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  • 1
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 233-245 
    ISSN: 0392-6737
    Keywords: Specific structure of inorganic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [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 ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1441-1447 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2546-2548 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 53 (1997), S. 168-174 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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