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  • 1
  • 2
    ISSN: 1432-0630
    Keywords: 79.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Reflection high energy electron diffraction has been used to investigate the amorphous to polycrystalline structure transition in silicon induced by laser pulse. The power density of the ruby laser pulse, in the free generation mode, has been maintained below the threshold to induce surface damage. Depth analysis has been carried out in 〈100〉 silicon crystal using the channeling effect technique.
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  • 3
    ISSN: 1432-0630
    Keywords: 61.80.x ; 68.20.-s ; 61.16.-d ; 42.50.Qm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Transition to single crystal of polycrystalline Si material underlying a Si crystal substrate of 〈100〉 orientation was obtained via laser irradiation. The changes in the structure were analyzed by reflection high energy electron diffraction and by channeling effect technique using 2.0 MeV He Rutherford scattering. The power density required to induce the transition in a 4500 Å thick polycrystalline layer is about 70 MW/cm2 (50ns). The corresponding amorphous to single transition has a threshold of about 45 MW/cm2.
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  • 4
    ISSN: 1432-0630
    Keywords: 61.70 ; 61.80
    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 effects of single-pulse ruby laser irradiation have been investigated in Si samples with disorder layers located at a depth of 2000 Å from the crystal surface and extending up to 8000 Å. This disorder was obtained by implantation with 350 keV N+ to a fluence of 2×1016/cm2. Channeling, diffraction and transmission electron microscopy were used to characterize the structure of the irradiated layers. After 1.5 J/cm2 irradiation the damaged layer reorders partially, while for about 2.0J/cm2 the surface single crystal becomes polycrystalline. At a higher energy density all the material undergoes the transition to single crystal. Calculations based on the liquid model accounts in part for the experimental results.
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  • 5
    ISSN: 1432-0630
    Keywords: 61.70.Tm ; x81.10.It
    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 damage left by high-current-density, ∼9 μA/cm2, implants of 120 keV phosphorus into 〈100〉 and 〈111〉 silicon oriented substrates was investigated as a function of the fluence in the range 4×1015–1.5×1016/cm2. The samples were analyzed by 2 MeV He+ channeling and transmission electron microscopy. Initially a buried amorphous layer forms at low fluences until the wafer temperature saturates at ∼450 °C at a fluence of ∼4.5×1015/cm2. As the fluence is further increased ion-assisted regrowth of this initial buried amorphous layer takes place and is 2 to 2.5 times faster (with respect to ion fluence) for 〈100〉 substrates than for 〈111〉 substrates. At higher fluences, most of the residual damage is located at a depth equal to the sum of the projected range and of the straggling. In the regrown layers twins are found in both orientations, and in some cases a hexagonal silicon phase is present at high fluences. The results are compared with the ion assisted regrowth of amorphous layers at well defined temperatures in the 250°–400 °C range.
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  • 6
    ISSN: 1432-0630
    Keywords: 79.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Channeling effect techniques with a 2.0 MeV He+ Rutherford backscattering and transmission electron microscopy were used to characterize the crystallized layers after Q-switched ruby laser irradiation of 4000 Å thick amorphous layer on 〈100〉 and 〈111〉 underlined crystal substrates. At a laser energy density of 2.5 J/cm2 the crystal layer on the 〈111〉 specimen contains a large density of stacking-faults, that on 〈100〉 specimen contains a very small amount of screw dislocation lines. High quality single-crystal layers have been obtained after irradiation at 3.5 J/cm2. From a comparison with the growth rate and defect structure observed in thermally annealed implanted-amorphous layers, we propose that crystal growth by 50 ns pulse laser annealing occurs by melting the amorphous layer.
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  • 7
    ISSN: 1432-0630
    Keywords: 61.80 ; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Ge samples implanted with 40 keV Pb at a fluence of 3×1015/cm2 were irradiated with ruby laser single pulses of 15ns duration. Reordering of the damaged layer occurs for energy density irradiation above 0.6 J/cm2. The Pb atoms redistribute with a large component at the sample surface which is easily etched off. The remaining part of Pb impurities is substitutionally located, and the concentration exceeds the solid solubility limit by three order of magnitude. The formation of the metastable solution is explained in terms of a transient liquid layer produced during laser irradiation.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 33 (1984), S. 107-111 
    ISSN: 1432-0630
    Keywords: 72.20 ; 79.20 ; 81
    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 transmitted energy density in thin single Si crystal, wafers is measured atλ=1.06 μm as a function of the incident energy density for a Nd laser pulse of 30 ns duration. Non-linear effects begin to become important at about 0.3 J/cm2. The contribution due to free-carriers is separated from the interband one by using measurements made at low energy density and at different sample temperatures in the 20°–150 °C range. The time dependence of the free-carrier concentration and of the lattice temperature is computed for different values of the Auger constant. The experimental data in the 0.2–2.5 J/cm2 energy density range are fitted with an Auger constant of 10−30 cm6s−1.
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  • 9
    ISSN: 0392-6737
    Keywords: Laser systems and laser beam applications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto La transizione amorfo-cristallo in GaAs impiantato è stata ottenuta mediante impulsi laser di potenza a λ=1.06 μm. La fusione dello strato superficiale è possibile in quanto lo strato amorfo è caratterizzato da un valore del coefficiente di assorbimento grande rispetto al materiale cristallino. I valori di soglia misurati sono di 0.8 J/cm2 per cristalli impiantati sia con 50 keV di Te che con 100 keV di Ar. Misure effettuate mediante incanalamento di ioni He+ da 2.0 MeV e spettroscopia dei fotoelettroni emessi a seguito d'irraggiamento con raggi X indicano che non vi è decomposizione apprezzabile a densità di energia prossime alla soglia. Per densità di energia molto piú alte del valore di soglia si osserva invece decomposizione superficiale e perdita di arsenico.
    Abstract: Резюме Исследуется переход аморфного состояния в монокристаллическое, индуцированный мощным импульсом неодимового лазера, в GaAs, имплантированном ионами, используя высокий козффициент поглощения в аморфных материалах. Плотность пороговой энергии составляет 0.8 Дж/см2 для внедренных ионов Te+ с энергией 50 кэВ и ионов Ar+ с энергией 100 кэВ. Эффект каналирования и техника рентгеновской фотоэлектронной спектроскопии указывают, что в узком окне плотности энергии немного выше порога не возникает заметного уменьщения As. Высокие плотности энергии вызывают потери Аз вблизи поверхностой области.
    Notes: Summary The amorphous-to-single crystal transition induced by high-power Nd laser pulse has been studied in ion-implanted GaAs by taking advantage of the high-absorption coefficient of amorphous material. A threshold energy density of about 0.8 J/cm2 has been measured for both 50 keV Te+ and 100 Ar+ implants. Channelling effect and X-ray photoelectron spectroscopy techniques indicate that no appreciable As loss occurs in a narrow energy density window just above threshold. High-energy densities cause instead As loss from the near surface region.
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  • 10
    ISSN: 0392-6737
    Keywords: Electron microscopy determinations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si mostra che lo stato quasi cristallino può essere formato in AlCr mediante una trasformazione dello stato solido dalla fase amorfa mediante irradiazione ionica a 150°C con ioni di Xe a 600 keV.
    Notes: Summary We have shown that the quasi-crystalline state can be formed in AlCr by a solid-state transformation from the amorphous phase by ion irradiation at 150°C with 600 keV Xe ions.
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