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  • 1
    Electronic Resource
    Electronic Resource
    Surface reaction pathways of methylamine on the Ni(111) surface (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4692-4700 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The interaction and bond scission sequence of methylamine, CH3NH2, on Ni(111) have been investigated by means of Auger electron spectroscopy and temperature programmed desorption under UHV conditions in the temperature range 87–800 K. Comparisons have been made to the NH3/Ni(111) and N/Ni(111) systems. Methylamine is found to absorb molecularly through its lone pair up to ∼330 K after which a dehydrogenation channel opens which competes with the desorption channel. The sequence of the initial bond breaking was investigated by measuring the initial reactive sticking coefficient of deuterium labeled molecules at 363 K. Methylamine decomposition was found to take place through both ends of the molecule, initially with a slight rate preference at the C end. The CN residue left on the surface by the dehydrogenation process resulted in self-poisoning of the active sites. This residual species was found to decompose at ∼530 K, leading to N2 desorption and the diffusion of carbon into the crystal at 700–800 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452683
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  • 2
    Electronic Resource
    Electronic Resource
    Dissociative chemisorption of O"2 on Cu(100). Effects of mechanical energy transfer and recoil
    Amsterdam : Elsevier
    Chemical Physics Letters 216 (1993), S. 413-417 
    Details
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0009-2614(93)90119-L
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  • 3
    Electronic Resource
    Electronic Resource
    Angular distributions of H2 thermal desorption: Coverage dependence on Ni(111) (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 6186-6191 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Temperature programmed desorption measurements for H2/Ni(111) yield two desorption states, β1(T=290 K) and β2(T=370 K) for saturation H coverage. The two states are found to have distinctly different angular distributions. β2-H2 desorption is strongly focused along the surface normal, while β1-H2 desorbs diffusely. The angular distribution of desorbing β1-H2 is very close to that for the CO/Ni(111) system which has a cos θ angular distribution. The different angular distributions can be explained by a model involving a coverage-dependent location of an activation energy barrier on the potential energy surface which describes the interaction of hydrogen with Ni(111).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451485
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  • 4
    Electronic Resource
    Electronic Resource
    Improved current transport properties of post annealed Y1Ba2Cu3O7−x thin films using Ag doping (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7062-7068 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of Ag doping on the transport properties of Y1Ba2Cu3O7−x thin films prepared by Y, BaF2, and Cu co-evaporation and optimized ex situ post annealing has been investigated. Both undoped and Ag doped films have values of Tc above 90 K, but Jc (77 K) is highly dependent on the nominal thickness (tnom) of the as-deposited film. For undoped films with tnom≤300 nm Jc (77 K) ((very-much-greater-than)106 A/cm2) decreases monotonically with increasing film thickness. Above 300 nm Jc (77 K) decreases rapidly to values below 5×105 A/cm2. Ag doped films with tnom≥200 nm have higher Jc (77 K) values than those of undoped films. Ag doped films have a maximum in Jc (77 K) around 250 nm. As for the undoped films, there is a large decrease in Jc (77 K) for Ag doped films with tnom≥300 nm. It was found that the higher values of Jc (77 K) for the Ag doped films were due to a better epitaxial growth of the YBCO compound. The low values of Jc (77 K) for both undoped and Ag doped single layer films with tnom≥300 nm were found to be due to the absence of 1–2–4 inclusions in these films. Based on these findings high Jc (77 K) films with tnom(approximately-greater-than)300 nm were grown by successive deposition and annealing of films with tnom〈300 nm on top of each other. A 2×150 nm undoped film was found to have a Jc (77 K) value of 4, 1×106 A/cm2. This is almost a doubling of the Jc (77 K) value as compared to the value for the 300 nm single layer undoped film (2,2×106 A/cm2). Ag doped double layer films of 2×150 nm and 2×215 nm had comparable Jc (77 K) values (5,8×106 and 5,6×106 A/cm2, respectively). In comparison with the undoped 2×150 nm film Jc (77 K) is thus further increased (by about 50%) when doping with Ag. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361473
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  • 5
    Electronic Resource
    Electronic Resource
    Dissociative sticking of CH4 on Ru(0001) (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 2637-2642 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this study the CH4 dissociation probability on Ru(0001) is found for various translational and vibrational energies. The absolute sticking values are determined from King and Wells experiments and carbon uptake curves. The carbon amount is determined from the recombination signal of carbon with oxygen obtained after the beam exposure when heating in an oxygen atmosphere. The measured sticking coefficient of CH4 is strongly enhanced both by increasing the translational and the vibrational energy of the CH4 molecule. A model is applied to the data and an estimate of the thermal activation energy for CH4 dissociation is found to be in good agreement with previous bulb experiments. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477985
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  • 6
    Electronic Resource
    Electronic Resource
    Modification of Ni(111) reactivity toward CH4, CO, and D2 by two-dimensional alloying (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 7289-7295 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Alloying Au into the outermost atomic layer of Ni(111) significantly alters the physical and chemical properties of the surface. The reactivity is investigated by the use of seeded supersonic molecular beams of CH4 and it is found that the nobleness of Au reduces the overall reactivity toward CH4. This is accounted for in an ensemble model resolving the sticking probability on Ni atoms having different nearest neighbor surroundings. Although a mean field description of site distributions is found to be a very good approximation it is improved by using experimentally determined ensemble statistics from STM images. The strong influence of the vibrational temperature on the sticking coefficients of CH4 vs translational energy on the pure Ni(111) is also demonstrated. Desorption energies of CO and D2 is observed to decrease approximately 25–30 kJ/mole as the coverage of Au is increased from 0.0 to 0.7 ML. In TPD spectra of deuterium saturated surface alloys a new clearly resolved desorption state is observed at 180–220 K with maximum intensity around θAu=0.3–0.4 ML. This state is clearly related to chemisorption sites involving both Au and Ni. A site model based on mean field statistics adequately accounts for the appearance of this state. The effect of Au is also evident in the TPD spectra of CO saturated Au/Ni(111) surface alloys where the saturation coverage decreases and new structure develops. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471395
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  • 7
    Electronic Resource
    Electronic Resource
    Enhanced Jc's of YBa2Cu3O7−x–Ag ex situ annealed coevaporated films on LaAlO3 (100) substrates (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2350-2352 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A 5× increase of the critical current density (Jc) at 77 K was obtained by coating a coevaporated 500 nm thick Y, BaF2, Cu film with 50 nm Ag prior to the ex situ annealing. Jc increased from 0.2 for uncoated samples to 1 MA/cm2 for the Ag-coated sample without severely affecting the zero resistance transition temperature (Tc0). Scanning electron microscopy showed that the surface morphology was improved and that the normally observed trellislike structure was greatly reduced. By combining electron microscopy and sputter assisted Auger analysis it was found that the Ag nucleated in droplets on the surface of the superconductor with only small amounts of Ag in the superconductor matrix. X-ray diffraction confirmed that the Ag-coated film was highly c-axis oriented. The increase in Jc is believed to be due to the improved surface properties of the superconductor, indicating that a larger amount of the film is c-axis oriented or that the single-crystalline grains are larger. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113038
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  • 8
    Electronic Resource
    Electronic Resource
    Response to "Comment on ‘Enhanced Jc's of YBa2Cu3O7−x–Ag ex situ annealed coevaporated films on LaAlO3 (100) substrates' '' [Appl. Phys. Lett. 67, 3650 (1995)] (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3652-3652 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115348
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular beam study of dissociative sticking of methane on Ni(100) (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 8255-8263 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper reports a detailed molecular beam study of the dissociative sticking of methane incident on clean Ni(100). It is demonstrated that the sticking coefficient depends strongly on the translational energy of the molecule. It is also observed that an increase in the vibrational energy of the methane leads to a dramatic enhancement of the sticking, emphasizing that the initial vibrational state is of crucial importance. These results are consistent with a mechanism of direct activated dissociative chemisorption where the dynamics is dominated by a barrier in the potential energy surface mainly located in the vibrational coordinates. Normal-energy scaling is only approximately observed. The effect of surface temperature is also investigated but is found to be smaller than activation by translational or vibrational energy. A simplified analysis in terms of state resolved sticking curves, Sν(Ei), considering only the vibrational C–H stretch modes of methane as relevant for the sticking, gives a good description of the data. These sticking curves enables a calculation of the thermal sticking coefficient which is found to be in excellent agreement with bulb experiments directly probing this. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468955
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  • 10
    Electronic Resource
    Electronic Resource
    Scanning kinetic spectroscopy and temperature-programmed desorption studies of the adsorption and decomposition of hydrogen cyanide on the nickel(111) surface (1988)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 92 (1988), S. 471-476 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100313a045
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