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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 1,423 records · Page 79
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Some Physical Properties of the New Intermetallic Compound NbCd{sub 2}

Solid solutions of cadmium in niobium and NbCd{sub 2} phase are formed by magnetron sputtering and coprecipitation on substrates moving relative to the flow of Nb and Cd particles. The NbCd{sub 2} phase can be described by a tetragonal unit cell with the parameters a = 0.84357 nm, c = 0.54514 nm, and c/a = 0.6426. A very high hole concentration in NbCd{sub 2} is established by studying the coating absorption and transmission spectra corresponding to the intermetallic-compound composition near the fundamental absorption edge, determining the band gap, and measuring the carrier mobility. Such a concentration is characteristic of a strongly degenerate semiconductor or metal. The band gap is determined to be 1.26 eV. The variation in the concentration of carriers and their mobility depending on the cadmium concentration in coatings of the Nb–Cd system confirms the occurrence of the NbCd{sub 2} phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Metal–insulator phase transition in hydrogenated thin films of V{sub 2}O{sub 3}

Temperature dependences of the electrical conductivity of thin vanadium sesquioxide V{sub 2}O{sub 3} films obtained by using the laser sputtering technique have been studied. A significant decrease (by four–five orders of magnitude) in the electrical conductivity has been observed below 150 K as a result of a metal–insulator phase transition. It is shown that hydrogenation of films lowers the temperature of this phase transition.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

The Influence of Relative Content of a Metal Component in a Dielectric Matrix on the Formation and Dimensions of Cobalt Nanocrystallites in Co{sub x}(MgF{sub 2}){sub 100 –} {sub x} Film Composites

The influence of relative content of a metal component on the phase composition and substructure of Co{sub x}(MgF{sub 2}){sub 100 –} {sub x} in a wide range of x = 16–63 at % is studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy. The layers of nanocomposite with a micron thickness have been obtained by the ion-beam sputtering of the target in the argon environment. The results reveal that the relative metal cobalt content in the MgF{sub 2} dielectric matrix strongly affects the phase composition and substructure of nanocomposites. With a lower content of cobalt, it is in the amorphous state in the form of clusters in the MgF{sub 2} nanocrystalline matrix. An increase of cobalt content to x = 29 at % on a sitall substrate and to x = 42 at % on a glass substrate in the X-ray amorphous MgF{sub 2} dielectric matrix leads to the formation of cobalt nanocrystals with a hexagonal crystallographic system, whose sizes are on the order of 10 nm. These are predominately oriented in the basis plane of the (001) hexagonal lattice of α-Со. A further increase of cobalt content to c = 59 at % enlarges the α-Со nanocrystals to ~20 nm with retaining the same orientation. In accordance with a fine structure analysis of XPS spectra of Со 2p and О 1s, cobalt is strongly oxidized on the surface of all the composites; only on the surface of samples with a low content of Co is X‑ray amorphous cobalt found in a metallic state along with cobalt oxide. The IR spectra of these samples with the lowest metal phase content exhibit the pronounced modes from the nanocrystalline MgF{sub 2} dielectric phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Influence of the Thickness of Gadolinium Layers on the Magnetic Properties and Magnetization Reversal Processes in Low-Dimensional Co/Gd/Co Systems

Structural and magnetic characteristics and behavior of thin-film Co/Gd/Co systems obtained by ion plasma sputtering in a magnetic field are reported. X-ray studies showed that cobalt layers in all investigated samples have a nanocrystalline structure. The mean roughness Ra of the surface of the samples does not exceed 0.5 nm and is independent of the Gd layer thickness. The shape of hysteresis loops observed for the Co/Gd/Co system depends of the thickness of the Gd layer, t{sub Gd}. The dependence of the saturation field H{sub S} on t{sub Gd} has an oscillatory character. This fact is explained by interaction of the Co layers through the intermediate Gd layer.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Charging Dielectrics when Bombarded with Ar{sup +} Ions of Medium Energies

A complex facility for measuring the kinetics of high-voltage charging potentials of the surface of massive dielectrics when irradiated with medium-energy Ar{sup +} ions has been created. Measurements of ion emission characteristics, accumulated charges and surface potential have shown effective charging to high positive potentials, close in value to the potential of an ion gun. It is assumed that sputtered ions dominate at the early stage of charging in the process of emission, while in the final stage of irradiation backreflected ions dominate.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

The Element Composition Variation in Lead Zirconate Titanate upon the Ion-Plasma Deposition: Experiment and Simulation

The element composition modification is experimentally studied in PZT thin films obtained via the RF magnetron sputtering with variable working gas pressure. The experimental data were interpreted through the statistic simulation of thermalization and diffusion of sprayed Pb, Zr, and Ti atoms during the ion-plasma deposition of PZT thin films. The simulation data are shown to adequately describe (within the limits of 5%) the change in element composition at various pressures of the gas environment. The study conducted enables one to produce PZT thin films with a set element composition, which is essential for optimizing the electric and physical properties of solid solutions at the morphotropic phase boundary.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Double-Lattice Magnetoplasmonic Structures Based on BIG and Perforated Gold Films

A method of manufacturing double-lattice magnetoplasmonic crystals with the structure (Au/BIG){sup 2}, in which the plasmon gold lattices are displaced relative to each other by half a period, has been presented. Gold films with thicknesses of about 40 nm have been formed by the ion-beam sputtering–deposition method, while the adhesive properties of the films allow the dimensional etching by a sharp-focused ion beam. It has been shown that the formation of the second plasmon lattice located on top of the 100 nm thick garnet layer allows the preserving of the periodicity of the first Au lattice. However, there is a significant influence of diffusion spreading on the lower lattice material, which leads to a decrease in its density. The dependence of the intensity magnetooptical effect in the geometry on the transmission as a function of the thickness of the upper lattice and presence of an additional layer of Ta{sub 2}O{sub 5} has been studied.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Photoluminescence of Cu{sub 2}O Crystals of Different Origins

Low-temperature luminescence spectra of Cu{sub 2}O crystals grown by different methods (copper oxidation, induction charge melting, magnetron sputtering, and hydrothermal), as well as natural crystals, have been compared. It is suggested that the high quality of natural crystals and crystals grown by the hydrothermal method is due to the fact that they grow for a long time at relatively low temperatures, which facilitates the minimization of stress.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Lattice Structure and Dynamics of Two-Layer Heterostructures of Barium–Strontium Titanate and Layered Bismuth Titanate of Various Thicknesses on a Magnesium Oxide Substrate

The lattice structure and dynamics of single-crystal Bi{sub 4}Ti{sub 3}O{sub 12} with a thickness from 4 to 430 nm on a (001)MgO substrate with a previously deposited Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} sublayer (4 nm) have been studied. The two-layer structures were prepared by radio-frequency sputtering of ceramic targets of the corresponding compositions. The X-ray diffraction studies performed at room temperature have shown that, in this heterostructure, axis c of the Bi{sub 4}Ti{sub 3}O{sub 12} unit cell is perpendicular to the substrate, and direction [100] has an angle of ±45° to the [100]MgO direction. At the thicknesses of Bi{sub 4}Ti{sub 3}O{sub 12} to ~40 nm, the film unit cell is compressed in the direction of a normal to the substrate plane and extended in the conjugate plane, and the sign of the deformation is changed at large thicknesses. It is found that the phonon mode frequency in the Bi{sub 4}Ti{sub 3}O{sub 12} film shift and additional peaks appear in the Raman spectra, which demonstrates an increase in the degree of monoclinic distortion of the film crystal structure as compared to the crystal structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Structure and Polarization Relaxation of Ba{sub 0.5}Sr{sub 0.5}Nb{sub 2}O{sub 6}/(001)Si Films

The structure and dielectric characteristics of strontium barium niobate thin films deposited on single-crystalline silicon substrates without buffer layers are studied. It is found that the c axis in these heterostructures runs largely normally to the substrate surface and the a and b axes are randomly oriented in the plane of the substrate. The polarization relaxation in such heterostructures is investigated. It is shown that the film–substrate interface in the heterostructures grown by rf cathode sputtering may contain a low amount of long-lived charged defects.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Surface Morphology and Structure of Plasma Coatings

Specific features of the structure formation in rapidly quenched high-cobalt alloy coatings formed by plasma sputtering have been investigated. The structural state of the investigated coatings has been identified by the X-ray diffraction technique. The sequence and kinetics of structural transformations occurring in the specified time-temperature heating regimes have been examined using differential thermal analysis. It has been established that heat generation and crystallization temperature depend on the conditions of formation of bulk amorphous coatings.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Specifics of Preparation of Storage Chambers for Ultracold Neutrons and EDM Spectrometer Sensitivity

Storage cells for ultracold neutrons (UCNs) are crucial parts of the experimental setup used to measure the electric dipole moment (EDM) of a neutron. The effect of the technology of preparation and sputtering of elements of UCN storage cells on the limiting operating voltage and on the capacity of these cells for long-term operation under high voltage with polarity switching was studied. A voltage magnitude of ±250 kV was obtained in tests of a neutron storage cell for the EDM spectrometer with a cell height of 9 cm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Anomalies in the Elastic and Inelastic Properties of Co{sub x}(PZT){sub 100 –x} Nanocomposites

The elastic (G) and inelastic (Q{sup –1}) properties of Co{sub x}(PZT){sub 100 –x} nanocomposites (x = 23–76 at %) obtained by ion-beam sputtering have been studied in the temperature range 200–900 K. Internal friction peaks associated with Co atom hopping inside metallic granules have been discovered at 236 K. It has been found that the peak height grows with metallic phase concentration. Above 750 K, curve Q{sup –1}(T) rises considerably because of vacancy diffusion in Co granules under conditions of confined space.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Composition, Structure, and Mechanical Properties of (Ti–Hf)N Coatings on Titanium Alloy

Variations of the composition, structure, and mechanical properties (hardness, elastic modulus) of (Ti–Hf)N coatings with increasing Hf content (Ti : Hf ratio) are reported. As test samples, VT6 titanium alloy plates covered by a magnetron-sputtered titanium hafnium nitride coating have been taken. To see how the coating characteristics depend on Hf content, samples with rated compositions (Ti{sub 0.9}Hf{sub 0.1})N, (Ti{sub 0.85}Hf{sub 0.15})N, (Ti{sub 0.8}Hf{sub 0.2})N, and (Ti{sub 0.7}Hf{sub 0.3})N have been studied. The surface and depth element distributions have been found, and the phase composition and the dependence of the titanium nitride lattice parameter on Hf content in the coating have been determined. The depth profiling of a coating’s hardness and elastic modulus has been conducted by instrumental indentation. Hardness and elastic modulus have been found to be maximal (~35 and ~500 GPa, respectively) in (Ti{sub 0.85}Hf{sub 0.15})N and (Ti{sub 0.8}Hf{sub 0.2})N coatings. In addition, the depth distribution of Hf in these coatings has turned out to be most uniform.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Anomalous Elastic and Inelastic Properties of the Co{sub x}(CaF{sub 2}){sub 100 –x} Nanogranular Composites

Elastic (G) and inelastic (Q{sup –1}) properties of the Co{sub x}(CaF{sub 2}){sub 100 –x} (x = 41–84 at %) nanocomposites fabricated with the aid of ion-beam sputtering are studied in a temperature interval of 170–750 K. Maximum internal friction related to hopping of Co atoms inside metal granules is revealed at a temperature of 227 K. It is shown that the maxima increase with increasing concentration of metal phase. A noticeable increase in dependence Q{sup –1}(T) at a temperature of greater than 675 K is caused by diffusion of vacancies in the Co granules under geometrical confinements.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Optical, Mechanical, and Thermal Properties of Free-Standing MoSi{sub 2}N{sub x} and ZrSi{sub 2}N{sub y} Nanocomposite Films

The optical, mechanical, and thermal properties of free-standing structures based on nitrided molybdenum and zirconium silicides have been studied. It has been shown that silicide nitriding considerably improves the thermal stability of films. While as-prepared amorphous MoSi{sub 2} and ZrSi{sub 2} films crystallize in the interval 330–370°C, nitriding of films has made it possible to increase their working temperatures in vacuum to 600–700°C (at least, for x ≥ 0.25, y ≥ 1.3). Tensile tests have shown that the ultimate strength of MoSi{sub 2}N{sub x} films (0 ≤ x ≤ 0.55) depends on nitrogen content only slightly. Comparison between the properties of MoSi{sub 2}N{sub x} and ZrSi{sub 2}N{sub y} films magnetron-sputtered at the same partial pressure of nitrogen has demonstrated that with transmission coefficients of films at a wavelength of 13.5 nm being close to each other, ZrSi{sub 2} films are more effective as protection coatings (they are less prone to oxidation and more degradation-resistant).

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

UV-assisted growth of transparent conducting layers based on zinc oxide

A comparative study of the microstructure and optical and electrical characteristics of gallium-doped ZnO films synthesized by magnetron sputtering with and without assistance to the growth process by UV radiation has been carried out. It was found that the UV assistance to the growth process of ZnO-based transparent conducting layers improves their electrical characteristics because of the formation of additional donor centers and the lower carrier scattering at grain boundaries, without any strong inf luence on the layer morphology and on the average optical transmittance in the visible spectral range.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

A New Limitation of the Depth Resolution in TOF-SIMS Elemental Profiling: the Influence of a Probing Ion Beam

New data concerning the influence of a probing beam of bismuth ions on the depth resolution in elemental depth profiling by secondary ion mass spectrometry (SIMS) have been obtained on a TOF.SIMS-5 system using the principle of two separate ion beams. It is established that the existing criterion of nondestructive character of the probing beam, on which this principle is based, is insufficient. Additional processes must be taken into account so as to formulate a more adequate criterion. A regime of depth profiling is proposed that allows the depth resolution to be improved at low energies of sputtering ions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗