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  • 1
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    Ellipsometric and optical study of amorphous hydrogenated carbon films (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A low-frequency plasma deposition system was used to prepare amorphous hydrogenated carbon (a-C:H) films. The growth energy was varied by changing the power and/or pressure of the plasma. Ellipsometry and optical absorption were used to obtain the optical energy gap, the density of states, and the refractive index. Ion sputtering was used in conjunction with ellipsometry and Auger electron spectroscopy to get absolute sputtering rates. The plasma deposited a-C:H is amorphous with an optical energy gap of approximately 2.0-2.4 eV. These a-C:H films have higher density and/or hardness, higher refractive index, and lower optical energy gaps with increasing energy of the particles in the plasma, while the density of states remains unchanged. These results are in agreement with, and give a fine-tuned positive confirmation to, an existing conjecture on the nature of the a-C:H films (Kaplan et al., 1985).
    Keywords: SOLID-STATE PHYSICS
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 133; 2339-234
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  • 2
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    Growth and characterization of epitaxial SrF2 on InP(100) (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The epitaxial growth of 100-262.5-nm SrF2 films on n-type and p-type (100)InP in a conventional baked UHV system at base pressure about 200 ptorr, temperature 250-350 C, and growth rate from less than 100 to about 200 pm/s. Substrates are chemicomechanically polished, degreased, bombarded with 500-eV Ar ions for 3-4 min at 350 C, and annealed for 23-30 min at 350 C, producing a slightly In-rich (In/P = 1.02) In-island-free surface with a (4 x 1) or (1 x 1) LEED structure. Films grown at 350 C and less than 100 pm/s are found to be smooth and free of cracks in most cases, with a highly faceted (1 x 1) LEED structure. The electrical properties of the SrF2 films are found to be acceptable only when the ohmic contacts are applied prior to the substrate prior to SrF2 growth.
    Keywords: SOLID-STATE PHYSICS
    Type: Journal of Vacuum Science and Technology A (ISSN 0734-2101); 4; 897-899
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  • 3
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    Plasma deposition of amorphous hydrogenated carbon films on III-V semiconductors (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Amorphous hydrogenated carbon films were grown on GaAs, InP and fused silica substrates using plasmas generated from hydrocarbon gases. Methane and n-butane sources were utilized. The effects of flow rate and power density on film growth were investigated. Carbon was the major constituent in the films. The degree of asymmetry at the carbon-semiconductor interface was approximately independent of the power density. Different H-C bonding configurations were detected by the technique of secondary-ion mass spectrometry. Band gaps up to 3 eV were obtained from optical absorption studies. Breakdown strengths as high as 600 MV/m were measured.
    Keywords: SOLID-STATE PHYSICS
    Type: Thin Solid Films (ISSN 0040-6090); 157; 97-104
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  • 4
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    Plasma deposited hydrogenated carbon on GaAs and InP (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The properties of diamond like carbon films grown by RF flow discharge 30 kHz plasma using methane are reported. The Cis XPS line shape of films showed localized hybrid carbon bonds as low as 40 to as high as 95 percent. Infrared spectroscopy and N(15) nuclear reaction profiling data indicated 35 to 42 percent hydrogen, depending inversely on deposition temperature. The deposition rate of films on Si falls off exponentially with substrate temperature, and nucleation does not occur above 200 C on GaAs and InP. Optical data of the films showed bandgap values of 2.0 to 2.4 eV increasing monotonically with CH4 flow rate.
    Keywords: SOLID-STATE PHYSICS
    Type: Journal of Vacuum Science and Technology A (ISSN 0734-2101); 3; 900-903
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  • 5
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    Rapid thermal annealing of Amorphous Hydrogenated Carbon (a-C:H) films (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Amorphous hydrogenated carbon (a-C:H) films were deposited on silicon and quartz substrates by a 30 kHz plasma discharge technique using methane. Rapid thermal processing of the films was accomplished in nitrogen gas using tungsten halogen light. The rapid thermal processing was done at several fixed temperatures (up to 600 C), as a function of time (up to 1800 sec). The films were characterized by optical absorption and by ellipsometry in the near UV and the visible. The bandgap, estimated from extrapolation of the linear part of a Tauc plot, decreases both with the annealing temperature and the annealing time, with the temperature dependence being the dominating factor. The density of states parameter increases up to 25 percent and the refractive index changes up to 20 percent with temperature increase. Possible explanations of the mechanisms involved in these processes are discussed.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-TM-89859 , E-3519 , NAS 1.15:89859
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  • 6
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    Boron nitride: Composition, optical properties and mechanical behavior (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at %. The carbon and oxygen impurities were in the 5 to 8 at % range. Boron-nitrogen and boron-boron bonds were revealed by X-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on III-V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-TM-89849 , E-3514 , NAS 1.15:89849
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  • 7
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    AlGaAs growth by OMCVD using an excimer laser (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: AlGaAs has been grown on GaAs by laser assisted OMCVD using an excimer laser, wavelength 193 nm, and a Cambridge OMCVD reactor. Films were grown at temperatures of 450 and 500 C with the laser beam parallel to the surface and impinging onto the surface at 15 deg from parallel. The samples were heated by RF coils while the laser beam was perpendicular to the gas flow. Typical gas flow parameters are 12 slm of H2, 15 sccm of Ga(CH3)3, 13 sccm of Al(CH3)3, and a pressure of 250 mbar. The initial energy density of the beam at the surface was 40 mJ/sq cm, the pulse rate was 20 pps, and the growth time was 7 min. The films were analyzed by Auger electron spectroscopy for the aluminum concentration and by TEM for the surface morphology.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-TM-88937 , E-3379 , NAS 1.15:88937
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  • 8
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    Improved synthesis of ceramic superconductors with alkaline earth peroxides - Synthesis and processing of Ba2YCu3O(7-x) (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Synthesis processes for the preparation of ceramic conductors Ba2YCu3O(7-x) from BaO2 or BaCO3 in flowing O2 or N2 are described, and the characteristics of the materials produced in these processes are compared. Results of EDAX, XRD, SEM, and dc resistivity analyses demonstrated that superconducting materials made from BaO2 were more homogeneous, denser, and more metallic than materials produced from BaCO3, because of the higher reactivity of BaO2. Potential applications of this processes are discussed.
    Keywords: SOLID-STATE PHYSICS
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  • 9
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    Study of deposition of YBa2Cu3O7-x on cubic zirconia (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Films of YBa2Cu3O7-x were grown on (100) cubic zirconia with 8 percent yttria by laser ablation from sintered targets of YBa2Cu3O7-x. The temperature of the zirconia substrate during growth was varied between 700 and 780 C. The atmosphere during growth was 170 mtorr of O2. The films were subsequently slowly cooled in-situ in 1 atm of O2. The best films were c-axis aligned and had a transition temperature of 87.7 K. The superconducting transition temperature and the X-ray diffraction analysis is reported as a function of the substrate temperature and of the angle between the laser beam and the target's normal.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-TM-102350 , E-5059 , NAS 1.15:102350 , Annual Conference on Superconductivity and Applications; Sep 19, 1989 - Sep 21, 1989; Buffalo, NY; United States
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  • 10
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    Carbon films grown from plasma on III-V semiconductors (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Dielectric carbon films were grown on n- and p-type GaAs and InP substrates using plasmas generated at 30 KHz from gaseous hydrocarbons. The effect of gas source, flow rate, and power on film growth were investigated. Methane and n-butane gases were utilized. The flow rate and power ranged from 30 to 50 sccm and 25 to 300 W, respectively. AES measurements show only carbon to be present in the films. The relative Ar ion sputtering rate (3 KeV) of carbon depends on the ratio power/pressure. In addition, the degree of asymmetry associated with the carbon-semiconductor interface is approximately power-independent. SIMS spectra indicate different H-C bonding configurations to be present in the films. Band gaps as high as 3.05 eV are obtained from optical absorption studies.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-TM-87140 , E-2766 , NAS 1.15:87140 , Meeting of the Electrochem. Soc.; Oct 11, 1985 - Oct 17, 1985; Las Vegas, NV; United States
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