Materials Literature
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We report silicon band-edge photoluminescence (PL) with photon energy of 1.1 eV and external quantum efficiency (EQE) better than ${10}^{\ensuremath{-}3}$ in samples prepared by high-temperature oxidation of porous silicon. The integrated PL intensity is insensitive to temperature. The EQE strongly depends on the anne…
Local-density-functional-theory (LDFT) calculations within the plane-wave pseudopotential framework are performed for two polar (111) and two nonpolar (100) MgO/Cu interfaces. The polar interfaces have larger works of adhesion than nonpolar ones, consistent with field-ion and electron-microscopy observations of (111)…
Accurate stopping powers of polyimide have been determined for mean energies (E) in the range of 200 keV≤E≤3200 keV for 4He ions and 550 keV≤E≤1550 keV for 1H ions, using the transmission method for foils with areal densities of 30–225 μg/cm2. The overall uncertainties of ∼2% are mainly due to the foil thickness deter…
A lattice instability of carbon nanotubes induced by a magnetic field perpendicular to the tube axis is studied in a k · p scheme. Both in-plane Kekulé and out-of-plane distortions are enhanced drastically with increase of a magnetic field independent of whether a nanotube is metallic or semiconducting and magnetic fl…
The electronic properties of thiophene oligomers (nT, n=2–8) have been investigated in the lowest excited triplet state. Theoretical calculations of the zero field splitting parameters and of the π-electron spin density have been performed and compared with previous experimental EPR results. The calculations are based…
Dimeric cyclotetramethylene carbonate (TeMC)2 was polymerized in bulk at 185°C. Either nBuSnCl3 or Sn(II)2-ethylhexanoate (SnOct2) were used as catalysts. SnOct2 proved to be somewhat less reactive, but high yields (up to 93%) and high viscosities (νinh up to 0.85 dL/g) were obtained with both catalysts. Viscosity-ave…
We consider the Seebeck coefficient in ${\mathrm{LaCrO}}_{3}$ and related transition-metal-oxide perovskites using a model for electronic conduction based on the electronic structure of the 3d orbitals of the B-site transition-metal cations. Relations for the Seebeck coefficient are presented for those perovskite syst…
Mechanisms for optical nonlinearities and ultrafast carrier dynamics in ${\mathrm{Cu}}_{\mathit{x}}$S nanocrystals (NC's) are studied using femtosecond pump-probe techniques and nanosecond Z-scan measurements. Depending on the copper deficiency, transient absorption is dominated either by state-filling-induced bleachi…
Electropolymerized porphyrin films on indium–tin–oxide substrates have been characterized using Rutherford backscattering spectrometry, absorption spectroscopy, electrical characterization methods and with step profiling. With these methods the density of the films (ρ=1.35 g/cm3) and the absorption coefficients α(λ) h…
We report on a detailed study of the dynamics of photoexcited carriers in red-emitting porous silicon at room temperature after excitation by 532-nm picosecond laser pulses. Experimental techniques of time-resolved absorption (pump and probe) and photoluminescence are used to cover a very large time interval ${10}^{\m…
Optical interband and intraband transitions in semiconductor quantum dots (QD's) are analyzed theoretically. It is found that three-dimensional confinement essentially modifies intraband matrix elements of the electron-photon interaction in the QD's as compared to the bulk materials. This effect is quite important for…
Polarization-selective computer-generated holograms made with form-birefringent nanostructures were designed, fabricated, and evaluated experimentally at 1.5 microm. The fabricated element showed a large polarization contrast ratio (>250:1) and a high diffraction efficiency (>40% for a binary phase level element). The…
We have studied ${\mathrm{Y}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ca}}_{\mathit{x}}$${\mathrm{TiO}}_{3}$ by photoemission and inverse-photoemission spectroscopy. Valence-band photoemission spectra show a d-band peak \ensuremath{\sim}1.4 eV below the Fermi level (${\mathit{E}}_{\mathit{F}}$), which evolves i…
The infrared optical constants of cubic and tetragonal zirconias were determined from the analysis of the reflectance spectra of yttria doped zirconia single crystals and undoped tetragonal zirconia powders, respectively. In the latter case, the reflectance spectrum was analyzed by an effective medium Theory, which ha…
By simulating the line shapes of a commonly observed S=1/2 electron paramagnetic resonance (EPR) center in polycrystalline chemical vapor deposited (CVD) diamond at 9.8, 14, 20, and 35 GHz, we conclude that the EPR signal, which we label H1, results from a unique defect with a single hydrogen atom \ensuremath{\sim}1.9…
We have investigated the degree of equilibrium swelling and the elastic modulus of networks prepared by end-linking oligo(dimethylsiloxane)s (ODMS) in solution as a function of polymer concentration at crosslinking. The molecular weight of ODMS is so low that entanglement couplings are not formed in uncrosslinked stat…
Laser ablation of graphite has been carried out using 1.06 μm radiation from a Q-switched Nd:YAG laser and the time of flight distribution of molecular C2 present in the resultant plasma is investigated in terms of distance from the target as well as laser fluences employing time resolved spectroscopic technique. At l…
The controversial relationship between the intrinsic 1.9 eV photoluminescence (the R band), the 2.0 and 4.8 eV excitation/optical absorption bands is examined for 11 specimens with different OH, Cl, and O2 concentrations and with different irradiation histories. The direct relation is found between the intensities of…
The liquid temperature at bubble wall ( T L , i ) is numerically calculated, including effect of the thermal conduction and that of the latent heat of non-equilibrium evaporation and condensation at the bubble wall under a condition of the picosecond sonoluminescence and that of nonlight-emission. It is concluded that…
${\mathrm{LaCrO}}_{3}$ is a wide-band-gap insulator which does not evolve to a metallic state even after hole doping. We report electronic structure of this compound and its Sr substituents investigated by photoemission and inverse photoemission spectroscopies in conjunction with various calculations. The results show…