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  • 1985-1989  (25)
  • 1975-1979  (2)
  • 1935-1939  (1)
  • 1
    Electronic Resource
    Electronic Resource
    A phenomenological description of strain relaxation in GexSi1−x/Si(100) heterostructures (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5837-5843 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe how in situ observation of strain relaxation of Gex Si1−x /Si(100) heterostructures in a transmission electron microscope enable us to obtain the fundamental parameters which describe the nucleation, propagation, and interaction of misfit dislocations. Activation energies and prefactors are obtained for the nucleation and propagation processes for x in the range 0.20–0.35, and a simple model to account for dislocation interactions is developed. These measured parameters are then incorporated into a predictive model of strain relaxation which successfully reproduces experimental data. This model relies only upon parameters which can be directly measured.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343604
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Detailed atomic scale structure of AlInAs/GaInAs quantum wells (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2688-2692 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantification of high-resolution transmission electron microscopy (HRTEM) lattice images and detailed luminescence line-shape analysis is used to determine the atomic structure of GaInAs quantum wells (QWs) between AlInAs barriers. By careful analysis of a statistically large number of HRTEM images, we are able to measure the standard deviation in the mean quantum-well width to better than one (200) monolayer. Statistical analysis of the temperature dependence of the luminescence yields QW width distribution functions and variations of the mean QW width across the sample with a precision of better than 0.2 nm in quantitative agreement with the transmission electron microscopy results. No large and smooth islands with monolayer steps in between but rather long-range mean band-gap fluctuations are observed. Spectral broadening is found to be induced by well-width-dependent roughness of inequivalent growth surfaces and by clustering in the barriers for extremely narrow wells of the order Lz≈1 nm. Our results indicate a pronounced surface roughening of InGaAs at 640 °C. The mean height of steps of a maximum width of 5 nm at the InGaAs surface increases from 1 to 2 monolayers for an increase of well width from ≈1 to 2.5 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342753
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  • 3
    Electronic Resource
    Electronic Resource
    Growth of GeSi/Si strained-layer superlattices using limited reaction processing (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2407-2409 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: SiGe/Si superlattices were grown using limited reaction processing. Each multilayer structure was fabricated in situ by changing the gas composition between high-temperature cycles. Commensurate SiGe alloy layers as thin as 15 nm were reproducibly deposited and were examined using transmission electron microscopy, sputtering Auger electron spectroscopy, and Rutherford backscattering. Si/SiGe interfaces are abrupt to within a few monolayers, establishing for the first time the use of a chemical vapor deposition technique to fabricate abrupt GeSi/Si-based heterostructures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337960
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of pulsed laser and furnace annealing of nitrogen-implanted silicon (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 193-196 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied pulsed ruby laser and furnace annealing of high-dose (D〉1017 N/cm2) 50-keV nitrogen-implanted silicon. Using Rutherford backscattering and channeling, transmission electron microscopy, and infrared transmission spectroscopy, we have compared liquid and solid phase regrowth, diffusion, impurity segregation, and nitride formation. As has been previously reported, during furnace annealing at or above 1200 °C nitrogen redistributes and forms a polycrystalline silicon nitride (Si3N4) layer. In contrast, pulsed laser melting produces a buried amorphous layer containing silicon and nitrogen with only very small amounts of polycrystalline silicon nitride below a layer of polycrystalline silicon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335707
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Misfit dislocations in pseudomorphic In0.23Ga0.77As/GaAs quantum wells: Influence on lifetime and diffusion of excess excitons (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2214-2216 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The recombination dynamics of excess charge carriers around misfit dislocations in strained layer GaAs/In0.23Ga0.77As/GaAs quantum wells are directly imaged with spectrally and time-resolved infrared cathodoluminescence imaging with subnanosecond time resolution. This unique experimental approach for the first time allows the imaging of excitonic lifetime around dislocations in such quantum wells. A strong reduction is observed. The quenching by more than two orders of magnitude of the quantum efficiency upon an increase of the line dislocation density from 4×103 to 5×106 m−1 is explained quantitatively by a diffusion model. The critical layer thickness is determined to agree well with the "mechanical equilibrium of forces'' model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344288
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  • 6
    Electronic Resource
    Electronic Resource
    Role of strained layer superlattices in misfit dislocation reduction in growth of epitaxial Ge0.5Si0.5 alloys on Si(100) substrates (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4723-4729 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the role of strained layer superlattices in threading dislocation reduction in the growth of Ge0.5Si0.5 alloys on Si(100) substrates by molecular-beam epitaxy. Several superlattice structures are studied with zero, negative, and positive net strains with respect to a Ge0.5Si0.5 buffer layer. Control samples consisting of uniform strained layers are also grown for each superlattice structure. Transmission electron microscopy analysis of defect densities is found to be hampered by defect losses from thin foils, particularly in the plan view geometry. It is found that although strained interfaces are effective at deflecting threading dislocations into the interfacial plane, little surface threading dislocation density reduction is observed as a function of the presence of the superlattices for dislocation densities of the order 108 cm−2. This observation may be understood in terms of threading dislocation propagation at strained interfacial planes, and a simple predictive model is developed for defect interaction probabilities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343223
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  • 7
    Electronic Resource
    Electronic Resource
    Higher excited electronic states in clusters of ZnSe, CdSe, and ZnS: Spin-orbit, vibronic, and relaxation phenomena (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 2237-2242 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Metal selenide clusters have been made and characterized, using the arrested precipitation colloidal technique. A comparison of sulfide and selenide spectra enables observation of the effect of changes in the highest occupied molecular orbitals upon cluster electronic properties. The first and second excited electronic states are both observed as a function of size in ZnSe clusters. The systematic dependence of the spectra lead to assignment of the higher state to a 1S-type hole based upon the split-off valence band. It is shown that the energy spectrum of discrete hole states is controlled by the spin-orbit energy and the isotropic hole mass in small, highly symmetrical clusters. This result contrasts with the heavy hole and light hole states observed for planar confinement. In (approximately-equal-to) 20 A(ring) diameter ZnS clusters, there is a strong vibronic temperature dependence in the excited state spectra, while in clusters of smaller gap materials such vibronic effects are very minor. We conjecture that lifetime broadening is severe in clusters of small gap materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451119
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Hybrid electronic properties between the molecular and solid state limits: Lead sulfide and silver halide crystallites (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 1406-1410 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Tiny single PbS crystals of ∼25 A(ring) diameter are synthesized and studied optically in low-temperature colloidal solutions. Electron microscopic examination shows a simple cubic rock salt structure with a lattice constant unchanged, within experimental error, from the bulk value. These crystallites lack the near infrared electronic absorption characteristic of bulk PbS. The small crystallite absorbance in the visible rises more steeply than does the bulk absorbance. These results reflect electron and hole localization if one considers the variation in effective mass across the band structure. A simple discussion of localization anywhere in the Brillouin zone is given. For the first time, crystallite syntheses are carried out in solvent mixtures that form transparent glasses upon cooling. The PbS spectra are independent of temperature (at current experimental resolution) down to 130 K, in contrast to earlier results for quantum size exciton peaks in ∼20 A(ring) ZnS crystallites. Previously published observations of size dependence in the excited state electronic properties of AgI and AgBr are explained as consequences of electron and hole localization in the small crystallites. AgBr appears to be the first indirect gap semiconductor to be examined in the regime where bulk properties are not fully formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449407
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  • 9
    Electronic Resource
    Electronic Resource
    Excited electronic states and optical spectra of ZnS and CdS crystallites in the ≈15 to 50 A(ring) size range: Evolution from molecular to bulk semiconducting properties (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 552-559 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Very small ZnS and CdS crystallites are made and stabilized in aqueous and methanolic media without organic surfactants. Low temperature (−77 °C) synthesis in methanol produces the smallest crystallites, (approximate)30 A(ring) diameter cubic CdS and 〈20 A(ring) diameter cubic ZnS. The crystallites are characterized by transmission electron microscopy and in situ optical spectroscopy (λ(approximately-greater-than)200 nm). The crystallites are too small to exhibit bulk band gaps in their optical spectra. In the band gap region, the small crystallites show a higher energy absorption threshold with a resolved spectral feature (quantum size exciton peak), not present in the spectra of larger crystals. The far ultraviolet spectra are unaffected by size at present resolution. These results can be understood in terms of the crystallite molecular orbitals, and an elementary confined electron and hole model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448727
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal stability of Si/GexSi1−x/Si heterostructures (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1900-1902 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal stability of Si/GexSi1−x/Si (100) heterostructures is studied by in situ electron microscope observations of the thermal relaxation process. Structures are observed to relax by misfit dislocation propagation at both strained interfaces, and are stable to significantly higher temperatures than equivalent strained GexSi1−x layers at a free surface. This observed difference in thermal stability between double and single interface structures is due at least in part to much lower dislocation velocities in the double interface structures, with a measured glide activation energy approximately twice as high as single interface structures. It is argued that this difference in glide activation energies may be due to a smaller kink nucleation activation energy in the single interface structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102165
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