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  • 1
    Electronic Resource
    Electronic Resource
    X-ray diffraction of nonuniform GexSi1−x/Si strained-layer superlattices (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7955-7956 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GexSi1−x/Si strained-layer superlattices have been studied by means of double-crystal x-ray rocking curves. Double peaks in the same order superlattice reflections or strong oscillation fringes near the superlattice peaks were observed in the rocking curves for two different samples. Good agreement between theoretical simulations and their experimental counterparts were obtained. Our results demonstrate that these phenomena are attributed to serious local variation in layer thickness and composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353949
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  • 2
    Electronic Resource
    Electronic Resource
    X-ray diffraction analysis of Si1−xGex/Si superlattices (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3474-3479 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si1−xGex/Si strained-layer superlattices grown by molecular-beam epitaxy on Si substrates were investigated by x-ray double-crystal diffraction and x-ray grazing incidence diffraction. Both coherent and incoherent interfaces between the two components of the superlattices were observed. By fitting computer-simulated double-crystal x-ray-diffraction rocking curves to the experimental data, it is determined that there exist graded variations in both the component thickness ratio t1/t2 (t1 and t2 are the thickness of the Si1−xGex and the Si layers, respectively) and the fraction x in one sample. The x-ray grazing incidence diffraction experiments reveal a lattice strain relaxation of about 27% in another sample. The lattice relaxation and the influence of variations of x and t1/t2 on the rocking curves are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351423
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  • 3
    Electronic Resource
    Electronic Resource
    Evolution of mosaic structure in Si0.7Ge0.3 epilayers grown on Si(001) substrates (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1292-1297 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we report a study of mosaic structures in partially relaxed Si0.7Ge0.3 epilayers grown on Si(001) substrates by x-ray double- and triple-axis diffractometry. The samples have different layer thicknesses and hence different degrees of strain relaxation. Our results show that, at early stages of strain relaxation, the films contain mosaic regions laterally separated by perfect regions. This is because the mosaic structure caused by a misfit dislocation is effectively localized in a lateral range of the layer thickness. Therefore, far from the dislocations, the film is virtually a perfect crystal. With the increase in the degree of strain relaxation, and consequently in the dislocation density, the mosaic regions of the layer expand while the perfect regions shrink and finally vanish completely. Moreover, our results indicate that the conventional method of estimating dislocation density from the x-ray rocking curve width fails in our case. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370884
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  • 4
    Electronic Resource
    Electronic Resource
    Evolution of island–pit surface morphologies of InAs epilayers grown on GaAs (001) substrates (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3700-3705 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a study of the morphological evolution of InAs layers grown on GaAs (001) substrates by molecular-beam epitaxy under In-rich conditions. The surface morphology of the InAs layers is characterized by a feature of island–pit combinations. We show that the vertical sizes of the islands and pits can grow simultaneously beyond the average layer thickness, up to several hundred nanometers. The composition of the islands is found to be ternary InxGa1−xAs rather than the expected binary InAs due to intermixing of the layer and substrate materials. We determine that this intermixing is caused by dissociation of the exposed GaAs at the pits, followed by migration of excess Ga atoms and their incorporation into the islands. The density of the island–pit combinations keeps nearly constant for different layer thicknesses. Eventually, as the layer grows beyond a certain thickness, the pits are filled up by the expanding islands, forming a nearly pure island morphology at the growth front. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1354637
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  • 5
    Electronic Resource
    Electronic Resource
    Recording long-term optical images of a Brownian particle in a Paul trap essentially free of thermally induced positional noise (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3566-3571 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show experimentally that the positional uncertainty in long-term images of a microparticle in a Paul trap in air can be reduced to the optical limit, and below the pseudopotential limit. For this damped system, far below any Mathieu instability, the particle's thermally induced positional noise is extremely sensitive to the phase of the driving field. Accumulating images strobed at the proper phase produces a long-term optical image which is essentially free of thermally induced positional noise. Although noise squeezing theory does not apply at such large dissipation, our results may be understood through recent theory of the Brownian parametric oscillator. Use of this theory coupled with our observations suggests that the extreme reduction in spatial variance observed by using our technique results from working in a low Reynolds number regime. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359932
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of surface roughness of InP (001) wafers by x-ray scattering (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4154-4158 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface roughness of polished InP (001) wafers were examined by x-ray reflectivity and crystal truncation rod (CTR) measurements. The root-mean-square roughness and the lateral correlation scale were obtained by both methods. The scattering intensities in the scans transverse to the specular reflection rod were found to contain two components. A simple surface model of surface faceting is proposed to explain the experimental data. The sensitivities of the two methods to the surface structure and the role of the resolution functions in the CTR measurements are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357366
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  • 7
    Electronic Resource
    Electronic Resource
    Strain and structural characterization of Zn1−xCdxSe laser structures grown on GaAs and InGaAs (001) substrates (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 81-88 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray reciprocal space mapping has been used to investigate the strain status of microgun-pumped blue and blue-green laser structures. The devices exploit graded-index, separate confinement Zn1−xCdxSe/ZnSe heterostructures grown on InGaAs or GaAs substrates by molecular-beam epitaxy. The location of the reciprocal lattice point of the ZnSe buffer layer within a normally forbidden region of reciprocal space indicates that the ZnSe buffer layer is unusually strained, with an appreciable biaxial tensile strain despite the smaller lattice parameter of the III–V substrate relative to ZnSe. We associate such a phenomenon with the presence of the highly strained laser structure coupled with preferential strain relaxation at the II–VI/III–V heterointerface. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362775
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  • 8
    Electronic Resource
    Electronic Resource
    Interference effects in x-ray double-crystal rocking curves of GexSi1−x/Si superlattices (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1320-1322 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interference effects in the x-ray double-crystal rocking curves of GexSi1−x/Si strained-layer superlattices have been simulated based on the x-ray dynamical scattering theory. We found that the A1BA2 type of structure due to unstable growth conditions causes a series of strong oscillation fringes beside the superlattice reflection satellite peaks. The positions and intensities of these oscillation fringes with respect to the superlattice satellite peaks are strongly correlated to the number of periods in the subsuperlattice layer B and the relative mean lattice mismatch between A and B with respect to the substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357794
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  • 9
    Electronic Resource
    Electronic Resource
    X-ray analysis of strain relaxation in strained-layer superlattices (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 810-814 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Theoretical simulations of x-ray double-crystal-diffraction rocking curves for strain-relaxed superlattices have been successfully carried out based on x-ray dynamical diffraction theory. The strain relaxation, the misorientation between the superlattice layers and the substrate, and the effect of peak broadening due to the formation of misfit dislocations have been taken into account. The influence of possible strain relaxation mechanisms and relaxation ratios on the rocking curves have been investigated. It was found that both the mechanism and degree of the strain relaxation of the superlattice can be determined by fitting the angular positions and the relative intensities of the experimental superlattice satellites. By using this method, an InxGa1−xAs/GaAs superlattice sample and a GexSi1−x/Si superlattice sample were analyzed. The different strain-relaxation mechanisms were found in these two samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357754
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  • 10
    Electronic Resource
    Electronic Resource
    Diffuse x-ray scattering from misfit dislocations in SiGe epitaxial layers with graded Ge content (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5013-5021 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theory has been developed describing x-ray diffuse scattering from misfit dislocations in epitaxial layers. This approach has been used for explaining the origins of diffuse x-ray scattering from SiGe layers with linearly graded Ge content. The distribution of the diffusely scattered intensity in reciprocal plane measured by triple-axis x-ray diffractometry has been compared with theoretical predictions and a good agreement has been achieved. It is demonstrated that the main part of the diffusely scattered intensity originates from random strains caused by misfit dislocations at the substrate–epilayer interface or in the relaxed part of the compositionally graded layers. The contribution of the threading dislocation segments to the diffuse scattering is rather small. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359728
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