Materials Literature
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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…
The first measurements are reported of frequency-dependent (ac) conductivity in thin films of amorphous phosphorus prepared by rf sputtering. The behavior of the ac conductivity \ensuremath{\sigma}(\ensuremath{\omega}) is broadly similar to that which has been observed previously in many other types of amorphous semic…
The electronic structure of \ensuremath{\alpha}-quartz and a-${\mathrm{SiO}}_{2}$ has been calculated using the tight-binding recursion method. For a-${\mathrm{SiO}}_{2}$ two structural models were used. The first one consisted of the continuous-random-network model constructed by Bell and Dean (BD). The second model…
1H NMR solid state techniques have been used to study bonding properties, location, and mobility of hydrogen in various phases of the hydrogen bronze HxMoO3. Temperature-dependent spectra characteristic of different degrees of intercalation have been observed, and furthermore, from measurements of the relaxation rate,…
The dielectric theory of electron-energy-loss spectroscopy (EELS) in the reflection geometry is reformulated so as to allow for an arbitrary compositional variation of the target material in the direction perpendicular to its surface. A new, general expression for the energy-loss spectrum is obtained in terms of an ex…
The energy dispersion of conduction (or unoccupied) bands of graphite has been studied by angle-resolved ultraviolet photoelectron spectroscopy. Photoemission peaks originating in the conduction bands were successfully separated from those of the valence bands by comparing two sets of angle-resolved ultraviolet photoe…
The increase in the current that flows in a negative point-to-plane corona discharge when a porous layer is present on the plane was studied by using a fast storage oscilloscope. It was found that the current increase is due primarily to an increase in the frequency of the Trichel pulses at the cathode, and less than…