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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2027

Low thermal budget dopant activation in shallow junctions of implanted Si via Tunable plasma enhanced annealing

Low thermal budget (LTB) annealing has become increasingly critical for shallow junctions as semiconductor devices are scaled down. Plasma Enhanced Annealing (PEA) has emerged as a promising LTB annealing process, however its mechanisms remain unclear. In this study, arsenic and boron implanted silicon wafers were subjected to helium or argon ion bombardment generated by annealing plasmas under controlled ion energies and doses in a home-built annealing reactor. The structural and electrical changes were characterized by four-point probe measurements, secondary ion mass spectrometry, Raman spectroscopy and spectroscopic ellipsometry. A pronounced reduction in sheet resistance, accompanied by a decrease in the damage layer thickness demonstrates the surface selective annealing capability of PEA process. Comparative studies using He and Ar plasmas and related ion bombardment reveal a dependence of activation efficacy on both ion species and the dopant implantation profile. Furthermore, a multi-step annealing mechanism is proposed, consisting of an initial (low dose) structural recovery stage followed by the generation of “extended” defects and concluded at large doses by an enhanced dopant activation. The proposed annealing kinetics are thought to be controlled by ion flux, dose and energy. Finally, these results highlight PEA as an effective, surface-selective, LTB approach for shallow-dopant activation and near surface annealing, and provide mechanistic insights into PEA processes.

dopant activation↗
DOE OSTI2022

Effect of proton irradiation temperature on persistent photoconductivity in zinc oxide metal-semiconductor-metal ultraviolet photodetectors

The electrical and structural characteristics of 50-nm-thick zinc oxide (ZnO) metal-semiconductor-metal ultraviolet (UV) photodetectors subjected to proton irradiation at different temperatures are reported and compared. The devices were irradiated with 200 keV protons to a fluence of 1016 cm−2. Examination of the x-ray diffraction (XRD) rocking curves indicates a preferred (100) orientation prior to irradiation, with decrease in crystal quality afterward. Additionally, peak shifts in XRD and Raman spectra of the control sample relative to well-known theoretical positions are indicative of tensile strain in the as-deposited ZnO films. Shifts toward theoretical unstrained positions are observed in the irradiated films, which indicates partial relaxation. Raman spectra also indicate increase in oxygen vacancies (VO) and zinc interstitial defects (Zni) compared to the control sample. Additionally, transient photocurrent measurements performed on each sample at different temperatures showed up to 2× increase in photocurrent decay time constants for irradiated samples vs the control. This persistent photoconductive behavior is linked to the activation of electron and hole traps near the surface, and to the desorption and reabsorption of O2 molecules on the ZnO surface under the influence of UV light. Using an Arrhenius model, trap activation energies were extracted and, by comparing with known energies from the literature, the dominant defects contributing to persistent photoconductivity for each irradiation condition were identified. The persistence of differences in photocurrent transients between different samples months after irradiation indicates that the defects introduced by the suppression of thermally activated dynamic annealing processes have a long-term deleterious effect on device performance.

Heuser, Thomas A. (ORCID:0000000225642400)↗
DOE OSTI2020

In Operando Calorimetric Measurements for Activated Carbon Electrodes in Ionic Liquid Electrolytes under Large Potential Windows

This study aims to investigate the effect of the potential window on heat generation in carbon-based electrical double layer capacitors (EDLCs) with ionic-liquid (IL)-based electrolytes using in operando calorimetry. The EDLCs consisted of two identical activated-carbon electrodes with either neat 1-butyl-1-methylpyrrolidinium bis(trifluoromethane-sulfonyl)imide ([Pyr 14 ][TFSI]) electrolyte or 1.0 m [Pyr 14 ][TFSI] in propylene carbonate (PC) as electrolyte. The instantaneous heat generation rate at each electrode was measured under galvanostatic cycling for different potential windows ranging from 1 to 4 V. First, the heat generation rates at the positive and negative electrodes differed significantly in neat IL owing to the differences in the ion sizes and diffusion coefficients. However, these differences were minimized when the IL was diluted in PC. Second, for EDLC in neat [Pyr 14 ][TFSI] at high potential window (4 V), a pronounced endothermic peak was observed at the beginning of the charging step at the positive electrode owing to TFSI - intercalation in the activated carbon. On the other hand, for EDLC in 1.0 m [Pyr 14 ][TFSI] in PC at potential window above 3 V, an endothermic peak was observed only at the negative electrode owing to the decomposition of PC. Third, for both neat and diluted [Pyr 14 ][TFSI] electrolytes, the irreversible heat generation rate increased with increasing potential window and exceeded Joule heating. This was attributed to the effect of potential-dependent charge redistribution resistance. Additionally, a further increase in the irreversible heat generation rate was observed for the largest potential windows owing to the degradation of the PC solvent. Finally, for both types of electrolyte, the reversible heat generation rate increased with increasing potential window because of the increase in the amount of ion adsorbed/desorbed at the electrode/electrolyte interface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Digestion processes and elemental analysis of oxide and sulfide solid electrolytes

Detailed elemental analysis is essential for a successful development and optimization of material systems and synthesis methods. This is especially relevant for Li- and Na-containing compounds, found in state-of-the-art and next-generation battery systems. Their materials’ properties and thus the final device performance strongly depend on the crystal structure, the stoichiometry, and defect chemistry, e.g., influencing charge carrier concentration and activation energies for vacancy transport. However, a detailed quantitative analysis of light elements in a heavy matrix, featuring a broad range of solubilities and vapor pressures, is often difficult and associated with large uncertainties and thus neglected in favor of just reporting the stoichiometry as “weighed in.” Here, in this work, we report several approaches to digest and dissolve various oxide and sulfide-based materials, used in next-generation Li batteries, for elemental analysis via optical emission spectroscopy. These include the most common solid electrolytes Li-La-Ti–O, a perovskite material (LLTO), and Li-La-Zr-O which has garnet structure (LLZO). Additionally, a facile thermal digestion process is reported for a surrogate sulfide solid electrolyte (Na 2 S). The digestion procedures reported here are suitable for almost any laboratory environment and, when applied, will improve understanding of the synthesis-structure–property correlations needed to advanced batteries with all solid-state configurations.

Malkowski, Thomas F.↗
DOE OSTI2026

Morphology-driven oxygen evolution performance of NiO x nanostructures and implications for hole transport in perovskite solar cells

Morphology-controlled nanostructures provide an effective strategy to modulate both oxygen evolution reaction (OER) activity and photovoltaic performance in perovskite solar cells (PSCs). However, achieving low OER overpotentials and high power conversion efficiency (PCE) simultaneously through morphology engineering remains challenging. In this work, nickel oxide (NiO x ) nanostructures with spindle-like (NiO x -NS) and plate-like (NiO x -NP) morphologies were synthesized and evaluated as bi-functional OER catalysts and hole transport layers (HTLs) in inverted PSCs. Structural and thermal analyses reveal that NiO x -NS crystallizes into a cubic phase at a lower temperature (300 °C), whereas NiO x -NP requires higher calcination temperatures, reflecting differences in precursor microstructure. Electrochemical measurements indicate that NiO x -NS calcined at 300 °C delivers the lowest OER overpotential (395 mV at 10 mA cm −2 ), outperforming NiO x -NP calcined at 400 °C (565 mV) and 500 °C (474 mV). This enhanced activity is ascribed to favorable surface strain, increased defect density, and advantageous facet exposure. When used as HTLs, NiO x -NS also delivers the highest PCE (13.25%) among all tested devices, exceeding those based on NiO x -NP and commercial NiO x , owing to improved hole extraction and interfacial contact. Overall, this study highlights the importance of morphology control and thermal processing in tailoring NiO x for multifunctional nanomaterials in electrocatalytic and photovoltaic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Editorial: Functionalization of porous materials for sustainable energy applications

Global energy demands are shifting toward a more sustainable future, with the goal of achieving carbon neutrality by 2050. Emerging technologies are driving this transition. The industry, academia, government, non-profit organizations, and the broader community are collaboratively working to reduce greenhouse gas (GHG) emissions and address climate change to ensure a sustainable future. According to the International Energy Agency, in 2022, the production, transportation, and processing of oil and gas resulted in 5.1 billion tons of CO 2 -equivalent emissions, representing nearly 15% of all energy-related GHG emissions. Moreover, the end-use of oil and gas accounted for an additional 40% of emissions. The IEA’s Net Zero Emissions by 2050 Scenario calls for immediate, collective action from the industry, transportation and other stakeholders to mitigate these emissions. In this effort, the development of energy materials will play a critical role in reducing emissions. Among these, porous materials offer an innovative solution, leveraging their high surface area, adjustable pore sizes, and chemical versatility to address these pressing challenges effectively. By carefully designing their nanostructures, the architecture and properties of these materials can be tailored for specific applications. Key factors such as chemical composition, particle size, pore distribution, and surface area optimization enhance the reactivity and energy conversion efficiency. Additionally, pre- and post-functionalization processes can introduce targeted chemical properties, further improving their performance. This Research Topic explores recent advancements in energy and materials science through four scholarly papers, showcasing innovative solutions for sustainable energy technologies while providing valuable insights into the unique properties and structure of porous materials (Figure 1). Li et al. present their work on highly defective NiFeV layered triple hydroxides, highlighting enhanced electrocatalytic activity and stability for oxygen evolution reactions (OER). Kovalskii et al. contribute a mini-review on hydrogen storage using hexagonal boron nitride (h-BN) and BN-based materials, offering an insightful overview of these promising materials. Chava et al. discuss their recent achievements in ceramic electrolytes used for improvement of performance of solid-state batteries. Lastly, Li et al. review the properties of porous materials with a focus on shrinkage behavior during the drying process, shedding light on key considerations for material design.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Self‐Trapped Hole Migration and Defect‐Mediated Thermal Quenching of Luminescence in α‐ and β‐Ga 2 O 3

Gallium oxide (Ga 2 O 3 ) is a promising ultrawide bandgap semiconductor for next-generation power electronics and optoelectronic devices. Here, temperature-dependent and polarization-resolved photoluminescence excitation spectroscopy data, complemented by hybrid-functional first-principles calculations, are presented, and a microscopic model is derived that explains the interplay of hole migration, defect trapping, and carrier recombination at defects underlying thermal quenching phenomena in α- and β-Ga 2 O 3 . In α-Ga 2 O 3 , the UV emission is attributed to self-trapped holes, while the blue luminescence arises from defect-related processes, including gallium split vacancies and their defect complexes. Calculations reveal an energy barrier of 88 meV for self-trapped hole migration in α-Ga 2 O 3 , consistent with activation energies from temperature-dependent photoluminescence. This enables efficient trapping by defects, enhancing blue luminescence and quenching UV emission. In β-Ga 2 O 3 , a higher migration barrier of 0.36 eV reduces the defect trapping, allowing the UV self-trapped hole emission to remain intense, with blue luminescence emerging only at elevated temperatures. These results establish a direct link between self-trapped hole migration, defect trapping, and thermal quenching of emission in both phases. The insights advance the understanding of carrier dynamics in ultrawide bandgap oxides and may guide defect engineering for high-performance functional devices.

Hajizadeh, Nima [Leibniz-Institut im Forschungsver↗
DOE OSTI2025

Synthetic active liquid crystals powered by acoustic waves.

Active nematic materials combine orientational order with activity at the microscopic level. Current experimental realizations of active nematics include vibrating elongated particles, cell layers, suspensions of elongated bacteria, and a mixture of bio-filaments with molecular motors. The majority of active nematics are of biological origin. The realization of a fully synthetic active liquid crystal comprised of a lyotropic chromonic liquid crystal energized by ultrasonic waves, is reported. This synthetic active liquid crystal is free from biological degradation and variability, exhibits phenomenology associated with active nematics, and enables precise and rapid activity control over a significantly extended range. It is demonstrated that the energy of the acoustic field is converted into microscopic extensile stresses disrupting long-range nematic order and giving rise to an undulation instability and proliferation of topological defects. The emergence of unconventional free-standing persistent vortices in the nematic director field at high activity levels is revealed. The results provide a foundation for the design of externally energized active liquid crystals with stable material properties and tunable topological defect dynamics crucial for the realization of reconfigurable microfluidic systems.

active matter↗
DOE OSTI2022

Raman spectroscopy of thermally perturbed carbon fibers: Discriminating spectral responses of modulus classes and defect types

The mechanical strength properties of carbon fibers are generally thought to be correlated with the presence of underlying atomic-level defects. These defects serve to break the underlying translational symmetry of the graphitic or graphene subunits of the fiber construction, resulting in the emergence of new Raman-active spectral features. However, historical attempts to classify the precise origin of defect contributions to the Raman spectra have been challenging because of indistinct and overlapping features in the carbon fiber Raman spectra. Further, while substantial research exists on high-temperature exposure in inert atmospheres for carbon fiber composites, comparatively less addresses microscale behaviors and Raman spectral alterations to monofilament carbon fibers exposed to high-temperature atmospheric environments. Here, we report Raman spectral responses of nine commercially available high-performance, polyacrylonitrile-based carbon fibers exposed to various atmospheric heat treatments. In this work, we introduce a model-independent characterization method, the integrated absolute difference, to quantify the spectral responses to heat treatment of different fiber modulus classes. We combine this new method with a newly reported strategy to standardize spectral fitting for carbon fibers. With this approach, we show that atomic-scale defects in the underlying fiber microstructure manifest in measurably distinct manners and have distinct responses to thermal perturbation. These combined approaches may lay the foundation for disentangling contributions from specific defects in the Raman spectra of carbon fibers.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Tuning Point Defects by Elastic Strain Modulates Nanoparticle Exsolution on Perovskite Oxides

Exsolution generates stable and catalytically active metal nanoparticles via phase precipitation out of a host oxide. An ability to control the size and dispersion of the exsolution particles is desirable for design of nanostructured (electro)catalysts. In this work, we demonstrate that tuning point defects by lattice strain affects both the thermodynamics and the kinetics of iron (Fe 0 ) exsolution on La 0.6 Sr 0.4 FeO 3 (LSF) thin film model. By combining in situ surface characterization and ab initio defect modeling, we show oxygen vacancy and Schottky defects to be the primary point defects formed upon Fe0 exsolution. Lattice strain tunes the formation energy, and thus the abundance of these defects, and alters the amount and size of the resulting exsolution particles. In addition, we find that the density of exsolved nanoparticles matches the concentration of oxygen vacancy pairs, thus pointing to the surface oxygen vacancy pairs as preferential nucleation sites for exsolution. The tensile-strained LSF with a facile formation of these critical point defects results in a higher Fe 0 metal concentration, a larger density of nanoparticles, and a reduced particle size at its surfaces. These results provide important mechanistic insights and highlight the role of point-defect engineering in designing nanostructured catalysts in energy and fuel conversion technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Rational design of stable sulfur vacancies in molybdenum disulfide for hydrogen evolution

Sulfur (S) vacancies in MoS 2 have been found to act as a new active center, which shows an unprecedented intrinsic HER activity under elastic strain. However, such S-vacancies are unstable and the activities are very sensitive to the vacancy concentration. A strategy to stabilize these abundant active sites is thus highly desirable. Herein, we rationally design a catalyst system to stabilize S-vacancies in the basal plane of $2H-$MoS 2 supported on defective vertical graphene network (VGN). The energetically favorable line-shaped S-vacancies in MoS 2 shows a consistently high HER activity that is insensitive to S-vacancy concentration. Moreover, the defective graphene support effectively stabilizes these S-vacancies. The optimized catalyst exhibits a superior HER activity with overpotential of 128 mV at 10 mA cm -2 and Tafel slope of 50 mV dec -1 . Most importantly, the catalyst shows greatly increased stability over 500 h; benchmarking the most stable nonprecious HER catalyst in acidic media to date.

2D heterostructure↗
DOE OSTI2022

Intercalation of Ca into a Highly Defective Manganese Oxide at Room Temperature

The utilization of oxide frameworks as intercalation cathodes for non-aqueous Ca-ion batteries potentially unlocks a new energy storage system that delivers high energy density. However, the slow kinetics of Ca 2+ in oxide electrodes strongly handicaps their activity and reversibility at room temperature. Here, nanocrystals of layered MnO x containing a high concentration of atomic defects and lattice water are shown to have remarkable electrochemical activity towards Ca 2+ , amounting to a capacity of ~130 mAh/g at room temperature. Multimodal characterization revealed the notable degree of intercalation by probing the structural, compositional and redox changes undertaken by the defective MnO x nanocrystals. The results suggest that the existence of atomic defects and lattice water played a role in improving Ca 2+ diffusivity in the oxide. These outcomes reaffirm the prospects for functional Ca-ion batteries using oxide cathodes under moderate conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Toward alcohol synthesis from CO hydrogenation on Cu(111)-supported MoS 2 – predictions from DFT+KMC

In the quest for cheap and efficient catalysts for alcohol synthesis from syngas, a material of interest is single-layer MoS2 owing to its low cost, abundancy, and flexible structure. Because of the inertness of its basal plane, however, it is essential to find ways that make it catalytically active. Herein, by means of density functional theory based calculations of reaction pathways and activation energy barriers and accompanying kinetic Monte Carlo simulations, we show that while S vacancy row structures activate the MoS 2 basal plane, further enhancement of chemical activity and selectivity can be achieved by interfacing the MoS 2 layer with a metallic support. When defect-laden MoS2 is grown on Cu(111), there is not only an increase in the active region (surface area of active sites) but also charge transfer from Cu to MoS 2 , resulting in a shift of the Fermi level such that the frontier states (d orbitals of the exposed Mo atoms) appear close to it, making the MoS 2 /Cu(111) system ready for catalytic activity. Finally, our calculated thermodynamics of reaction pathways lead to the conclusion that the Cu(111) substrate promotes both methanol and ethanol as the products, while kinetic Monte Carlo simulations suggest a high selectivity toward the formation of ethanol.

2D materials↗
DOE OSTI2024

Active nematic ratchet in asymmetric obstacle arrays

We numerically investigate the effect of an asymmetric periodic obstacle array in a two-dimensional active nematic. We find that activity in conjunction with the asymmetry leads to a ratchet effect or unidirectional flow of the fluid along the asymmetry direction. The directional flow is still present even in the active turbulent phase when the gap between obstacles is sufficiently small. We demonstrate that the dynamics of the topological defects transition from flow mirroring to smectic-like as the gap between obstacles is made smaller, and explain this transition in terms of the pinning of negative winding number defects between obstacles. This also leads to a nonmonotonic ratchet effect magnitude as a function of obstacle size, so that there is an optimal obstacle size for ratcheting at fixed activity.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Photosynthesis of a Photocatalyst: Single Atom Platinum Captured and Stabilized by an Iron(III) Engineered Defect

Single atom (SA), noble metal catalysts are of interest due to high projected catalytic activity while minimizing cost. Common issues facing many synthesis methodologies include complicated processes, low yields of SA product, and production of mixtures of SA and nanoparticles (NPs). Herein we report a simple, room-temperature synthesis of single Pt-atom decorated, anatase Fe-doped TiO 2 particles that leverages the Fe dopant as an engineered defect site to photodeposit and stabilize atomically dispersed Pt. Both particle morphology and Fe dopant location are based on thermodynamic principles (Gibbs-Wulff construction). CO-DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) reveals absence of bridge-bonded CO signal, confirming atomically dispersed Pt. XAS (x-ray absorption spectroscopy) of both Pt and Fe indicates Fe-O-Pt bonding that persists through catalytic cycling. Mass balance indicates Pt loading on single particles is 2.5 wt% Pt; single Pt-atom decorated nanoparticle yield is 17%. Pt containing particles show more than an order-of-magnitude increased photo-oxidation efficiency relative to particles containing only Fe. High single-atom-Pt yield, ease of synthesis, and high catalytic activity demonstrate the utility and promise of this method. In conclusion, the principles of this photodeposition synthesis allow for its generalizability towards other SA metals of catalytic interest.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Thermal activation of low-density Ga implanted in Ge

The nuclear spins of low-density implanted Ga atoms in Ge are interesting candidates for solid state-based qubits. To date, activation studies of implanted Ga in Ge have focused on high densities. Here, we extend activation studies into the low-density regime. We use spreading resistance profiling and secondary ion mass spectrometry to derive electrical activation of Ga ions implanted into Ge as a function of the rapid thermal anneal temperature and implant density. We show that for our implant conditions, the activation is best for anneal temperatures between 400 and 650 °C with a maximum activation of 69% at the highest fluence. Below 400 °C, remaining implant damage results in defects that act as superfluous carriers, and above 650 °C, surface roughening and loss of Ga ions are observed. The activation increased monotonically from 10% to 69% as the implant fluence increased from 6×1010 to 6×1012 cm−2. The results provide thermal anneal conditions to be used for initial studies of using low-density Ga atoms in Ge as nuclear spin qubits.

Foster, Natalie D. (ORCID:0000000235712054)↗
DOE OSTI2021

Quantum Embedding Theory for Strongly Correlated States in Materials

Quantum embedding theories are promising approaches to investigate strongly correlated electronic states of active regions of large-scale molecular or condensed systems. Notable examples are spin defects in semiconductors and insulators. We present a detailed derivation of a quantum embedding theory recently introduced, which is based on the definition of effective Hamiltonians. The effect of the environment on a chosen active space is accounted for through screened Coulomb interactions evaluated using density functional theory. Importantly, the random phase approximation is not required, and the evaluation of virtual electronic orbitals is circumvented with algorithms previously developed in the context of calculations based on many-body perturbation theory. In addition, we generalize the quantum embedding theory to active spaces composed of orbitals that are not eigenstates of Kohn–Sham Hamiltonians. Finally, we report results for spin defects in semiconductors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗