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  • 1
    Electronic Resource
    Electronic Resource
    Structural modifications in the amino acid lysine induced by soft x-ray irradiation (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 8392-8398 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The amino acid DL-lysine has been investigated using the surface-sensitive probe XPS (x-ray photoelectron spectroscopy). The XPS data confirm that solid-state lysine exists in the zwitterionic form. However, during the course of x-ray irradiation in the experiment, the molecule was observed to decompose. A decomposition mechanism consistent with the data has been proposed which involves transformation of the zwitterion to a free base, followed by decarboxylation, to produce 1,5-diaminopentane and CO2 gas. It would appear that caution should be exerted when studying amino acids using XPS if long x-ray irradiation times are employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466786
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  • 2
    Electronic Resource
    Electronic Resource
    High-temperature ohmic contact to n-type 6H-SiC using nickel (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1317-1319 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Specific contact resistances measured at elevated temperatures for Ni ohmic contacts to 6H-SiC were reported. The specific contact resistances were measured with the linear transmission line method at both room temperature and at 500 °C and yielded values 〈5×10−6 Ω cm2 at both temperatures. The trend shows a decreasing contact resistance at higher temperatures. The annealed metal film is a nickel silicide with substantial mixing of C throughout the silicide layer. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358936
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  • 3
    Electronic Resource
    Electronic Resource
    The interaction of atomic oxygen with thin copper films (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 2318-2323 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A source of thermal, ground-state atomic oxygen has been used to expose thin copper films at a flux of 1.4×1017 atoms/cm2 s for times up to 50 min for each of five temperatures between 140 and 200 °C. Rutherford backscattering spectroscopy was used to characterize the oxide formed during exposure. The observations are consistent with the oxide phase Cu2O. The time dependence and the temperature dependence of the oxide layer thickness can be described using oxide film growth theory based on rate limitation by diffusion. Within the time and temperature ranges of this study, the growth of the oxide layers is well described by the equation L(T,t)=3.6×108 exp(−1.1/2kBT)t12, where L, T, and t are measured in angstroms, degrees Kelvin, and minutes, respectively. The deduced activation energy is 1.10±0.15 eV, with the attendant oxidation rate being greater than that for the corresponding reaction in molecular oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462028
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of surface segregation on wetting of liquid metal alloys (1988)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 92 (1988), S. 3925-3934 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100324a047
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  • 5
    Electronic Resource
    Electronic Resource
    Comparative oxidation studies of SiC(0001¯) and SiC(0001) surfaces (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 2558-2563 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comparison of the kinetics of oxidation at 995 and 1345 K of the SiC(0001¯) and SiC(0001) crystal faces is made. The oxidation rate on the SiC(0001¯) (C-rich face) is higher at both temperatures. SiO2 is formed. At 1345 K, the initial oxidation process is retarded by excess surface carbon. When the excess carbon is volatilized by either CO or CO2 formation, the oxidation rate is higher at 1345 K than at 995 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337121
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  • 6
    Electronic Resource
    Electronic Resource
    Reaction chemistry at the Si (100) surface—control through active-site manipulation (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3750-3754 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal desorption methods have been used to investigate the interaction of propylene (C3H6) with Si(100)-(2×1). The adsorption characteristics depend strongly on the availability of active sites at the Si(100) surface. Reactivity is enhanced by production of active sites during ion prebombardment. Adsorption of C3H6 to a disordered, ion-bombarded Si(100) surface results in nearly complete dissociation of C3H6 for ion fluences as small as 1015 Ar+ ions/cm2. In contrast, for a thermally annealed and ordered Si(100) surface, only 65% of the C3H6 dissociates. The remainder of the propylene chemically bonds to the surface as an undissociated molecule which desorbs intact at 550 K. The increase in reactivity is due to an increase in dissociative chemisorption which occurs at defect sites produced by ion bombardment. Reactivity is suppressed by capping of active sites using atomic hydrogen preadsorption. Hydrogen passivates the Si(100) surface by occupation of silicon dangling bonds, which prevents adsorption of C3H6. By controlling the number and kind of active surface sites in this way, it is possible to manipulate the reactive ability of the Si(100) surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337586
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  • 7
    Electronic Resource
    Electronic Resource
    Comparative electron spectroscopic studies of surface segregation on SiC(0001) and SiC(0001¯) (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 2842-2853 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron spectroscopic comparison of the C-rich SiC(0001¯) and Si-rich SiC(0001) surfaces after cleaning and disordering by Ar+ ion sputtering and subsequent annealing is reported. The chemical behavior of the two disordered surfaces differs significantly. Three distinct temperature regions with different carbon surface segregation kinetics are discernible on SiC(0001¯). On SiC(0001) only one temperature region for C-segregation is observed. Below 900 K, no spectroscopic differences between the two crystal surfaces are observed. Between 900 and 1300 K, both faces are terminated by a surface graphite layer and the C-rich face shows an additional carbon surface segregation process. Above 1300 K, the C-terminated surface graphitizes at a higher rate than the Si-terminated surface. Massive graphitization on both surfaces above 1300 K is attributed to Si(g) sublimation from the SiC surfaces. The results demonstrate that extensive surface disordering of polar SiC faces does not destroy the memory for the polarity of the original crystal insofar as high-temperature surface chemistry is concerned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337068
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  • 8
    Electronic Resource
    Electronic Resource
    Wettability of transition metal boride eutectic alloys to graphite (1987)
    Springer
    Journal of materials science 22 (1987), S. 2421-2430 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The wetting of nickel, platinum and palladium boride eutectics (Ni55B45, Ni62B38, Pd72B28, and Pt72B28) to polycrystalline graphite has been studied by sessile drop and surface analytical techniques. The wettability is critically influenced by surface segregation of low-level bulk impurities in the alloys. At the melting temperature, the impurities segregate to the surface of the liquid alloy and inhibit wetting. A poorly-wetted droplet with a large contact angle results. Good wetting results by introducing materials into the contact system which possess high chemical reactivity to the major segregant species, either as a surface coating or by incorporation into the alloy during manufacture. The materials act to suppress segregation by tying up the alloy impurities through compound formation. The results indicate that the use of surface sensitive techniques in the study of wetting is essential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01082126
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  • 9
    Electronic Resource
    Electronic Resource
    Looming crisis in graduate science education: Where are America's top science students? (1994)
    Springer
    Journal of science education and technology 3 (1994), S. 57-63 
    Details
    ISSN: 1573-1839
    Keywords: Graduate education ; sciences ; physics ; recruiting ; employment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract Only 750 physics doctorates were awarded to American students during 1990–1991 from a population base of over 248 million people. Even institutions such as MIT are having difficulty attracting enough top American students to its graduate programs in the sciences. We discuss some of the reasons for the decline in domestic student participation in the sciences and offer several nuts-and-bolts methods to reverse this trend. Key ingredients include graduate student recruiting, motivational activities to promote the excitement of being a professional scientist, and a reeducation of employers to look more favorably toward hiring students from the basic sciences. The methods have resulted in dramatic changes in the composition of recent graduate classes; at Auburn University we now admit an incoming class composed of over 70% domestic students.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01575816
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