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  • 1
    Electronic Resource
    Electronic Resource
    Annealing-environment effects in the epitaxial regrowth of ion-beam-amorphized layers on CaTiO3 (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1519-1527 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of water-vapor ambients on the solid-state epitaxial regrowth of ion-beam-amorphized, near-surface layers on single-crystal CaTiO3 have been investigated using Rutherford backscattering-channeling spectroscopy, time-resolved reflectivity, and cross-sectional transmission electron microscopy (TEM). The presence of water vapor in the annealing atmosphere increases the thermally induced epitaxial regrowth rate and, within the temperature range studied (400–550 °C), decreases the activation energy for this process. TEM micrographs from samples which were partially regrown in high-H2O-concentration atmospheres revealed uneven amorphous/crystalline interfaces with fluctuations on the order of 5–10 nm. Samples annealed in water-vapor-deficient atmospheres exhibited very flat interfaces after partial epitaxial regrowth. The morphologies of these interfaces are explained in terms of a segregation of hydrogen ahead of the regrowth interface. Additionally, it has been determined that the absence of oxygen does not affect the regrowth rate. Samples annealed in oxygen concentrations as low as 10−21 atm exhibit growth rates that are identical to those measured for air-annealed CaTiO3 samples. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360244
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrogen catalyzed crystallization of strontium titanate (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2711-2718 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystallization rate of amorphous strontium titanate is enhanced by more than an order of magnitude during thermal annealing in water vapor as compared to a dry ambient. Time resolved optical reflectivity (TRR) has been combined with Rutherford backscattering spectrometry (RBS) and ion channelling to investigate this effect. Thin amorphous films (0.6 μm) were produced on single-crystal substrates of (100) strontium titanate by bombardment with 1.9 or 2.0 MeV Pb ions. Specimens were annealed under controlled ambient conditions (H2O, D2O, vacuum, 265–430 °C) and the solid phase epitaxial crystallization monitored in situ by TRR (633 nm). The TRR data were calibrated ex situ by transmission electron microscopy and RBS measurements. Isotope substitution, nuclear reaction analysis, and secondary-ion-mass spectrometry were utilized to reveal the uptake of hydrogen and oxygen into the implanted layer. Hydrogen is identified as the only species which penetrates to the crystal/amorphous interface. It is shown that the crystallization rate is proportional to the concentration of diffusing hydrogen (H or D) at the interface. The data show that the effect of water vapor, or more precisely, hydrogen, is to reduce the activation energy of crystallization from 2.1 to 1.0 eV. It is concluded that hydrogen, provided by the dissociation of water molecules at the surface, is a catalyst in the crystallization of amorphous strontium titanate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357574
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  • 3
    Electronic Resource
    Electronic Resource
    Diamond nanocrystals formed by direct implantation of fused silica with carbon (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3007-3018 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report synthesis of diamond nanocrystals directly from carbon atoms embedded into fused silica by ion implantation followed by thermal annealing. The production of the diamond nanocrystals and other carbon phases is investigated as a function of ion dose, annealing time, and annealing environment. We observe that the diamond nanocrystals are formed only when the samples are annealed in forming gas (4% H in Ar). Transmission electron microscopy studies show that the nanocrystals range in size from 5 to 40 nm, depending on dose, and are embedded at a depth of only 140 nm below the implanted surface, whereas the original implantation depth was 1450 nm. The bonding in these nanocrystals depends strongly on cluster size, with the smaller clusters predominantly aggregating into cubic diamond structure. The larger clusters, on the other hand, consist of other forms of carbon such as i-carbon and n-diamond and tend to be more defective. This leads to a model for the formation of these clusters which is based on the size dependent stability of the hydrogen-terminated diamond phase compared to other forms of carbon. Additional studies using visible and ultraviolet Raman Spectroscopy, optical absorption, and electron energy loss spectroscopy reveal that most samples contain a mixture of sp2 and sp3 hybridized carbon phases. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1388857
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of Ti3+ in sapphire by co-implantation of Ti and O ions (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 424-426 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have demonstrated that co-implantation of Ti and O ions into c-axis oriented α-Al2O3 substrates followed by thermal annealing can substantially increase the fraction of Ti ions present in the optically active 3+ oxidation state. Evidence for the presence of Ti3+ is given by the observation of strong luminescence over the wavelength range ∼600–900 nm under Ar laser excitation and by the presence of the characteristic absorption band at ∼450–550 nm. We have studied the luminescence intensity as a function of implantation and annealing parameters and have found that there is a strong dependence on the ratio of implanted Ti and O and on the annealing temperature. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125775
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics of solid phase epitaxy in buried amorphous Si layers formed by MeV ion implantation (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 925-927 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The kinetics of solid phase epitaxy have been measured in buried amorphous Si layers produced by ion implantation. Crystallization occurs simultaneously at both amorphous/crystalline interfaces of the buried layer. By collecting time resolved reflectivity data simultaneously at λ=1152 nm and λ=632.8 nm it is possible to accurately determine the crystallization rates at both interfaces. Both interfaces crystallize at a constant rate that is comparable to the intrinsic rate found for thick amorphous surface layers before rate retardation due to H infiltration has occurred. Thus, buried amorphous Si layers provide a suitable environment for studies of the intrinsic growth kinetics of amorphous Si. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116945
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