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  • 1
    Digitale Medien
    Digitale Medien
    Strain relaxation of Si/Ge multilayers: Coherent islands formation and their evolution as a function of the strain (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1441-1447 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on a structural study of Si/Ge multilayers grown by molecular-beam epitaxy on (100)-Si substrates. The analyses have been performed by using transmission electron microscopy, high-resolution x-ray diffraction, and secondary-ion-mass spectrometry. The investigated specimens differ in number of periods, period thickness, and in the Si/Ge periods thickness ratio. In particular, we investigate the interdiffusion of the Ge atoms in each superlattice period of the epilayer and in the epilayer as whole. The interdiffusion causes a broadening of the nominal thickness of the Ge layer producing a SixGe1−x alloy. Furthermore, the Ge content in the multilayer periods increases as a function of the growth time, i.e., the superlattice periods close to the sample surface contain more Ge atoms if compared to the periods close to the substrate/superlattice interface. We find two steps in the strain relaxation: (i) In each period the strain energy density is partially reduced by the formation of coherent islands; (ii) at a certain value of the strain energy density the shape of the islands changes and the structures relax partially or completely the accumulated strain energy by nucleation of extended defects. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360982
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  • 2
    Digitale Medien
    Digitale Medien
    Structural characterization of lattice matched AlxIn1−xAs/InP and GayIn1−yAs/InP heterostructures by transmission electron microscopy and high-resolution x-ray diffraction (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2403-2410 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In this work we report on transmission electron microscopy and high-resolution x-ray diffractometry studies of lattice matched AlxIn1−xAs/InP and GayIn1−yAs/InP epilayers grown by molecular beam epitaxy on InP(100) substrates. High-resolution and diffraction contrast electron microscopy measurements show the presence of different contrast zones in the epilayers. The analysis of high-resolution x-ray diffraction measurements and computer simulations ascribe these zones to the presence of a compositional gradient in the epilayers. A comparison among investigated samples grown under slightly different growth conditions combined with an analysis of the crystal defects is presented. Growth-induced small variations in the chemical composition of the epilayer can produce differences in the structural quality of the epitaxial layer. Finally, a few monolayers thick and highly strained film of InAsP, is observed in all investigated samples at the substrate/epilayer interface. The formation of this interface layer is explained by the exchange of As and P during exposure of the InP surface to As4 before the growth. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360162
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  • 3
    Digitale Medien
    Digitale Medien
    Coherent islands as preferential sites for sticking of Ge atoms in Si/Ge multilayers: Formation of conical shaped defects (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2546-2548 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In this work we investigate the role of coherent islands in the strain relaxation mechanism of Si/SixGe1−x multilayers by using conventional transmission electron microscopy, high-resolution transmission electron microscopy, and transmission electron spectroscopic imaging. The samples investigated were grown by molecular beam epitaxy and they differ in the number of periods, period thickness, and in the Si/Ge layer thickness ratio. The formation of defect free coherent islands in strained SixGe1−x layers is at the origin of the peculiar morphology of the interfaces (waviness). We show that coherent islands act as preferential sticking sites for Ge adatoms, producing regions of higher Ge concentration. The higher concentration of Ge corresponding to the greater lattice spacing on the top of the coherent islands depletes the relevant strained layers. The corresponding accumulation of strain energy produces the formation of "conical-shaped defects.'' Inside these conical-shaped defects the elastic energy is relieved by nucleation of dislocations. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.117734
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  • 4
    Digitale Medien
    Digitale Medien
    Effects of the Elastic Stress Relaxation on the HRTEM Image Contrast of Strained Heterostructures (1997)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 53 (1997), S. 168-174 
    Details
    ISSN: 1600-5724
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: In this work, the effects of the elastic relaxation of compositional stresses caused by the finite size of transmission electron microscopy (TEM) specimens on the image contrast of high-resolution transmission electron microscopy (HRTEM) micrographs of strained heterostructures made by cubic materials are investigated. The reduced spatial dimensions, owing to the thinning process of strained heterostructures, cause modification of the atomic positions in the thinned specimens with respect to the bulk ones. This deformation is a function not only of the specimen thickness but also of the thinning crystallographic direction. The results show that the strains of an elastically relaxed structure can vary by 15% as a function of the thinning direction ([100] or [011]). The bending of the atomic columns caused by the elastic relaxation phenomena in HRTEM specimens of strained semiconductor materials can cause a strong background-intensity variation in the HRTEM images. This effect is a function of the structure of the investigated materials, indicating that information on the background intensity variation, owing to the non-uniform lattice distortion of an elastically relaxed heterostructure made by cubic materials, is contained in the {200} beams. Thus, the influence of the elastic relaxation cannot be neglected whenever HRTEM is used to deduce the local chemical composition or the local unit cell in strained cubic materials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0108767396012378
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  • 5
    Digitale Medien
    Digitale Medien
    Optical Properties of Nanoscale Silicon Particles Obtained by CO〈sub〉2〈/sub〉 Laser Induced Reactions in a Flow Reactor (1996)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 235-238 (Oct. 1996), p. 967-972 
    Details
    ISSN: 1662-9752
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/02/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.235-238.967.pdf
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  • 6
    Digitale Medien
    Digitale Medien
    Convergent-beam electron diffraction analysis of GaSe crystals grown from the melt by different doping elements (1991)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 233-245 
    Details
    ISSN: 0392-6737
    Schlagwort(e): Specific structure of inorganic compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Summary A systematic investigation of the structural modifications of GaSe crystals, grown from the melt by different doping elements, has been performed by convergent-beam electron diffraction technique, in order to analyse the dependence of the structure on the doping atoms. Iodine-doped crystals have shown the ɛ-2H hexagonal and γ-3R rhombohedral polytypes. The structure of crystals doped either by silver, or copper, or cadmium, or zinc, or arsenic has been proved a mixture of the ɛ-2H hexagonal and of γ, 9 R, 12 R, 15 R rhombohedral phases. Ingots doped either by zinc or arsenic have shown the ɛ polytype prevailing in some zones and the γ structure in the other ones. The ɛ modification is dominant in ingots doped by the remaining atoms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02463999
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  • 7
    Digitale Medien
    Digitale Medien
    Detection of magnetic circular dichroism using a transmission electron microscope (2006)
    [s.l.] : Nature Publishing Group
    Nature 441 (2006), S. 486-488 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] A material is said to exhibit dichroism if its photon absorption spectrum depends on the polarization of the incident radiation. In the case of X-ray magnetic circular dichroism (XMCD), the absorption cross-section of a ferromagnet or a paramagnet in a magnetic field changes when the helicity ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/nature04778
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