Materials Literature
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Raman spectroscopy is applied to the study of the structure of polycrystalline silicon films. The analysis of the transversal optical phonon Raman line shows its complex structure consisting of two dominant contributions, centered at about 519 and 517 cm−1 and attributed to two dominant groups of grains with different…
Samples of poly( p -phenylene sulfide) obtained by different thermal and/or mechanical treatments are found to exhibit the same crystal structure. Conformational and packing analysis performed by molecular mechanics have given the lowest energy conformation of the polymer chain in the crystal state and the lowest ener…
Crystallization of polyethylene terephthalate and i-polypropylene in nonisothermal conditions is studied by means of differential scanning calorimetry. Measurements, carried out at several constant cooling rates, are interpreted in terms of a new theory1,2 that takes into account effects related to a transient, nonste…
Extended x-ray-absorption fine-structure has been utilized to measure the composition dependence of the Ge-Ge and Ge-Si bond lengths in both crystalline and amorphous ${\mathrm{Ge}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}$ alloys. Utilizing a new sample preparation technique, transmission measurements were performed over…
The hole effective-mass Hamiltonian for the semiconductors with wurtzite structure is given. The effective-mass parameters are determined by fitting the valence-band structure near the top with that calculated by the empirical pseudopotential method. The energies and corresponding wave functions are calculated with th…
Photoluminescence (PL) and Zeeman effect measurements in near-infrared luminescence bands in Cr-doped 4H and 6H SiC are presented. The PL spectrum consists of two no-phonon lines (NPLs) at 1.1583 and 1.1898 eV in 4H SiC and three NPLs at 1.1556, 1.1797, and 1.1886 eV in 6H SiC. The observed Zeeman splittings and tempe…
The dynamics of hot electrons, induced by femtosecond pulses, is investigated in silver nanoparticles embedded in a glass matrix. A detailed temporal and spectral study of the plasmon resonance is reported when the laser excitation density is varied over three orders of magnitude. It is compared in the same spectral r…
We use molecular-dynamics simulations of a polymer film confined between two walls to isolate the factors that control where an adhesive bond breaks. Failure occurs either at the wall/film interface (adhesive failure) or within the film (cohesive failure). Most theories relate the location of failure to equilibrium in…
The structures and melting of n-hexanol, n-heptanol, n-octanol, and n-nonanol monolayers adsorbed on graphite have been studied by x-ray diffraction and compared with our previous results on n-alcohols with shorter chain length. All the monolayers take similar herringbone or related structures consisting of a pair of…
A new Zintl phase Ba 4 In 8 Sb 16 was obtained from a direct element combination reaction of the elements in a sealed graphite tube at 700 °C, and its structure was determined by single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic space group Pnma (No. 62) with a = 10.166(3) Å, b = 4.5239(14)…
Optical emission study of the laser ablation plasma plume during the preparation of diamond-like carbon (DLC) films using KrF excimer (248 nm) pulsed laser deposition (PLD) has been carried out by means of a monochromator equipped with an intensified optical multichannel analyzer. In high vacuum (1×10−7 Torr), the emi…
We describe a method for the explicit determination of the segment density profile φ(z) of surface-attached polymer brushes with multiple angle of incidence null-ellipsometry. Because the refractive index contrast between the brush layer and the solvent is weak, multiple reflections are of minor influence and the elli…
Quasi-isothermal temperature-modulated differential scanning calorimetry was employed in a study of thermoreversible structural changes in the melting range of semicrystalline polymers. The results indicated a reversible melting and crystallization process occurring at the fold surfaces of crystallites of polyethylene…
We present a microscopic characterization of composite thin films made of CdSe semiconductor nanocrystals (quantum dots) dispersed in a polynorbornene-based block copolymer with surface-passivating and electron transport functionalities. We used two types of nanocrystals, CdSe with pure organic capping groups (“bare”)…
The resistivity and thermopower of ${\mathrm{Na}}_{1+x}{\mathrm{Co}}_{2}{\mathrm{O}}_{4}$ and ${\mathrm{Na}}_{1.1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{Co}}_{2}{\mathrm{O}}_{4}$ are measured and analyzed. In ${\mathrm{Na}}_{1+x}{\mathrm{Co}}_{2}{\mathrm{O}}_{4},$ whereas the resistivity increases with x, the thermo…
The incipient crystallization of needlelike forms of organic salts, such as ammonium dl-tartrate or ammonium oxalate, has been used for the templating of sol−gel reactions to produce hollow silica fibers and filaments with geometrically shaped channels. By judicious control of both the crystallization and hydrolysis−c…
In the present work, we study the sensitivity of the near-edge x-ray absorption fine structure (NEXAFS) spectroscopy to ion induced defects in polycrystalline diamond films. The ion bombardment of hydrogenated films is performed using 30 keV Xe+ ions at room temperature for doses ranging from 2×1013 ions/cm2, producin…
CdS nanoparticles (NP), 22 Å, have been synthesized from cadmium 2-ethylhexanoate in DMSO as a uniformly sized dispersion. After ripening, CdS exhibits a sharp excitonic emission peak at 402 nm, while in freshly prepared dispersions a broad trapped emission at 510 nm dominates. By using one- and two-dimensional NMR sp…
The nonradiative recombination of an exciton due to a collision with another exciton (i.e., Auger recombination) is the dominant loss mechanism for excitons at high densities in photoexcited ${\mathrm{Cu}}_{2}\mathrm{O}.$ The principal evidence is that (a) the observed lifetime of excitons shortens substantially at hi…
The full-potential linearized augmented plane wave method has been employed to determine electronic density of states, $1s$ core level shifts, and total $1s$ core ionization energies for the isoelectronic compounds graphite, diamond, ${\mathrm{C}}_{3}{\mathrm{N}}_{4},$ and graphitic ${\mathrm{C}}_{11}{\mathrm{N}}_{4}.…