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  • 1
    Electronic Resource
    Electronic Resource
    Characterization and modelling of the strain fields associated with InGaAs layers on V-grooved InP substrates (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 6016-6023 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of lattice-matched or compressively strained InGaAs layers were grown by gas source molecular beam epitaxy on V grooved InP substrates, with grooves bounded by {211}A or {111}B facets. The stress field associated with the layers was measured by the degree of polarization technique, and compared to the predictions of analytical or finite element models. Good agreement was found for the {211}A V grooves, but both the nominally lattice-matched and compressively strained layers grown on {111}B V grooves displayed similar degree of polarization maps. Analytical electron microscopy demonstrated that the {211}A V-groove samples had the targeted composition, but the {111}B samples showed much higher In/Ga ratios at the bottom of the groove than the expected values. Indium enrichment at the bottom of the groove led to defect formation there, and left the V groove of both the lattice-matched and compressively strained samples under a net compressive force. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366468
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  • 2
    Electronic Resource
    Electronic Resource
    Growth of strained InGaAs layers on InP substrates (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2185-2196 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of InGaAs films, compressively or tensilely strained, were grown on (001)InP substrates at 490 °C by gas source molecular beam epitaxy. Compressively strained (−0.5%) (and lattice matched) layers were morphologically stable, but layers grown under tension (+0.5 to +0.6% strain) developed facets on (113)A or (114)A planes. In the first stages of growth of films under tension, and throughout all stages of growth for the compressively strained films, a fine scale (10 nm wavelength) composition modulation was found in the [110] direction. In the later stages of growth of films under tension, the regions of composition segregation were confined to the peaks and valleys of the faceted surface. Regions of high and low stress concentration (the valleys and the peaks) exhibit In/Ga ratios higher or lower, respectively, than the flat faceted surfaces. The elastic strain energy built into the film, associated with the [110] composition modulation, depends on the ratio of the modulation wavelength to film thickness. In films grown under tension, facet coarsening provides a means for the system to reduce the strain energy associated with segregation. Faceting (and facet coarsening) leads to a reduction in the misfit strain energy stored in the film. However, an analysis of the first stages of faceting shows that faceting cannot be explained as a roughening transition. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364271
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  • 3
    Electronic Resource
    Electronic Resource
    Initial stages of misfit dislocation formation in compressively strained Si-Ge short period superlattices (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4625-4629 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The initial stages of strain relaxation in two (SimGen)p short period superlattices grown on Si have been studied by transmission electron microscopy. Relaxation occurs by the formation of 60° dislocations which terminate at heterogeneous sources close to the surface of the sample. The rate of strain relaxation in the short period superlattices has been compared to the rate in homogeneous Si1−xGex layers grown in the same chamber and having equivalent effective stresses to drive the dislocations. The rate of dislocation nucleation was observed to be much higher in the short period superlattices. This was attributed to the tendency for Ge island formation during the growth of the superlattices, leading to localized strain centers which act as easy dislocation sources on annealing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357298
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  • 4
    Electronic Resource
    Electronic Resource
    Misfit strain relaxation in GexSi1−x/Si heterostructures: The structural stability of buried strained layers and strained-layer superlattices (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 1850-1862 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The critical thickness-strain relationships for buried strained layers and strained-layer superlattices (SLSs) are derived using an energy balance model. Relaxation of the entire heterostructure and individual strained layers by both 60° type a/2〈011〉 and pure edge dislocations is considered. GexSi1−x/Si heterostructures designed to investigate the stability regimes predicted by the model were grown by molecular-beam epitaxy. The extent of relaxation and the detailed dislocation structure were assessed in annealed structures by x-ray rocking curve analysis, transmission electron microscopy, and Nomarski microscopy of etched samples. Comparison of metastable as-grown and post-growth annealed microstructures revealed the evolution of misfit dislocation structure as equilibrium was approached on annealing in the temperature range 600–900 °C. The predominant relaxation mechanism for most GexSi1−x/Si heterostructures was by 60° a/2 〈011〉 misfit dislocations at the first strained-layer/substrate interface. However, for SLSs with strained layers exceeding their individual critical thickness, pairs of dislocations and prismatic loops on (011) planes were observed entrained within the GexSi1−x layers. The agreement between experimentally observed relaxation behavior and the critical thickness versus strain predictions of the energy balance model is remarkable. Superlattices and buried strained layers were found to be only slightly more stable than an uncapped strained layer of the equivalent strained-layer thickness. Interdiffusion was observed at annealing temperatures above 800 °C; annealing at 900 °C for 30 min was sufficient to eliminate the strain and composition modulation in a superlattice with a 55-nm period and x=0.25. The relative influence of the various strain relaxation mechanisms is discussed for the alloy range 0〈x〈1 and for geometries with strained-layer dimensions varying from 0.8 to ∼500 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345613
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  • 5
    Electronic Resource
    Electronic Resource
    Enhanced band-gap blueshift due to group V intermixing in InGaAsP multiple quantum well laser structures induced by low temperature grown InP (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3199-3201 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence and cross-sectional transmission electron microscopy, combined with x-ray compositional analysis, have been used to study quantum well intermixing in an InGaAsP quantum well laser structure. Quantum well intermixing is induced by capping the samples with a layer of InP grown at low temperature (300 °C) and subjecting them to rapid thermal anneal treatments in the temperature range 600–800 °C. The presence of the low temperature InP layer, which contains an abundance of nonequilibrium point defects, significantly enhances the intermixing on annealing, producing a large band-gap blueshift. The microscopy results show good broadening with smeared interfaces, and the compositional analysis suggests this can be attributed to the intermixing of group V atoms. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1374231
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  • 6
    Electronic Resource
    Electronic Resource
    Dislocation relaxation in InAsyP1−y films deposited onto (001) InP by gas-source molecular beam epitaxy (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3194-3196 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The strain relaxation of InAsyP1−y layers grown on (001) InP substrates by gas-source molecular beam epitaxy was examined using transmission electron microscopy (TEM) and cathodoluminescence (CL) imaging. InAsyP1−y films with a thickness of 190 A(ring) were prepared, systematically varying the As content from y=0.30 and 0.77, corresponding to a lattice mismatch between 0.97% and 2.5%. Relaxation was anisotropic, with 60° misfit dislocations lying predominantly along [11¯0], with a much lower density of dislocations along [110]. For y(approximately-greater-than)0.48, CL and plan-view TEM observations show slip traces which make angles of about ±40° with the [11¯0] direction. These slip traces correspond to pure-screw dislocation segments (gliding on {111}) cross slipping to glide on planes approximately parallel to {011}.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110196
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  • 7
    Electronic Resource
    Electronic Resource
    Helium bubbles in silicon: Structure and optical properties (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1319-1321 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon samples were implanted with 20 keV He at various temperatures. The damage and the size of the He bubbles created during the implantation were measured with Raman spectroscopy and transmission electron microscopy. Room temperature implantation with 2.5×1017 He atoms/ cm2 produced an amorphized layer with a high density of small voids (∼5 nm). After annealing at 923 K the amorphous layer was recrystallized, but still contained extended defects. The He bubbles coalesced forming large bubbles in the implanted region. Implantation at 723 K left the Si essentially crystalline, but with a large number of defects. The He bubbles created at this temperature were larger than after room temperature implantation. Light emitting properties of this porous material are briefly discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113228
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  • 8
    Electronic Resource
    Electronic Resource
    A study of combustion synthesis of Ti-Al intermetallic compounds (1996)
    Springer
    Journal of materials science 31 (1996), S. 3707-3713 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The mechanisms involved in the combustion synthesis of Ti-Al intermetallics have been studied by quenching partially transformed pellets to suppress the reaction prior to its completion. The reaction steps leading to the formation of TiAl3, TiAl or Ti3Al were found to be similar in all three compositions used for the study. In each case the initial product detected by X-ray diffraction was TiAl3, while substantial dissolution of Ti into molten Al was found. At the same time the molten Al-Ti liquid adsorbed oxygen, and on quenching the partially transformed pellet, a glass was formed from the liquid. If the combustion synthesis process was completed, the oxygen-rich liquid decomposed, yielding a mixture of oxides and intermetallic compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00352784
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  • 9
    Electronic Resource
    Electronic Resource
    The effects of nitrogen additions to a cobalt-chromium surgical implant alloy (1987)
    Springer
    Journal of materials science 22 (1987), S. 575-580 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The efficacy of adding nitrogen to a Co-Cr surgical implant alloy in order to improve tensile and fatigue properties has been investigated. Using the heat treatments described in Part 1 of this study, the tensile properties of specimens with nominally 0.14, 0.19, 0.21 and 0.33 wt% carbon were evaluated in air at room temperature. The fatigue testing consisted of a rotating beam fatigue test at room temperature in air, at a frequency of 10 Hz. The results of the mechanical tests indicated that interstitial nitrogen additions to low carbon alloys (nominally 0.14 wt % carbon) increased the yield strength while maintaining good ductility. However, this beneficial effect was not apparent for the material tested in fatigue, possibly because of the overriding influence of inherent flaws within the heat treated testpieces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160771
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  • 10
    Electronic Resource
    Electronic Resource
    The effects of nitrogen additions to a cobalt-chromium surgical implant alloy (1987)
    Springer
    Journal of materials science 22 (1987), S. 565-574 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The determination of the feasibility of adding nitrogen to a cobalt-chromium implant alloy was undertaken with the ultimate goal of the work being the improvement of the static and fatigue properties of the alloy. Nitrogen additions were made using high-temperature heat treatments in a nitrogen-containing gas atmosphere. The effects of the nitrogen additions were characterized in this study using several techniques. The maximum solid solubility of nitrogen in the alloy at 1200° C (the heat-treatment temperature) was found to be approximately 0.35 wt % N. X-ray diffraction using nitrogen heat-treated powder samples indicated that the addition of nitrogen in solution resulted in a lattice dilation lying in the range of 0.0021 to 0.0035 nm per wt % N. Above the solubility limit, Cr2N and Cr2(CN) were present at the nitrogen heat-treatment temperatures in the form of large second-phase particles. Ageing of the alloy containing approximately 0.35 wt % N at 400° C resulted in the precipitation of CrN. A study of the nitrogen distribution suggested that the diffusion of nitrogen ms affected by the carbon content of the cobalt-base alloy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160770
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