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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3354-3360 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystal morphologies and phase composition of diamond crystallites during bias enhanced nucleation and initial growth stages in microwave plasma chemical vapor deposition were investigated. Diamond nuclei were first formed in the central regions of substrates and then propagated to the sample edges. During the course of bias nucleation, excessive ion bombardment induced secondary nucleation sites on the already formed nuclei. The secondary nucleation deteriorated the overall alignment of the growing crystals. Hence, the elimination of secondary nucleation and homogeneous nucleation over substrates are fundamental requirements for the deposition of large-area uniformly oriented diamond films. Decreasing reactant pressure was found to be effective for improving plasma homogeneity and consequently nucleation uniformity. The results of bias enhanced nucleation within a pressure range from 8 to 20 Torr showed that the lower pressure of reactants enlarged the area of oriented diamond films. However, the optimum bias and duration of nucleation was found to be specific for each pressure. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3432-3436 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study, high-quality ZnO:Al (ZAO) films were prepared by using dc reaction magnetron sputtering technology. The effect of Al doped in ZnO films on electrical and optical properties and its scattering mechanism were discussed in detail. The results showed that Al2O3 could be effectively removed by controlling oxygen flow and Al-doped concentration during deposition of ZnO:Al films. Zn, Al, and oxygen elements were well distributed through the films. For highly degenerated ZnO:Al semiconductor thin films, it was revealed that ionized impurity scattering dominated the Hall mobility of the films in the low-temperature range; while the lattice vibration became a major scattering mechanism in the high-temperature range. The grain-boundary scattering only played a major role in the ZAO films with small grain size (as compared to the electron mean-free path). The photoelectric properties of ZAO films showed that the lower resistivity (∼5×10−4 Ω cm) was obtained, and transmittance in the visible range and reflectance in the IR region were above 80% and 60%, respectively. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Clinical and experimental dermatology 28 (2003), S. 0 
    ISSN: 1365-2230
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Bullous pemphigoid (BP) is an inflammatory subepidermal blistering disease associated with autoantibodies that recognize hemidesmosomal proteins. In addition to autoantibodies, the cell-mediated immune reaction is considered to play an important part in blister formation. Objectives To investigate some T-cell activation markers and inflammatory cytokines in the blister fluid and sera of patients with BP. Methods We measured soluble CD4 (sCD4) and soluble CD8 (sCD8), which have been, respectively, associated with CD4 and CD8 T-cell activation. Enzyme-linked immunosorbent assays were also used to quantify the production of the leucocyte chemoattractant interleukin (IL) -8 and of the cytokines IL-1α, IL-1β, IL-6, IL-10 and tumour necrosis factor-α in the blister fluid and sera of 11 patients with BP. Results The mean ± SD level of sCD4 in patients’ blisters (42·4 ± 25·0 units mL−1) was significantly elevated (P 〈 0·005) compared with that in their sera (11·2 ± 8·9) and that in the suction blisters of 10 healthy people (11·4 ± 5·4; P 〈 0·005). Mean ± SD IL-8 concentrations in BP blisters (4683·6 ± 3878·1 pg mL−1) were much higher than those in their sera (17·1 ± 18·9; P 〈 0·001), and were very significantly elevated (P 〈 0·005) in comparison with those in suction blisters of healthy persons (512 ± 292). sCD4 levels in BP blisters were inversely related to IL-10 levels (P = 0·03, r2 = 0·85), IL-8 levels were positively related to sCD8 levels (P = 0·01, r2 = 0·54), and IL-1β levels were positively related to sCD8 concentrations (P 〈 0·005, r2 = 0·65). Conclusions The correlations suggest that there is a delicately orchestrated network of cytokines and cell-mediated immunity operating in BP blisters.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7001-7004 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamic processes of the free excitonic transitions in GaN grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. The recombination lifetimes of the A and B excitons have been measured at different temperatures and excitation intensities, from which radiative recombination lifetimes of about 0.35 and 0.3 ns for the A and B excitons, respectively, have been obtained. An increase in excitation power has resulted in a drastic enhancement in the radiative decay rate as well as in the exciton photoluminescence quantum yield, suggesting the excitonic transitions may provide gain for laser actions in GaN. The high quality as well as high purity of the investigated MOCVD sample has been demonstrated by the observations of (1) the free A- and B-excitonic transitions, (2) excited states of the free excitons, (3) narrow free excitonic emission linewidths (1.7 meV at 10 K), (4) low electron concentration, and (5) high electron mobilities (∼600 cm2/V s). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 236-241 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single crystals of GaN were grown on (0001), (011¯2) Al2O3 and (0001)Si 6H-SiC substrates using an atmospheric pressure metalorganic chemical-vapor-deposition reactor. The relationship has been studied between the thermal stability of the GaN films and the substrate's surface polarity. It appeared that the N-terminated (0001) GaN surface grown on (0001)Si 6H-SiC has the most stable surface, followed by the nonpolar (112¯0) GaN surface grown on (011¯2) Al2O3, while the Ga-terminated (0001) GaN surface grown on (0001) Al2O3 has the least stable surface. This is explained with the difference in the atomic configuration of each of these surfaces which induces a difference in their thermal decomposition.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7648-7650 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We calculate the optical gain and threshold current density of strained-layer InGaAs/AlGaAs quantum-well lasers with the band-gap renormalization effects taken into account. It is found that the band-gap renormalization shifts the lasing wavelength as much as 30 nm which is much larger than the allowed bandwidths, ±6 nm, of 980 nm Er-doped optical fiber amplifiers. We also try to optimize the graded-index separate-confinement-heterostructure optical waveguide layer in order to maximize the optical confinement factor and to reduce its fabrication dependence. The threshold current densities are calculated for the optimized structures for which the gain peak positions are predicted to be within the allowed bandwidths of 980 nm. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4515-4519 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we present a crystallographic model to describe the epitaxial growth of wurtzite-type thin films such as gallium nitride (GaN) on different orientations of sapphire (Al2O3) substrates. Through this model, we demonstrate the thin films grown on (00⋅1)Al2O3 have a better epilayer-substrate interface quality than those grown on (01⋅2)Al2O3. We also show the epilayer grown on (00⋅1)Al2O3 are gallium-terminated, and both (00⋅1) and (01⋅2) surfaces of sapphire crystals are oxygen-terminated.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3964-3967 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-quality thin aluminum nitride films were grown on different orientations of sapphire substrates by metalorganic chemical vapor deposition. (00⋅1) AlN thin film grown on (00⋅1) Al2O3 has better crystallinity than (11⋅0) AlN on (01⋅2) sapphire. Full width at half maximum of a rocking curve is 97.2 arcsec, which is the narrowest value to our knowledge. A crystallographic model between AlN thin films and sapphire substrates was proposed to explain the process of crystal growth. "Extended atomic distance mismatch'' which is the mismatch of atomic distance for a longer period was introduced. It is shown that the mismatch is relaxed by edge-type dislocations. Extended atomic distance mismatch was used to interpret the results that (00⋅1) AlN has better crystallinity than (11⋅0) AlN, but (11⋅0) GaN has better crystallinity than (00⋅1) GaN.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5534-5536 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of naturally layered intermetallic compound SmMn2Si2 with textured structure have been studied. There exist a ferromagnetic transition at 35 K and two antiferromagnetic transitions at 120 and 230 K. The antiferromagnetic state below 230 K exhibits different magnetoresistance, with a negative magnetoresistance of 3%–4% for current I applied perpendicular to the c axis and with a positive magnetoresistance effect of about 4%–6% for current I parallel to the c axis. The observed magnetoresistance is likely to be related to magnetovolume effects. In the ferromagnetic state, a positive magnetoresistance with a maximum increase of 22% under an applied field of 5 T is observed at 4 K, and both H ⊥ I and H (parallel) I configurations show positive magnetoresistance. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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