Materials Literature
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The switching kinetics of polarization reversal using lead zirconate titanate (PZT) thin-film capacitors for nonvolatile memories has been analyzed in terms of the Ishibashi model. A practical 16 kbit PZT memory was used in this work. The polarization reversal ratio agrees well with the theoretical model of the first…
Step-flow crystal growth is possible on a very large scale on Si(111). The growth mode changes at the $(7\ifmmode\times\else\texttimes\fi{}7)\ensuremath{-}(``1\ifmmode\times\else\texttimes\fi{}1'')$ phase-transition temperature. Nucleation of new steps can be controlled by intentionally introducing contaminants or par…
We investigate the variation of the electromigration driving force felt by Na adatoms in the vicinity of other adatoms, adatom rows, and small planar islands. The wind valence tensor is computed by a model calculation for noncompact Na clusters on a semi-infinite flat jellium substrate that carries an electrical curre…
Exciton states confined in a spherical quantum dot (QD) are studied in a weak confinement regime with the consideration of the electron-hole exchange interaction and induced surface charge density. Except for special cases, most exciton states are longitudinal (L)--transverse (T) mixed modes. With an increase of radiu…
Bacterial cell walls are cross-linked in the final step of biosynthesis by specific D-alanyl-D-alanine(DD)-peptidases/transpeptidases. The natural substrates of these enzymes should therefore be segments of peptidoglycan, but high specificity for such structures has yet to be demonstrated. The binding of dipeptides to…
We start with an analysis of the Raman spectra of Ge nanocrystals obtained in previous studies and demonstrate that in many cases the observed experimental peak attributed to Ge in fact originates from the Si substrate. We further compare various experimental ways to separate the Ge signal from that of the substrate a…
We have measured the energy- and momentum-dependent loss function of ${\mathrm{Li}}_{2}{\mathrm{CuO}}_{2}$ single crystals by means of electron energy-loss spectroscopy in transmission. Using the same values for the model parameters, the low-energy features of the spectrum as well as published Cu ${2p}_{3/2}$ x-ray ph…
Slow dynamics in a fluid are studied in one of the most basic systems possible: polydisperse hard spheres. Monodisperse hard spheres cannot be studied as the slow down in dynamics as the density is increased is preempted by crystallization. As the dynamics slow they become more heterogeneous, the spread in the distanc…
We present molecular-dynamics simulations of the atomic arrangement in molten and amorphous germanium. We start with 512 atoms in a supercell and then heat it above the melting temperature. Subsequent rapid quenching results in a continuous random network (CRN) with a radial distribution function (RDF) in excellent ag…
To elucidate the effect of the aspect ratio of protein on the diffusion in gels, the diffusion of a rodlike protein, tropomyosin, in two kinds of polysaccharide gels, agarose and carrageenan, has been investigated by electronic speckle pattern interferometry method and compared with that of a globular protein, myoglob…
We present a growth model for single-walled carbon nanotubes (SWNTs) based on experimental observation and energetic considerations. Carbon rings, observed experimentally and suggested to be fullerene precursors, are the templates for SWNTs nucleation. SWNTs grow by addition of C2 radicals to catalytically induced rea…
Density-functional theory calculations using the periodic slab approach are carried out to investigate the relaxed structures of the regular MgO and CaO(100) surfaces. Both local density and gradient corrected approximations to the exchange-correlation energy are employed and slab orbitals are expanded in Gaussian ato…
STM, NEXAFS, XPS, and TPR have been used to characterize the adsorption and reactivity of methyl pyruvate on Pt{111}. In the absence of coadsorbed hydrogen, methyl pyruvate polymerizes at room temperature yielding polymer chains, partly dendritic. The STM and XPS data provide independent estimates of the average lengt…
We studied resonant electron tunneling through individual CdSe and CdS nanocrystals in two types of configuration. With nanocrystals electrodeposited on bare gold, the spectra show resonant tunneling via discrete unoccupied (CB region) and occupied levels (VB region) at positive and negative bias, respectively. In thi…
The influence of potassium comodification on the structure-property relationships of base (Pb1−3/2xLax)(ZryTi1−y)O3 [(PLZT) 100x/100y/100(1−y)] ceramics has been investigated. Studies were performed by dielectric response, electrically induced polarization and strain methods, and transmission electron microscopy. For…
Ab initio calculations have been performed in order to investigate a recently proposed polarizable model [M. C. C. Ribeiro, Phys. Rev. B 61, 3297 (2000)] for molecular dynamics (MD) simulation of the molten salt Ca0.4K0.6(NO3)1.4. On the basis of the electronegativity equalization method, polarization effects in the M…
Plate impact experiments were conducted on a γ-titanium aluminide (TiAl) based ordered intermetallic alloy. Stress measurements were recorded using manganin stress gauges supported on the back of TiAl targets using polymethylmethacrylate windows. The Hugoniot in stress-particle velocity space for this TiAl alloy was d…
We reexamine the putative Peierls transition in a (5,5) metallic nanotube. We show that the conduction electrons at the Fermi level do not couple to the longitudinal acoustic phonon but rather to a folded-in graphene zone edge phonon having the proper K\'ekul\'e modulation symmetry. The calculation for the mean-field…
Fluorescence and absorption spectra of ${\mathrm{Pr}}^{3+}:\mathrm{PrOCl}(\mathrm{PrPr})$ were measured in the range from $11500{\mathrm{cm}}^{\ensuremath{-}1}$ to $22500{\mathrm{cm}}^{\ensuremath{-}1}$ under pressures up to 16 GPa. From these spectra, the pressure dependence of the energy-level scheme of the ${4f}^{2…
This work deals with photoluminescence study of silicon nanoparticles produced by CO2-laser-induced decomposition of SiH4 mixed to helium in a controlled atmosphere reactor. By adjusting the pressure of both reactor and precursor gas and its dilution rate in helium, we were able to control, to a certain extent, the si…