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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 7045-7049 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The damage produced in crystalline silicon by Ge-ion implantation at 130 keV is studied as a function of fluence. Rutherford backscattering measurements in channeling configuration and reflectivity measurements in the 1.5–6.5 eV energy range are presented and discussed. The results obtained by both techniques are in agreement on the determination of the amorphization threshold. The dielectric functions, obtained by the Kramers–Kronig analysis and checked through ellipsometric measurements at one selected wavelength, are well reproduced by finite sets of classical harmonic oscillators. It is possible to describe the behavior of the oscillator parameters through analytical functions of a single variable related to the amount of damage. In a representative case, the damage depth profile is obtained after the removal of controlled amounts of silicon by anodic oxidation, and good agreement is found with the Rutherford backscattering results.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1384-1387 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: K–Te photocathodes deposited on a Mo substrate have been successfully used as an electron source in the free electron laser of University of Twente. Long lifetimes have been measured: after more than 20 h of operation in the accelerator a K–Te cathode with 4.75% initial quantum efficiency still displays a 1.1% quantum efficiency at 259 nm. Moreover, the quantum efficiency of this cathode versus operation time can be fitted by an exponential decay curve, which saturates asymptotically to a 1.03% value, suggesting that a quantum efficiency close to 1% could be sustained for very long operation times. Films degraded by use can be recovered to a quantum efficiency which is close to the initial value, by heating the substrate at temperatures between 100 and 330 °C. A new procedure to obtain K–Te cathodes with high (up to 11%) quantum efficiencies is described. © 1997 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3641-3643 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter the photoemissive properties of K–Te films produced under ultrahigh vacuum conditions are reported. K–Te photocathodes were fabricated by vapor deposition of Te and K onto a Mo substrate into the preparation chamber of the Free Electron Laser of the University of Twente. The highest quantum efficiency obtained at 259 nm was 11.1%, measured just after evaporation; this value decreased in a few minutes to a stable quantum efficiency of 8.3%. The reported results show that K–Te can be considered a promising material for the use as a photocathode in photoinjectors. © 1996 American Institute of Physics.
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have monitored the structural evolution of Co(tCo)/Cu(4×tCo) multilayers when tCo ranges from 12 to 2 Å. The investigation has been performed by studying their magnetization and giant magnetoresistance, since these properties are complementary in providing information about the structure of the magnetic species into the samples. In particular, in the intermediate range of thickness, we observed no correspondence between magnetic and magnetoresistive behavior. Finally, at sufficiently low thickness, the samples exhibit noninteracting superparamagnetic features. This kind of evolution has been ascribed to the progressive fragmentation of Co layers. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3447-3449 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Visible photoluminescence has been observed at cryogenic temperatures from crystalline Si bombarded with He and exposed to H either as plasma or gas in the 250–450 °C temperature range. The experimental results are consistent with the formation of Si nanoparticles produced by He segregation, which is responsible for exciton localization, and H passivation of the nonradiative recombination centers. © 1995 American Institute of Physics.
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  • 6
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of coercive field and of the ratio between the remanent and saturation magnetization of granular Co/Cu films grown by sequential sputtering has been studied with magneto-optic Kerr effect measurements in the temperature range 8.5–60 K. The observed temperature dependence of coercive field does not fit any of the plausible Tx laws commonly used to describe systems of single-domain ferromagnetic particles. We worked out a generalized model, which also includes temperature effects related to nonuniform single-domain particle size distribution. The model predictions account well for the observed temperature behavior of both coercive field and ratio between the remanent and saturation magnetization. © 2001 American Institute of Physics.
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of a displacement field in single crystal silicon resulting from high dose hydrogen implantation and subsequent heat treatments has been investigated by MeV 4He+ Rutherford backscattering in channeling conditions, double crystal x-ray diffraction, and transmission electron microscopy. The results obtained in samples annealed for various times in the temperature range 220–350 °C have been explained in terms of a kinetic model which assumes the formation of clusters of hydrogen molecules. The growth of the displacement field is thermally activated with an activation energy of 0.50±0.05 eV, suggesting that the limiting process could be the release of hydrogen atoms bounded to defects created by ion implantation. © 1998 American Institute of Physics.
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Solid-phase epitaxial growth was studied in germanium-implanted 〈100〉 silicon wafers as a function of germanium fluence, annealing temperature, and time. MeV He Rutherford backscattering in channeling conditions, cross-sectional transmission electron microscopy, double-crystal x-ray diffraction, and secondary-ion mass spectroscopy techniques were used to characterize the samples. At low fluences, up to 1×1015 cm−2 at 130 keV, the crystallization kinetics is similar to that measured on self-amorphized silicon. In the high-dose samples, prepared by multiple implants with a total dose of 3.12×1016 cm−2, the growth rate at fixed temperatures decreases. A comparison with literature data, obtained by similar experiments performed on amorphized uniform GexSi100−x films prepared by molecular-beam epitaxy or chemical-vapor deposition, reveals that the concentration gradient, unavoidable in implanted samples mainly at the end of the ion range region, is strictly connected with the observed decrease.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1491-1493 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cs–K–Te films have been fabricated under ultrahigh vacuum by vapor deposition of Te, K, and Cs onto a Mo substrate into the preparation chamber of the free electron laser of the University of Twente. Their photoemission properties are reported in this letter. The average quantum efficiency at 259 nm measured on 5 evaporated Cs–K–Te photocathodes is 22.5%, whereas the best quantum efficiency obtained at 259 nm is 23.4%. To our knowledge, this is the highest quantum efficiency at 259 nm reported so far, being about twice that of Cs2Te photocathodes. The reported results demonstrate that Cs–K–Te photocathodes are very promising for the use in photoinjectors. © 1997 American Institute of Physics.
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