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  • American Vacuum Society  (5)
  • 1995-1999  (5)
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Verlag/Herausgeber
  • American Vacuum Society  (5)
Sprache
Erscheinungszeitraum
  • 1995-1999  (5)
Jahr
Fachgebiete(RVK)
  • 1
    Online-Ressource
    Online-Ressource
    American Vacuum Society ; 1995
    In:  Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Vol. 13, No. 3 ( 1995-05-01), p. 1310-1315
    In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, American Vacuum Society, Vol. 13, No. 3 ( 1995-05-01), p. 1310-1315
    Kurzfassung: The combination of secondary neutral mass spectrometry (SNMS) and resonance ionization spectroscopy (RIS) has been shown to be a powerful tool for the detection of low levels of elemental impurities in solids. Drawbacks of the technique have been the laser-repetition-rate-limited, low duty cycle of the analysis and the fact that RIS schemes are limited to determinations of a single element. These problems have been addressed as part of an ongoing program to explore the usefulness of RIS/SNMS instruments for the analysis of naturally occurring samples. Efficient two-color, two-photon (1+1) resonance ionization schemes were identified for Mo and for four platinum-group elements (Ru, Os, Ir, and Re). Careful selection of the ionization schemes allowed Mo or Ru to be measured simultaneously with Re, Os, or Ir, using two tunable dye lasers and an XeCl excimer laser. Resonance frequencies could be switched easily under computer control, so that all five elements can be rapidly analyzed. In situ measurements of these elements in metal grains from five meteorites were conducted. From the analyses, estimates of the precision and the detection limit of the instrument were made. The trade-off between lower detection limits and rapid multielement RIS analyses is discussed.
    Materialart: Online-Ressource
    ISSN: 0734-2101 , 1520-8559
    RVK:
    Sprache: Englisch
    Verlag: American Vacuum Society
    Publikationsdatum: 1995
    ZDB Id: 1475424-1
    ZDB Id: 797704-9
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Online-Ressource
    Online-Ressource
    American Vacuum Society ; 1995
    In:  Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Vol. 13, No. 3 ( 1995-05-01), p. 1628-1632
    In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, American Vacuum Society, Vol. 13, No. 3 ( 1995-05-01), p. 1628-1632
    Kurzfassung: It was shown recently that nanocrystalline diamond films can be grown using fullerenes as precursors in an argon microwave plasma without the addition of hydrogen or oxygen. Extensive fragmentation of C60 in the microwave discharge leads to a copious production of the carbon dimer molecule, C2, as evidenced by intense Swan-band emission. Here we have investigated hydrogen–methane–argon plasmas and found that high argon fractions (≳50%) lead to intense C2 emission, indicating significant production of C2 in the plasma. In situ measurements of the substrate reflectivity were used to determine the growth rate. A correlation between the C2 emission intensity and growth rate was observed. These results prompted us to propose a scheme for diamond film growth on the (100)–(2×1): H reconstructed diamond surface with C2 as the growth species. Each surface carbon atom (bonded twice to carbons in the bulk, once to a surface carbon, creating a ‘‘dimer’’ and then forming a five-membered ring) is terminated with hydrogen. With C2 as the growth species, no hydrogen abstraction reactions are required because its very high energy of adsorption (815 kJ/mol C) allows the C2 molecule to insert directly into the dimer bonds. A second C2 can form across the adjoining trough. The added carbons then dimerize, forming a new (2×1) surface on a new layer with dimer rows orthogonal to the original rows.
    Materialart: Online-Ressource
    ISSN: 0734-2101 , 1520-8559
    RVK:
    Sprache: Englisch
    Verlag: American Vacuum Society
    Publikationsdatum: 1995
    ZDB Id: 1475424-1
    ZDB Id: 797704-9
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    American Vacuum Society ; 1999
    In:  Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena Vol. 17, No. 2 ( 1999-03-01), p. 705-709
    In: Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, American Vacuum Society, Vol. 17, No. 2 ( 1999-03-01), p. 705-709
    Kurzfassung: We have investigated the field emission properties of diamond films grown under substrate bias conditions in a microwave plasma chemical vapor deposition system, with a substrate temperature of 800 °C, microwave power of 600 W, and a total pressure of 11 Torr. One group of films was grown with a substrate bias of −100 V in gas mixtures of 1% N2 and 1%–20% CH4 in H2, while a second group of films was grown with a substrate bias ranging from +100 to −150 V in a gas mixture of 1%N2–10%CH4–89%H2. The field emission performance in terms of threshold field and emission current improved considerably as a function of increasing CH4 concentration and negative bias voltage. Ultraviolet Raman analysis showed that the field emission enhancement resulting from an increase in CH4 concentration from 1% to 5% correlates with a decrease in the sp3 bonding character in the diamond film. The dependence of field emission on negative bias voltage appears to be correlated with ion bombardment-induced damage in the film during growth. The scanning electron microscopy image of the film grown with −150 V bias showed: smaller surface topographic features as compared to films grown under 0 and +100 V bias. The film grown with a bias of −150 V showed the lowest threshold field (∼2.0 V/μm) corresponding to an emission current density of 12.7 μA/cm2. J vs E0 measurements across a length of 40 mm over the film showed a uniform threshold field (2.0±0.55 V/μm). The film grown with a positive bias (+100 V) showed a relatively poor field emission performance.
    Materialart: Online-Ressource
    ISSN: 1071-1023 , 1520-8567
    RVK:
    Sprache: Englisch
    Verlag: American Vacuum Society
    Publikationsdatum: 1999
    ZDB Id: 3117331-7
    ZDB Id: 3117333-0
    ZDB Id: 1475429-0
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Online-Ressource
    Online-Ressource
    American Vacuum Society ; 1998
    In:  Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Vol. 16, No. 3 ( 1998-05-01), p. 1779-1784
    In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, American Vacuum Society, Vol. 16, No. 3 ( 1998-05-01), p. 1779-1784
    Kurzfassung: We have used the ion spectroscopic techniques of direct recoil spectroscopy and mass spectroscopy of recoiled ions to demonstrate that low energy reactive ion sputtering of Ge is capable of removing surface impurities such as carbon. The experiments were performed in a vacuum chamber maintained at 3.5×10−7 Torr. At these pressures, physical sputtering using noble gas is not effective for cleaning Ge surfaces as carbon redeposits onto the surface. In this article, we demonstrate that reactive sputtering of Ge using 4.0 keV nitrogen at a Ge surface temperature of ∼740 K and above removes surface carbon and deposits nitrogen on the Ge surface. Heating the nitrogen exposed Ge surface to above ∼880 K results in the desorption of nitrogen and generates an atomically clean Ge surface, under poor vacuum conditions.
    Materialart: Online-Ressource
    ISSN: 0734-2101 , 1520-8559
    RVK:
    Sprache: Englisch
    Verlag: American Vacuum Society
    Publikationsdatum: 1998
    ZDB Id: 1475424-1
    ZDB Id: 797704-9
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Online-Ressource
    Online-Ressource
    American Vacuum Society ; 1999
    In:  Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Vol. 17, No. 5 ( 1999-09-01), p. 2634-2641
    In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, American Vacuum Society, Vol. 17, No. 5 ( 1999-09-01), p. 2634-2641
    Kurzfassung: We have modeled, designed, built, and tested a novel reflectron time-of-flight (TOF) analyzer, which is capable of performing surface analysis using both secondary ion mass spectroscopy (SIMS) and mass spectroscopy of recoiled ions (MSRI). All elements (including H and He) can be identified, with isotopic resolution, using both MSRI and SIMS. For ions of a given mass, the higher energy ions penetrate further into the reflectron before being turned around while the lower energy ions do not penetrate as deeply. By properly adjusting both the experimental geometry and the reflectron voltages, all ions of a given mass arrive at the detector simultaneously—resulting in enhanced mass resolution compared with simple TOF detection. SIM spectra are complicated by molecular fragments in addition to elemental ions. In MSRI only elemental ions are detected. As a result, data analysis in MSRI is less complicated than in SIMS. Being able to use a single analyzer to selectively obtain SIMS or MSRI data provides complementary surface information. MSRI has a number of unique capabilities for surface studies. In situ, real-time surface analysis can be performed during film growth at pressures of ∼2.5 mTorr at the substrate by differentially pumping both the ion source and the reflectron analyzer region. It has been demonstrated that the ratio of the positive to negative ion yield is phase specific; for example, one can clearly distinguish the different forms of carbon (diamond versus graphite versus amorphous carbon) during film growth. MSRI analysis of poorly conducting surfaces is possible.
    Materialart: Online-Ressource
    ISSN: 0734-2101 , 1520-8559
    RVK:
    Sprache: Englisch
    Verlag: American Vacuum Society
    Publikationsdatum: 1999
    ZDB Id: 1475424-1
    ZDB Id: 797704-9
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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