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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Influence of oxygen on the optical and electrical properties of magnetron-sputtered indium tin oxide thin films at ambient temperature

Indium Tin Oxide (ITO) thin films are commonly used as transparent conductive layers in the production of solar cells. ITO films are typically heat-treated at temperatures exceeding 200 °C after magnetron sputtering to optimize the physical, optical, and electrical characteristics for photovoltaic devices. Here, this high temperature heating procedure greatly limits the use of potential substrates, particularly those comprised of low-temperature-rated polymers. Herein, we examine the physical, optical, and electrical transport effects of oxygen:argon plasmas during radio frequency magnetron sputtering of ITO on glass and flexible polymer surfaces without subsequent heat treatment. ITO thin films were characterized via sheet resistance testing, UV-Vis spectroscopy, X-ray diffraction, and scanning electron microscopy imaging. Sheet resistance measurements revealed an increase in surface resistance with increasing oxygen concentration during sputtering. UV-Vis optical transmittance measurements demonstrated an improvement in optical transmittance with an increase in oxygen concentration reaching a maximum transmittance at an oxygen concentration of 1-2 %. Most importantly, it was discovered that producing bilayers of ITO with pure argon sputtered plasmas followed by oxygen:argon plasmas produced ITO thin films with suitable resistance and transmittance without the need for high temperature post annealing. These results highlight a methodology for the deposition of ITO thin films on temperature sensitive substrates for flexible photovoltaics and low-cost module production.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Multi-frequency recirculating planar magnetrons

The multi-frequency recirculating planar magnetron (MFRPM) is the first magnetron capable of simultaneous generation of significantly different output frequencies (1 and 2 GHz) in a single operating pulse. Design and simulation of a prototype MFRPM were followed by hardware fabrication and experimental verification using the Michigan Electron Long Beam Accelerator with a Ceramic insulator at −300 kV, 1–5 kA, and 0.14–0.23 T axial magnetic field. Preliminary results demonstrated simultaneous generation of microwave pulses near 1 GHz and 2 GHz at powers up to 44 MW and 21 MW, respectively, with peak total efficiencies up to 9%.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Boron carbide films with reduced nodular defect density deposited by full-face erosion radio-frequency magnetron sputtering

Boron carbide coatings deposited by sputtering with conventional planar magnetrons exhibit nodular growth defects. Here, we demonstrate that the density of nodular defects in B 4 C films can be greatly reduced by using a full-face-erosion magnetron source that achieves a more uniform target erosion by sweeping the confining magnetic field over the target surface. Here, we systematically study properties of B 4 C films deposited on substrates with different tilt angles and demonstrate deposition of ultrathick films with compressive residual stress below 200MPa.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Phase Formation and Electronic Structure Peculiarities in the Al{sub 1–} {sub x}Si{sub x} Film Composites under the Conditions of Magnetron and Ion-Beam Sputtering

The peculiarities of the phase composition and electronic structure of aluminum–silicon composite films near the Al{sub 0.75}Si{sub 0.25} composition obtained by the magnetron and ion-beam sputtering methods on a Si(100) silicon substrate are studied using the X-ray diffraction techniques and ultrasoft X-ray emission spectroscopy. In addition to silicon nanocrystals of about 25 nm in size, an ordered solid solution corresponding to the previously unknown Al{sub 3}Si phase is formed in magnetron sputtering on a polycrystalline Al matrix. Films obtained by ion-beam sputtering of the composite target are found to be monophasic and contained only one phase of an ordered solid solution of aluminum silicide Al{sub 3}Si of the Pm3m cubic system with the primitive cell parameter a = 4.085 Å. However, subsequent pulsed photon annealing of the composite with different radiation doses from 145 to 216 J/cm{sup 2} gives rise to the partial decomposition of the Al{sub 3}Si phase with the formation of free metallic aluminum and silicon nanocrystals with sizes in the range from 50 to 100 nm, depending on the pulsed photon radiation dose.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

High-rate magnetron sputter deposition of low-stress boron carbide films on tilted substrates

Boron carbide is attractive for several applications, including nuclear fuel capsules for inertial confinement fusion (ICF). The fabrication of ICF capsules involves the deposition of ultrathick coatings with density and thickness uniformity on submicron length scales on non-planar (spherical) substrates. Such a deposition requires control of the deposition rate, residual stress, and film microstructure. Here, we systematically study the direct-current magnetron sputter deposition of B 4 C coatings with a full-face-erosion magnetron source as a function of substrate tilt and Ar working gas pressure. Film properties are correlated with results of plasma diagnostics and predictions of Monte Carlo simulations of ballistic sputtering and gas-phase transport. The fabrication of low-stress amorphous B 4 C films with deposition rates of 7μm/h is demonstrated.

Kawasaki, K. [Lawrence Livermore National Laborato↗
DOE OSTI2017

Progress in Developing Novel Double-Shell Metal Targets Via Magnetron Sputtering

Double shell inertial confinement fusion targets represent a unique platform for achieving ignition. They consist of a low-Z outer ablator, a high-Z inner pusher layer, and low density foam layer sandwiched in-between. There is the possibility that double shell targets may achieve ignition at lower ion temperatures due to the containment of radiation and conduction losses as well as requiring smaller convergence ratios. We have explored using magnetron sputtering to make the inner high-Z pusher layers and have demonstrated a W-Cr bilayer inner shell design. An Al-Be mixture was explored as one of the outer ablator materials. This material takes advantage of Al x-ray M-band absorption to reduce pre-heating and still retain Be high ablation speeds. Typical commercial Al-Be materials suffer from phase separation. However, by using magnetron sputtering we have been able to demonstrate homogeneous Al-Be ablator coatings. The sputtered material forms with nano-sized grains and has demonstrated excellent machinability. As a second type of shell explored, pushered single shells can exploit large density gradients to stabilize Rayleigh-Taylor instabilities during compression. Sharp gradients will have higher ignition yields and larger grading lengths will be more stable. We were able to demonstrate pushered single shells made from W-Be gradient layers with various grading slopes and provide simulated results showing that the grading profiles can be influenced by the coating rates of two components.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electron dynamics in radio frequency magnetron sputtering argon discharges with a dielectric target

Abstract We demonstrate a self-consistent and complete description of electron dynamics in a typical electropositive radio frequency magnetron sputtering (RFMS) argon discharge with a dielectric target. The electron dynamics, including the electron power absorption dynamics in one radio frequency (RF) period, is studied via a fully kinetic 2d3v particle-in-cell/Monte Carlo collision (PIC/MCC) electrostatic simulation. The interplay between the fundamental plasma parameters is analyzed through their spatiotemporal dynamics. Due to the influence of magnetic trap on the electron transport, a spatially dependent charging that perturbs the electric potential is observed on the dielectric target surface, resulting in a spatially dependent ion energy distribution along the target surface. The E × B drift-to-discharge current ratio is in approximate agreement with Bohm diffusion. The electron power absorption can be primarily decoupled into the positive Ohmic power absorption in the bulk plasma region and the negative pressure-induced power absorption near the target surface. Ohmic power absorption is the dominant electron power absorption mechanism, mostly contributed by the azimuthal electron current. The power absorption due to electron inertial effects is negligible on time-average. Both the maximum power absorption and dissipation of electrons appear in the bulk plasma region during the second half of the RF period, implying a strong electron trapping in magnetron discharges. The contribution of secondary electrons is negligible under typical RFMS discharge conditions.

Physics↗
DOE OSTI2023

Radio-frequency magnetron sputter deposition of ultrathick boron carbide films

The deposition of thick B 4 C films with low residual stress by conventional direct-current magnetron sputtering is accompanied by the formation of dust particulates contaminating the target, chamber, and substrates and leading to the formation of nodular defects in films. Here, we demonstrate that the formation of particulates is greatly reduced during radio-frequency magnetron sputtering (RFMS). We systematically study properties of B 4 C films deposited by RFMS with a substrate temperature of 330 °C, a target-to-substrate distance of 10 cm, Ar working gas pressure in the range of 4.5–12.0 mTorr (0.6–1.6 Pa), and substrate tilt angles of 0°–80°. All films are x-ray amorphous. A columnar structure develops with increasing either Ar pressure or substrate tilt. For columnar films, the column tilt angle decreases with increasing Ar pressure, which we attribute to a corresponding increase in the width of the distribution of impact angles of deposition flux. In contrast to the Keller–Simmons rule, the deposition rate increases with increasing Ar pressure, which suggests a better coupling of the RF energy to the plasma processes that lead to target sputtering at higher pressures. There is a critical substrate tilt angle above which the total residual stress is close to zero. This critical substrate tilt angle is ~0° for an Ar pressure of 12 mTorr (1.6 Pa). The lower residual stress state, necessary for depositing ultrathick films, is characterized by a larger concentration of nanoscale inhomogeneities and decreased mechanical properties. Based on these results, RFMS deposition of 60-μm-thick B 4 C films is demonstrated.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Nanoscale Cu{sub 2}O films: Radio-frequency magnetron sputtering and structural and optical studies

Nanoscale copper (I) oxide layers are formed by magnetron-assisted sputtering onto glassy and silicon substrates in an oxygen-free environment at room temperature, and the structural and optical properties of the layers are studied. It is shown that copper oxide formed on a silicon substrate exhibits a lower degree of disorder than that formed on a glassy substrate, which is supported by the observation of a higher intensity and a smaller half-width of reflections in the diffraction pattern. The highest intensity of reflections in the diffraction pattern is observed for Cu{sub 2}O films grown on silicon at a magnetron power of 150 W. The absorption and transmittance spectra of these Cu{sub 2}O films are in agreement with the well-known spectra of bulk crystals. In the Raman spectra of the films, phonons inherent in the crystal lattice of cubic Cu{sub 2}O crystals are identified.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Lithium nitride coatings deposited by magnetron sputtering on sulfide electrolytes for solid-state batteries

Lithium nitrides have been considered as promising candidates for interfacial layers in solid-state lithium batteries (SSBs). Previously reported lithium nitride (Li 3 N) coatings were mostly prepared by the reaction between lithium metal and nitrogen gas, which makes it challenging for their thickness control and integration in SSBs. In this study, we prepare Li 3 N via magnetron sputtering for the first time, and apply the resulting coating directly on sulfide solid-state electrolyte. A much smaller impedance increase associated with improved cycling performance is observed in lithium metal symmetric cell. These results demonstrate the feasibility of depositing Li 3 N via magnetron sputtering and its application in SSBs.

25 ENERGY STORAGE↗
DOE OSTI2024

Anomalous Retrograde Drifts in Obstructed Magnetron Microdischarges: a Consequence of a Field Reversal in the Anode Sheath?

The goal of this project was to carry out experiments at the Plasma Collaborative Research Facility (Princeton Plasma Physics Laboratory) aimed at confirming or refuting the hypothesis that an electric field reversal occurs in the near-anode region of a strongly obstructed planar magnetron microdischarges. Magnetron discharges are magnetized plasmas with E x B field topologies, and variants of such discharges are widely used in materials processing. The topologies are also similar to that of Hall thrusters used in space propulsion. Understanding the structure of these discharges will aid in developing reliable simulations that are intended to facilitate the further development of such technologies, as the field reversals, presumed to be due to strong axial-driven electron transport, provides further insight into transport properties. The possible existence of such a field reversal is hinted at because of the retrograde-propagating (i.e., negative E x B) spokes or gradient-driven drift instabilities seen in the high speed videos and segmented anode probing of the plasma. The presence of this field reversal should be reflected in the ion dynamics, particularly, in an ion drift towards the anode. The proposed experiments to be conducted at the PCRF are to characterize this anode-directed ion drift using state-of-the-art laser-induced fluorescence velocimetry. In particular, we seek to see if the near-anode ion velocity reverses direction when the external circuit is varied to alter the electron current demand imposed at the anode. Such an ion velocity reversal would confirm the mechanism, which is that the highly obstructed (small gapped) discharge produces strong axial gradients in plasma density, driving more electrons towards the anode then that demanded by the external circuit.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Performance Characterization of a Solenoid-type Gas Valve for the H- Magnetron Source at FNAL

The magnetron-style H- ion sources currently in operation at Fermilab use piezoelectric gas valves to function. This kind of gas valve is sensitive to small changes in ambient temperature, which affect the stability and performance of the ion source. This motivates the need to find an alternative way of feeding H2 gas into the source. A solenoid-type gas valve has been characterized in a dedicated off-line test stand to assess the feasibility of its use in the operational ion sources. H- ion beams have been extracted at 35 keV using this valve. In this study, the performance of the solenoid gas valve has been characterized measuring the beam current output of the magnetron source with respect to the voltage and pulse width of the signal applied to the gas valve.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Recent Operation of the FNAL Magnetron H- Ion Source

This paper will detail changes in the operational paradigm of the Fermi National Accelerator Laboratory (FNAL) magnetron H- ion source due to upgrades in the accelerator system. Prior to November of 2012 the H- ions for High Energy Physics (HEP) experiments were extracted at ~18 keV vertically downward into a 90 degree bending magnet and accelerated through a Cockcroft-Walton accelerating column to 750 keV. Following the upgrade in the fall of 2012 the H- ions are now directly extracted from a magnetron at 35 keV and accelerated to 750 keV by a Radio Frequency Quadrupole (RFQ). This change in extraction energy as well as the orientation of the ion source required not only a redesign of the ion source, but an updated understanding of its operation at these new values. Discussed in detail are the changes to the ion source timing, arc discharge current, hydrogen gas pressure, and cesium delivery system that were needed to maintain consistent operation at >99% uptime for HEP, with an increased ion source lifetime of over 9 months.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Superlattice-Structured Films by Magnetron Sputtering as New Era Electrodes for Advanced Lithium-ion Batteries

Sustaining sound structures in Si-based anodes is extremely challenging because of the high volumetric expansion that occurs upon cycling. To maintain high capacities over cycles, new designs rely on engineering-specific hierarchical geometries and/or optimized composite compositions such that at least one of the multiple elements serves as buffer and/or electron conductive pathways in the electrodes. In this paper, we report an innovative design in which alternating layers of periodic atomic structures involving multiple elements form a new anode material for lithium-ion batteries. In this work, a superlattice-structured amorphous film made using Si, Mo, and Cu is fabricated by a simple and scalable magnetron sputtering process for the first time. This continuous and repetitive superlattice formation along the film thickness provides a homogeneous stress-strain distribution. The Mo-Cu layer in the superlattice acts as an inactive-conductive layer and as a backbone to handle the volume expansion of active Si upon cycling. This nano-functional superlattice approach enables harnessing the high energy density of Si while maintaining its structural stability. As a result, the electrode exhibits high specific capacity and capacity retention even at high cycling rates. The possible use of the film in a full cell is also evaluated by cycling it vs. the LiMn 1.5 Ni 0.5 O 4 cathode. The full cell maintains a stable capacity of about 900 mAh g anode -1 over 150 cycles, at ~600 mA g -1 rate. The remarkable performance of this nano-functional superlattice film is found to be promising as anodes for applications that require high energy, long calendar life, and excellent abuse tolerance such as electric vehicle batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Probing layered structure of Inconel 625 coatings prepared by magnetron sputtering

Coating/substrate interface and oxide layers present in Inconel 625 film may cause significant impacts on its corrosion behavior. However, layered structure of Inconel 625 coatings remains poorly understood due to its requirement of high spatial resolution. Here we have applied X-ray reflectometry (XRR) to probe the layered structure of magnetron-sputtered Inconel 625 film with atomic spatial resolution. Our results indicate that there exists a 2 nm thick Cr-rich Inconel sublayer underneath the principal film. On top of the principal film, it is found a 2 nm thick oxide layer mainly consisting of NiO. In addition, we detected ~2 Å contamination layer on the sapphire substrate, although argon ion sputter cleaning had been applied to the substrate prior to deposition. By comparing the coatings with different deposition time, we observed that the thickness of principal Inconel 625 layer grows linearly with deposition time, with all other layers remaining constant. Our findings provide insight into the layered structures of Inconel 625 coatings with atomic-scale spatial resolution, and provide directions for future efforts that aim to improve the corrosion resistance of Inconel 625 coatings.

14 SOLAR ENERGY↗
DOE OSTI2018

Accounting for the Complex Surface Structure in Ellipsometric Studies of the Effects of Magnetron Sputtering Modes on the Growth and Optical Properties of In{sub 2}O{sub 3} Films

The efficiency of invoking additional information on optical transmission in solving the inverse problem of ellipsometry by a minimization method is demonstrated in practice for In{sub 2}O{sub 3} fi doped and nondoped with Sn on Al{sub 2}O{sub 3} (012) substrates. This approach allows the thickness and refractive index of thin films with rough surfaces to be uniquely determined. Solutions of the inverse problem in the framework of one-, two-, and multilayer models are compared. The last provides the best description of the experimental data and the correct parameters of the samples. The dependences of the investigated properties of films produced with different magnetron sputtering modes are found using the above methods and models and do not contradict general concepts about the film formation by this material.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Easy Controlled Properties of Quaternary FeNiCrCd Thin Films Deposited from a Single dc Magnetron Sputtering Under the Influence of Deposition Rate

The quaternary FeNiCrCd thin films were produced from a single FeNiCrCr source on a commercial flexible polymer substrate using one dc magnetron sputtering technique. For that, a series of the films with a thickness of 50 nm were produced at different deposition rates of 0.02, 0.04, 0.06, and 0.08 nm/s, separately. In this study, as far as concerned, this was the first time that structural and magnetic properties of FeNiCrCd thin films were investigated. According to compositional analysis, the Fe and Cr contents slightly decreased with increasing deposition rate while Ni was almost constant, whereas those of the amount of Cd atoms increased. However, the atomic amounts of Fe and Cd in the films are quite different from those of the source material. The change of the atomic contents in the films from the source may be attributed to the relatively different bond energy/melting point of metals which have different contents sputtered from source material since this physical parameter is very significant for the sputtering process. For crystal structural analysis, a combination of hexagonal close-packed (hcp) and body-centered cubic (bcc) were observed. The peak intensity of the bcc-dominated planes decreased while the hcp-dominant plane increased since the change in peak intensities is compatible with the compositional analysis with increasing deposition rate. And, the grain sizes decreased gradually from 40.1 to 23.4 nm, with increasing deposition rate from 0.02, to 0.08 nm/s. Also, the film surfaces transformed from a rough to smooth surfaces with decreasing grain sizes as deposition rate increased. For magnetic analysis, the saturation magnetization M{sub s} values decreased as 1030, 773, 730, and 217 emu/cm{sup 3} with increasing deposition rate as 0.02, 0.04, 0.06, and 0.08 nm/s, respectively. In the same manner, the coercivity H{sub c} values were found as 11, 7, 6, and 2 Oe with the deposition rate of 0.02, 0.04, 0.06, and 0.08 nm/s, respectively. The decrease of the H{sub c} may have primarily come from the transformation of rough to smooth surface of the films. It may also be said that the films showed soft magnetic properties due to their low H{sub c} values with increasing deposition rate. Thus, the magnetic properties of the quaternary FeNiCrCd alloy films were seen to be easily improved with the deposition rate parameter for potential use in different industrial applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Magnetic and Magnetotransport Characteristics of Cr-Substituted Ni{sub 55}Mn{sub 34}Sn{sub 11} Thin Films Grown by Magnetron Sputtering

Highly oriented Cr-substituted Ni{sub 55}Mn{sub 34}Sn{sub 11} Heusler thin films having thickness ~ 400 nm were deposited by Ultrahigh vacuum dc magnetron sputtering on MgO (100) substrates. At room temperature, the films exhibit a mixture of dominant L2{sub 1} cubic austenite phase, as revealed by the intense (002) and (004) peaks, along with small fraction of the orthorhombic–martensitic phase. Surface morphology of the thin films showed distribution of Cr-rich and Cr-deficit regions together with patterned and aligned magnetic domains, thus bringing out the inherent room temperature ferromagnetism of the film. At temperatures above the Curie temperature, T{sub C} ~ 321 K, the magnetic behaviour of the films is seen to follow the Curie law rather than the Curie–Weiss law. Ferromagnetic to antiferromagnetic transition appears at T{sub N} ~ 247 K, which gives rise to exchange bias at low temperatures due to the coexistence of the two magnetic orders. This phase coexistence also leads to the formation of a spin glass state deep into the martensitic region. The film exhibits metal-like nature at high temperature and semiconductor-like behaviour with the lowering of temperature. A reentrant metallic state is observed at T ≤ 38 K during cooling that persists up to ≤ 62 K in warming cycle. The hysteresis in the ρ–T curve spread over a very wide temperature range confirms the magnetic phase coexistence in the martensitic state in the present thin films. The magnetoresistance (MR) first increases (2.4% at 300 K and H = 50 kOe) with temperature and maximizes to around ~ 3.25% at T = 150 K and then starts decreasing. Its value in the glassy state is very small. This shows that a magnetic liquid like state is more conducive to larger MR.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗