Materials Literature
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Six different classes of water-soluble polyphosphazenes have been synthesized and characterized. Several of the new polymers have been cross-linked to yield materials that absorb water to form hydrogels. This chapter examines the underlying concepts used in this work and describes the use of this chemistry to prepare…
First-principles calculations based on density-functional theory and the pseudopotential method have been used to investigate the influence of gradient corrections to the standard local-density-approximation technique on the equilibrium structure and energetics of rutile ${\mathrm{TiO}}_{2}$ and ${\mathrm{SnO}}_{2}$ p…
We have performed spatially resolved measurements of the charge-density-wave (CDW) response to bipolar current pulses. These measurements directly yield the distribution of the CDW phase slip, the temporal evolution of the CDW elastic-force and strain profiles, and the local relationship between the phase-slip rate an…
The Ag/MgO(100) interface has been studied by EXAFS. At room temperature, in agreement with previous investigations, silver at low coverage is shown to form a two-dimensional layer at the MgO(100) surface. EXAFS data demonstrate that the lattice parameter of the silver overlayer is expanded so as to fit the MgO parame…
Various approximate methods for the calculation of vibrational second hyperpolarizabilities are assessed on the basis of results for CH4, NH3, H2O, HF, and CO2. Three specific variations of the perturbation-theoretic approach are analyzed. These are defined by the types of terms retained in expansions which involve el…
Lanthanum modified lead zirconate titanate (PLZT) ceramics near a crossover between normal and relaxor ferroelectric states for Zr/Ti ratios of 40/60, 20/80, and 0/100 were investigated by dielectric spectroscopy, Sawyer–Tower polarization techniques and transmission electron microscopy. It was found possible to induc…
This book deals with the phenomenological theory of first-order structural phase transitions, with a special emphasis on reconstructive transformations in which a group-subgroup relationship between the symmetries of the phases is absent. It starts with a unified presentation of the current approach to first-order pha…
The energy dependence of the electron lifetime in graphite was measured using femtosecond time-resolved photoemission spectroscopy. The lifetime was found to be inversely proportional to the excitation energy above the Fermi level, i.e., $({E\ensuremath{-}E}_{F}{)}^{\ensuremath{-}1}$, in sharp contrast to that of meta…
Artificial superlattices consisting of antiferroelectric PbZrO3 (PZO) and ferroelectric PbTiO3 (PTO) have been fabricated by a multi-ion-beam sputtering technique. The epitaxial PZO and PTO layers were sequentially grown on (100)Pt/MgO substrates at a low substrate temperature of 415 °C with a periodicity from 5 to 10…
Photoluminescence of CdSe nanocrystals in a glass matrix was investigated at low temperature with size-selective excitation. The emission spectrum consists of a line a few meV below the excitation laser energy (denoted the F line) and a two-phonon replica superimposed on a broadband. The energy difference between the…
The dynamics of band-edge photoluminescence (PL) in CdS nanocrystals (NC's) dispersed in a glass matrix are studied with the femtosecond up-conversion technique. The time-resolved PL spectra exhibit several discrete features (three of them are in the NC energy band gap) which are not pronounced in a cw PL spectrum. Th…
Using Hall effect measurements, we have investigated carrier transport in a high-conductivity layer formed in the surface region of as-deposited homoepitaxial diamond films prepared by chemical vapor deposition. The results of undoped and B-doped films were compared to those obtained from an oxidized B-doped film. It…
A highly tetrahedrally bonded, hydrogenated amorphous carbon (ta-C:H) has been deposited from an acetylene-fed plasma beam source. The plasma beam source is operated to provide a highly ionized, monoenergetic plasma beam of ${\mathrm{C}}_{2}$${\mathrm{H}}_{2}^{+}$ ions. The resulting films are characterized in terms o…
We report on electrical resistance measurements of an individual carbon nanotube down to a temperature $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}20\mathrm{mK}$. The conductance exhibits a $\mathrm{ln}T$ dependence and saturates at low temperature. A magnetic field applied perpendicular to the tube axis incr…
We calculate the transverse effective charges of zincblende compound semiconductors using Harrison's tight-binding model to describe the electronic structure. Our results, which are essentially exact within the model, are found to be in much better agreement with experiment than previous perturbation-theory estimates.…
A three-dimensional structure of two carbon nanotubes (CN) joined by a connecting region containing a pentagon and heptagon pair is given by the use of a projection method. The connecting joint is uniquely determined for the given two chiral vectors of CN by a vector which defines a three-dimensional dihedral angle. T…
The electronic structures of a wide range of early transition-metal (TM) compounds, including Ti and V oxides with metal valences ranging from 2+ to 5+ and formal d-electron numbers ranging from 0 to 2, have been investigated by a configuration-interaction cluster model analysis of the core-level metal 2p x-ray photoe…
Superlattices of $\mathrm{Si}/{\mathrm{SiO}}_{2}$ have been grown at room temperature with atomic layer precision using state of the art molecular beam epitaxy and ultraviolet ozone treatment. Photoluminescence was observed at wavelengths across the visible range for Si layer thicknesses $1<d<3\phantom{\rule{0ex…
Possible origins of ``colossal magnetoresistance'' (CMR) behavior in the ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ca}}_{\mathit{x}}$${\mathrm{MnO}}_{3}$ system are studied using the local spin-density method. These calculations allow the quantification of the effects of Mn d--O p hybridization tha…
Field-induced insulator-to-metal transitions have been found in ${\mathrm{Pr}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}(0.3<~x<~0.5)$ single crystals, which are accompanied by a melting of the insulating charge-ordered (i.e., ${\mathrm{Mn}}^{3+}$/${\mathrm{Mn}}^{4+}$ ordered) state. The tra…