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  • Articles: DFG German National Licenses  (19)
  • 1995-1999  (10)
  • 1990-1994  (9)
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  • Articles: DFG German National Licenses  (19)
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  • 1
    Electronic Resource
    Electronic Resource
    Two-dimensional damage distribution induced by ion implantation in Si under arbitrarily shaped mask edges: Simulations and cross-sectional transmission electron microscopy observations (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5117-5123 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method is presented to calculate two-dimensional defect distributions induced by ion implantation through openings in a masking layer. It is shown that a realistic description of this model requires depth-dependent lateral standard deviations to describe the dopant and the damage point response functions. Further refinements of the theory include arbitrary shapes for the mask edges and different materials in the masking layer and in the substrate. Cross-sectional electron microscopy observations have been carried out to visualize the two-dimensional extension of amorphous layers created by As implantation in silicon for different mask edge angles. It is shown that the theory fits well the cross-sectional transmission electron microscopy observations. More generally, this study shows that for abrupt mask edges, the lateral extension of the two-dimensional defect profile beneath the mask edge is directly governed by scattering of the ions and of the subsequent recoil atoms and, as a direct consequence, by the lateral standard deviation of the damage point response function. For tapered mask edges, however, the contribution of ions that pass through the mask edge region before damaging the substrate may be very high with respect to scattering effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352041
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  • 2
    Electronic Resource
    Electronic Resource
    Phosphorus-enhanced diffusion of antimony due to generation of self-interstitials (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1623-1629 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a series of experiments, the influence of phosphorus diffusion at high concentrations on the diffusion of an antimony marker layer was investigated. The marker layer was separated from the surface by a 4 μm layer of epitaxially grown silicon. To reduce the effects of implantation enhancement and phosphorus precipitation on the diffusion of the antimony marker layer, the phosphorus was implanted into a polysilicon layer deposited on top of the single-crystalline substrate. It was found that the diffusion of the antimony marker layer is already reduced by the epilayer. From these diffusion coefficients, upper limits for the fractional diffusivity of antimony were derived. In contrast to previous investigations, the diffusion of the antimony marker layer was found to be enhanced below regions where phosphorus was implanted. A comparison of diffusion in FZ and CZ samples shows that this enhanced diffusion of antimony can be explained only by an injection of self-interstitials from the phosphorus-doped region. Since the polysilicon layer was found to recrystallize, this self-interstitial injection can be the result of phosphorus diffusing mainly via self-interstitials, phosphorus precipitation, or both. Using Boltzmann–Matano analysis and antimony diffusivity data, the fractional diffusivity of phosphorus via self-interstitials was estimated to be lower than 0.71 at 950 °C. Possible sources of error in this estimation are discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360256
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  • 3
    Electronic Resource
    Electronic Resource
    Lateral damage extension during masked ion implantation into GaAs (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4303-4307 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied both experimentally and theoretically the generation of damage in GaAs due to ion implantation through mask openings of small dimensions. We show that it is possible to master the generation of damage, i.e., the amorphization phenomenon in the direction perpendicular to the ion beam and close to the mask edges. A theoretical model is used to simulate the ion implantation process and damage accumulation through Ti–Au masks. After comparing the shape of the crystalline/amorphous interfaces as revealed by cross-sectional electron microscopy with our simulations, this model is used to predict the evolution of the two-dimensional damage distributions beneath the mask edges as functions of ion beam and implantation mask parameters. Undamaged regions of nanometer dimensions can be preserved even when using masks of reasonable dimensions (100–200 nm). This can be done only by adjusting the ion beam parameters through the accurate simulation of the two-dimensional damage generation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363378
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  • 4
    Electronic Resource
    Electronic Resource
    Transient enhanced diffusion of boron in presence of end-of-range defects (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 2855-2861 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The presence of a supersaturation of Si self-interstitials in ion implanted silicon has been shown to be the origin of several physical phenomena such as transient enhanced diffusion (TED) of boron, the formation of extended defects at the projected range of implanted atoms at doses below the amorphization threshold, and the formation of end-of-range (EOR) defects in the case of a preamorphization stage. In this article, we discuss the relation between boron anomalous diffusion and end-of-range defects. Modeling of the behavior of these defects upon annealing allows one to understand why and how they affect dopant diffusion. This is possible through the development of the Ostwald ripening theory applied to extrinsic dislocation loops. This theory is shown to give access to the variations of the mean supersaturation of Si self-interstitial atoms between the loops and also to be responsible for anomalous diffusion. This initial supersaturation is, before annealing, at least five decades larger than the equilibrium value and exponentially decays with time upon annealing with activation energies that are the same as the ones observed for TED. It is shown that this time decay is precisely at the origin of the transient enhancement of boron diffusivity through the interstitial component of boron diffusion. Side experiments shed light on the effect of the proximity of a free surface on the thermal behavior of EOR defects and allow us to quantitatively describe the space and time evolutions of boron diffusivity upon annealing of preamorphized Si layers. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366117
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  • 5
    Electronic Resource
    Electronic Resource
    High strain effects evidenced by Raman scattering in arsenic clusters in As-implanted GaAs (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1927-1929 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman scattering has been used to track structural information on arsenic clusters in GaAs obtained by annealing of high dose As-implanted GaAs layers. Beyond the good crystalline quality of both the clusters and the matrix, high tensile stresses within the precipitates have been originally deduced from the A1g and Eg mode frequency shifts. The results are well explained in terms of the difference between the thermal expansion coefficients of the two materials. The temperature dependence of the stresses corroborates this interpretation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113279
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  • 6
    Electronic Resource
    Electronic Resource
    Formation of P precipitates during annealing of InP grown by gas source molecular beam epitaxy at low temperature (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1638-1640 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied by transmission electron microscopy the structural changes that take place in monocrystalline InP grown by gas source molecular beam epitaxy at low temperature upon annealing at about 600 °C. It is shown that the partial relaxation of the crystal which is observed by x rays is due to the formation of small precipitates (3–7 nm). Electron diffraction experiments show that the structure of these precipitates is cubic with a simple cube-to-cube orientation relationship with the substrate. Most probably, these precipitates are of alpha-white cubic P which is known to be insulating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108611
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  • 7
    Electronic Resource
    Electronic Resource
    Formation of As precipitates in GaAs by ion implantation and thermal annealing (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1271-1273 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that it is possible to regrow an amorphous GaAs layer created by high dose As implantation at room temperature. If implantation parameters are carefully selected, As precipitates may be formed in the regrown layer with structural characteristics the same as those observed in semi-insulating GaAs grown by molecular beam epitaxy at low temperature. Transmission electron microscopy has been used to study the structure of these precipitates in connection with the structural defects which are seen in the layer. This process appears promising for the formation of low cost semi-insulating GaAs layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108704
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  • 8
    Electronic Resource
    Electronic Resource
    Structural characterization of low-temperature molecular beam epitaxial In0.52Al0.48As/InP heterolayers (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 989-991 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic study of the structural quality and arsenic content of as-grown In0.52Al0.48As/InP layers deposited on InP by molecular beam epitaxy at temperatures between 150 and 450 °C was performed using transmission electron microscopy and particle-induced x-ray emission. We found that the amount of As incorporated in the layers generally increases with decreasing growth temperature, with the crystalline quality of the layers being good at growth temperatures higher than 200 °C. At 150 °C, a large density of pyramidal defects is formed, the defects are related to the very large amount of excess As incorporated into the layer. The mechanisms leading to the formation of these defects are discussed. At 200 °C, however, the amount of excess As is lower than expected, and wavy streaks of diffuse scattering are seen in electron diffraction. It is shown that small ordered domains of the CuPt type on the group III atoms are responsible for these features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106483
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of the boron doping level on the thermal behavior of end-of-range defects in silicon (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 365-367 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of the doping level on the formation and growth of end-of-range (EOR) defects is studied. Transmission electron microscopy observations have been performed on boron doped Si wafers (from 1015 to 1020 atom3) preamorphized with germanium and subjected to rapid thermal annealing. When increasing the doping level up to a few 1018 atom3, a delay in the coarsening process encountered by the loops is observed while above this threshold the EOR defects quickly disappear. These results are interpreted by considering three possibly concomitant phenomena: the formation of boron/Si-interstitial clusters, the gettering of boron at the loop periphery, and a change from the intrinsic to the extrinsic regime for self-diffusion. Moreover, an estimate of the effective trapping efficiency of boron is reached and gives about 1±0.3 Si interstitial per boron atom, a value consistent with the one obtained from studies of B transient enhanced diffusion. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119563
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and regeneration of reactive polymers bearing triphenylphosphine dichloride functional groups using triphosgene (1996)
    Springer
    Polymer bulletin 37 (1996), S. 415-421 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A new methodology is described for the synthesis of reactive polymers bearing triphenylphosphine dichloride groups by the use of triphosgene. These materials show high reactivity for the room temperature conversion of benzyl alcohol to benzyl chloride. In one hour, yields higher than 90% were achieved using reactive copolymers with up to 25 w% divinylbenzene (DVB). The functional groups can be easily and efficiently regenerated using 1.0 mol of triphosgene for every 2.6 moles of phosphine in the polymer. Preliminary results showed up to 40% conversion of benzyl alcohol in column reactions using regenerated polymers at 5 to 10 min contact times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00556799
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