interface is buffered with the organic hole transport material (HTM), 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene, MAPbI3 begins to degrade at 1.2 V; degradation liberates ions that subsequently enable Au migration. Thresholds are insensitive to MAPbI3 thickness or choice of organic HTM or oxide cathode, which suggests that these reactions are driven electrochemically; the electric field across the device is less important. These results have profound implications for understanding in operando degradation pathways of optoelectronic perovskite devices that are varied in terms of interface structures, active material compositions, and ranges of external stressors.

42 ENGINEERING↗
DOE OSTI2024

Superhydrophobic Array Devices for the Enhanced Formation of 3D Cancer Models

During the metastatic cascade, cancer cells travel through the bloodstream as circulating tumor cells (CTCs) to a secondary site. Clustered CTCs have greater shear stress and treatment resistance, yet their biology remains poorly understood. We therefore engineered a tunable superhydrophobic array device (SHArD). The SHArD-C was applied to culture a clinically relevant model of CTC clusters. Using our device, we cultured a model of cancer cell aggregates of various sizes with immortalized cancer cell lines. These exhibited higher E-cadherin expression and are significantly more capable of surviving high fluid shear stress-related forces compared to single cells and model clusters grown using the control method, helping to explain why clustering may provide a metastatic advantage. Additionally, the SHArD-S, when compared with the AggreWell 800 method, provides a more consistent spheroid-forming device culturing reproducible sizes of spheroids for multiple cancer cell lines. Overall, we designed, fabricated, and validated an easily tunable engineered device which grows physiologically relevant three-dimensional (3D) cancer models containing tens to thousands of cells.

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

Pick-and-Place Transfer of Arbitrary-Metal Electrodes for van der Waals Device Fabrication

Van der Waals electrode integration is a promising strategy to create nearly perfect interfaces between metals and 2D materials, with advantages such as eliminating Fermi-level pinning and reducing contact resistance. However, the lack of a simple, generalizable pick-and-place transfer technology has greatly hampered the wide use of this technique. Here, we demonstrate the pick-and-place transfer of prefabricated electrodes from reusable polished hydrogenated diamond substrates without the use of any sacrificial layers due to the inherent low-energy and dangling-bond-free nature of the hydrogenated diamond surface. The technique enables transfer of arbitrary-metal electrodes and an electrode array, as demonstrated by successful transfer of eight different elemental metals with work functions ranging from 4.22 to 5.65 eV. We also demonstrate the electrode array transfer for large-scale device fabrication. The mechanical transfer of metal electrodes from diamond to van der Waals materials creates atomically smooth interfaces with no interstitial impurities or disorder, as observed with cross-section high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy. As a demonstration of its device application, we use the diamond transfer technique to create metal contacts to monolayer transition metal dichalcogenide semiconductors with high-work-function Pd, low-work-function Ti, and semimetal Bi to create n- and p-type field-effect transistors with low Schottky barrier heights. We also extend this technology to air-sensitive materials (trilayer 1T’ WTe 2 ) and other applications such as ambipolar transistors, Schottky diodes, and optoelectronics. This highly reliable and reproducible technology paves the way for new device architectures and high-performance devices.

2D materials↗
DOE OSTI2023

Construction of a Compact Array of Microplasma Jet Devices and Its Application for Random Mutagenesis of Rhodosporidium toruloides

A small and efficient DNA mutation-inducing machine was constructed with an array of microplasma jet devices (7 × 1) that can be operated at atmospheric pressure for microbial mutagenesis. Using this machine, we report disruption of a plasmid DNA and generation of mutants of an oleaginous yeast Rhodosporidium toruloides. Specifically, a compact-sized microplasma channel (25 × 20 × 2 mm 3 ) capable of generating an electron density of greater than 10 13 cm –3 was constructed to produce reactive species (N 2 *, N 2 +, O, OH, and H α ) under helium atmospheric conditions to induce DNA mutagenesis. The length of microplasma channels in the device played a critical role in augmenting both the volume of plasma and the concentration of reactive species. First, we confirmed that microplasma treatment can linearize a plasmid by creating nicks in vitro. Second, we treated R. toruloides cells with a jet device containing 7 microchannels for 5 min; 94.8% of the treated cells were killed, and 0.44% of surviving cells showed different colony colors as compared to their parental colony. Microplasma-based DNA mutation is energy-efficient and can be a safe alternative for inducing mutations compared to conventional methods using toxic mutagens. In conclusion, this compact and scalable device is amenable for industrial strain improvement involving large-scale mutagenesis.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

On-device lead sequestration for perovskite solar cells

Perovskite solar cells (PSCs) face obstacles on their way towards commercialization. Potential issues with lead toxicity and leaching from devices remain relatively unexplored. It is desirable to develop strategies that avoid potential Pb leakage to the environment, although enhanced physical encapsulation can lessen Pb leakage from devices when subjected to mild environmental damage. We present a new chemical approach for on-device sequestration (>96%) of lead leakage caused by severe device damage without sacrificing the efficiency and stability of PSCs under normal operation.

14 SOLAR ENERGY↗
DOE OSTI2022

Multiparameter laser performance characterization of liquid crystals for polarization control devices in the nanosecond regime

Abstract Interactions of liquid crystals (LC’s) with polarized light have been studied widely and have spawned numerous device applications, including the fabrication of optical elements for high-power and large-aperture laser systems. Currently, little is known about both the effect of incident polarization state on laser-induced–damage threshold (LIDT) and laser-induced functional threshold (LIFT) behavior at sub-LIDT fluences under multipulse irradiation conditions. This work reports on the first study of the nanosecond-pulsed LIDT’s dependence on incident polarization for several optical devices employing oriented nematic and chiral-nematic LC’s oriented by surface alignment layers. Accelerated lifetime testing was also performed to characterize the ability of these devices to maintain their functional performance under multipulse irradiation as a function of the laser fluence at both 1053 nm and 351 nm. Results show that the LIDT varies as a function of input polarization by 30–80% within the same device, while the multipulse LIFT (which can differ from the nominal LIDT) depends on irradiation conditions such as laser fluence and wavelength.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Scalable fabrication of an array-type fixed-target device for automated room temperature X-ray protein crystallography

X-ray crystallography is one of the leading tools to analyze the 3-D structure, and therefore, function of proteins and other biological macromolecules. Traditional methods of mounting individual crystals for X-ray diffraction analysis can be tedious and result in damage to fragile protein crystals. Furthermore, the advent of multi-crystal and serial crystallography methods explicitly require the mounting of larger numbers of crystals. To address this need, we have developed a device that facilitates the straightforward mounting of protein crystals for diffraction analysis, and that can be easily manufactured at scale. Inspired by grid-style devices that have been reported in the literature, we have developed an X-ray compatible microfluidic device that can be used to trap protein crystals in an array configuration, while also providing excellent optical transparency, a low X-ray background, and compatibility with the robotic sample handling and environmental controls used at synchrotron macromolecular crystallography beamlines. At the Stanford Synchrotron Radiation Lightsource (SSRL), these capabilities allow for fully remote-access data collection at controlled humidity conditions. Furthermore, we have demonstrated continuous manufacturing of these devices via roll-to-roll fabrication to enable cost-effective and efficient large-scale production.

chemical engineering↗
DOE OSTI2024

Trade-off between processability and device performance in donor–acceptor semiconductors revealed using discrete siloxane side chains

Donor–acceptor polymeric semiconductors are crucial for state-of-the-art applications, such as electronic skin mimics. The processability, and thus solubility, of these polymers in benign solvents is critical and can be improved through side chain engineering. Nevertheless, the impact of novel side chains on backbone orientation and emerging device properties often remains to be elucidated. Here, we investigate the influence of elongated linear and branched discrete oligodimethylsiloxane (oDMS) side chains on solubility and device performance. Thereto, diketopyrrolopyrrole–thienothiophene polymers are equipped with various oDMS pendants (PDPPTT-Si n ) and subsequently phase separated into lamellar domains. The introduction of a branching point in the siloxane significantly enhanced the solubility of the polymer, as a result of increased backbone distortion. Simultaneously, the charge carrier mobility of the polymers decreased by an order of magnitude upon functionalization with long and/or branched siloxanes. This work unveils the intricate balance between processability and device performance in organic semiconductors, which is key for the development of next-generation electronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Antifouling strategies for protecting bioelectronic devices

Bioelectronic devices are playing an increasingly important role in many areas of our lives. They power a significant portion of medical diagnostics and are becoming more and more important for delivery of therapeutics and monitoring of chronic symptoms. However, surface fouling phenomena, and especially biofouling in complex biological fluids, restricts the performance of these devices and severely reduces their useful lifespan. In this Research Update, we discuss the main principles and strategies that researchers use to prevent fouling and minimize or remove the foulants from bioelectronic device surfaces. We also survey a variety of antifouling approaches that can enhance device performance.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Evidence for a thermally driven charge-density-wave transition in 1T-TaS 2 thin-film devices: Prospects for GHz switching speed

We report on the room-temperature switching of 1T-TaS 2 thin-film charge-density-wave devices, using nanosecond-duration electrical pulsing to construct their time-resolved current–voltage characteristics. The switching action is based upon the nearly commensurate to incommensurate charge-density-wave phase transition in this material, which has a characteristic temperature of 350 K at thermal equilibrium. For sufficiently short pulses, with rise times in the nanosecond range, self-heating of the devices is suppressed, and their current–voltage characteristics are weakly nonlinear and free of hysteresis. This changes as the pulse duration is increased to ~200 ns, where the current develops pronounced hysteresis that evolves nonmonotonically with the pulse duration. By combining the results of our experiments with a numerical analysis of transient heat diffusion in these devices, we clearly reveal the thermal origins of their switching. In spite of this thermal character, our modeling suggests that suitable reduction of the size of these devices should allow their operation at GHz frequencies.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Intersubband transitions in nonpolar and semipolar III-nitrides: Materials, devices, and applications

In the last two decades, the third-generation wide bandgap semiconductor III-nitrides have revolutionized a myriad of electronic and photonic devices and applications, including power electronics, extreme-environment electronics, RF amplifiers, and optoelectronics such as light-emitting diodes and laser diodes. Recently, III-nitride heterostructures (e.g., AlGaN/GaN) based intersubband transition (ISBT) has garnered considerable research interest for infrared (IR), terahertz (THz), and ultrafast optoelectronics (e.g., photodetectors and quantum cascade lasers) due to its large conduction band offset, large optical phonon energy, and promising room-temperature operation. This paper presents a comprehensive review on the recent progress and challenges of III-nitrides based ISBT from the perspectives of materials, structures, devices, and applications, with a focus on nonpolar and semipolar III-nitrides. Various device structures have been demonstrated for III-nitrides based ISBT, including quantum wells, dots, and wires, among which AlGaN/GaN quantum wells are the most widely used. The effects of device parameters, crystal orientations, and doping on the ISBT properties of AlGaN/GaN quantum wells are discussed. Although the room-temperature operation is still elusive, theoretical and experimental studies show that nonpolar and semipolar III-nitrides based ISBT exhibits tunable ISBT wavelength from far-IR to THz spectral range with higher efficiency compared with polar c-plane ISBT. This review can serve as a gateway to and an important reference for the recent progress and challenges of III-nitrides based ISBT and its potential applications in sensing, communication, ultrafast optoelectronics, and integrated photonics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Self-consistent integrated modeling of combined hybrid discharge-laser produced plasma devices for extreme ultraviolet metrology

Discharge- and laser-produced plasma (DLPP) devices are being used as light sources for extreme ultraviolet (EUV) generation. A key challenge for both, DPP and LPP, is achieving sufficient brightness to support the throughput requirements of nanometrology tools. To simulate the environment of a hybrid DLPP device and optimize the EUV output, we have developed an integrated HEIGHTS-DLPP computer simulation package. The package integrates simulation of two evolving plasmas (DPP and LPP) and includes modeling of a set of integrated self-consistent processes: external power source and plasma energy balance, plasma resistive magnetohydrodynamics, plasma heat conduction, detailed radiation transport (RT), and laser absorption and refraction. We simulated and optimized DLPP devices using Xe gas as a target material. We synchronized the external circuit parameters, chamber gas parameters, and laser beam temporal and spatial profiles to achieve maximum EUV output. The full 3D Monte Carlo scheme was integrated for detailed RT and EUV output calculations in Xe using more than 3600 spectral groups. The modeling results are in good agreement with Julich Forschungszentrum experimental data. Theoretical models, developed and integrated into the HEIGHTS package, showed wide capabilities and flexibility. In conclusion, the models and package can be used for optimization of the experimental parameters and settings, investigation of DLPP devices with complex design, analyzing the impact of integrated spatial effects and working timeline arrangement on the final EUV output, and EUV source size, shape, and angular distribution.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Two-dimensional perovskite heterostructures for single crystal semiconductor devices

Two-dimensional (2D) perovskites have gained much attention lately owing to their excellent optoelectronic properties, chemical tunability, and environmental stability. Multiple methods have been devised to synthesize high quality 2D perovskite single crystals, and recent progress in fabricating its heterostructures is notable as well. In particular, with growing interest in 2D van der Waals heterostructures, 2D perovskites have become a strong candidate as a new building block for heterostructures to reveal unique physical properties across different interfaces. Until now, various heterostructure devices of 2D perovskite single crystals with other types of 2D materials such as transition metal dichalcogenides (TMDs) and graphene have been studied, which have shown intriguing results including interlayer excitons and enhanced electronic properties. Here, we introduce various synthetic approaches to realize 2D perovskite single crystals and unique characteristics of their single crystal heterostructures fabricated with precision, possessing sharp interfaces. Moreover, recent studies of semiconductor devices based on 2D perovskite single crystal heterostructures are discussed in-depth. New perspectives to further the horizon in the field of 2D perovskite heterostructures are suggested in this work including the consideration of metal–2D material van der Waals contact, application of dry transfer techniques, electric bias driven ion diffusion studies, and nanocrystal array fabrication. 2D perovskite heterostructure single crystal devices factoring in these novel perspectives will further uncover the true potential of these materials for highly efficient and stable semiconductor devices.

Physics↗
DOE OSTI2023

Modeling of the spray-induced wall stress acting on the ignition assistance device

This research introduces a novel wall-stress model called the Spray-Induced Wall Stress (SIWS) model, which considers the effects of spray-wall impingement and the resulting formation of wall stress within the Lagrangian spray modeling framework. The primary objective of this paper is to provide a mathematical description of the fundamental physics underlying the model. Subsequently, the proposed model is validated using existing experimental data. Here, the remainder of the study focuses on the practical application of the model to an ignition assistance device. Specifically, this device is installed in a compression ignition engine and designed to enhance ignition in aviation-fueled high-altitude aircraft propulsion systems. The research sheds light on the mechanical impulse caused by the high-speed impact of the spray jet, leading to the accumulation of mechanical stress on the rigid body of the ignition assistance device. Previous studies on fluid-structure interaction have only considered the interaction between the gas phase and the solid wall. However, the SIWS model incorporates the additional impact of the impinging liquid spray jet. Consequently, the simulated stress distribution on the ignition assistance device can be estimated by considering both the gas-phase-induced term and the spray-induced term simultaneously.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2024

When in-memory computing meets spiking neural networks—A perspective on device-circuit-system-and-algorithm co-design

This review explores the intersection of bio-plausible artificial intelligence in the form of spiking neural networks (SNNs) with the analog in-memory computing (IMC) domain, highlighting their collective potential for low-power edge computing environments. Through detailed investigation at the device, circuit, and system levels, we highlight the pivotal synergies between SNNs and IMC architectures. Additionally, we emphasize the critical need for comprehensive system-level analyses, considering the inter-dependencies among algorithms, devices, circuit, and system parameters, crucial for optimal performance. An in-depth analysis leads to the identification of key system-level bottlenecks arising from device limitations, which can be addressed using SNN-specific algorithm–hardware co-design techniques. This review underscores the imperative for holistic device to system design-space co-exploration, highlighting the critical aspects of hardware and algorithm research endeavors for low-power neuromorphic solutions.

Physics↗
DOE OSTI2024

DECAF Cross-device characterization of tokamak disruptions indicated by abnormalities in plasma vertical position and current

Abnormal (deviating from target) variations in the plasma vertical position Z and current I p (such as vertical displacements, transient I p 'spikes' and quenches) constitute common elements of a disruption, a phenomenon that is to be mitigated, or ultimately avoided in future reactor-relevant tokamaks. While those abnormalities are generally recognized cross-shot and cross-device, details in terms of appearance (or not) and order of those abnormalities in disruption event chains is bound with the plasma state at the time of the chain initiation. Detection of those abnormalities is thus indicative not only of the onset of the plasma collapse itself, but also of the disruption driving cause that is promoted at the particular plasma state. Here, occurrence of disruptions, explored via detection of a Ip quench, and analysis of disruption event chains constituted by Ip and Z abnormalities, is reported for in total 7 full years of operation of 3 devices (KSTAR, MAST-U and NSTX-U) using the DECAFTM code expanded tools and capabilities. It is shown that the disruption occurrence depends not only on details of the plasma state, but also on (device-dependent) technical elements of the shot exit scenario. A year-to-year change in main disruption causes and a reduction of the disruptivity rate, bound with device and operation upgrades, are reported. Particular trigger instances of disruption event chains (and the full chains, when applicable) are shown to occupy different parts of the operation space diagrams, in accordance with prior expectation. Plasma elongation is identified as an important factor influencing details of the chains and its role will be further explored.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Multi-machine validation of plasma initiation modelling and prospects for future devices: Predicting plasma initiation using only hardware design and control room input data

This paper reports on the generic prediction capability of full electromagnetic plasma initiation modelling with DYON, which was carried out for the first time in fusion research by the joint modelling of the International Tokamak Physics Activity—Integrating Operation Scenario group. The following devices were included in the experiment database: VEST (spherical torus, copper coils, Stainless steel wall, R/a = 0.3 m/0.2 m, V v = 3.7 m 3 ), MAST-U (spherical torus, copper coils, C wall, R/a = 0.7 m/0.5 m, V v = 55 m 3 ), EAST (conventional tokamak, superconducting coils, metallic wall, R/a = 1.85 m/0.5 m, V v = 38 m 3 ), DIII-D (conventional tokamak, copper coils, C wall, R/a = 1.67 m/0.65 m, V v = 35 m 3 ), and KSTAR (conventional tokamak, superconducting coils, C wall, R/a = 1.8 m/0.5 m, V v = 55 m 3 ). Despite the different hardware features of the devices, the required operating spaces of the loop voltage induction and prefill gas pressure for inductive plasma initiation in each device were successfully reproduced by the predictive simulations with DYON using only the individual hardware design and the control room input data for each discharge. This successful validation across multiple machines demonstrates that the full electromagnetic DYON modelling can capture the essential physics of inductive plasma initiation. The simulation settings commonly employed for all modelling and the modifications necessary to account for the discrepancies between individual devices are reported. Predictions for ITER based on the multi-machine validation indicate that a wide range of prefill gas pressures exists for the Townsend breakdown and the plasma burn-through (0.01–1.5 mPa).

DYON↗