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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Defect Stability in CdTe Based on Formation Energies and Migration Barriers

Native point defects are thought to play a key role in CdTe, either as compensation centers in intentionally doped material, as a source of conductivity in nominally undoped material, or as electron–hole recombination centers. Here, the discussion of their concentration and impact has often centered only on formation energies and transition levels. Using hybrid density functional calculations, including the effects of spin–orbit coupling (SOC), we discuss the stability of native point defects in CdTe based on their formation energies and migration barriers. We show that although Cd interstitials are the lowest energy donor defects, they are unstable at room temperature due to a low migration barrier. They are important for maintaining charge neutrality during growth or annealing at high temperatures, but once the material is brought to room temperature, they are not frozen in as often assumed and are expected to anneal out, leaving the other more stable defects to determine the conductivity. Taking this into account in the solution of the charge neutrality equation, we are able to predict the conductivity type and carrier concentrations that are in good agreement with experimental observations.

14 SOLAR ENERGY↗
DOE OSTI2020

Surface Charge and Electrostatic Spin Crossover Effects in CoN 4 Electrocatalysts

Carbon materials doped with nitrogen and 3d transition metals have attracted a great deal of interest for catalyzing electrochemical reactions such as water splitting, oxygen reduction, and carbon dioxide reduction. Here, we employed density functional theory to study Co–N-doped carbon as electrocatalysts for the oxygen reduction and oxygen evolution reactions. Specifically, we investigated the interplay among adsorption energies, the spin state of the CoN 4 active center, and the applied potential. We found that adsorption energies strongly depend on both the applied potential and the spin state of the Co center. Furthermore, spin state transitions induced by the applied potential also play an important role in determining the adsorption energies. Here, this effect originates from a different potential of zero charge and capacitance of each spin state.

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

Origin of the enhanced Nb3Sn performance by combined Hf and Ta doping

Abstract In recent years there has been an increasing effort in improving the performance of Nb 3 Sn for high-field applications, in particular for the fabrication of conductors suitable for the realization of the Future Circular Collider (FCC) at CERN. This challenging task has led to the investigation of new routes to advance the high-field pinning properties, the irreversibility and the upper critical fields ( H Irr and H c2 , respectively). The effect of hafnium addition to the standard Nb-4Ta alloy has been recently demonstrated to be particularly promising and, in this paper, we investigate the origins of the observed improvements of the superconducting properties. Electron microscopy, Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS) and Atom Probe Tomography (APT) characterization clearly show that, in presence of oxygen, both fine Nb 3 Sn grains and HfO 2 nanoparticles form. Although EXAFS is unable to detect significant amounts of Hf in the A15 structure, APT does indeed reveal some residual intragrain metallic Hf. To investigate the layer properties in more detail, we created a microbridge from a thin lamella extracted by Focused Ion Beam (FIB) and measured the transport properties of Ta-Hf-doped Nb 3 Sn. H c2 (0) is enhanced to 30.8 T by the introduction of Hf, ~ 1 T higher than those of only Ta-doped Nb 3 Sn, and, even more importantly the position of the pinning force maximum exceeds 6 T, against the typical ~ 4.5–4.7 T of the only Ta-doped material. These results show that the improvements generated by Hf addition can significantly enhance the high-field performance, bringing Nb 3 Sn closer to the requirements necessary for FCC realization.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A perspective on the pathway to a scalable quantum internet using rare-earth ions

The ultimate realization of a global quantum internet will require advances in scalable technologies capable of generating, storing, and manipulating quantum information. The essential devices that will perform these tasks in a quantum network are quantum repeaters, which will enable the long-range distribution of entanglement between distant network nodes. Here, in this review, we provide an overview of the primary functions of a quantum repeater and discuss progress that has been made toward the development of repeaters with rare-earth ion doped materials while noting challenges that are being faced as the technologies mature. We give particular attention to erbium, which is well suited for networking applications. Finally, we provide a discussion of near-term benchmarks that can further guide rare-earth ion platforms for impact in near-term quantum networks.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Charge density wave fluctuation driven composite order in layered kagome metals

The newly discovered kagome metals AV 3 Sb 5 (A = K, Rb, Cs) offer an exciting route to study exotic phases arising due to interplay between electronic correlations and topology. Besides superconductivity, these materials exhibit a charge-density wave (CDW) phase occurring at ~ 100 K, whose origin still remains elusive. The robust multi-component 2 × 2 CDW phase in these systems is of great interest due to the presence of an unusually large anomalous Hall effect. In quasi-2D systems with weak inter-layer coupling fluctuation driven exotic phases may appear. In particular in systems with multi-component order parameters fluctuations may lead to establishment of composite order when only products of individual order parameters condense while the individual ones themselves remain disordered. Here we argue that such fluctuation-driven regime of composite CDW order may exist in thin films of kagome metals above the CDW transition temperature. It is suggested that the melting of the Trihexagonal state in the material doped way from the van Hove singularities gives rise to a pseudogap regime where the spectral weight is concentrated in small pockets and most of the original Fermi surface is gapped. Our findings suggest possible presence of exotic phases in the weakly coupled layered kagome metals, more so in the newly synthesized thin films of kagome metals.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

A guide on modeling electrostatics of semiconductor detectors in COMSOL Multiphysics ® for DRiFT

Adding a new semiconductor detector into the detector response function toolkit (DRiFT) requires a model of the electric potential and the electric field. To get an accurate electrostatics model, the geometry of the detector should be modeled as closely to the real geometry as feasible, including the semiconductor materials, doping layers and concentrations, and contacts. Since the electric field and potential are used to calculate the induced signal, the results of the detector response functions are largely influenced by the electrostatics models. Initial electrostatics models were completed using Silvaco, however, this document provides guidance on using COMSOL Mulitphysics ® (COMSOL) to model the detectors to give users additional flexibility. Guidance on using COMSOL and its user interface are mostly left out of this document, but best practices for geometry, modeling methods, and data format/exporting are included to help users generate models that are compatible with DRiFT, prevents bugs, issues, and inaccuracies during charge collection calculations. The following summary provides an overview of the document.

42 ENGINEERING↗
DOE OSTI2023

Elastomeric reflection suppressor

Various embodiments of the present technology generally relate to reflection suppressors. More specifically, some embodiments use elastomeric materials doped with optical absorbers for temporary suppression of Fresnel reflections for multiple substrates spanning wide spectral and angular bandwidth. The refractive index of the elastomer can be tuned to match a substrate and thereby minimize reflection. Some embodiments can use the addition of different absorptive dopants to allow for either broadband or wavelength-selective reflection suppression. As performance is limited only by index mismatch, both spectral and angular performance significantly exceed that of anti-reflection coatings. After use, these light traps may be removed and reused without damaging the substrate. These films have uses in spectroscopic ellipsometry, holography, and lithography.

Miller, David↗
DOE OSTI2022

Enabling high energy lithium metal batteries via single-crystal Ni-rich cathode material co-doping strategy

High-capacity Ni-rich layered oxides are promising cathode materials for secondary lithium-based battery systems. However, their structural instability detrimentally affects the battery performance during cell cycling. Here, we report an Al/Zr co-doped single-crystalline LiNi<:sub>0.88 Co 0.09 Mn 0.03 O 2 (SNCM) cathode material to circumvent the instability issue. We found that soluble Al ions are adequately incorporated in the SNCM lattice while the less soluble Zr ions are prone to aggregate in the outer SNCM surface layer. The synergistic effect of Al/Zr co-doping in SNCM lattice improve the Li-ion mobility, relief the internal strain, and suppress the Li/Ni cation mixing upon cycling at high cut-off voltage. These features improve the cathode rate capability and structural stabilization during prolonged cell cycling. In particular, the Zr-rich surface enables the formation of stable cathode-electrolyte interphase, which prevent SNCM from unwanted reactions with the non-aqueous fluorinated liquid electrolyte solution and avoid Ni dissolution. To prove the practical application of the Al/Zr co-doped SNCM, we assembled a 10.8 Ah pouch cell (using a 100 μm thick Li metal anode) capable of delivering initial specific energy of 504.5 Wh kg- 1 at 0.1 °C and 25 °C.

25 ENERGY STORAGE↗
DOE OSTI2023

Dopant for improving casting and electroplating performance

Systems, methods, components, and parts are provided for improving casting and electroplating performance of a plated cast part by doping a semiconductor material with an electrically active dopant before mixing the semiconductor material into a base material. The doped semiconductor material improves the castability of the base material and has an improved electrical conductivity which is closer to that of the base material such that a consistency of a subsequent plating on the part is improved.

Young, Barbara Diane↗
DOE OSTI2021

Optimization of Source Material for in-situ Arsenic Doping via Vapor Transport Deposition of CdTe Films

In-situ doping of CdTe/CdSeTe films with arsenic is performed using pre-doped source material prepared by high pressure Bridgman (HPB) melt growth. Arsenic level in the source material is varied from 1018-1020 cm-3. Correspondingly, dopant incorporation in the films prepared using vapor transport deposition (VTD) varied from 3x1017 cm-3–1x1018cm-3. In this range, dopant activation is found to inversely correlate with the dopant incorporation, suggesting compensation. The results from this study indicate film properties can be adjusted by source material.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2021

Doped gate dielectric materials

A field effect transistor having at least a gate, source, and drain electrodes and a semiconductor channel for controlling transport of charge carriers between the source and drain electrodes, the gate being insulated from the channel by an dielectric, at least a portion of the dielectric disposed between the gate electrode and the semiconductor channel being doped or imbued with the an element which if doped or imbued into a semiconductor material would cause the semiconductor to be p-type. The p-type element used to dope or imbue the gate dielectric is preferably Mg.

Cao, Yu↗
DOE OSTI2022

Doped gate dielectrics materials

A field effect transistor having at least a gate, source, and drain electrodes and a semiconductor channel for controlling transport of charge carriers between the source and drain electrodes, the gate being insulated from the channel by an dielectric, at least a portion of the dielectric disposed between the gate electrode and the semiconductor channel being doped or imbued with the an element which if doped or imbued into a semiconductor material would cause the semiconductor to be p-type. The p-type element used to dope or imbue the gate dielectric is preferably Mg.

Cao, Yu↗
DOE OSTI2020

Aspects of the normal state resistivity of cuprate superconductors

Planar normal state resistivity data taken from three families of cuprate superconductors are compared here with theoretical calculations from the recent extremely correlated Fermi liquid theory (ECFL). The two hole doped cuprate materials LSCO and BSLCO and the electron doped material LCCO have yielded rich data sets at several densities δ and temperatures T, thereby enabling a systematic comparison with theory. The recent ECFL resistivity calculations for the highly correlated t-t'-J model by us give the resistivity for a wide set of model parameters. After using X-ray diffraction and angle resolved photoemission data to fix parameters appearing in the theoretical resistivity, only one parameter, the magnitude of the hopping t, remains undetermined. For each data set, the slope of the experimental resistivity at a single temperature-density point is sufficient to determine t, and hence the resistivity on absolute scale at all remaining densities and temperatures. This procedure is demonstrated to give a fair account of the entire data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Heavy boron doping in superconducting carbon materials

Here we examine physical properties of heavily boron-doped sp 3 -hybridized carbon allotropes: cubic diamond, hexagonal diamond, and body centered tetragonal C 4 . The structural similarity between cubic diamond and hexagonal diamond leads to similar responses to substitutional boron doping. On the other hand, body centered tetragonal C 4 exhibits distinct structural and electronic properties because of its characteristic structure. Our study also shows that the superconducting transition temperatures up to 60 K are possible in heavily doped carbon materials despite their various atomistic structures.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Developing a Low Cost, High Volume and Scalable Manufacturing Technology for Undoped and Heavily P-Type Doped CdTe Feedstock Materials (Final Report)

The goal of this project was to establish a cost-effective and scalable production approach of feedstock (CdTe and Cd-Se-Te) for the solar industry, with the material properties necessary to improve performance and reduce costs. The primary focus was to develop a CdTe synthesis and growth process that pushed the p-type doping of CdTe to previously unattainable levels, while creating a path to scalable production. In our approach, the first step was bulk CdTe growth doped with Group V dopants (P, As, and Sb) using the Modified Vertical Bridgman (MVB) and high Pressure Bridgman (HPB) techniques, and the second step was examination of films deposited by Close-Spaced Sublimation (CSS) and Vapor Transport Deposition (VTD) using this specialized feedstock.

14 SOLAR ENERGY↗
DOE OSTI2021

Ca2+-Doped CeBr3 Scintillating Material

2021 ANS Annual Meeting Conference Papers; June 13-16, 2021 | Omni / Convention Center | Providence, RI; https://epsr.ans.org/meeting/?m=310

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

A plausible method of preparing the ideal p-n junction interface of a thermoelectric material by surface doping

Recent advances in two-dimensional (2D) crystals make it possible to realize an ideal interface structure that is required for device applications. Specifically, a p-n junction made of 2D crystals is predicted to exhibit an atomically well-defined interface that will lead to high device performance. Using angle-resolved photoemission spectroscopy, a simple surface treatment was shown to allow the possible formation of such an interface. Furthermore, Ta adsorption on the surface of a p-doped SnSe shifts the valence band maximum towards the higher binding energy due to the charge transfer from Ta to SnSe that is highly localized at the surface due to the layered structure of SnSe. As a result, the charge carriers of the surface are changed from holes of its bulk characteristics to electrons, while the bulk remains as a p-type semiconductor. This observation suggests that the well-defined interface of a p-n junction with an atomically thin n-region is formed between Ta-adsorbed surface and bulk.

36 MATERIALS SCIENCE↗