Materials Literature
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The growth of nematic films near a wall close to the nematic-isotropic transition is studied for planar boundary conditions. If the nematic phase wets the wall, near the onset of bulk nematic behavior the nematic film near the wall is in a Kosterlitz-Thouless low-temperature phase. The transition to this phase can be…
We show that the \ensuremath{\alpha}-(AlMnSi) crystal structure is closely (and systematically) related to that of the icosahedral Al-Mn-Si alloys. Using a modification of the ``projection'' method of generating icosahedral structures from six-dimensional lattices, we find a simple description of the \ensuremath{\alph…
The dielectric permittivity and loss of 1-cyanoadamantane have been measured under isothermal conditions in the frequency range, 100-2*10 5 Hz and the temperature range, 80-350K in the glassy crystal, supercooled (metastable) and stable (disordered) crystals and partially ordered crystalline states. Two relaxation reg…
X-ray measurements performed on a variety of materials demonstrate that it is possible to observe diffuse scattering that originates in the abrupt change of density at a crystal surface. Such a discontinuity gives rise, in general, to rods of scattering in reciprocal space which are most intense close to the Bragg pea…
A model of intercalation is presented which can be used for sophisticated three-dimensional computer simulations of staging kinetics. A realistic microscopic description of the intercalation process and of the stage-3 to stage-2 transition has been obtained for the first time. Stage disorder and three-dimensional effe…
Field-assisted ion exchange has been used to extend the profile repertoire and to speed the ion exchange process for gradient-index (GRIN) applications. Profiles are predicted for various ion mobility ratios and time-varying electric fields. Profile control is demonstrated by silver for sodium exchange in an aluminosi…
A set of MS-Xα calculations on the MoFe3S4 (SH)3−6 ion is reported. Three levels of theoretical models are considered: spin-restricted, C3v symmetry, which is most easily compared with the traditional ligand-field picture; spin-polarized, C3v symmetry; and spin-polarized, Cs symmetry. An MS=3/2 ground state correspond…
The results of refractive-index measurements in ZrF4–BaF2–LaF3–AlF3 glass and the effects of the addition of NaF are described. The dispersion properties are not enhanced by the addition of NaF, as shown by increased material dispersion M at long wavelengths and decreased crossover wavelength λ0.
A model has been developed which predicts the chromatic properties of gradient-index materials based on the composition of the glass. It yields a gradient Abbe number and a gradient partial dispersion which can be used by the lens designer in the design of achromatic gradient-index lens systems. Over 100 glasses with…
Within a new theoretical approach the current and energy decay in amorphous semiconductors is studied. The relaxation of photoexcited carriers observed by transient photoconductivity experiments in amorphous silicon and chalcogenides can well be described by an algebraic power-law decay. The theoretical explanation is…
The intensity and energy shift of the Ge 3d surface core-level photoemission is determined with the use of synchrotron radiation. Cl- and Br-terminated Ge(111)?(hy(1\ifmmode\times\else\texttimes\fi{}1) surfaces are used to calibrate the absolute coverage CTHETA and to obtain accurate line shapes. We find binding-energ…
The adsorption of chlorine on Si(111)-(7\ifmmode\times\else\texttimes\fi{}7) has been studied with various photoemission techniques with the use of synchrotron radiation. At room temperature, bonding of one, two, and three chlorine atoms to a Si surface atom was observed with Si 2p core-level shifts of 930, 1830, and…
The problem of localization of phonons in disordered materials is studied in the framework of the weak-localization theory. Quantum correction to phonon diffusion is calculated by the resummation technique of maximally crossed diagrams in two and three dimensions. The strong energy dependence of the elastic mean free…
The structure of molecular beam deposited microcrystalline silicon and germanium films prepared under different growth conditions has been analyzed by conventional transmission electron microscope (TEM) and Raman scattering (RS) and compared to electrical conductivity experiments. The TEM measurements yield an average…
Optical absorption spectra corresponding to the 4 A 2 g → 2 E g transition of Cr 3+ in RCrO 3 (R=Er, Ho, Dy and Tb) were investigated. The exciton lines ( R ) with Davydov splitting, and an electric dipole band ( R ') at lower energy side were observed in all compounds. From the temperature and external magnetic field…
The theory of secondary electron emission (SEE), which was proposed by Feder and Pendry, is extended. The new argument allows us to predict not only the fine structure but also all the features of SEE spectra. The secondary electron current is described as a multiplication of the fine structure part, which is easily o…
Two perturbation methods are compared for the theories of the cyclotron resonance line shape for electron-phonon systems. The line-shape functions in schemes designated as ``moderately weak coupling'' and ``extremely weak coupling'' by Choi and Chung are obtained using Mori's method of calculation. The results agree e…
The impact ionization coefficients for electrons and holes in both (100)- and (111)-oriented Si have been determined from photocurrent measurements performed on reach-through avalanche photodiodes. The results for both orientations are similar, indicating that the ionization coefficients are isotropic. Monte Carlo cal…
Several microwave absorbers have been characterized in terms of transmittance and reflectance at frequencies between 35 GHz and 3 THz. The materials studied were a series of iron-loaded cast epoxy absorbers known as Eccosorb. Measurements show that reflectance and absorption coefficient increase with the iron density.…
Physical properties of the CDW state of 1 T -TiSe 2 such as electronic band structures are investigated on the basis of the band-type Jahn-Teller model by extending our microscopic theory of lattice instability in the normal phase. The results are summarized as follows: (i) The triple- q CDW state is more stable than…