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  • 1
    Electronic Resource
    Electronic Resource
    Cross sections for He scattering from surface imperfections: Vacancies and CO adsorbates on Pt(111) (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3722-3731 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Total cross sections for He scattering from isolated imperfections on surfaces are calculated using the Sudden approximation, and in some cases also by a numerically exact, time-dependent quantum-mechanical wave packet method. Systems studied include: CO adsorbates on Pt(111); mono-, di-, and trivacancies on Pt(111). The main results are: (1) the incidence angle and energy dependence of the cross section for He/[Pt(111)+CO] are very sensitive to the CO distance from the Pt plane. Interactions with the adsorbate image have little effect on the cross section. (2) The cross sections for clusters of vacancies are given within 10% or better, by the geometric sum of the monovacancy cross sections, the latter being treated as circles centered at each monovacancy. (3) The dependence of the cross section on the energy is sufficiently sensitive to distinguish between the "electron density hole'' and "electron density hump'' models for vacancies and vacancy clusters. (4) The Sudden approximation compares well with the exact quantum-mechanical results at typical experimental energies, when the incidence angle is not too far from the normal. These results indicate that experimental measurements of He scattering cross sections as a function of energy and incidence angle, combined with Sudden or wave packet scattering calculations, can provide detailed information on surface defects and their interactions with gas-phase atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454712
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  • 2
    Electronic Resource
    Electronic Resource
    Growth-induced uniaxial anisotropy in grazing-incidence deposited magnetic films (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2030-2032 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The deposition angle dependence of the in-plane magnetic anisotropy in ultrathin Co films on Cu(001) has been investigated by using the magneto-optic Kerr effect. Grazing-incidence molecular beam epitaxy of Co has been found to result in a uniaxial magnetic anisotropy, whose strength increases with increasing deposition angle. The measured magnetic anisotropy is related to the formation of elongated adatom structures during growth. Calculations of the deposition dynamics reveal that the uniaxial magnetic anisotropy and surface morphology originate from a redistribution of incident atom flux. This redistribution is caused by long-range attractive forces between incident atoms and substrate atoms. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1312865
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  • 3
    Electronic Resource
    Electronic Resource
    Manipulation of growth modes in heteroepitaxy: Ni/Cu(111) (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3492-3494 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Growth manipulation methods, which have been successfully used to improve the growth of homoepitaxial films, are applied to molecular beam epitaxy of the heteroepitaxial system Ni/Cu(111). The procedures applied are temperature reduction during nucleation and pulsed ion bombardment during deposition. While the first does not lead to smoother films, the ion beam assisted growth is successful in reducing the film roughness. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117222
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  • 4
    Electronic Resource
    Electronic Resource
    The scattering of thermal He atoms at ordered and disordered surfaces (1985)
    Springer
    Applied physics 38 (1985), S. 153-160 
    Details
    ISSN: 1432-0630
    Keywords: 79.20.Rf ; 68.20+t ; 68.45.Da
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The use of thermal energy atom scattering (TEAS) as a surface investigation tool is reviewed. Specific properties of thermal He scattering, which are particularly advantageous in surface analysis, are discussed; the main causes which hampered so far the broad application of this technique to the investigation of ordered surfaces are analysed. The recent development of TEAS based on the exploitation of the large cross section for He diffuse scattering of adsorbates and vacancies is reviewed. This development extends the capabilities of TEAS to a straightforward investigation of various aspects of disordered surfaces so far hardly accessible to other methods. Examples concerning the lateral distribution of adsorbates and defects, the mutual attraction and repulsion, 2D-phase transitions, mobility and surface diffusion are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616492
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  • 5
    Electronic Resource
    Electronic Resource
    Hydrogen adsorption on clean and oxygen covered Pt(111) (1991)
    Springer
    Catalysis letters 9 (1991), S. 195-204 
    Details
    ISSN: 1572-879X
    Keywords: Hydrogen adsorption-on-platinum ; hydrogen sticking probability ; oxygen covered platinum ; precursor state ; energy dependent dissociation of D2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dissociative adsorption of hydrogen on oxygen covered Pt(111) has been investigated using molecular beam techniques. The D2-sticking probability has been measured as a function of oxygen coverage (0 〈 ΘO 〈 0.25 ML) and angle of incidence for two incident energies, 14 and 63 meV. In addition, the order of the oxygen layer has been measured using thermal He-scattering. The measurements show clear evidence for the existence of two distinct adsorption processes both on the oxygen covered and on the clean Pt(111) surface, i.e. in the limit were ΘO approaches zero: an activated process which depends on the total oxygen coverage and a non activated process which is sensitive only to the amount of locally ordered oxygen. The non activated process can be explained in terms of a mechanism involving a short living precursor state. The picture for the activated process is less clear. The dependence of this process on the incident energy seems strong evidence for a mechanism involving a barrier to dissociation directly upon impact, whereas the dependence on the oxygen coverage supports previously reported experiments which seem to be only compatible with a precursor mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00773178
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