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  • Chemistry  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 10 (1987), S. 338-342 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Multi-element (52Cr, 56Fe and 66Zn) implanted GaAs samples have been prepared specially for SIMS calibration. Absolute chemical measurements gave retained ion doses which agreed to within 12% of the nominal implanted dose (2.0 × 1014 atoms cm-2). Comparative SIMS depth profiles with five instruments gave Cr mode depth data which showed a variability of 5%. After data normalization to a common mode depth (168 nm) the shape of all profiles showed good agreement. SIMS anàlysis of similar samples containing lower dose implants (1.0 × 1013 atoms cm-2) showed that ∼50% of the Cr was contained in the near surface region (0-0.03 μm). This surface peak was not observed in profiles of samples which had been singly implanted with Cr. It is proposed that the Cr surface peak results from radiation enhanced out-diffusion initiated by the subsequent Fe implant. Whilst the high dose multi-implant samples showed a similar Cr surface accumulation, its magnitude in relation to the ion implanted dose, was smaller. These samples therefore form reliable calibration specimens for the simultaneous determination of the secondary ion responses of Cr, Fe and Zn in GaAs.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 665-672 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A chemical bevelling technique has been developed to synthesize high-magnification bevels in gallium arsenide for SIMS linescanning and imaging. Bevels have been prepared in gallium arsenide substrate material, in gallium arsenide implanted with aluminium and in two delta-doped (aluminium) GaAs test structures. The accuracy, sensitivity, dynamic range and depth resolution-depth characteristics of the bevel and linescan approach have been compared to conventional SIMS depth profiling. Images of the bevelled structures have been used to obtain a quick view of the features of interest. Linescans have yielded an aluminium profile from the aluminium implant that is very similar to that from a SIMS depth profile. Linescan results from the aluminium deltas in gallium arsenide indicate that depth resolutions of a few nanometers can be retained to depths of several microns. The depth resolution of the deltas has been measured as a function of bevel magnification and a theory has been developed to explain the results. A peak width (resolution) of 2.2 nm for an aluminium delta has been achieved at a bevel magnification of 6000 using a 15 keV 16O2+ ion beam, and a depth resolution limit of 1.3 nm has been deduced by extrapolation to infinite bevel magnification. The combined effects of beam-induced mixing, microtopography and the escape depth of the secondary ions is a broadening of 2.0 nm for these conditions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 723-728 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Enhancements in the secondary ion yields of Si+ and As+ ions were observed in SIMS depth profiles of Si delta-doped layers in GaAs when using oxygen primary ions. A systematic SIMS study of the enhancement in the intensity of the Si+ ion was carried out using a special test structure consisting of a series of layers with Si areal densities ranging from 0.01 monolayer (ML) to 2 ML (1 ML = 6.3 × 1014 Si cm-2). The enhancement effect was observed with layers above about 0.2 ML coverage and leads to erroneous measurements of the Si areal density for such layers. It was found that the level of the enhancement depended upon both the energy and angle of incidence of the oxygen ions. For a 2 ML delta, the level of the enhancement obtained with 5 keV O2+ ions at normal incidence was a factor of 1.2. However, using the same ion energy but changing the angle of incidence to 60° from the normal the enhancement obtained was almost a factor of 5. The enhancement was greatest when conditions for high depth resolution were used so that it was not possible simultaneously to achieve high depth resolution and accurate areal density measurements. The enhancements could not be removed by ratioing the silicon intensities to the As matrix lines (for which the enhancements are different). The enhancement effect was not observed when Xe+ or Cs+ primary ions were used and is predominantly an oxygen-induced artefact.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Problems associated with the secondary ion mass spectrometry (SIMS) depth profiling of periodic doping structures are discussed with reference to experiments on a boron-in-silicon modulation doping structure and a boron-antimony silicon super-lattice, both grown by silicon molecular beam epitaxy (MBE). The effects of uneven etching during SIMS analysis are compared with the effects of dopant diffusion during growth. Uneven etching is modelled with an algorithm in which the macrotopography of the crater base is described in terms of an unevenness function f(x, y). Simulation depth profiles involve passing craters of this topography f(x, y) through specified, laterally homogeneous, doping distributions ρp(z) in a series of equal depth interations. The predicted SIMS signal is proportional to the amount of dopant sputtered per depth iteration. The model explains the peak shapes and the loss of depth resolution with depth that are observed experimentally. The effects of dopant diffusion during growth are found by re-heating parts of the wafer to the growth temperature for various periods of time and then SIMS depth profiling them (thermal cycling).
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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