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  • 1
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 174-176 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have studied the dynamics of thermal relaxation of highly metastable films of SiGe/Si(100) in situ in the transmission electron microscope (TEM). This makes it possible to study the early stages of strain relaxation, and thus obtain information about the nucleation of dislocations. We find that, when care is taken not to introduce artifacts during sample preparation, relaxation occurs by the multiplication of "precursor dislocations'' through a mechanism similar to the Frank–Read mechanism. An individual nucleation site is observed, confirming the model previously proposed.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1522-1524 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Far-infrared magnetotransmission spectroscopy has been employed to study p-type modulation-doped strained Si1−xGex/Si quantum wells grown by atmospheric pressure chemical vapor deposition at magnetic fields up to 23 T. The cyclotron resonance (CR) mass of the two-dimensional hole gas (2DHG) in a strained 7.5 nm Si0.63Ge0.37 quantum well was determined to be (0.29±0.02)m0 for a 2D hole density of 2.3×1012/cm2 at 3 K. The CR mass of 2DHGs in strained Si1−xGex is comparable to previous measurements of the CR mass of 2DHGs in strained InyGa1−yAs with similar 2D hole densities.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 924-926 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Si/Si1−xGex heterostructures on improved silicon-on-sapphire substrates were grown epitaxially by ultrahigh vacuum chemical vapor deposition for application as p-channel field effect transistors. High-resolution triple-axis x-ray diffraction was used to analyze these structures quantitatively and to evaluate their thermal stability. Outdiffusion of Ge from the strained Si1−xGex quantum well was observed after annealing at 850 °C. The amount of outdiffusion was comparable to that observed in Si1−xGex structures on bulk Si wafers. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2148-2150 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effect of thermal annealing on Si/SiGe heterostructures is studied using Raman spectroscopy. The structures consisted of Si on relaxed Si0.8Ge0.2 where the top Si thickness was 20–30 nm. Micro-Raman spectroscopy with 488 nm incident radiation revealed no significant shift in the strained Si peak position with thermal annealing at temperatures up to 1100 °C for 30 s. However, the intensity of the Si peak was systematically reduced with increasing thermal processing, a result which is attributed to interdiffusion at the Si/SiGe interface resulting in an apparent thinning of the Si cap layer. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Helgoland marine research 24 (1973), S. 54-77 
    ISSN: 1438-3888
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Summary 1. Recent advances in underwater research are reviewed and critically discussed. New technologies include deep-sea diving apparatus, saturation diving from underwater habitats, submersibles and remote-controlled vehicles. The fields of application include increasingly ecology and animal behaviour. 2. The term “underwater experimentation” is defined and examples provided to illustrate pertinent research. 3. Underwater experimentation is compared to laboratory experimentation. The latter is restricted to a limited set of suitable organisms, which are subjected to “controlled” but frequently quite “artificial” conditions. Furthermore, only systems of a very low degree of complexity can be studied in the laboratory. Underwater experimentation is limited by the restricted performance of man under in situ conditions. Automatisation of experimental units and use of remote-controlled vehicles are proposed to enhance man's underwater capacity. 4. The need for the design of underwater experiments, especially for system analysis, is emphasized. There is an increasing demand for predictive models to anticipate the potential impacts of civilisation on the marine environment.
    Notizen: Kurzfassung In den letzten zehn Jahren sind Unterwasseruntersuchungen zu einem nicht mehr wegzudenkenden und wichtigen Bestandteil marinbiologischer Forschungen geworden. Die technische Entwicklung dieser methodologisch definierten Disziplin führte vom Schwimm- und Gerätetauchen zu Tauchbooten, Unterwasserhäusern und ferngesteuerten Fahrzeugen. Die Anwendungsbereiche umfassen Beobachtung und Aufsammlung bis zur genauen Messung und Probennahme für ökologische Untersuchungen. Echte experimentelle Arbeit wird jedoch noch immer fast ausschließlich im Laboratorium durchgeführt. Daher ist Experimentation noch immer auf eine begrenzte Auswahl an „haltbaren“ Organismen, eine begrenzte Zahl simulierbarer und kontrollierbarer Faktoren und insbesonders an einen begrenzten Komplexitätsgrad der Untersuchungsobjekte gebunden. Dies ist um so bedauerlicher, als sich in der Ökologie immer deutlicher die Notwendigkeit von Systemanalysen abzeichnet. Der gegenwärtige Standard in Unterwasserbeobachtung und Datengewinnung und die Entwicklung von Multivariatentechniken macht es möglich, die „kontrollierten Bedingungen“ im Laboratorium — die zu oft eine gefährliche Vereinfachung sind — durch die „gemessenen Bedingungen“ in situ zu ersetzen. Die Dringlichkeit experimenteller Arbeit an ökologischen Systemen kann nicht genug betont werden in einer Zeit, in der wir versuchen müssen, mit den Einflüssen unserer Zivilisation auf die natürlichen Lebensräume fertigzuwerden, Voraussagen treffen und Modelle entwickeln zu können.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1573-5117
    Schlagwort(e): epiphytes ; macroalgae ; Cystoseira (host plant) ; seasonality ; eutrophication ; Mediterranean
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Epiphytic macroalgal assemblages growing on Cystoseira species were examined at typical oligotrophic and eutrophic sites of the east coast of Attica (Aegean Sea, Greece) from November 1995 to September 1996. The epiphytic patterns of C. spinosa Sauvageau thriving in the oligotrophic area of Dikastika and of C. compressa (Esper) Gerloff & Nizzamudin growing in the eutrophic environment of Avlida, were compared through a cross-transplantation experiment. Seasonality effects on epiphytic assemblages were observed. The species composition was exclusive for each locality, reflecting differences in the trophic status of the two sites. No specific pattern of epiphytes' distribution was found on the hosts. The prolific epiphytic growth in the oligotrophic site resulted in a reduction of the photosynthetic tissue of both hosts (C. spinosa and the transplanted C. compressa) and the survivorship of host plants was not negatively affected by the physical drag caused by the high epiphyte densities. Cystoseira spinosa survived in oligotrophic conditions despite its heavy epiphytic load. C. compressa was also able to cope with the adverse epiphytic influence in the eutrophic conditions of Avlida; although being perennial, it sheds parts of its stipe and branches before the resting period and sprouts prior to other algae at the beginning of spring.
    Materialart: Digitale Medien
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