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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3085-3089 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, surface relaxation and its effects on the electronic and structural properties of porous silicon are studied by using the total-energy pseudopotential formalism within the density-functional theory. Our model is based on a 32-atom supercell, where columns of atoms are removed and saturated with hydrogen atoms. Samples with 4.4%, 13.6%, 16.8%, 28.9%, and 41.3% porosity are analyzed in detail. The results show a clear expansion of the system along the pore direction as the porosity increases. Moreover, this expansion is very sensitive to the hydrogen-atom concentration and a linear dependence is observed. The dependence of the band gap and the effective mass on the porosity are also analyzed. Here, the hydrogen-atom number and pore shapes are observed to play a fundamental role. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3274-3276 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Moderate pressure techniques (P=20 kbar) have been used to prepare Tl2−xCdxMn2O7 (0≤x≤0.4) pyrochlore-like materials. The x=0.2 compound has been characterized by neutron powder diffraction, magnetic, magnetotransport, and Hall measurements. This material is ferromagnetic below TC=110 K. Both electrical resistance and magnetoresistance (MR) are enhanced with respect to stoichiometric Tl2Mn2O7, due to the drastic reduction in the number of carriers (electrons) induced by hole doping. MR(0.5 T) is higher than 106% at 120 K, and MR(9 T) is 30% at room temperature. We show that hole doped derivatives of Tl2Mn2O7 are promising candidates in which to search for large bulk magnetoresistance. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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