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  • 2000-2004  (64)
  • 1990-1994  (15)
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  • 1
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract MOCVD-grown heterostructures with one or several InxGa1−x N layers in a GaN matrix have been studied by transmission electron microscopy. In heterostructures with thick InGaN layers, a noncoherent system of domains with lateral dimensions (∼50 nm) on the order of the layer thickness (∼40 nm) is formed. In the case of ultrathin InGaN inclusions, nanodomains coherent with the GaN matrix are formed. The content of indium in nanodomains, determined by the DALI method, is as high as x≈0.6 or more, substantially exceeding the average In concentration. The density of the nanodomains formed in the structures studied is n≈(2–5)×1011 cm−2. In the structures with ultrathin InGaN inclusions, two characteristic nanodomain sizes are observed (3–6 and 8–15 nm).
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  • 3
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract InGaN/GaN structures with dense arrays of InGaN nanodomains were grown by metallorganic chemical vapor deposition. Lasing in vertical direction occurs at low temperatures, indicating ultrahigh gains (∼ 105 cm−1) in the active region. Fabrication of an effective AlGaN/GaN distributed Bragg reflector with reflectivity exceeding 90% enables vertical lasing at room temperature in structures with a bottom distributed Bragg reflector, despite the absence of a well-reflecting upper mirror. The lasing wavelength is 401 nm, and the threshold excitation density is 400 kW/cm2.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4150-4155 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The origin of the "coffee-bean" strain contrast is studied, that is observed in the plan-view transmission electron microscopy (TEM) images of CdSe/ZnSe quantum dot structures. The samples were grown by two different methods: standard molecular-beam epitaxy at 350 °C and atomic layer epitaxy at 230 °C with annealing at 340 °C after the CdSe deposition. The nominal CdSe thickness was above 3 ML. In situ reflection high energy electron diffraction during the growth or during the annealing shows the transition from the two- (2D) into the three-dimensional (3D) surface morphology for both samples. The coffee-bean contrast is usually assigned to three-dimensional islands which are generated after the morphological 2D/3D transition. It is found that the coffee-bean contrast in plan-view TEM images is alternatively associated with pairs of stacking faults on {111} lattice planes which are inclined against each other. The stacking faults, which are bound by Shockley partial dislocations, are preferably generated in the vicinity of the Cd-rich regions (large islands) of the CdZnSe layer where Cd concentrations of more than 40% are found. © 2001 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3695-3699 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth and vertical organization of CdSe quantum dots in three-layer stacks consisting of CdSe with a nominal thickness of 2.5 monolayers (ML) and ZnSe spacers with thicknesses between 10 and 20 ML was investigated by reflection high energy electron diffraction during the growth and different transmission electron microscopy techniques. The samples were grown by molecular beam epitaxy at 400 °C. It was found that up to 10 ML spacer thickness all three CdSe layers and ZnSe spacers form one broad (Cd, Zn)Se alloy layer with a small Cd concentration containing Cd-rich islands with a size of ∼15 nm. For spacers with a larger thickness (12–20 ML) three separated ternary (Cd, Zn)Se layers are observed which contain Cd-rich inclusions (small islands) with a size of less than 10 nm. A preferential vertical correlation of the small islands occurs for the 12 ML spacer thickness. With increasing spacer thickness, the number of the correlated small islands is reduced displaying a tendency to uncorrelated growth. © 2001 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 640-642 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Molecular beam epitaxy is used to grow different types of ZnSe/CdSe/ZnSe heterostructures. The topography of the bare CdSe surface studied with in situ atomic force microscopy is compared with high-resolution transmission electron microscopy data on overgrown structures. The growth procedure critically influences morphology and Cd distribution. Only use of thermal activation after low-temperature CdSe deposition enables the accomplishment of a distinct Stranski–Krastanov (SK) morphology with three-dimensional islands with a core of pure CdSe. Interdiffusion effects during activation of the SK transition as well as overgrowth are of minor importance. © 2002 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7323-7329 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: CdMgTe/CdTe superlattices with a high degree of structural perfection were grown on CdTe and Cd0.975Zn0.025Te substrates by molecular-beam epitaxy. The structural properties of the superlattices, i.e., the morphology of the layers and the state of strain relaxation, were examined by transmission electron microscopy and x-ray diffractometry. High-resolution transmission electron microscopy (HRTEM) reveals the structural quality of the superlattices on an atomic scale. The width of the chemical transition between the CdTe and CdMgTe layers was determined by HRTEM using chemically sensitive imaging conditions. Two different mechanisms of misfit dislocation generation could be observed in situ in the electron microscope studying a cross-section specimen of a superlattice which was originally fully strained.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3788-3794 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A continuous buried β-FeSi2 layer was obtained by implantation of 200 keV Fe+ ions into Si(111) wafers at elevated temperature. During the subsequent rapid thermal annealing at 1150 °C for 10-s, a continuous buried layer of the metallic α-FeSi2 phase is formed. During the second annealing step at 800 °C, the α phase is completely transformed into the semiconducting β phase. The epitaxial relationship between the β-FeSi2 and the silicon substrate was investigated by transmission electron microscopy. It was found that the β-FeSi2(010) plane grows parallel to the Si(111) substrate. Two different azimuthal orientations were observed. For the first azimuthal orientation, the β-FeSi2[001] direction is oriented almost parallel to one of the three Si〈110〉 directions lying in the interface. In the second azimuthal orientation, the β-FeSi2[100] direction lies parallel to one of the Si〈110〉 directions in the interface. The lattice parameter mismatch and the growth mechanism must be considered to be the main reasons for the epitaxial relationship of the Si(111)/β-FeSi2/Si(111) heterostructures studied in this investigation. The orientation of the β-phase is likely to be predetermined by the orientation of the α-phase which is formed during the first annealing step. Different orientation relationships were observed for β-FeSi2 prepared by solid phase epitaxy and ion beam synthesis without high-temperature annealing.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2099-2101 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of different growth conditions on the In distribution in ultrathin InGaN insertions in a GaN matrix is investigated by high-resolution transmission electron microscopy and an appropriate image evaluation technique. It is demonstrated that the indium distribution represents dense arrays of In-rich nanodomains inserted in a layer with a lower indium concentration. The sizes of the In-rich regions are about 4–5 nm at a growth temperature of 720 °C. Increasing the growth temperature leads to a strong decrease in the of nanoisland density and, also, a moderate decrease in their lateral size. Increasing the trimethylindium/trimethylgallium ratio strongly increases the density of the islands, but the lateral size remains weakly effected. The observations are in agreement with a thermodynamic model of island formation including entropy effects. © 2002 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4426-4428 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, we report the investigation of In segregation in InAs/AlAs heterostructures. InAs layers with different thicknesses were grown by molecular beam epitaxy on GaAs (001) substrates. The layers were investigated by transmission electron microscopy. Profiles of the chemical composition of the InAs layers in the [001] direction were deduced from high-resolution lattice fringe images using the composition evaluation by lattice fringe analysis method. The segregation efficiency was derived by fitting the measured In concentration profiles with the segregation model of Muraki et al. [K. Muraki et al., Appl. Phys. Lett. 61, 557 (1992)]. We obtain efficiency of R=0.77±0.03 for the segregation of In in AlAs/InAs at a temperature of 530 °C. © 2001 American Institute of Physics.
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