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  • 1
    Electronic Resource
    Electronic Resource
    Unique x-ray diffraction pattern at grazing incidence from misfit dislocations in SiGe thin films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 89-96 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Grazing-incidence x-ray diffraction (GIXD) permits the direct measurement of in-plane lattice parameters of SiGe films that are too thin to yield good results from normal-geometry triple-axis techniques. A unique "X''-shaped pattern has been seen in H–K reciprocal space maps of diffracted x-ray intensity from SiGe films that have relaxed via a modified Frank–Read mechanism. Contours of intensity are seen along the 〈110〉 directions from the (4¯00) reciprocal lattice peak with the introduction of the first dislocations. For higher dislocation densities the X-shaped contours are anisotropically distorted and a satellite peak, corresponding to the lattice parameter for a partially relaxed film, becomes identifiable at lower H. In contrast, H–K reciprocal-space contours from thin SiGe films that have relaxed by roughening and subsequent random nucleation of dislocations display broad, oval-shaped contours centered at the (4¯00) reciprocal lattice point for the film. Numeric simulations of GIXD from a variety of dislocation arrangements were performed in order to understand the origin of the X pattern. We show that this pattern arises from an array of long misfit dislocations running in the 〈110〉 directions. The anisotropic distortion of the X pattern arises at higher dislocation densities from orthogonal intersections of dislocations with equal Burgers vector, which are characteristic of dislocation networks generated by the modified Frank–Read mechanism. We also verify that the measured values of the in-plane lattice parameter, together with the out-of-plane lattice parameter determined from the symmetric (004) reflection, lead to accurate calculation of the composition and strain in these SiGe layers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362776
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  • 2
    Electronic Resource
    Electronic Resource
    Relaxation of SiGe thin films grown on Si/SiO2 substrates (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7240-7246 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The relaxation in Si/SiGe bilayers grown on top of SIMOX wafers has been studied. By judiciously choosing the thickness ratios of the Si and SiGe, it is possible to relax the bilayer through the glide of dislocations exclusively in the Si layer, leaving the top SiGe layer relaxed and (mostly) dislocation free. This approach is completely different from previously proposed ways of reducing the number of threading dislocations in SiGe films because at no stage during the relaxation process are new threads introduced in the top SiGe layer. It is shown that the Si/SiGe bilayer behaves as a free-floating foil constrained to remain flat by the substrate, even at temperatures as low as 700 °C. The relaxation is shown to proceed until the strain left in the Si layer is too low for dislocations to glide. When the temperature is raised to 1050 °C, interdiffusion between the two layers forces the dislocation network to move into the SiGe through glide. The original network of 60° dislocations can then react to form a network of edge dislocations, which had never been observed before in this system. At such high temperature, glide is no longer the limiting factor for relaxation, and almost complete relaxation is attained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356682
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  • 3
    Electronic Resource
    Electronic Resource
    Nucleation of dislocations in SiGe layers grown on (001)Si (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3968-3977 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comprehensive x-ray-diffraction study of the variation of the tilt angle between a Si1−xGex layer and the (001) Si substrate is presented. Such measurements provide the basis of a new method for determining the nucleation activation energy of misfit dislocations. A detailed model, independent of the particular relaxation mechanism, is derived which relates the tilt angle to the nucleation activation energy on the different slip systems and to the density of misfit dislocations. The model has been applied to the modified Frank–Read mechanism observed in graded samples. Relaxation occurs in such samples for strain in the range 0.002≤ε≤0.006 with an activation energy of about 4 eV. The critical thickness for growth of a strained layer is shown to be smaller when the substrate is miscut than when it is well oriented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356992
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of intermediate phases, Ni3Si2 and Pt6Si5: Nucleation, identification, and resistivity (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 3458-3466 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation of Ni3Si2 from the reaction of Ni2Si with NiSi, and that of Pt6Si5 from the reaction of Pt2Si with PtSi have been investigated by Rutherford backscattering, x-ray diffraction, resistance measurements, and optical and electronic microscopy. Standard x-ray diffraction patterns were calculated for Pt6Si5 and for the high-temperature form (hexagonal) of Pt2Si. These are shown to match experimental diffraction patterns. Both Ni3Si2 and Pt6Si5 form quite suddenly (at 470 and 535 °C, respectively) according to the pattern of nucleation-controlled reactions which are anticipated when the free energies of formation of the new phases are sufficiently small. These observations are discussed with respect to the absence of both Ni3Si2 and Pt6Si5 from the sequence of phases which form when Ni and Pt thin films react with Si. Resistivity measurements are reported for Ni3Si2, Pt6Si5, and for the two forms (low and high temperature) of Pt2Si.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336815
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  • 5
    Electronic Resource
    Electronic Resource
    Diffusion of Sb, Ga, Ge, and (As) in TiSi2 (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5335-5345 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gallium, Sb, and Ge were implanted into thick (about 400 nm) layers of TiSi2 prepared by metal-silicon reaction. The diffusion of the implanted atoms was analyzed by means of secondary ion mass spectrometry. Gallium was introduced because a former study had shown that the usual p-type dopant B does not diffuse in TiSi2. Germanium was used in lieu of a Si tracer. Its diffusion characteristics are compared to those of P and As (as well as Si) which had been investigated previously. Germanium and Ga diffuse readily above 600 °C, but Sb does not. Its diffusion appears to be limited to grain-boundary effects. Accumulations of the diffusing atoms are observed (except for Sb) at the silicide-silicon interface. These are due to kinetic effects, namely fast diffusion at grain boundaries and interfaces, rather than to real adsorption which is an equilibrium condition. Because diffusion in intermetallic compounds has been shown to be significantly affected by variations in stoichiometry, experiments were conducted with films implanted not only with foreign atoms but with Ti as well. These did not lead to significantly different observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340399
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  • 6
    Electronic Resource
    Electronic Resource
    Disilicide solid solutions, phase diagram, and resistivities. II. TaSi2-WSi2 (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2203-2211 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The preparation of TaSi2-WSi2 alloys from the reaction of Si with Ta-W films allows one to explore the constitution diagram of the TaSi2-WSi2 pseudobinary system. The structure of the alloys has been investigated by means of Rutherford backscattering, x-ray diffraction, and transmission electron microscopy. The "equilibrium'' phase diagrams for the system TaSi2-WSi2 and for TiSi2-WSi2 are compared in light of simple ideas of alloy theory based on the consideration of the electron to atom ratios. The resistivity of the alloys is analyzed in terms of what has been established about the transport properties of the disilicides and of possible contributions of structural defects, mostly stacking faults, to scattering processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337981
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  • 7
    Electronic Resource
    Electronic Resource
    Oxidation studies of SiGe (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1724-1728 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the kinetics and mechanism of oxidation of SiGe alloys deposited epitaxially onto Si substrates by low-temperature chemical vapor deposition. Ge is shown to enhance oxidation rates by a factor of about 3 in the linear regime, and to be completely rejected from the oxide so that it piles up at the SiO2/SiGe interface. We demonstrate that Ge plays a purely catalytic role, i.e., it enhances the reaction rate while remaining unchanged itself. Electrical properties of the oxides formed under these conditions are presented, as well as microstructures of the oxide/substrate, Ge-enriched/SiGe substrate, and SiGe/Si substrate interfaces, and x-ray photoemission studies of the early stages of oxidation. Possible mechanisms are discussed and compared with oxidation of pure silicon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342945
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal relaxation of pseudomorphic Si-Ge superlattices by enhanced diffusion and dislocation multiplication (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4693-4698 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pseudomorphic Si/Si-Ge strained layer superlattices are metastable and will relax to lower-energy, less strained, states on thermal annealing. Such relaxation may occur by the generation of misfit dislocation or by compositional homogenization of the superlattice. The particular mechanism adopted is shown to depend on the initial dislocation density of the structures. In cases where a significant portion of the strain is accommodated by an array of misfit dislocations in the as-grown state there is a propensity to relax by generating additional misfit dislocations. In the case of structures where only a very small fraction of the misfit is relieved by dislocations in the as-grown state, additional relaxation does not involve the multiplication of dislocations but proceeds by the interdiffusion of Si and Ge towards the homogenizing of the superlattice structure. This strain-enhanced diffusion has previously been observed in metals and we confirm its existence in semiconductor systems as well. The implication of the above observations on device structures and the growth of such layers is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343245
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  • 9
    Electronic Resource
    Electronic Resource
    Near band-edge photoluminescence in relaxed Si1−xGex layers (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2488-2490 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Near band-gap photoluminescence was observed at low temperatures from relaxed Si1−xGex layers with 0.17〈x〈0.32 grown on Si(001) by ultrahigh vacuum chemical vapor deposition. The luminescence from undoped samples was dominated at low temperature and low excitation densities by recombination of excitons bound to alloy fluctuations exhibiting the smallest full width at half-maximum, 2.44 meV, reported for relaxed epitaxial Si1−xGex layers. Excitons bound to phosphorous and boron were also observed as was free exciton recombination. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114617
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  • 10
    Electronic Resource
    Electronic Resource
    Relaxation mechanism of Ge islands/Si(001) at low temperature (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2317-2319 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strained layers generally relax by dislocation glide. Here, using UHV-TEM, we study growth of Ge islands on Si(001) at (approximately-less-than)350 °C. We find that, although conventional relaxation (i.e., via glide of 60° dislocations) is suppressed, the islands grow relaxed from the outset, by direct incorporation of sessile 90° dislocations into the edge of the growing island. Paradoxically, the low-temperature islands are more fully relaxed than those grown at higher temperature. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115138
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