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  • 1
    Electronic Resource
    Electronic Resource
    Auger and x-ray photoemission spectroscopy study on Cs2Te photocathodes (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3024-3030 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of Cs2Te have been produced and analyzed by Auger depth profiling and x-ray photoemission spectroscopy (XPS). The formation of the photoemissive material passes through different phases, each of them has been characterized by XPS and by its total yield in the spectral region 3.5–5 eV. Copper and molybdenum substrates have been considered. While Mo behaves to all practical purposes like an ideal support for Cs2Te, strong diffusion from the substrate material into the photoemissive film has been observed on photocathodes fabricated on Cu. The ruggedness of the photocathodes has been tested by exposing them to a few hundred Langmuirs of different gases, namely O2, CO2, CO, N2, and CH4. The last three have no effect on the photocathode lifetime, while a substantial reduction of the quantum efficiency has been observed after the exposure to oxygen. The main reason for this is the formation of a thick cesium oxide layer at the surface of the photocathode. However, the oxygen pollution can be partially recovered by the combined effect of heating the photocathode at 230 °C and illuminating the poisoned material with the 4.9 eV radiation. No rejuvenation has been observed under the effect of the temperature or the radiation alone. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363161
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  • 2
    Electronic Resource
    Electronic Resource
    Primary-beam diffraction modulated electron emission (PDMEE) for surface structural analysis (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 852-856 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Scattering interference of primary exciting electrons leads to a dependence of the Auger emission intensity on the beam incidence angle. For beam energy in the kiloelectron-volt range, maxima in the Auger yield occur when the primary beam is aligned with low-index crystal axes, therefore the Auger angular intensity distribution directly reflects the symmetries and the degree of local order. We investigated the potential for this effect, primary-beam diffraction modulated electron emission (PDMEE) to be used for surface structural characterization, in comparison with the Auger electron/photoelectron diffraction (AED/PD) technique. The angular intensity distributions of both low and high kinetic energy Auger electrons were measured on both GaAs and InP (110) surfaces. We show, by using highly collimated energetic electron beams, that the angular resolution is significantly improved in PDMEE with respect to AED/PD. Unlike the AED/PD case, the angular intensity distribution is independent of the kinetic energy of the Auger electrons, therefore low-energy, surface-sensitive electrons also directly reflect crystal symmetries, owing also to the fact that the specific momentum character of the Auger electrons can be neglected. Anisotropy in the intensity angular distribution as large as 70% was measured, comparable to AED/PD anisotropy values. Both a retarding field (low-energy electron diffraction optics) and a dispersion field cylindrical mirror analyser were used for PDMEE analysis, and instrumental performances are discussed comparatively.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740211206
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  • 3
    Electronic Resource
    Electronic Resource
    AES, EELS and XPS study of ion-induced GaAs and InP(110) surface and subsurface modifications (1990)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 16 (1990), S. 59-64 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Low-energy Ar+-induced modifications of III-V semiconductor (110) surfaces have been investigated. XPS, angle-resolved AES and Auger profiles have been used to check the in-depth composition over the range of tens to hundreds of angstroms. The actual composition of the sputtered surfaces has been determined by either the elemental standard method or normalization to the cleaved surface signals. Auger and XPS lineshape analysis and EELS spectra provided information on the chemical state of the components in the sputter-altered region.GaAs and InP surfaces have been found to be metal enriched, the enrichment being larger at high ion beam energy. The 5 keV Ar+bombardment of the cleaved InP target results in the steady-state composition In(67)P(33) at the surface. The composition is graded in the subsurface region up to the stoichiometric value In(50)P(50). Although the sputter-altered GaAs region can be depicted roughly as As-depleted, the As concentration is larger at the surface than in the subsurface region. The surface ‘spike’ and the subsurface ‘dip’ in the As concentration strongly depend on the ion beam energy in terms of both the intensity and the extension in depth. These results indicate that As radiation-enhanced Gibbsian segregation and P preferential sputtering are the dominant mechanisms of surface modification in GaAs and InP, respectively.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740160115
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