Materials Literature
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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…
Subbandgap absorption of chemical-vapor-deposition diamond films, with nitrogen contents varying from 10 to 132 ppm has been explored by the constant-photoconductivity method (CPM), photothermal-deflection spectroscopy (PDS) and electron spin resonance (ESR). The spectra measured by PDS increase monotonically and are…
The pressure phase diagram of κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Cl is determined by measuring the intralayer and interlayer resistivities. With increase of pressure, nonmetallic behavior of resistivity is suppressed and a metallic phase is stabilized, yielding the phase reentrance near critical pressure region. Concurrently,…
Visible photoluminescence (PL) bands around 2 eV were studied in 60Co γ-irradiated (dose<1 MGy) oxygen-deficient-type amorphous SiO2 (a-SiO2) excited by 2–4 eV photons. In addition to the well-known 1.9 eV PL band due to nonbridging oxygen hole centers, another PL band was observed at 2.2 eV when excited by 3.8…
The electronic properties of carbon nanotubes having polygonized cross sections instead of purely circular ones, such as recently observed using transmission electron microscopy, are investigated with plane-wave ab initio pseudopotential local-density-functional calculations and simple tight-binding models. Strong ${\…
We have observed Raman scattering from acoustic phonons confined in Si nanocrystals. It was found that the Raman spectra depend strongly on the size of the nanocrystals and the peaks shift to higher frequencies as the size decreases. We also found that the depolarized Raman spectra appear at much lower frequencies tha…
BACKGROUND: Several perfusion balloon catheters are under investigation for local drug delivery; however, sustained tissue drug levels are difficult to achieve with these techniques. To overcome this problem, sustained-release, biodegradable nanoparticles represent a potential alternative for prolonged local delivery.…
The viscoelastic properties of various crosslinked natural rubbers, NR, were investigated by mechanical spectroscopy. The glass transition temperature, Tg, was found to be dependent on both the crosslink density and the crosslink type. Higher values of Tg were obtained for sulfur-crosslinked NR than for peroxide-cross…
Using molecular dynamics computer simulations we investigate how the glass transition and the properties of the resulting glass depend on the cooling rate with which the sample has been quenched. The system we study is a two component Lennard-Jones model which is coupled to a heat bath whose temperature is decreased f…