Search NASA⌕ Search

SEARCH · Search NASA

Results for “MAGNETRONS”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Cathodic NH 4 + leaching of nitrogen impurities in CoMo thin-film electrodes in aqueous acidic solutions

Electrocatalytic reduction of dinitrogen (N 2 ) to ammonium (NH 4 + ) in acidic aqueous solutions was investigated at ambient temperature and pressure using a cobalt–molybdenum (CoMo) thin-film electrode prepared by magnetron reactive sputtering. Increased concentrations of ammonium ions (NH 4 + ) were consistently detected in the electrolyte using ion chromatography (IC) after constant-potential electrolysis at various potentials (≤-0.29 V vs. RHE). Using a newly developed analytical method based on ammonia derivatization, performing the experiments with 15 N 2 -labelled gas led however to the detection of increased 14 NH 4 + concentrations instead of 15 NH 4 + . X-ray photoelectron spectroscopic (XPS) analysis of the electrode surface revealed the presence of Mo[triple bond, length as m-dash]N and Mo–NH x species. Several contamination sources were identified that led to substantial increases in the concentration of ammonium ions, including 15 NH 3 impurities in 15 N 2 gas. The observed ammonium concentrations can be consistently ascribed to leaching of nitrogen ( 14 N) impurities incorporated in the CoMo film during the sputtering process. Therefore, researchers in the field are urged to adopt extended protocols to identify and eliminate sources of ammonia contamination and to very carefully monitor the ammonium concentrations in each experimental step.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Effect of gas ratio on tribological properties of sputter deposited TiN coatings

Titanium nitride (TiN) coatings were deposited on Si, corning glass, pins of mild steel (MS, ϕ3mm), aluminium (Al, ϕ4mm) and brass (ϕ6mm) substratesby DC magnetron sputtering. The argon and nitrogen (Ar:N{sub 2})gas ratio was precisely controlled by Mass Flow Controller (MFC) and was varied systematically at diffract values of 10:10,12:08, 16:04 and 18:02sccm. The structural properties of TiN coatings were characterized by X-ray diffraction (XRD) and its surface topography was studied using field emission scanning electron microscopy (FE-SEM). The tribological properties of TiN coatings were investigated using pin-on-disc tribometer.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structural and morphological properties of mesoporous carbon coated molybdenum oxide films

In the present study, we report the structural and morphological properties of mesoporous carbon coated molybdenum oxide films. The deposition of films was carried out in a two-step process, the first step involves deposition of molybdenum and carbon bilayer thin films using DC magnetron sputtering. In the second step the sample was ex-situ annealed in a muffle furnace at different temperatures (400°C to 600°C) and air cooled in the ambient atmosphere. The formation of the meso-porous carbon clusters on molybdenum oxide during the cooling step was investigated using FESEM and AFM techniques. The structural details were explored using XRD. The meso-porous carbon were found growing over molybdenum oxide layer as a result of segregation phenomena.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

The confinement of phonon propagation in TiAlN/Ag multilayer coatings with anomalously low heat conductivity

TiAlN/Ag multilayer coatings with a different number of bilayers and thicknesses of individual layers were fabricated by DC magnetron co-sputtering. Thermal conductivity was measured in dependence of Ag layer thickness. It was found anomalous low thermal conductivity of silver comparing to TiAlN and Ag bulk standards and TiAlN/TiN multilayers. The physical nature of such thermal barrier properties of the multilayer coatings was explained on the basis of reflection electron energy loss spectroscopy. The analysis shows that nanostructuring of the coating decreases the density of states and velocity of acoustic phonons propagation. At the same time, multiphonon channels of heat propagation degenerate. These results demonstrate that metal-dielectric interfaces in TiAlN/Ag coatings are insurmountable obstacles for acoustic phonons propagation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Suppression effect of silicon (Si) on Er{sup 3+} 1.54μm excitation in ZnO thin films

We have investigated the photoluminescence (PL) characteristics of ZnO:Er thin films on Si (100) single crystal and SiO{sub 2}-on-silicon (SiO{sub 2}) substrates, synthesized by radio frequency magnetron sputtering. Rutherford backscattering/channeling spectrometry (RBS), X-ray diffraction (XRD) and atomic force microscope (AFM) were used to analyze the properties of thin films. The diffusion depth profiles of Si were determined by second ion mass spectrometry (SIMS). Infrared spectra were obtained from the spectrometer and related instruments. Compared with the results at room temperature (RT), PL (1.54μm) intensity increased when samples were annealed at 250°C and decreased when at 550°C. A new peak at 1.15μm from silicon (Si) appeared in 550°C samples. The Si dopants in ZnO film, either through the diffusion of Si from the substrate or ambient, directly absorbed the energy of pumping light and resulted in the suppression of Er{sup 3+} 1.54μm excitation. Furthermore, the energy transmission efficiency between Si and Er{sup 3+} was very low when compared with silicon nanocrystal (Si-NC). Both made the PL (1.54μm) intensity decrease. All the data in experiments proved the negative effects of Si dopants on PL at 1.54μm. And further research is going on.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Structure and enhanced thermochromic performance of low-temperature fabricated VO 2 /V 2 O 3 thin film

For VO 2 -based smart window manufacture, it is a long-standing demand for high-quality thin films deposited at low temperature. In this paper, the thermochromic films of VO 2 were deposited by a magnetron sputtering method at a fairly low temperature of 250 °C without subsequent annealing by embedding a V 2 O 3 interlayer. V 2 O 3 acts as a seed layer to lower the depositing temperature and buffer layer to epitaxial grow VO 2 film. The VO 2 /V 2 O 3 films display high solar modulating ability and narrow hysteresis loop. Finally, our data can serve as a promising point for industrial production with high degree of crystallinity at a low temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Fabrication and efficiency measurement of a Mo/C/Si/C three material system multilayer Laue lens

In this letter we report on the manufacturing of a multilayer Laue lens (MLL) consisting of a multilayer stack with three materials: molybdenum and silicon as absorber and spacer layer, respectively, and carbon as transition layers. The design has four layers per period: Mo/C/Si/C. It yields 6000 zones, and provides an aperture of 50 μm. This allows the MLL structure to accept a large portion of the coherent part of the beam and achieving a small spot size. The MLL deposition was made by magnetron sputtering at the Fraunhofer IWS, the sectioning was done by laser cutting and subsequent focused ion beam milling to a thickness that provides a good efficiency for a photon energy of 12 keV. The diffraction efficiency as a function of the tilting angle has been measured at beamline 1-BM of the Advanced Photon Source. An efficiency of almost 40% has been achieved. This shows that the material system performs well compared to MLLs made of two-materials and that it is in an excellent agreement with the numerically calculated efficiency for a comparable molybdenum/silicon bilayer system lens. Here, we conclude that the three material system offers high efficiencies and is advantageous for stress reduction in MLLs.

36 MATERIALS SCIENCE↗
DOE OSTI2017

A metal-insulator transition study of VO 2 thin films grown on sapphire substrates

In this paper, vanadium thin films were deposited on sapphire substrates by DC magnetron sputtering and then oxidized in a tube furnace filled with oxygen under different temperatures and oxygen flow rates. The significant influence of the oxygen flow rate and oxidation temperature on the electrical and structural properties of the vanadium oxide thin films were investigated systematically. It shows the pure vanadium dioxide (VO 2 ) state can only be obtained in a very narrow temperature and oxygen flow rate range. The resistivity change during the metal-insulator transition varies from 0.2 to 4 orders of magnitude depending on the oxidation condition. Large thermal hysteresis during the metal-insulator phase transition was observed during the transition compared to the results in literature. Proper oxidation conditions can significantly reduce the thermal hysteresis. Finally, the fabricated VO 2 thin films showed the potential to be applied in the development of electrical sensors and other smart devices.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of surface tension and viscosity on gold and silver sputtered onto liquid substrates

Here, we report on DC magnetron sputtering of gold and silver onto liquid substrates of varying viscosities and surface tensions. We were able to separate the effects of viscosity from surface tension by depositing the metals onto silicone oils with a range of viscosities. The effects of surface tension were studied by depositing the metals onto squalene, poly(ethylene glycol), and glycerol. It was discovered that dispersed nanoparticles were formed on liquids with low surface tension and low viscosity whereas dense films were formed on liquids with low surface tension and high viscosity. Nanoparticles were formed on both the liquid surface and within the bulk liquid for high surface tension liquids. Our findings can be used to tailor the metal and liquid interaction to fabricate particles and films for various applications in optics, electronics, and catalysis.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Hard x-ray standing-wave photoemission insights into the structure of an epitaxial Fe/MgO multilayer magnetic tunnel junction

The Fe/MgO magnetic tunnel junction is a classic spintronic system, with current importance technologically and interest for future innovation. The key magnetic properties are linked directly to the structure of hard-to-access buried interfaces, and the Fe and MgO components near the surface are unstable when exposed to air, making a deeper probing, nondestructive, in-situ measurement ideal for this system. We have thus applied hard X-ray photoemission spectroscopy (HXPS) and standing-wave (SW) HXPS in the few kilo-electron-volt energy range to probe the structure of an epitaxially grown MgO/Fe superlattice. The superlattice consists of 9 repeats of MgO grown on Fe by magnetron sputtering on an MgO(001) substrate, with a protective Al 2 O 3 capping layer. We determine through SW-HXPS that 8 of the 9 repeats are similar and ordered, with a period of 33 ± 4 Å, with the minor presence of FeO at the interfaces and a significantly distorted top bilayer with ca. 3 times the oxidation of the lower layers at the top MgO/Fe interface. There is evidence of asymmetrical oxidation on the top and bottom of the Fe layers. We find agreement with dark-field scanning transmission electron microscope (STEM) and X-ray reflectivity measurements. Through the STEM measurements, we confirm an overall epitaxial stack with dislocations and warping at the interfaces of ca. 5 Å. We also note a distinct difference in the top bilayer, especially MgO, with possible Fe inclusions. Finally, we thus demonstrate that SW-HXPS can be used to probe deep buried interfaces of novel magnetic devices with few-angstrom precision.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Time-resolved laser-induced desorption spectroscopy (LIDS) for quantified in-situ hydrogen isotope retention measurement and removal from plasma facing materials

A laboratory scale laser induced thermal desorption spectroscopy system is developed and tested on tungsten-deuterium and titanium-deuterium codeposits, and its feasibility as a hydrogenic inventory measurement diagnostic is demonstrated over a range of retention values from 5 × 10 19 m -2 to 7 × 10 23 m -2 for absorbed laser power densities as low as 8 MW m -2 . Codeposit layer samples are grown by magnetron sputtering and immersed in a weak argon rf plasma. A 1 kW fiber laser (λ = 1100 nm) heats the samples up to a peak surface temperature ranging from 900 to 1500 K using pulse widths of 0.5 and 1 s. Spectral line emission from Balmer series Dα and Hα from thermally desorbed deuterium and hydrogen, as well as line emission from argon, are monitored as a function of time using an optical spectrometer with maximum temporal resolution of 1 ms. To correct for wall recycling and pumping speed, and to accurately measure the time evolution of the laser-induced thermal desorption, the raw Dα signal is deconvolved with the system response function, which is obtained by injecting a short burst of D 2 to approximate an impulse. Calibration is done with a standard D 2 leak, and laser induced desorption spectroscopy deuterium retention values are found to be in good agreement with companion measurements made using conventional temperature programmed desorption on samples from the same codeposit batch.

36 MATERIALS SCIENCE↗
DOE OSTI2020

High quality epitaxial thin films and exchange bias of antiferromagnetic Dirac semimetal FeSn

FeSn is a topological semimetal (TSM) and kagome antiferromagnet (AFM) composed of alternating Fe 3 Sn kagome planes and honeycomb Sn planes. This unique structure gives rise to exotic features in the band structures such as the coexistence of Dirac cones and flatbands near the Fermi level, fully spin-polarized 2D surface Dirac fermions, and the ability to open a large gap in the Dirac cone by reorienting the Néel vector. In this paper, we report the synthesis of high-quality epitaxial (0001) FeSn films by magnetron sputtering. Using FeSn/Py heterostructures, we show a large exchange bias effect that reaches an exchange field of 220 Oe at 5 K, providing unambiguous evidence of antiferromagnetism and strong interlayer exchange coupling in our films. Field cycling studies show steep initial training effects, highlighting the complex magnetic interactions and anisotropy. Importantly, our work provides a simple, alternative means to fabricate FeSn films and heterostructures, making it easier to explore the topological physics of AFM TSMs and develop FeSn-based spintronics.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The role of water vapor during the synthesis of hydrogen doped In 2 O 3

Hydrogen-doped In 2 O 3 synthesized using magnetron sputtering or atomic layer deposition in the presence of water vapor has high transparency in the near infra-red region and mobility values that are almost three to four times of those in commercially used In 2 O 3 :Sn at a much lower carrier concentration. However, simple questions like what happens when water molecules enter In 2 O 3 or why the dominant charge carrier changes from an oxygen vacancy in In 2 O 3 :Sn to H + in In 2 O 3 are not clear. Using hybrid functional based density functional theory calculations, in this study we show that water molecules spontaneously split into H + and OH – . The H + interstitial bonds with an oxygen in In 2 O 3 , and the OH – interstitial occupies a vacant lattice site or is trapped by an oxygen vacancy. Thus, in agreement with experimental findings, our results suggest that the concentration of oxygen vacancies decreases as the partial pressure of water increases. The charge transition level, ϵ ( – / + ) , of a hydrogen interstitial and the Fermi level at which the formation energies of OH – and H + are equal lie above the conduction band minimum, suggesting that the H + interstitial has a lower formation energy. In addition, water molecules do not exhibit any propensity to form clusters, meaning that H + ions can diffuse and remain spatially separated from each other.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Tilted fluctuation electron microscopy

Fluctuation electron microscopy (FEM) is a scanning nanodiffraction-based method that offers a unique approach to characterizing nanometer-scale medium-range order (MRO) in disordered materials. In addition to determining the degree of MRO, careful analysis of scanning nanodiffraction data can also be used to determine strain in thin film amorphous samples. We applied FEM to characterize the strain and MRO of magnetron sputtered amorphous tantalum (a-Ta) thin films over a range of tilt angles from 0° to 45° in order to measure any deviations between the in-plane and out-of-plane strain and MRO. We validate our approach using electron diffraction simulations of FEM experiments for a-Ta. We measure anisotropic strain in the simulated a-Ta diffraction patterns and find that the experimental a-Ta is isotropically strained within the accuracy of our method. Our approach provides a workflow for acquiring tilted scanning nanodiffraction data, determining the relative strain and ordering as a function of in- A nd out-of-plane directions, and removing any artifacts induced in FEM data due to strain. We also describe some limitations of the tilted FEM method when applied to thin films with very low strains.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Sputter-deposited low-stress boron carbide films

Significant challenges have been faced in the manufacturing of low-stress B 4 C films. Here, we demonstrate a set of process parameters for direct-current magnetron sputter deposition of smooth, high-purity, amorphous B 4 C films with near-zero total residual stress and with thicknesses up to 10 μm. Films are characterized by a combination of high-energy ion scattering, x-ray diffraction, electron microscopy, and stress measurements based on substrate curvature. In order to facilitate the process transfer to other sputtering geometries, the favorable deposition conditions are correlated with distributions of landing energies and incident angles of depositing species estimated by Monte Carlo simulations of ballistic collisions and gas phase atomic transport. Based on such simulations, a decrease in compressive stress with increasing Ar working gas pressure is attributed to the corresponding broadening of the angular distribution of depositing species and associated atomic shadowing effects.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Reactive co-sputtering of ternary Au–Ta–O films with tunable electrical resistivity

Heavy-metal-based films with high electrical resistivity are needed for hohlraums for magnetically-assisted inertial confinement fusion. Here, we study ternary Au-Ta-O films deposited by reactive direct-current magnetron co-sputtering from elemental Au and Ta targets in an oxygen containing atmosphere. By varying O content, the electrical resistivity of films can be tuned in a wide range of ~ 100 - 40,000 μΩ cm. With increasing O content, a drastic increase in resistivity occurs at ~ 45 at.% of O, separating regimes with two different dominant conduction mechanisms attributed to metallic conduction through the Au-Ta alloy matrix (for ≲ 45 at.% of O) and tunneling across insulating Ta 2 O 5 layers separating conducting islands (for ≳ 45 at.% of O). Post-deposition annealing at 300 °C leads to the segregation of Au into ~ 50-nm islands, sharply decreasing the resistivity for films with ≳ 45 at.% of O but not for the metal-like films with lower O content.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Ferroelectric Al1 − xBxN–GaN heterostructures

This report demonstrates Al0.93B0.7N thin films grown epitaxially on n-type GaN (0002)/c-plane sapphire substrates by reactive magnetron sputtering at 300 °C. At 200 nm film thickness, the Al0.93B0.07N layers exhibit partially relaxed substrate-induced epitaxial strain, a 0.16° wide (0002) rocking curve, in-plane crystallographic registry, and sub-nanometer surface roughness. Electrically, the stack shows robust hysteresis over three frequency decades, a remanent polarization of ∼125 μC/cm2, a strongly frequency dependent coercive field, highly uniform dc leakage currents, and endurance >106 field cycles. This report validates possibilities for ferroelectric nitride integration into conventional III-nitride heterostructures with high crystalline fidelity, high electrical resistivity, and persistent hysteresis. Such materials are synthesizable at thermal budgets and temperatures compatible with back-end-of-the-line boundary conditions.

Physics↗