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  • 1990-1994  (21)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Photochemical preparation of crystalline silicon nanoclusters (1991)
    s.l. : American Chemical Society
    Chemistry of materials 3 (1991), S. 989-992 
    Details
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/cm00018a003
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  • 2
    Electronic Resource
    Electronic Resource
    Strain symmetrization effects in pseudomorphic Si1−yCy/Si1−xGex superlattices (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 739-741 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on strain and stability measurements on pseudomorphic Si1−yCy/Si1−xGex superlattices which are synthesized by solid source molecular beam epitaxy on silicon (100) substrate. The strain in the superlattices alternates between tensile and compressive in the individual Si1−yCy and Si1−xGex alloy layers, respectively. A symmetrical strain distribution can be achieved directly on silicon by adjusting the carbon and the germanium content and/or the thickness of the individual layers. X-ray diffraction and transmission electron microscopy are applied to investigate the structural properties and the thermal stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111051
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  • 3
    Electronic Resource
    Electronic Resource
    Formation of β-SiC nanocrystals by the relaxation of Si1−yCy random alloy layers (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 324-326 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work we consider the relaxation behavior of Si1−yCy random alloys grown epitaxially on Si, with 0.005(approximately-greater-than)y(approximately-greater-than)0.05. The Si1−yCy layers are under tensile strain as grown and at annealing temperatures below 900 °C the relaxation of strain is achieved by dislocation formation, in a fashion similar to SiGe relaxation. However, at temperatures in excess of 900 °C the C, which at lower temperatures remained in substitutional sites, precipitates out of the lattice, this removes all of the tensile strain from the layer. The nature of this precipitation is to form single crystal, nanoparticles of β-SiC with the same lattice orientation as the Si lattice in which they are created. These nanoparticles are of uniform diameter (3±1 nm for y=0.005 Si1−yCy material) and randomly dispersed throughout the original Si1−yCy region. This ability to produce nanocrystals of wide band-gap material within the Si matrix should enable the exploration of mesoscopic phenomena. The nanoparticles once formed also block the movement of dislocations, thus locking in any strain fields associated with the dislocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111195
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  • 4
    Electronic Resource
    Electronic Resource
    Dislocation nucleation barrier in SiGe/Si structures graded to pure Ge (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2845-2847 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-resolution triple-axis x-ray diffraction measurements were used to study strain relaxation in the individual layers of a SiGe/Si structure step-graded to pure Ge. The tilt of each layer is explained by extending the model previously proposed for obtaining the nucleation activation energy of dislocations to account for the reduced miscut of the growth surface as the sample relaxes and the variation in the materials properties with alloy composition. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112511
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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Mechanism and conditions for anomalous strain relaxation in graded thin films and superlattices (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4230-4243 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Compositionally graded films of SiGe/Si(100) and GaInAs/GaAs were grown under different conditions in order to investigate the different modes of strain relaxation associated with the compositional grading. We show that, when the growth conditions are very clean and the gradient is shallow enough (about 1% misfit per half micron), very good, relaxed films are obtained. This coincides with the introduction of large numbers of dislocations in the substrate itself, which is counter-intuitive at first since the substrate is under negligible strain. We show that this introduction of dislocations is the result of the activation of novel Frank–Read-like sources located in the graded region, and is directly correlated to the lack of other low energy nucleation sites for dislocations. We detail the conditions of growth necessary for this phenomenon to occur, and show that it operates both for the SiGe/Si system and the GaInAs/GaAs system. Pure, relaxed Ge films have been grown in this manner on Si(100), with a defect density as low as 106/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350803
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  • 8
    Electronic Resource
    Electronic Resource
    New approach to the growth of low dislocation relaxed SiGe material (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1856-1858 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this growth process a new strain relief mechanism operates, whereby the SiGe epitaxial layer relaxes without the generation of threading dislocations within the SiGe layer. This is achieved by depositing SiGe on an ultrathin silicon on insulator (SOI) substrate with a superficial silicon thickness less than the SiGe layer thickness. Initially, the thin Si layer is put under tension due to an equalization of the strain between the Si and SiGe layers. Thereafter, the strain created in the thin Si layer relaxes by plastic deformation. Since the dislocations are formed and glide in the thin Si layer, no threading dislocation is ever introduced in to the upper SiGe material, which appeared dislocation free to the limit of the cross sectional transmission electron microscopy analysis. We thus have a method for producing very low dislocation, relaxes SiGe films with the additional benefit of an SOI substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111778
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  • 9
    Electronic Resource
    Electronic Resource
    Crystallographic tilting resulting from nucleation limited relaxation (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 140-142 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the crystallographic tilt in thick relaxed Si0.7Ge0.3 layers grown on vicinal (001) Si substrates, with and without a step graded intermediate layer, as a function of the angle of miscut away from the exact (001) surface. In both cases, the tilt angle has the same azimuthal orientation as the miscut, but is opposite in sign, and varies linearly with the angle of miscut. The tilt is significantly larger for samples with intermediate graded layers, reaching 0.6° for an angle of miscut of 2°. We interpret these data by noting that relaxation of layers grown on top of a compositionally graded buffer occurs by a nucleation limited mechanism, whereas relaxation in samples grown without graded buffers is glide limited. The miscut affects the activation energy of nucleation, which is an exponential effect, while it linearly changes the glide force applied on dislocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109351
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal stability of Si1−xCx/Si strained layer superlattices (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2758-2760 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal stability of epitaxial silicon-carbon alloys grown by molecular beam epitaxy on (001) silicon was investigated using high resolution x-ray diffraction, transmission electron microscopy, and secondary ion mass spectroscopy measurements. Different superlattices, with alloy compositions of Si0.997C0.003, Si0.992C0.008, and Si0.985C0.015, all nominally 6 nm thick, with 24 nm Si spacer layers were employed. Annealing studies determined that there are different pathways to strain relaxation in this material system. At annealing temperatures of 900 °C and below, the structures relax only by interdiffusion, indicating that these layers are stable during typical device processing steps. At temperatures of 1000 °C and above, SiC precipitation dominates with enhanced precipitation in the Si1−xCx layers with the highest initial carbon content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106868
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