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  • PLASMA PHYSICS  (3)
  • SOLID-STATE PHYSICS  (3)
  • 2020-2022
  • 2005-2009
  • 1990-1994  (6)
  • 1990  (6)
  • 1
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    Direct spectroscopy of electron and hole scattering (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A new spectroscopy has been developed for the first direct probe of carrier-carrier scattering in materials. This spectroscopy provides spatial and energy resolution of the scattering process and has been used to investigate transport, scattering phenomena, and hot-carrier creation in two important metal-semiconductor systems. A theoretical treatment of this scattering spectroscopy yields excellent agreement with experimental spectra and provides direct evidence that carrier-carrier scattering is a dominant energy-loss mechanism in hot-carrier transport.
    Keywords: SOLID-STATE PHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 64; 2679-268
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    NASCAP/LEO calculations of current collection (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: NASCAP/LEO is a 3-dimensional computer code for calculating the interaction of a high-voltage spacecraft with the cold dense plasma found in Low Earth Orbit. Although based on a cubic grid structure, NASCAP/LEO accepts object definition input from standard computer aided design (CAD) programs so that a model may be correctly proportioned and important features resolved. The potential around the model is calculated by solving the finite element formulation of Poisson's equation with an analytic space charge function. Five previously published NASCAP/LEO calculations for three ground test experiments and two space flight experiments are presented. The three ground test experiments are a large simulated panel, a simulated pinhole, and a 2-slit experiment with overlapping sheaths. The two space flight experiments are a solar panel biased up to 1000 volts, and a rocket-mounted sphere biased up to 46 kilovolts. In all cases, the authors find good agreement between calculation and measurement.
    Keywords: PLASMA PHYSICS
    Type: NASA, Marshall Space Flight Center, Current Collection from Space Plasmas; p 334-351
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Physical processes associated with current collection by plasma contactors (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Recent flight data confirms laboratory observations that the release of neutral gas increases plasma sheath currents. Plasma contactors are devices which release a partially ionized gas in order to enhance the current flow between a spacecraft and the space plasma. Ionization of the expellant gas and the formation of a double layer between the anode plasma and the space plasma are the dominant physical processes. A theory is presented of the interaction between the contactor plasma and the background plasma. The conditions for formation of a double layer between the two plasmas are derived. Double layer formation is shown to be a consequence of the nonlinear response of the plasmas to changes in potential. Numerical calculations based upon this model are compared with laboratory measurements of current collection by hollow cathode-based plasma contactors.
    Keywords: PLASMA PHYSICS
    Type: NASA, Marshall Space Flight Center, Current Collection from Space Plasmas; p 190-200
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Dependence of millimeter wave surface resistance on the deposition parameters of laser ablated YBa2Cu3O(x) thin films (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Measurements of millimeter-wave surface resistance versus temperature have been performed for YBa2Cu3O(x) thin films on 100 line-type SrTiO(3) substrates using a TE(011) cylindrical copper cavity at 80 GHz. The 0.6-micron thick films were grown at several deposition temperatures in the range 690 C to 810 C by means of a pulsed excimer laser ablation technique. A surface resistance minimum (60 milliohm at 77 K) near 770 C is shown to correlate with a minimum in c-axis lattice parameter (11.72 A). The highest value of Tc also occurs near this temperature. The surface resistance of films deposited at 790 C on 110 line-type LaAlO3 subtrates is lower, reaching 8 milliohm at 98 GHz and 80 K, demonstrating the influence of substate material on film quality.
    Keywords: SOLID-STATE PHYSICS
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Plasma contactor modeling with NASCAP/LEO - Extending laboratory results to space systems (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: In the laboratory, hollow cathode-based plasma contactors have been observed to both emit and collect ampere-level electron currents with low impedance. The laboratory behavior of hollow cathode-based plasma contactors and the limited space experience with hollow cathodes suggest that, for many applications, a hollow cathode-based plasma contactor is the ideal device to provide electrical connection with the space plasma. In order to confidently extend the laboratory experience to the low-earth-orbit environment, a series of plasma contactor computer models has been developed. Calculations show that a hollow cathode plasma contactor that collects 0.5 A in the laboratory will only collect 2.4 mA in space. The simplest way to boost the collected current is to increase the gas flow. A mole of gas is enough to collect ampere level currents for 5-1/2 hours.
    Keywords: PLASMA PHYSICS
    Type: AIAA PAPER 90-0726
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Silicon carbide semiconductor device fabrication and characterization (1990)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A number of basic building blocks i.e., rectifying and ohmic contacts, implanted junctions, MOS capacitors, pnpn diodes and devices, such as, MESFETs on both alpha and beta SiC films were fabricated and characterized. Gold forms a rectifying contact on beta SiC. Since Au contacts degrade at high temperatures, these are not considered to be suitable for high temperature device applications. However, it was possible to utilize Au contact diodes for electrically characterizing SiC films. Preliminary work indicates that sputtered Pt or Pt/Si contacts on beta SiC films are someways superior to Au contacts. Sputtered Pt layers on alpha SiC films form excellent rectifying contacts, whereas Ni layers following anneal at approximately 1050 C provide an ohmic contact. It has demonstrated that ion implantation of Al in substrates held at 550 C can be successfully employed for the fabrication of rectifying junction diodes. Feasibility of fabricating pnpn diodes and platinum gated MESFETs on alpha SiC films was also demonstrated.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-CR-186354 , NAS 1.26:186354 , AD-A231299
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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