Materials Literature
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Combinatorial laser molecular-beam epitaxy method was employed to fabricate epitaxial Zn1−xMnxO thin films in a high throughput fashion. Local structures around Mn were investigated for these c-axis-oriented epitaxial films by fluorescence x-ray absorption fine structure measurements. It was shown that Mn substitution…
Photo-oxidation of densely packed monolayer of CdSe quantum dots (QDs) was studied by time-resolved photoluminescence (PL) spectroscopy. Electrons yielded in QDs by the strong laser-pulse irradiation can assist the oxidation of CdSe QDs. Such rapid photo-oxidation does not introduce more nonradiative defects, instead,…
We present a theoretical study of the optical properties of quantum dots containing a single paramagnetic ion. The eigenvalue problem of an electron-hole pair in interaction with a localized spin is solved. In Mn-doped nanocrystals of II-VI semiconductors such as CdTe the fundamental absorption line splits into six co…
Co-doped TiO2 (anatase) films prepared by spray pyrolysis at 500 °C are investigated for the possible existence of room temperature ferromagnetism (RTF). These films were characterized by x-ray diffraction, Raman spectroscopy, and x-ray photoelectron spectroscopy at room temperature, followed by studies of the tempera…
Temperature influences Ostwald ripening through its effect on interfacial energy, growth rate coefficients, and equilibrium solubility. We have applied a distribution kinetics model to examine such temperature effects. The model accounts for the Gibbs–Thomson influence that favors growth of larger particles, and the d…
In this paper, an interpretation of the high-frequency crossover, observed for glass formers at temperature far above the glass transition, is described in terms of the large change in the heterogeneous character of the dynamics. For five prototypical glass formers, dielectric relaxation data spanning many decades wer…
Dielectric measurements are reported for the α-relaxation in polystyrene (PS) of varying molecular weights. Although the segmental relaxation dispersion was essentially invariant to Mw, the Tg-normalized temperature dependence (fragility) increases systematically with molecular weight. The latter result corroborates d…
The effect of pH on the self-assembly and disassembly of nanoparticle aggregates (clusters) of amine modified silica spheres (50 nm) and carboxylic acid modified gold (7 nm) or cadmium selenide (6 nm) spheres was investigated using electron microscopy and infrared and electronic spectroscopy. 4-Mercaptobenzoic acid (M…
We present an ab initio study of the stability and defect reactions of neutral and charged H interstitial (${\mathrm{H}}_{i}$) and H vacancy (${\mathrm{H}}_{v}$) in ${\mathrm{K}\mathrm{H}}_{2}{\mathrm{P}\mathrm{O}}_{4}$ (KDP). We find that while there is no interaction between the neutral ${\mathrm{H}}_{i}$ and the ho…
We report results from molecular dynamics simulations of the freezing and melting, at ambient temperature (T=300 K), of a bilayer of liquid water induced by either changing the distance between two confining parallel walls at constant lateral pressure or by lateral compression at constant plate separation. Both transi…
Optimization of carbon nanotube bundles containing a distribution of nanotube diameters always gives structures with packing defects that form relatively large interstitial channels. Experimental data for CH4, Ar, and Xe adsorption are compared with simulations. Low coverage experimental isosteric heats are in excelle…
In this paper, we review the construction of low-dimensional manifolds of reduced description for equations of chemical kinetics from the standpoint of the method of invariant manifold (MIM). MIM is based on a formulation of the condition of invariance as an equation, and its solution by Newton iterations. A grid-base…
A phase control by photoirradiation is successfully achieved in a spin-Peierls system of the organic radical crystal, 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA), which exhibits optical and magnetic bistability around room temperature with a large hysteresis loop. A nanosecond laser pulse is found to induce a transiti…
Atomic force microscopy was used to study the embedding of gold nanoparticles into the surface of polystyrene films. The rate of embedding was determined at temperatures near the bulk glass transition temperature T(g) by measuring the apparent nanosphere height as a function of annealing time. In particular, relative…
ZnO nanowires have been grown on sapphire and Si substrates using catalytic growth. A strong near-band-gap ultraviolet emission is observed at room temperature. By carefully studying the temperature dependence of ZnO wire emission, we found that the room-temperature UV emission contains two different transitions; one…
We report on an extensive study of craze formation in glassy polymers. Molecular dynamics simulations of a coarse-grained bead-spring model were employed to investigate the molecular level processes during craze nucleation, widening, and breakdown for a wide range of temperature, polymer chain length N, entanglement l…
We report the observation of hole cyclotron resonance (CR) in InMnAs/(Al,Ga)Sb heterostructures in a wide temperature range covering both the paramagnetic and ferromagnetic phases. We observed two pronounced resonances that exhibit drastic changes in position, linewidth, and intensity at a temperature higher than the…
In this work we analyze an Aharonov-Bohm interferometer in the tunneling regime. In this regime, current magnification effect which arises in presence of transport currents is absent. A slight modification in the form of a quantum well incorporated in one of the arms leads to revival of current magnification. Systemat…
Metamaterials, which contain engineered subwavelength microstructures, can be designed to have positive or negative ε and μ at desired frequencies. In this letter, we demonstrate a metamaterial which has a “plasmonic” response to electromagnetic waves in the terahertz (THz) range. The sharp change of reflection and tr…
Many nanoparticles have short-range interactions relative to their size, and these interactions tend to be “patchy” since the interatomic spacing is comparable to the nanoparticle size. For a dispersion of such particles, it is not a priori obvious what mechanism will control the clustering of the nanoparticles, and h…