Materials Literature
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Complex clusters the size of small proteins can be generated in reduced molybdate solutions by linking defined fragments. An example of this is the giant cluster (NH 4 ) 25±5 [Mo 154 (NO) 14 O 420 (OH) 28 (H 2 O) 70 ]·ca. 350 H 2 O with a molar mass of more than 30000 gmol −1 , the anion of which is shaped like a tire…
A two-dimensional electron system is expected to form a Wigner lattice at zero temperature but at very high electron densities even at T=0 one expects a phase transition from a crystal to a gas phase. For a Wigner lattice on a dielectric layer, a T=0 melting was also predicted at very low electron densities. Here we e…
The different allotropic forms of boron nitride have been investigated by $^{11}\mathrm{B}$ NMR and spin-lattice relaxation measurements. In the material with hexagonal symmetry the central transition is broadened by second-order quadrupole perturbation and the related quadrupole frequency ${\ensuremath{\nu}}_{\mathit…
The resistance of planar barriers is discussed for a variety of situations in which different sources of scattering act incoherently, allowing a semiclassical approach. This includes single barriers, a sequence of identical parallel barriers, and identical barriers at random angles simulating grain boundaries. Existin…
Third-order nonlinear-optical-susceptibility spectra \ensuremath{\Vert}${\mathrm{\ensuremath{\chi}}}^{(3)}$(-3\ensuremath{\omega};\ensuremath{\omega},\ensuremath{\omega},\ensuremath{\omega})\ensuremath{\Vert} have been obtained for free-standing porous silicon films by third-harmonic-generation (THG) measurements in a…
Effect of impurities on the high-field magnetization process in a frustrated antiferromagnet CuFeO 2 is studied for powder samples of CuFe 1- x Al x O 2 (0≤ x ≤0.1) and CuFe 1- x Cr x O 2 (0≤ x ≤0.08) using a pulse magnet up to 38 T. For the pure Fe compound distinct magnetization anomalies are successively observed a…
The free surface of a homologous series of low molecular weight liquid crystals 4-cyano-4′-n-alkyl-biphenyls (nCB, n=5,6,7,8) is studied by reflection ellipsometry. On approaching the bulk isotropic–nematic transition temperature TNI from the isotropic phase, the growth of a nematic layer at the surface is observed. T…
The defects of the Si(001)-${\mathrm{SiO}}_{2}$ interface have been studied by the electron-paramagnetic-resonance (EPR) technique taking advantage of the high specific surface area of porous silicon. This interface is characterized by the presence of two interface defects ${\mathit{P}}_{\mathit{b}0}$ and ${\mathit{P}…
A major problem for diamond coating applications is that diamond films tend to exhibit poor adherence on many substrates and typically disbond at thicknesses of the order of a few micrometers principally because of residual stresses. Residual stresses are composed of thermal mismatch stresses and intrinsic tensile fil…
A self-consistent tight-binding formalism is described. The self-consistency is achieved by the introduction of a chemical hardness matrix and a generalization of the H\"uckel model to make the tight-binding Hamiltonian an implicit functional of the charge density. Studies of the band structures of diamond and face-ce…
Transport and magnetic measurements including the magnetic resonance of 51 V nuclei have been carried out for misfit-layer compounds (La 1- y R y S) 1+α VS 2 (R=Sr and Pb, 0≤ y ≤1.0). The results indicate that the system is in the Mott insulating state at high temperatures, at least in the y region near α/(1+α) which…
We discuss the potential of an ideal photovoltaic cell with charge carrier multiplication by impact ionization. Thermodynamics requires that carrier multiplication modifies luminescence as well. Such a cell may be described as a hot-carrier cell where interband equilibrium is inhibited and where thermalization is rest…
The dynamic structure factor S(q,\ensuremath{\omega}) of electrons in single-crystal Si was measured with 1.6-eV resolution by means of inelastic x-ray scattering spectroscopy for ${\mathbf{q}}_{\mathrm{\ensuremath{\parallel}}}$ [100], [110], and [111] with 0.37q2.06 a.u. using synchrotron radiation from the DORIS sto…
In order to interpret relatively strong second-harmonic generation (SHG) in centrosymmetric molecular films such as ${\mathrm{C}}_{60}$ and copper phthalocyanine (CuPc), higher-order contributions to bulk SHG have been considered. The contributions examined were of electric quadrupole, magnetic dipole, electric quadru…
Due to its small size, the carbon atom has a very low solubility in a silicon crystal. In spite of this, we show that carbon atoms adsorbed on top of a silicon surface readily migrate into substitutional sites below the surface, leading to a narrow layer of a highly concentrated alloy. This was demonstrated by deposit…
We investigate correlations between the atomic-scale structure and the global electronic and vibrational properties in amorphous carbon versus mass density. The model structures have been generated by applying different annealing regimes using a density-functional-based nonorthogonal tight-binding molecular dynamics.…
By the use of ultraviolet laser pulses of microsecond and millisecond duration it is shown that the chemistry of the transformations of Kapton by UV laser radiation is strongly dependent on the intensity (power/unit area) of the laser beam. With these long pulses, the polymer was not ablated. The decomposition resulte…
59 Co and 139 La NMR measurements have been performed to study the microscopic magnetic properties closely related with the spin state of a trivalent cobalt ion in LaCoO 3 . The temperature-independent 59 Co and 139 La Knight shifts below ∼ 30 K clearly revealed the presence of a nonmagnetic ground state at low temper…
Film stability and structure formation inside a liquid film containing colloidal particles are investigated by Monte Carlo (MC) numerical simulations and by analytical methods. The effective pair interaction between particles is calculated from the Ornstein–Zernike theory with Percus–Yevick closure. Consistent with th…
Using the tight binding molecular dynamics method (TBMD), the structural and dynamical properties of graphitic tubules are studied. The phonon dispersion and density of states of graphitic tubules with various helicities and diameters are calculated. Phonon modes in tubules are softened by the curvature when compared…