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  • 1
    Electronic Resource
    Electronic Resource
    Photocurrent spectroscopy of InxGa1−xAs/GaAs multiple quantum wells (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2230-2232 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photocurrent spectra of InxGa1−xAs/GaAs multiple quantum well structures grown by molecular beam epitaxy are studied in the presence of electric fields perpendicular to the heterointerface. Several Δn=0 allowed and Δn≠0 forbidden excitonic transitions are observed. Both negative and positive shifts of exciton transitions are found. Good agreement is found between the photocurrent observations and calculations using a multiband effective-mass approach, taking into account the strain-induced splitting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101132
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  • 2
    Electronic Resource
    Electronic Resource
    Parametric study of AlAs/GaAs superlattice double-barrier diodes (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 207-209 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum well diodes with barriers formed by thin, short-period binary AlAs/GaAs superlattices were fabricated and found to have very high peak-to-valley current ratios. The effects of varying the AlAs and GaAs layers in the barriers are studied. The peak current density is found to decrease by orders of magnitude for monolayer increases in the AlAs layer thicknesses. Tunneling current peaks due to both resonance levels in the quantum well and resonance levels in the superlattice barriers are observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100132
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of AlAs/GaAs superlattice barriers using electrical barrier height analysis (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4765-4767 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical barrier height measurements on n+-GaAs–insulator–n-GaAs structures with short-period AlAs/GaAs superlattices forming the insulator show the effective conduction-band discontinuity (ΔEC) of a superlattice barrier (SLB) to be defined by the lowest superlattice energy state. Five structures with different AlAs and GaAs SLB layer thicknesses are investigated. A SLB with GaAs layers greater than 10 monolayers is found to have a ΔEC defined by Γ-valley states in the GaAs layers, while a SLB with GaAs and AlAs layers less than 10 monolayers and with thicker AlAs layers than GaAs layers is found to have a ΔEC defined by X-valley states in the AlAs layers. The SLB with GaAs and AlAs layers less than 10 monolayers and thicker GaAs layers than AlAs layers behaves as a random alloy. Negative differential resistance is observed in the current-voltage characteristic of the sample whose barrier height is defined by Γ-valley states in the GaAs layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341194
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  • 4
    Electronic Resource
    Electronic Resource
    AlGaAs/GaAs double barrier diodes with high peak-to-valley current ratio (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 121-123 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the largest peak-to-valley current (PVC) ratios to date from AlGaAs/GaAs double barrier (either alloy barrier or superlattice barrier) diodes. PVC ratios as high as 3.6 and 21.7 were obtained from an AlAs/GaAs superlattice barrier structure at 300 and 77 K, respectively. In an alloy barrier structure with x=0.42 (x=0.3), PVC ratios of 3.9 (2.2) and 14.3 (7.0) were observed at 300 and 77 K, respectively. We attribute these excellent results to a "two-step'' spacer layer incorporated in the devices studied which facilitated the growth of high material quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98588
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  • 5
    Electronic Resource
    Electronic Resource
    THE EFFECT OF STRAIN RATE ON THE TENSILE AND FRACTURE PROPERTIES OF BS 4360 ‘A’ GRADE SHIP STEEL (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 14 (1991), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The results of high rate tensile and compact tension fracture toughness tests conducted on BS 4360 ‘A’ grade ship steel are presented. Tensile results are reported for strain rates within the range 10–2–103/s and fracture toughness values at rates of increase of J integral within the range 103–106 N/mm/s. The tensile properties of upper yield, lower yield and UTS are shown to be linearly dependent on the logarithm of strain rate whilst fracture toughness is shown to decrease with increasing loading rate prior to approaching a minimum value. The decrease in fracture toughness with increasing test rate is shown to be related to a change in the micro-mechanism of fracture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1991.tb00648.x
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  • 6
    Electronic Resource
    Electronic Resource
    A STUDY OF SPECIMEN SIZE ON J-R CURVE BEHAVIOUR (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 14 (1991), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper presents results from an experimental programme to study size effects in J-R curves. Results are presented from unloading compliance R curve tests on different sized single edge notch bend specimens of nickel aluminium bronze and compared with previously published R curve data on a Ti3A1-2.5V titanium and an HY 100 steel alloy. The crack growth resistance was measured in terms of the standard fracture resistance J, J corrected for crack growth and the J modified parameter proposed by Ernst. It was observed that following a region of size independence small specimen J-R curves could fall either above or below the large specimen curve. It was found that although the limit to J controlled crack growth could be extended the limit is not unique but dependent on material type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1991.tb00706.x
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  • 7
    Electronic Resource
    Electronic Resource
    THE EFFECT OF SPECIMEN SIZE ON THE J R-CURVE BEHAVIOUR OF A TITANIUM ALLOY (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 12 (1989), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— —This paper presents preliminary results from a large experimental programme to study geometry and size effects in J R-curves, The results presented were obtained from unloading compliance R-curve tests performed at room temperature on different sized single-edge-notch-bend specimens made from Ti-3Al–2V alloy. The crack growth resistance was measured in terms of the standard fracture resistance J (i.e. not corrected for crack growth), J corrected for crack growth, and the J modified parameter proposed by Ernst. It was found that the best agreement was exhibited by the R-curves based on the standard fracture resistance J, which displayed reasonable size independence up to, and in many cases beyond crack growths corresponding to 50% of the initial uncracked ligament.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1989.tb00538.x
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  • 8
    Electronic Resource
    Electronic Resource
    THE EFFECT OF SPECIMEN SIZE ON THE CTOD R-CURVE BEHAVIOUR OF A TITANIUM ALLOY (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 12 (1989), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— —This paper presents preliminary results from a large experimental programme to study geometry and size effects in CTOD R-curves. The results presented were obtained from unloading compliance R-curve tests performed at room temperature on different sized single-edge-notch bend specimens made from Ti–3Al–2V alloy. The crack growth resistance was measured in terms of both the conventional CTOD, δ0, (i.e. as defined in BS 5762) and CTOD corrected for crack growth, δR. It was found that the δ0 and δR R-curves were independent of specimen size up to crack extensions corresponding to approximately 10–15% of the original uncracked ligament. Also, after crack extensions of 30–40% of the initial ligament the δ0 and δR R-curves exhibited well defined upswings. The upswing in the CTOD R-curves is thought to be a result of a reduction in crack tip constraint.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1989.tb00539.x
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  • 9
    Electronic Resource
    Electronic Resource
    RATE-DEPENDENT DEFORMATION AND FRACTURE OF α-TITANIUM (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 14 (1991), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Aspects of combined rate-dependent deformation and crack growth in α-titanium at room temperature are examined. Results are presented for tests carried out on pre-cracked three point loaded single edge notch bend and compact tension specimens subjected to constant crack opening displacement rates and constant load. Curves of the ratio of the reference stress to the yield stress as a function of the ratio of the plastic displacement to specimen width are found to be different for different rates. The stress difference between continuously loaded curves and curves obtained from load relaxation tests (“relaxed” curves) is found to be similar to uniaxial results. Earlier uniaxial tests show that the “relaxed” curve represents a boundary below which no further creep takes place. The pre-cracked specimen constant load curves cross the “relaxed” curve, even though the contribution from crack growth to the overall deformation is found to be small. Sustained load crack growth is observed to take place under contained yielding conditions and the sustained load resistance curves are found to be different for different reference stresses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1991.tb00007.x
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  • 10
    Electronic Resource
    Electronic Resource
    EXPERIMENTAL CHARACTERISATION OF DYNAMIC TENSILE AND FRACTURE TOUGHNESS PROPERTIES (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 12 (1989), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— —An experimental procedure for obtaining material tensile and fracture toughness properties at rates applicable to shock loading is reported. A variant of the key curve approach to determine dynamic J-R curves is described and results are presented for a nickel aluminium bronze alloy for actuator loading rates in the range 0.75–7500 mm/s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1989.tb00550.x
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