Advances in material sciences are paving the way for use of synthetic diamond
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Massive polarons in large-energy-gap polymers
We present evidence for the existence of defect states with large mass and low mobility in the conducting polymer polyaniline. This large-energy-gap polymer has been shown to have properties significantly different from many other conducting polymers. Photoinduced infrared absorption studies presented here are consist…
Intrinsic negative-resistance effect in mixed-stack charge-transfer crystals
A stable and reproducible negative-resistance effect has been observed in various mixed-stack organic charge-transfer crystals having ionicities close to the neutral-ionic phase boundary. Systematic studies on several kinds of single crystals indicate that this effect is an intrinsic property, arising from the dynamic…
Photoinduced magnetization in dilute magnetic (semimagnetic) semiconductors
Optically induced magnetization was studied in narrow-gap ${\mathrm{Hg}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Te in zero external magnetic field as a function of composition, excitation energy, and temperature. These experimental results, together with previously published data for ${\mathr…
Morphological studies of micelle formation in block copolymer/homopolymer blends
The micellar structure of poly(styrene-butadiene) diblock copolymer/polystyrene homopolymer blends has been investigated by small angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) as a function of copolymer concentration, copolymer block molecular weights, and homopolymer molecular weight. The S…
Threshold energy for photogeneration of self-trapped excitons in SiO2
The excitation spectrum of the 2.8-eV luminescence band of crystalline Si${\mathrm{O}}_{2}$ has been measured in a photon energy range between 6 and 14 eV at 77 K. We find that the onset of the 2.8-eV luminescence occurs at 8.3 eV, which is nearly equal to the fundamental optical absorption edge of Si${\mathrm{O}}_{2}…
Electronic structure of Si-skeleton materials
The electronic structures of Si-skeleton chainlike [one-dimensional (1D)] and planar [two-dimensional (2D)] materials have been calculated by the first-principles local-density-functional method. 1D Si-skeleton material (chain polysilane) has a directly-allowed-type band structure with a band gap of about 4 eV. Interc…
Free-expansion melting of a colloidal monolayer
A two-dimensional melting transition has been observed in a freely expanding colloidal monolayer lattice formed of 1.01-\ensuremath{\mu}m polystyrene microspheres in an aqueous suspension between two parallel optical flats. The correlation functions computed from digitized images of the particle distribution within a…
Raman scattering and photoluminescence inCu2O under hydrostatic pressure
Excitonic transitions and phonon frequencies in ${\mathrm{Cu}}_{2}$O were measured by luminescence and Raman spectroscopy at hydrostatic pressures up to 8.5 GPa and at a temperature of 6 K. The exciton Rydberg energy is found to decrease at a rate of -2.4 meV/GPa. The band gap increases at a rate of 12.5 meV/GPa, whic…
Adsorption kinetics and isotopic equilibration of oxygen adsorbed on the Pd(111) surface
Oxygen adsorption on the Pd(111) surface has been studied at 100 and 300 K by temperature programmed desorption (TPD) and isotopic mixing experiments. At 100 K, the sticking coefficient is determined to be 1 up to the coverage of 0.3 O/Pd. The saturation coverage is 0.62 O/Pd, 27% of which dissociates during thermal d…
The deposition and study of hard carbon films
Carbon films have been deposited by rf plasma decomposition of methane at 50–1400 V negative bias and 1.3×10−3–1.3×10−1 mbar pressure. Hardness, internal stress, density, hydrogen content, and infrared absorption depending on the preparation parameters have been measured. From the IR measurements the ratio of sp3 to s…
Simple octagonal and dodecagonal quasicrystals
Penrose tilings have become the canonical model for quasicrystal structure, primarily because of their simplicity in comparison with other decagonally symmetric quasiperiodic tilings of the plane. Four remarkable properties of the Penrose tilings have been exploited in the analysis of the physical issues: (1) the clas…
Luminescence of F and F + centers in magnesium oxide
Time-resolved spectra of luminescence from F and ${F}^{+}$ centers in MgO excited at 248 nm are reported over 8 decades of time and intensity, from 20 ns to 2 s. The decay time of F and ${F}^{+}$ luminescence has been measured at temperatures ranging from 90 to 573 K. The luminescence yield and spectra were studied as…
Biexciton states in semiconductor quantum dots and their nonlinear optical properties
Biexciton states in semiconductor quantum dots (spherical microcrystallites) are investigated variationally, and the biexciton binding energy and the oscillator strength are calculated as a function of the quantum-dot radius, the electron-to-hole mass ratio, and the dielectric constant ratio of the semiconductor to th…
Optical properties of a suspension of metal spheres
The Mie theory is used to find the in situ electric dipole polarizability of a sphere of arbitrary size and material. This size-dependent polarizability, together with the Clausius-Mossotti equation, yields an effective dipole generalization of the Maxwell Garnett equation for spheres of nonzero size. Calculated effec…
On the Angle Dependence of the Magnetoresistance in Quasi-Two-Dimensional Organic Superconductors
The dependence of the title is shown to originate in a singular angle dependence of the distribution width of the area of the semiclassical closed orbits under the magnetic field in the reciprocal space. In quasi-two-dimensional metals with a cylindrical Fermi surface, the distribution width of the area of the orbits…
Raman spectra ofc-Si1−xGexalloys
We observe several weak features between 420 and 470 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in addition to the normally observed Si-Si (\ensuremath{\sim}500 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$), Si-Ge (\ensuremath{\sim}400 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$), and Ge-Ge (\ensuremath{\sim}300 ${\mathr…
Calculation of the band gap for small CdS and ZnS crystallites
The tight-binding approximation and the recursion method are used to study the size dependence of the band gap for small CdS and ZnS crystallites (20--2500 atoms). Because of the lack of accurate experimental data, a simple model of the crystal is considered; one which has no dangling bonds and a symmetrical shape. It…
Effects of a corona discharge on the charge stability of Teflon FEP negative electrets
Measurements of TSD together with surface potential were used to study negative corona discharge effects on the charge stability of Teflon FEP electrets. During charging, liquid formation over the sample surface (clearly visible for long-time corona irradiation) was concluded to be responsible for a decreasing in the…
Dispersion of the linear electro-optic coefficients and the non-linear susceptibility in GaP
The linear electro-optic effect in GaP has been investigated in the wavelength range 0.552-1.2 mu m at applied electric field frequencies of 200 Hz and 9.45 GHz. The dispersion of the clamped and unclamped electro-optic coefficients is measured and the fitted constants in the formula describing the clamped electro-opt…