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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

ECR Nb Films Grown on Amorphous and Crystalline Cu Substrates: Influence of Ion Energy

In the pursuit of niobium (Nb) films with similar performance with the commonly used bulk Nb surfaces for Superconducting RF (SRF) applications, significant progress has been made with the development of energetic condensation deposition techniques. Using energetic condensation of ions extracted from plasma generated by Electron Cyclotron Resonance, it has been demonstrated that Nb films with good structural properties and RRR comparable to bulk values can be produced on metallic substrates. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. Particular attention is given to the nucleation conditions to create a favourable template for growing the final surface exposed to SRF fields. The influence of the deposition energy on film growth on copper substrates is investigated with the characterization of the film surface, structure, superconducting properties and RF performance.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Thin Films Development For Superconducting RF Applications

Significant progress has recently been made in the development of niobium (Nb) films for Superconducting RF (SRF) applications using energetic condensation of ions extracted from plasma generated by Electron Cyclotron Resonance. Nb films with RRR comparable to bulk values are readily produced on both metallic and insulating substrates. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. Particular attention is given to the nucleation conditions to create a favorable template for growing the final surface exposed to SRF fields. The influence of the deposition energy is investigated with the characterization of the film surface, structure, superconducting properties and RF performance. With a similar approach, High Power Impulse Magnetron Sputtering (HiPIMS) is investigated for the development of multilayer SIS (superconductor-insulator-superconductor) structures which have the theoretical prospect to reach RF performance beyond bulk Nb. This paper presents results on the correlation of the surface and material characteristics with the superconducting properties and RF surface impedance for Nb and multilayered NbTiN-based SIS films produced on a variety of substrates.

Zhao, X.↗
NASA NTRS1976

Ion beam sputter modification of the surface morphology of biological implants

The surface chemistry and texture of materials used for biological implants may significantly influence their performance and biocompatibility. Recent interest in the microscopic control of implant surface texture has led to the evaluation of ion beam sputtering as a potentially useful surface roughening technique. Ion sources, similar to electron bombardment ion thrusters designed for propulsive applications, are used to roughen the surfaces of various biocompatible alloys or polymer materials. These materials are typically used for dental implants, orthopedic prostheses, vascular prostheses, and artificial heart components. Masking techniques and resulting surface textures are described along with progress concerning evaluation of the biological response to the ion beam sputtered surfaces.

Weigand, A. J.↗
DOE OSTI2012

Temporal stability of Y Ba Cu O nano Josephson junctions from ion irradiation

We investigate the temporal stability of YBa2Cu3O7 Josephson junctions created by ion irradiation through a nano-scale implant mask fabricated using electron beam lithography and reactive ion etching. A comparison of current-voltage characteristics measured for junctions after fabrication and eight years of storage at room temperature show a slight decrease in critical current and increase in normal state resistance consistent with broadening of the weaklink from diffusion of defects. Shapiro step measurements performed 8 years after fabrication reveal that device uniformity is maintained and is strong evidence that these devices have excellent temporal stability for applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

Titanium in silicon: Lattice positions and electronic properties

Secondary ion mass spectroscopy (SIMS) and deep level transient spectroscopy measurements were carried out on Czochralski (Cz)- and float-zone-grown (FZ) Si crystals, which were implanted with Ti ions and annealed in the temperature range 600–900 °C. The electrical behavior of Ti atoms is found to be different in Cz- and FZ-Si annealed at 650 °C, although the Ti SIMS profiles are similar. It is argued that interstitial Ti atoms (Ti{sub i}) in FZ-Si crystals interact with implantation-induced vacancies and take a substitutional position (Ti{sub s}). No energy levels which can be assigned to Ti{sub s} have been detected in this work or in previous experimental literature. However, previous calculations suggest that Ti{sub s} is a deep acceptor in Si. We show from density functional calculations that by taking proper account of interactions within the d-shell of the Ti impurity the electronic structure of Ti{sub s} has no levels in the band gap. The calculations show that Ti{sub i} is more energetically favorable than Ti{sub s} and that Ti{sub i} binds more strongly to the silicon vacancy than interstitial oxygen does, explaining the observed differences between FZ- and Cz-irradiated materials.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Formation of Precipitates in Si Implanted with {sup 64}Zn{sup +} and {sup 16}O{sup +} Ions

The results of studying the surface Si layer and precipitate formation in CZ n-Si(100) samples sequentially implanted with {sup 64}Zn{sup +} ions with a dose of 5 × 10{sup 16} cm{sup 2} and energy of 100 keV and {sup 16}O{sup +} ions with the same dose but an energy of 33 keV at room temperature so that their projection paths R{sub p} = 70 nm would coincide are presented. The post-implantation samples are annealed for 1 h in an inert Ar medium in the temperature range of 400–900°C with a step of 100°C. The profiles of the implanted impurities are studied by time-of-flight secondary ion mass spectrometry. The Si surface is visualized using a scanning electron microscope, while the near-surface layer is visualized with the help of maps of elements formed by Auger electron spectroscopy with profiling over depth. The ZnO(002) texture is formed in an amorphized Si layer after the implantation of Zn and O ions. ZnO(102) crystallites of 5 nm in size are found in a recrystallized single-crystalline Si layer after annealing in Ar at 700°C.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Indistinguishable telecom band photons from a single Er ion in the solid state

Atomic defects in the solid state are a key component of quantum repeater networks for long-distance quantum communication1. Recently, there has been significant interest in rare earth ions, in particular Er 3+ for its telecom band optical transition that allows long-distance transmission in optical fibres. However, the development of repeater nodes based on rare earth ions has been hampered by optical spectral diffusion, precluding indistinguishable single-photon generation. Here, we implant Er 3+ into CaWO 4 , a material that combines a non-polar site symmetry, low decoherence from nuclear spins and is free of background rare earth ions, to realize significantly reduced optical spectral diffusion. For shallow implanted ions coupled to nanophotonic cavities with large Purcell factor, we observe single-scan optical linewidths of 150 kHz and long-term spectral diffusion of 63 kHz, both close to the Purcell-enhanced radiative linewidth of 21 kHz. This enables the observation of Hong–Ou–Mandel interference between successively emitted photons with a visibility of V = 80(4)%, measured after a 36 km delay line. We also observe spin relaxation times T 1,s = 3.7 s and T 2,s > 200 μs, with the latter limited by paramagnetic impurities in the crystal instead of nuclear spins. Furthermore, this represents a notable step towards the construction of telecom band quantum repeater networks with single Er 3+ ions.

42 ENGINEERING↗
NASA NTRS1985

Charged particle modification of ices in the Saturnian and Jovian systems

The modification by ion bombardment of the surfaces of icy objects in the Saturnian and Jovian systems is discussed. Chemical changes in ices are induced by breaking of bonds and by implantation of incident ions. Long-term irradiation by fast ions produces physical changes such as increasing the surface reflectivity and ability to scatter light. On large satellites, molecules which are ejected by ion bombardment are redistributed across the surfaces of large satellites. For small satellites and ring particles bombarded by ions, such as those of Saturn, most or all of the sputtered material is lost to space, forming a neutral torus in the locale of the satellite orbits and rings and supplying ions to the magnetosphere. Noting the existence of such a torus, the sputter erosion and possible stabilization of the E-ring of Saturn is discussed.

Johnson, R. E.↗
NASA NTRS1977

Ion-beam-sputter modification of the surface morphology of biological implants

The surface chemistry and texture of materials used for biological implants may significantly influence their performance and biocompatibility. Recent interest in the microscopic control of implant surface texture has led to the evaluation of ion-beam sputtering as a potentially useful surface roughening technique. Ion sources, similar to electron-bombardment ion thrusters designed for propulsive applications, are used to roughen the surfaces of various biocompatible alloys or polymer materials. These materials are typically used for dental implants, orthopedic prostheses, vascular prostheses, and artificial heart components. Masking techniques and resulting surface textures are described along with progress concerning evaluation of the biological response to the ion-beam-sputtered surfaces.

Weigand, A. J.↗
NASA NTRS1981

Passivation of carbon steel through mercury implantation

An experiment, in which carbon steel samples were implanted with mercury ions from a broad beam ion source and their corrosion characteristics in air were evaluated, is described. Mercury doses of a few mA min/square cm at energies of a few hundred electron volts are shown to effect significant improvements in the corrosion resistance of the treated surfaces. In a warm moist environment the onset of rusting was extended from 15 min. for an untreated sample to approximately 30 hrs. for one implanted at a dose of 33 mA min/square cm with 1000 eV mercury ions.

Wilbur, P. J.↗
NASA NTRS1993

Oxygen isotopes implanted in the LDEF spacecraft

Secondary ion mass spectrometry was used to study oxygen implanted in the surface of copper from the Long Duration Exposure Facility (LDEF). Oxidation that occurred in orbit shows a characteristic oxygen isotope composition, depleted in O-18. The measured depletion is comparable to the predicted depletion (45 percent) based on a model of the gravitational separation of the oxygen isotopes. The anomalous oxygen was contained within 10nm of the surface. Tray E10 was calculated to have received 5.14 x 10(exp 21) atoms of oxygen cm(sup -2) during the LDEF mission and so there is sufficient anomalous implanted oxygen present in the surface to obtain a reliable isotopic profile.

Saxton, J. M.↗
DOE OSTI2025

Irradiation-induced gas production in REBCO-based magnet materials used for future compact fusion reactors

Nuclear fusion is an enticing alternative to current sources of energy, with multilayered Rare-Earth Barium Copper Oxide (REBCO) coated conductors deemed pivotal in the race toward fully realized, commercially viable, and magnetic confinement fusion reactors. In this study, we simulated the ion spectrum expected to evolve from REBCO's nickel-based Hastelloy C-276 substrate and copper stabilizer in an affordable robust compact-like reactor. We then emulated this gas production through helium implantation to investigate changes in materials and superconducting properties. Our results revealed that the substrate and stabilizer are capable of producing protons energetic enough to recoil throughout the tape thickness in appreciable doses, and alphas energetic enough to deposit 7.54 × 1014 ions/cm2 or 50.1 helium appm in the superconducting layer over a 30-year reactor lifetime. The superconducting layer of SuperPower® tapes exhibited at least double the swelling rate of the other major layers, and both SuperPower and Fujikura Ltd. tapes displayed microstructural changes in the REBCO layer not observed in isotropic metals. For the estimated lifetime fluence, the Fujikura tapes showed a ∼1 K reduction in critical temperature and a 32% degradation in critical current for compact reactor-relevant conditions (16 T, 20 K). Nuclear transmutation, low-temperature solder implantations, gas-ion evolution, the influence of gas production on vortex dynamics, and other related considerations are also discussed.

Reis, Chris↗
NASA NTRS1983

Electron microscopic observations of hydrogen implantation in ilmenites

Hydrogen ion beams were found to form submicrometer, bumpy textures on the surface of ilmenite grains. From this effect, it is believed that similar bumpy textures seen on lunar ilmenite, pyroxene, and olivine grains are likely to be caused by solar wind irradiation. As a consequence, the concentration of bumpy textured grains may be a useful index of surface maturity for lunar soils. An attempt was made to search for grains with these bumpy textures in interplanetary dust and lunar and meteoritic regolith breccias in order to obtain information about the duration of their exposure to the solar wind. Solar wind irradiation was simulated on natural, terrestrial ilmenite. Hydrogen ion beams were directed at small grains and polished sections which were then examined by electron microscopy.

Blanford, G. E.↗
NASA NTRS2020

The Role of Solar Wind Ion Processing in Space Weathering of Olivine: Unraveling the Paradox of Laboratory Irradiation Results Compared to Observations of Natural Samples

Ion irradiation by the solar wind plays a major role in space weathering. Among its multiple effects are ion damage and implantation processes that alter the crystal structure as well as chemical composition of the outer few 100 nanometers of space exposed regolith grains. This forms a portion of the space weathered rims on lunar and asteroidal regolith grains that is uniquely ion-processed. One aspect of these ion-processed grain rims is the possible link between their widths, and degree of ion damage, and the length of exposure of their host grain on the topmost surface of lunar and asteroidal regoliths. Ultimately, quantifying this link relies on laboratory ion irradiation experiments to calibrate the ion fluence or dose at which different degrees and depths of ion damage occur. Here we discuss evidence, specifically from the mineral olivine, suggesting there may be limitations in extrapolating the results of laboratory ion irradiation experiments to natural ion irradiation by the solar wind.

Christoffersen, R.↗
DOE OSTI2019

Structure and Properties of Zn-Implanted Si Near-Surface Layer Modification Depending on Irradiation Fluence of {sup 132}Xe{sup 26+} Ions with Energy of 167 MeV

Single-crystal n-Si(100) wafers are implanted with {sup 64}Zn{sup +} ions with an energy of 50 keV and dose of 5 × 10{sup 16} cm{sup –2}. Then the samples are irradiated with {sup 132}Xe{sup 26+} ions with an energy of 167 MeV in the range of fluences from 1 × 10{sup 12} to 5 × 10{sup 14} cm{sup –2}. The surface and cross section of the samples are visualized by scanning electron microscopy and transmission electron microscopy. The distribution of implanted Zn atoms is studied by time-of-flight secondary-ion mass spectrometry. After irradiation with Xe, surface pores and clusters consisting of a Zn–ZnO mixture are observed at the sample surface. In the amorphized subsurface Si layer, zinc and zinc-oxide phases are detected. After irradiation with Xe with a fluence of 5 × 10{sup 14} cm{sup –2}, no zinc or zinc-oxide clusters are detected in the samples by the methods used in the study.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Optical activity and defect/dopant evolution in ZnO implanted with Er

The effects of annealing on the optical properties and defect/dopant evolution in wurtzite (0001) ZnO single crystals implanted with Er ions are studied using a combination of Rutherford backscattering/channeling spectrometry and photoluminescence measurements. The results suggest a lattice recovery behavior dependent on ion dose and involving formation/evolution of an anomalous multipeak defect distribution, thermal stability of optically active Er complexes, and Er outdiffusion. An intermediate defect band occurring between the surface and ion-induced defects in the bulk is stable up to 900 °C and has a photoluminescence signature around 420 nm well corresponding to Zn interstitials. The optical activity of the Er atoms reaches a maximum after annealing at 700 °C but is not directly associated to the ideal Zn site configuration, since the Er substitutional fraction is maximal already in the as-implanted state. In its turn, annealing at temperatures above 700 °C leads to dissociation of the optically active Er complexes with subsequent outdiffusion of Er accompanied by the efficient lattice recovery.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗