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  • 1
    Electronic Resource
    Electronic Resource
    The fractal structure and the dynamics of aggregation of synthetic melanin in low pH aqueous solutions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 25-29 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have used static and dynamic light scattering to study the dynamics of aggregation of synthetic melanin, an amorphous biopolymeric substance, in low pH aqueous solution. We have found that, depending on the final pH value of the solutions, there existed two regimes of the aggregation kinetics, one corresponding to diffusion limited aggregation (DLA), and the other corresponding to reaction limited aggregation (RLA). The precipitates formed in these two regimes can be characterized by fractal structures. We have found fractal dimensions of df =1.8 for the DLA clusters and df =2.2 for the RLA clusters. These results agree well with the proposed limits of the fractal dimensions of the gold aggregates formed in aqueous solutions by Weitz et al.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456528
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  • 2
    Electronic Resource
    Electronic Resource
    X-ray study of planar defects in highly oriented pyrolytic graphite (HOPG) (1987)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 418-425 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A detailed X-ray study of HOPG reveals extensive wings on the 00.l Bragg reflections whose width in a scan normal to 00.l is comparable to the mosaic spread. These wings, which are absent in single-crystal profiles, are attributed to rotational or twist (T) defects between perfect substacks of pyrolyzed graphite. Along 11.l, the twists destroy coherence and produce an effective 'particle-size' broadening. The average substack size, or spacing between T defects, is estimated through profile fitting to be about 110 Å. The lateral extent of T defects is comparable to a mosaic-block size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767387099227
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  • 3
    Electronic Resource
    Electronic Resource
    Stacking disorder in a stage-4 FeCl3–graphite intercalation compound (1988)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 897-904 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: X-ray scattering measurements have been made in situ on highly oriented pyrolytic graphite intercalated with FeCl3 to stage 4 in a sealed glass tube at 620 K. It has been found that the FeCl3 is in a two-dimensional liquid state at this temperature and that the stacking of the sets of ordered graphite layers (ABAB) that bound the intercalant is nearly random. Through a novel modeling of L scans for 10.L, 11.L, 20.L, 21.L, 30.L and 22.L, a good fit has been achieved by using 60% of a preferred (A-A) stacking of sets with a broad lateral distribution about the ordered position. The remaining 40% of the sets are stacked with complete translational randomness, without regard to the normal graphite crystallography. This sliding randomness remains compatible with Daumas-Herold domain formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767388005677
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray diffraction study of basal-(ab)-plane structure and diffuse scattering from silver atoms in disordered stage-2 Ag0.18TiS2 (1983)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 39 (1983), S. 298-305 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: X-ray results are presented on the crystallographic parameters in the basal (ab) plane and the short-range-order diffuse scattering from intercalated silver atoms in disordered stage-2 Ag0.18TiS2 at room temperature. The silver atoms in the intercalated plane occupy the octahedral sites and the in-plane temperature parameter of the silver atoms has a value of B = 3.0 ± 0.1 Å2, suggesting both weak bonding and correspondingly rapid diffusion. Rodlike diffuse scattering parallel to c* at .0, .0 and their equivalent positions is observed and reveals the two-dimensional (2D) feature of the disordered state. From analyzing this 2D diffuse intensity by the method of Borie & Sparks [Acta Cryst. (1971), A27, 198-201], the planar short-range-order parameters were determined. A comparison of this planar short-range order with the 2D Ornstein-Zernike correlation function demonstrates the long-range nature of the 2D short-range order with a correlation range κ-1 of 4.88 ± 0.4 Å. Using a linearized mean-field approximation for the correlation functions of a binary Ising system well above Tc developed by Clapp & Moss [Phys. Rev. (1966), 142, 418-427], a set of oscillatory atomic-pair interaction potential ratios was obtained where the direct interactions were significant out to at least four to five neighbors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767383000707
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Some Aspects of Structural Disorder in Solids (1973)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Materials Research 3 (1973), S. 293-315 
    Details
    ISSN: 0084-6600
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.ms.03.080173.001453
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  • 7
    Electronic Resource
    Electronic Resource
    Interface properties of (In,Ga)Sb/InAs heterostructures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8379-8383 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interfaces between (In,Ga)Sb and InAs(100) grown by molecular-beam epitaxy have been investigated by x-ray diffraction, x-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy. The InAs on (In,Ga)Sb interface has been found to be significantly broader than the reverse one and the asymmetry is the result of mixing between arsenic and antimony. The studies of the growth surfaces have shown a persistent presence of antimony on an InAs surface suggesting a lower, antimony-rich, surface free energy. This energy imbalance indicates a driving mechanism behind the mixing of the group-V elements as the growth of InAs on (Ga, In)Sb is commenced. The band offset of the InAs on (Ga,In)Sb has been determined by XPS. The In 4d and Ga 3d to valence-band maximum binding energy differences for bulk InAs and GaSb were obtained by fitting the experimental valence-band density of states (VBDOS) to the experimentally broadened, theoretical VBDOS. The core-level separation between In 4d and Ga 3d peaks from the InAs/GaSb structure was determined by fitting Gaussian–Lorentzian functions to the peaks. The band offset was determined to be 0.62±0.1 eV. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362557
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  • 8
    Electronic Resource
    Electronic Resource
    Epitaxial growth of Sb/GaSb structures: An example of V/III-V heteroepitaxy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 21-27 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The requirements for heteroepitaxial growth of Sb on both GaSb and GaAs, and the subsequent growth of GaSb on Sb, using molecular-beam epitaxy are described. These systems serve as examples of the heteroepitaxy of group-V elements with III-V compounds, i.e., between materials utilizing different bonding and possessing different electronic properties. The quality of the films was determined using high-resolution four-circle x-ray diffraction, and comparisons were made between different structures. GaSb was found to grow (111) oriented on Sb (111) with an inverted stacking sequence. A simple epitaxial model is proposed to explain this. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359373
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  • 9
    Electronic Resource
    Electronic Resource
    Metastable surface ordering in strain relaxed Si0.5Ge0.5 epitaxial layers grown at high temperature (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 531-533 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied compositional ordering in the near surface region of 3500 Å thick unstrained Si0.5Ge0.5(001) samples grown by chemical vapor deposition. Measuring asymptotic Bragg scattering along integer and half-integer truncation rods, we found a type of metastable ordering at this surface which is characterized by integer/half-integer reflections along the integer order truncation rods. We show unambiguously that those scattering features originate from a thin layer at the surface. Annealing at 750 °C extinguished these reflections irreversibly, while the reflections of the RS3 bulk structure were not affected. Anomalous scattering at the Ge K edge also confirmed the existence of a new structure in the near surface region. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123177
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  • 10
    Electronic Resource
    Electronic Resource
    X-ray analysis of spontaneous lateral modulation in (InAs)n/(AlAs)m short-period superlattices (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 219-221 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The lateral composition modulation in (InAs)n/(AlAs)m short-period superlattices was studied by means of synchrotron x-ray diffraction. By choosing specific diffraction vectors having a large component closely parallel to the modulation direction, we are able to observe a number of lateral satellite peaks around the zero-order short-period superlattice peak. A model, incorporating both composition and strain, is used to simulate the intensities of these satellites. Our results provide a quantitative fit and permit the evaluation of the composition amplitude. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1338499
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