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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Wake-up and fatigue mechanisms in ferroelectric Hf 0.5 Zr 0.5 O 2 films with symmetric RuO 2 electrodes

In this work, the mechanisms leading to wake-up and fatigue in ferroelectric hafnium zirconium oxide thin film devices with symmetric RuO 2 electrodes are investigated via polarization, relative permittivity, dielectric nonlinearity, pyroelectric coefficient, and microfocus X-ray diffraction (XRD) measurements. The devices are observed to wake-up for up to 10 3 bipolar pulsed field cycles, after which fatigue occurs with the polarization approaching zero following 10 8 cycles. Wake-up is accompanied by a decrease in both high-field permittivity and hysteresis loop pinching and an increase in pyroelectric coefficient, indicating that the wake-up process involves a combination of transformations from the tetragonal to the orthorhombic phase and domain depinning from defect redistribution. Fatigue is observed to coincide with an increase in irreversible domain wall motion and a decrease in pyroelectric coefficient. Finite pyroelectric coefficients are measured on fully fatigued devices, indicating that domain pinning is a strong contributor to fatigue and that fatigued devices contain domain structures that are unable to switch under the fields applied for measurement. Microfocus XRD patterns measured on each device reveal that the phase constitution is qualitatively unaffected by the field cycling and resultant polarization fatigue. This data indicates that the wake-up process has contributions from both phase transformations and domain depinning, whereas the fatigue process is driven primarily by domain pinning, and the near-zero measured switchable polarization is actually a poled device with immobile domains. These observations provide insight into the physical changes occurring during field cycling of HfO 2 -based ferroelectrics while examining a possible oxide electrode material for silicon CMOS device implementation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Multistate resistance in TaN/(Hf,Zr)O 2 /Ta ferroelectric tunnel junctions

Ferroelectric tunnel junctions (FTJs) utilizing hafnium zirconium oxide (HZO) have emerged as promising non-volatile memory elements for microelectronics, compatible with back end of line (BEOL) complementary–metal–oxide semiconductor fabrication. This study investigates asymmetric electrode TaN/HZO/Ta devices with a 6 nm thick HZO layer as FTJs for multistate resistive memory applications. The individual FTJs exhibit a resistance ratio exceeding 10× when utilized as a binary state device, with pulsing between −1.7 and +1.4 V to set the high resistance state (HRS) and low resistance state (LRS), respectively. Following with reduced write voltage pulses allows the ferroelectric device to operate with a selection of over 32 distinct resistance states (2 5 bits) between the LRS and HRS. This work then explores the stability of the resistance states during write/read pulse cycling, along with the stability of the state after multiple read pulses. Accessing the multibit state shows stability within 50 reads with the binary state remaining stable for more than 4000 reads pulses. With their multistate tunability and versatility, FTJs hold promise as BEOL memory elements for compute-in-memory (CiM) arrays, binary digital memory, or weighted vector matrix multiplication applications with low power consumption during computations.

CMOS↗
DOE OSTI2026

Equation of state for Hf, Ta, W, Re, Os, Ir, Pt, and Au to multi-terapascal pressures from density-functional theory

We present the zero-temperature equation of state (pressure dependence of compression) and phase stability predictions for the 5d-transition metals obtained from all-electron density-functional theory (DFT) calculations. The results compare favorably with experiments but extend beyond current experimental capabilities to 10 TPa. Our study reveals phase changes that are explained from the calculated electronic structure. The cubic face-centered and body-centered structures (fcc and bcc), together with two-, three-, and four-layered hexagonal structures, play major roles under compression. The results’ dependence on the electron exchange and correlation in the DFT approach is investigated, and it is shown that the impact of the choice, while significant at lower pressures, diminishes in the terapascal regime. We further illustrate that the normal parabolic trends in atomic volume and bulk modulus with atomic number, due to the occupation of bonding and anti-bonding 5d states, break down at TPa pressures, suggesting drastically different chemical bonding at these extreme conditions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Isomers and Dark Matter: 180m Ta and 178m Hf [Slides]

Dark matter has attractive gravitational interactions. It does not interact with light, or has very small electromagnetic coupling. It is stable, or has a lifetime much longer than the age of the Universe. No departure model from the law of gravity explains all data, whereas particle dark matter can.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Integral Experiment Validation of Hafnium with TEX-HEU and TEX-Hf [Slides]

Lead by Lawrence Livermore National Laboratory under the U.S. Department of Energy's Nuclear Criticality Safety Program. The goal of TEX is to provide integral benchmark experiments than span the entire neutron energy spectrum and incorporate high-priority materials. TEX includes two test bed configurations providing a baseline for comparison to better understand the contribution of additional materials

Highly Enriched Uranium↗
DOE OSTI2023

The Performance of FBMC-SS in Challenging HF Channel Environments

Provide overview of FBMC-SS waveform Discuss parameters used for simulated results herein Present simulated results in challenging channel environments Cases: 2 path channel with 2nd path frequency offset 2 path MLD and “VP” channels Large narrowband interferer Highly congested interference case Highly dynamic interference case Clarify previously presented results Make conclusions from presented results

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2020

Materials Data on Hf23Se25 by Materials Project

Hf23Se25 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are twenty-three inequivalent Hf sites. In the first Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.70–2.76 Å. In the second Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.72–2.75 Å. In the third Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.75 Å. In the fourth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.77 Å. In the fifth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.70–2.78 Å. In the sixth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.77 Å. In the seventh Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.79 Å. In the eighth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.72–2.74 Å. In the ninth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.70–2.76 Å. In the tenth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.76 Å. In the eleventh Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.70–2.75 Å. In the twelfth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.77 Å. In the thirteenth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.70–2.75 Å. In the fourteenth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.75 Å. In the fifteenth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.72–2.75 Å. In the sixteenth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.72–2.74 Å. In the seventeenth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.75 Å. In the eighteenth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.70–2.77 Å. In the nineteenth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.72–2.74 Å. In the twentieth Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.74 Å. In the twenty-first Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.74 Å. In the twenty-second Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.75 Å. In the twenty-third Hf site, Hf is bonded to six Se atoms to form a mixture of distorted corner, edge, and face-sharing HfSe6 pentagonal pyramids. There are a spread of Hf–Se bond distances ranging from 2.69–2.76 Å. There are twenty-five inequivalent Se sites. In the first Se site, Se is bonded to six Hf atoms to form distorted SeHf6 pentagonal pyramids that share corners with five SeHf6 pentagonal pyramids, edges with three SeHf6 pentagonal pyramids, an edgeedge with one SeHf5 trigonal bipyramid, and a faceface with one SeHf6 pentagonal pyramid. In the second Se site, Se is bonded in a distorted pentagonal planar geometry to five Hf atoms. In the third Se site, Se is bonded to six Hf atoms to form a mixture of distorted corner, edge, and face-sharing SeHf6 pentagonal pyramids. In the fourth Se site, Se is bonded to six Hf atoms to form distorted SeHf6 pentagonal pyramids that share corners with five SeHf6 pentagonal pyramids, a cornercorner with one SeHf5 trigonal bipyramid, edges with two SeHf6 pentagonal pyramids, and faces with two SeHf6 pentagonal pyramids. In the fifth Se site, Se is bonded in a distorted pentagonal planar geometry to five Hf atoms. In the sixth Se site, Se is bonded to six Hf atoms to form a mixture of distorted corner, edge, and face-sharing SeHf6 pentagonal pyramids. In the seventh Se site, Se is bonded in a distorted pentagonal planar geometry to five Hf atoms. In the eighth Se site, Se is bonded in a distorted pentagonal planar geometry to five Hf atoms. In the ninth Se site, Se is bonded to six Hf atoms to form a mixture of distorted corner, edge, and face-sharing SeHf6 pentagonal pyramids. In the tenth Se site, Se is bonded to six Hf atoms to form a mixture of distorted corner, edge, and face-sharing SeHf6 pentagonal pyramids. In the eleventh Se site, Se is bonded in a distorted pentagonal planar geometry to five Hf atoms. In the twelfth Se site, Se is bonded in a distorted pentagonal planar geometry to five Hf atoms. In the thirteenth Se site, Se is bonded to five Hf atoms to form distorted SeHf5 trigonal bipyramids that share corners with seven SeHf6 pentagonal pyramids, a cornercorner with one SeHf5 trigonal bipyramid, edges with four SeHf6 pentagonal pyramids, and a faceface with one SeHf6 pentagonal pyramid. In the fourteenth Se site, Se is bonded in a distorted pentagonal planar geometry to five Hf atoms. In the fifteenth Se site, Se is bonded to six Hf atoms to form distorted SeHf6 pentagonal pyramids that share corners with five SeHf6 pentagonal pyramids, corners with two equivalent SeHf5 trigonal bipyramids, edges with three SeHf6 pentagonal pyramids, and a faceface with one SeHf6 pentagonal pyramid. In the sixteenth Se site, Se is bonded in a distorted pentagonal planar geometry to five Hf atoms. In the seventeenth Se site, Se is bonded to six Hf atoms to form distorted SeHf6 pentagonal pyramids that share corners with five SeHf6 pentagonal pyramids, a cornercorner with one SeHf5 trigonal bipyramid, edges with three SeHf6 pentagonal pyramids, edges with two SeHf5 trigonal bipyramids, and faces with two SeHf6 pentagonal pyramids. In the eighteenth Se site, Se is bonded to six Hf atoms to form distorted SeHf6 pentagonal pyramids that share corners with six SeHf6 pentagonal pyramids, a cornercorner with one SeHf5 trigonal bipyramid, edges with three SeHf6 pentagonal pyramids, edges with two SeHf5 trigonal bipyramids, and a faceface with one SeHf6 pentagonal pyramid. In the nineteenth Se site, Se is bonded to six Hf atoms to form distorted SeHf6 pentagonal pyramids that share corners with seven SeHf6 pentagonal pyramids, a cornercorner with one SeHf5 trigonal bipyramid, edges with three SeHf6 pentagonal pyramids, an edgeedge with one SeHf5 trigonal bipyramid, a faceface with one SeHf6 pentagonal pyramid, and a faceface with one SeHf5 trigonal bipyramid. In the twentieth Se site, Se is bonded to six Hf atoms to form distorted SeHf6 pentagonal pyramids that share corners with six SeHf6 pentagonal pyramids, corners with two SeHf5 trigonal bipyramids, edges with two SeHf6 pentagonal pyramids, an edgeedge with one SeHf5 trigonal bipyramid, and faces with two SeHf6 pentagonal pyramids. In the twenty-first Se site, Se is bonded to six Hf atoms to form distorted SeHf6 pentagonal pyramids that share corners with six SeHf6 pentagonal pyramids, corners with four SeHf5 trigonal bipyramids, edges with three SeHf6 pentagonal pyramids, and faces with two SeHf6 pentagonal pyramids. In the twenty-second Se site, Se is bonded to five Hf atoms to form distorted SeHf5 trigonal bipyramids that share corners with six SeHf6 pentagonal pyramids, a cornercorner with one SeHf5 trigonal bipyramid, edges with four SeHf6 pentagonal pyramids, and a faceface with one SeHf6 pentagonal pyramid. In the twenty-third Se site, Se is bonded in a distorted pentagonal planar geometry to five Hf atoms. In the twenty-fourth Se site, Se is bonded to six Hf atoms to form distorted SeHf6 pentagonal pyramids that share corners with seven SeHf6 pentagonal pyramids, a cornercorner with one SeHf5 trigonal bipyramid, edges with three SeHf6 pentagonal pyramids, an edgeedge with one SeHf5 trigonal bipyramid, a faceface with one SeHf6 pentagonal pyramid, and a faceface with one SeHf5 trigonal bipyramid. In the twenty-fifth Se site, Se is bonded in a distorted pentagonal planar geometry to five Hf atoms.

36 MATERIALS SCIENCE↗