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In previous papers, we introduced a novel analysis technique of the impedance spectroscopy of organic light emitting diodes to elucidate their layer-to-layer carrier dynamics and proposed a novel carrier transport model. In this article, we will discuss the carrier dynamics in the voltage region where the layer-to-layer dynamics cannot be distinguished. There appear several specific characteristic features in frequency- and voltage-dependence of complex impedance, the negative impedance, and the diffusion impedance. In the negative bias voltage region, where neither carrier injection nor accumulation occurs, conductance shows ω1/2 frequency dependence. On the other hand, at the higher voltage region where all the semicircles in Cole-Cole plot coalesce, there appear two types of negative impedance, which have ω1/2 and a Debye-like frequency dependence. We consider that the ω1/2 dependences are attributed to the diffusion impedance (Warburg impedance) coupled with and without the interfacial charge transfer reaction. The Debye-like negative impedance is attributed to the carrier trap at the interface of the Alq3 layer. [ABSTRACT FROM AUTHOR]

We report on the photopolymerization dynamics and the volume holographic recording properties of a thiol-ene based nanoparticle-polymer composite (NPC) doped with a blue-sensitive photoinitiator, Darocur® TPO, by using a highly coherent blue diode laser operating at a wavelength of 404 nm. Our study indicates that volume gratings recorded in the NPC amount to meeting the material requirements of refractive index modulation and material recording sensitivity for holographic data storage media. It is also found that polymerization shrinkage of recorded NPC gratings is higher than that of the same thiol-ene based NPC with a green (523 nm)-sensitive photoinitiator, Irgacure® 784/BzO2. We attribute such a difference in shrinkage to the photopolymerization dynamics at these recording wavelengths. We show that this shrinkage increase at 404 nm can be mitigated to some extent by controlling the thiol-ene stoichiometry in the NPC. [ABSTRACT FROM AUTHOR]

Thermal diffusivity and thermal conductivity of single crystals of Nd3+ doped GdVO4, YVO4, LuVO4, and Y3Al5O12 are precisely measured over a wide range of doping concentration from 0.5 to 15 at. % by temperature wave analysis. Thermal diffusivity serves as the most sensitive parameter to detect the effect of doping on thermal properties, where Nd3+ doped GdVO4 exhibits a decrease in thermal diffusivity (it has changed about 20% in their values in the c axis) but an increase in heat capacity (only 1.7%). It has long been understood that the thermal conductivity of YVO4 is inferior to that of Y3Al5O12; however, the thermal conductivity of YVO4 in the c axis shows the highest value in all four crystals compared at 1 at. % of Nd3+ doping concentration. Thermal conductivity exhibits a decrease (∝[variant_greek_epsilon]-1/2, [variant_greek_epsilon]: mass variance) with an increase of doping concentration, that is characteristic of Klemens’ point defect model for the phonon scattering. In the numerical fitting, the anisotropic decrease of thermal conductivity in different crystal axes, [100], [001], and [110], is reflected as the different phonon velocities. The simulated and the experimental thermal conductivity show the various decreasing curvatures indicating that the effect of mass difference of the host and the doping cations serves as an important factor, as with the crystallographic anisotropy, on the thermal conductivity of the doped single crystals. [ABSTRACT FROM AUTHOR]

For the purpose of investigating the photon energy dependence of the photoinduced abiotic synthesis of organic molecules, gas mixtures that simulate typical planetary atmospheres, including a carbon source (CO or CH4), a nitrogen source (N2 or NH3), and H2O, were irradiated with synchrotron radiation through a vacuum-ultraviolet transmitting window. Three kinds of window material, fused silica, synthetic quartz, and MgF2, were used as a high-energy-cutting filter, whose absorption-edge energies are 6.4, 8.1, and 10.5 eV, respectively. Three types of gas mixture, Titan-type (CH4–N2–H2O), comet-type (CO–NH3–H2O), and primitive-Earth-type (CO–N2–H2O), were irradiated with vacuum-ultraviolet photons in the three energy ranges. After the irradiation, amino-acid formation yields in the acid-hydrolyzed solution of the product were measured with a high-performance liquid chromatograph method. From the Titan- and comet-type mixtures, amino acids were detected by irradiation with photons lower than 8.1 eV. For both mixtures, the averaged quantum yields of glycine generation in the photon energy region of 7–10.5 eV were of the order of 10-5, which was larger by about one order than that in the region 5–8 eV. On the other hand, from the primitive-Earth-type mixture, amino-acid formation was difficult to detect even with irradiation as high as 10.5 eV, even though amino acids were generated in comparable yields from the Titan- and comet-type mixtures by irradiation with soft x rays or proton beam, whose energies are much higher. These results suggest that the vacuum ultraviolet light is a more effective energy source for the generation of the precursors of bioorganic compounds in extraterrestrial environments than in primitive-Earth atmosphere. [ABSTRACT FROM AUTHOR]

To investigate the photonic band structure of a drilled alternating-layer photonic crystal (DALPC), light transmittances were measured. Electron beam lithography was used to prepare Si/SiO[sub 2]/air DALPCs that had four periods in the z direction with air holes penetrating the whole structure. The transmittances of TE/TM polarized lights were measured for three directions (Γ–X, Γ–Y, Γ–Z). There was a common transmittance attenuated band at a wavelength of around 1.4 μm in the transmission spectra for all measured directions and polarizations. This agreed well with the photonic band gap (PBG) predicted by calculation. The results supported the good potential of Si-based DALPCs as full PBG materials. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Reports on the material selectivity in synchrotron radiation-stimulated etching of silicon dioxide and silicon. Rate differences in synchrotron radiation (SR)-stimulated etching among several kinds of silicon dioxide and silicon materials; Impact of impurity doping into polycrystalline silicon; Basic properties of SR-stimulated etching.

Applies the Raman scattering spectroscopy to an evaluation of silicon-on-insulator substrates formed by high-dose oxygen-ion implantation. Verification of fabrication uniformity of the substrates; Raman peak frequency and sample temperature dependence on laser power density on sample surface; Peak separation by changing laser wavelength.

Provides information on an experimental study investigating the impurity incorporation kinetics during modified-Lely growth of silicon carbide (SiC) in terms of several growth parameters. Methodology used to conduct the study; Results of the study; Discussion on the results.

The lattice distortion and the transmuted-Ge related luminescence in neutron-transmutation-doped (NTD) GaN are studied by combining Rutherford backscattering spectroscopy/channeling, Raman scattering, and photoluminescence methods. The lattice displacement of Ga atoms of ∼0.12 Å from the 〈0001〉 row is estimated from the normalized angular yield profiles, preserving the single crystallinity in as-irradiated GaN with a minimum yield (Χ[sub min]) of 7%. A 2.84 eV emission band observed in 600 °C annealed NTD-GaN is associated with the Ga interstitial, supporting the lattice distortion. Two emission bands at 2.90 eV and 2.25 eV observed in 1000 °C annealed NTD-GaN are assigned to a negatively charged DX-like center of Ge at Ga site and a complex defect attributed to Ge at Ga site and Ga vacancy, respectively. [ABSTRACT FROM AUTHOR]

Oxygen precipitate behavior of nitrogen-doped Czochralski-grown silicon (CZ-Si) crystals is investigated. It is found that nitrogen doping enhances oxygen precipitation after heat treatment. The oxygen precipitate volume density in nitrogen-doped crystals after heat treatment does not change regardless of the heat treatment temperature, while the oxygen precipitate volume density of crystals which are not nitrogen doped decreases as the heat-treatment temperature increases. The characteristics of precipitation behavior in nitrogen-doped CZ-Si crystals are due to the "grown-in" oxygen precipitates, which already exist in an as-grown state with a high volume density. The oxygen precipitation growth of nitrogen-doped crystals is found to be an oxygen diffusion limited process, the same as in the case of the oxygen precipitation growth of crystals which are not nitrogen doped. The formation mechanism of grown-in oxygen precipitates will also be discussed in this article. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the abiotic synthesis of amino acids by x-ray irradiation of simple inorganic gases. Relationship between the amount of amino acids and the total energy absorbed by gas molecules; Antipodal optical isomers generated; Production of the precursors of amino acids.

Examines the fabrication of porous silicon carbide (SiC) using single crystal 6H-SiC having wider indirect band gap than silicon crystals. Observation of blue-green luminescence at room temperature; Clarification on the origin of luminescence in porous Si; Association between luminescence intensity and porosity.

Reports that silicon photoepitaxy excited by synchrotron radiation (SR) has been observed. Reconstruction reflection high-energy electron diffraction pattern exhibited by the surface of the as-grown film; SR-irradiation growth rate.

Tungsten/beryllium multilayers were coated onto lamellar diffraction gratings using a neutral atom beam sputtering technique. Boundary roughness of the multilayer was estimated to be 6.0 Å as a standard deviation. Diffraction efficiency of the multilayer-coated grating was measured using monochromatized synchrotron radiation. [ABSTRACT FROM AUTHOR]

Reports on polytype-controlled crystal growth of silicon carbide (SiC) carried out by using a sublimation method. X-ray diffraction pattern of SiC.

A synchrotron radiation beamline and reaction chamber were constructed for the study of synchrotron radiation excited photochemical reactions, especially for their application to semiconductor processes. Characteristics of this experiment and experimental results with chemical vapor deposition and etching in this beamline are described. The potential of this new application is discussed. [ABSTRACT FROM AUTHOR]

Examines the link between the water blocking effect and the point defect in electron cyclotron resonance plasma chemical vapor deposition silica films. Detection of the electron spin resonance signal; Water trapping ability of the silicon dangling bonds; Implications for hot-carrier degradation prevention in devices.