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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 199 records · Page 11

Optical constants of magnetron sputtered Pt thin films with improved accuracy in the N- and O-electronic shell absorption regions

We introduce an experimental, self-consistent determination of the optical constants (refractive index) of Pt using a combination of photoabsorption and reflectance data in the photon energy range 25–778 eV, which includes the N- and O-shell electronic absorption edges of Pt. We compare our new experimental values with Pt optical constant data sets from the literature. Our Pt optical constant values demonstrate highly resolved absorption-edge fine structure around the O 2,3 and N 6,7 edges in both the absorptive and dispersive portions of the refractive index, which were missing in the earlier literature.

36 MATERIALS SCIENCE↗

Optical constants of magnetron sputtered aluminum in the range 17–1300 eV with improved accuracy and ultrahigh resolution in the L absorption edge region

This work determines a new set of EUV/x-ray optical constants for aluminum (Al), one of the most important materials in science and technology. Absolute photoabsorption (transmittance) measurements in the 17–1300 eV spectral range were performed on freestanding Al films protected by carbon (C) layers, to prevent oxidation. The dispersive portion of the refractive index was obtained via the Kramers–Kronig transformation. Our data provide significant improvements in accuracy compared to previously tabulated values and reveal fine structure in the Al L 1 and L 2,3 regions, with photon energy step sizes as small as 0.02 eV. The implications of this work in the successful realization of EUV/x-ray instruments and in the validation of atomic and molecular physics models are also discussed.

74 ATOMIC AND MOLECULAR PHYSICS↗

High figure-of-merit p -type transparent conductor, Cu alloyed ZnS via radio frequency magnetron sputtering

p-type transparent conducting Cu alloyed ZnS thin films from Cu$_{{x}}$ Zn$_{{1-x}}$ S targets ($x = 0.1$ , 0.2, 0.3, 0.4, and 0.5) were deposited on glass substrates via radio frequency sputtering. x-ray diffraction and TEM–SAED analysis show that all the films have sphalerite ZnS as the majority crystalline phase. In addition, films with 30% and 40% Cu show the presence of increasing amounts of crystalline Cu2S phase. Conductivity values ≥400 S ${\rm cm}^{-1}$ were obtained for the films having 30% and 40% Cu, with the maximum conductivity of 752 S ${\rm cm}^{-1}$ obtained for the film with 40% Cu. Temperature dependent electrical transport measurements indicate metallic as well as degenerate hole conductivity in the deposited films. The reflection-corrected transmittance of this Cu alloyed ZnS (40% Cu) film was determined to be ≥75% at 550 nm. In conclusion, the transparent conductor figure of merit ($\Phi_{{\rm TC}}$ ) of the Cu alloyed ZnS (40% Cu), calculated with the average value of transmittance between 1.5 to 2.5 eV, was ≈276 $\mu{\rm S}$ .

36 MATERIALS SCIENCE↗

Erosion rates of diffuse and constricted magnetron discharges in helium over aluminium, gallium, molybdenum, and tantalum

Magnetically-enhanced discharge plasmas in light monatomic gases such as helium may have applicability in future electric power grid switches. For practical use of a gas discharge switch in power conversion the net cathode erosion rate must be sufficiently low to enable stable operation over an extended life. We have found that magnetically-enhanced He plasmas at pressures of 200–800 mTorr can operate in one of several distinct modes that are characterized by the plasma geometry (diffuse, constricted) and motion (stationary, orbiting, slow). The erosion rates of various cathode materials (aluminium, gallium, molybdenum, and tantalum) were measured in both diffuse and constricted, magnetized He plasmas. The constricted orbiting (CO) mode exhibited a lower erosion rate than either the diffuse stationary or constricted slow modes, even when comparing loss rates against a cathode material that was more liable to sputter (e.g. aluminium versus molybdenum). However, the erosion rate for operation in the CO mode was still found to be significantly higher than required for practical use in a gas discharge switch.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗