Materials Literature
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We use the anomalous x-ray diffraction technique to investigate the nature of the tantalum displacement pattern in the modulated phase of the charge-density-wave compound (TaSe4)2I. In addition to the known acousticlike modulation, we find the first direct evidence for the condensation of opticlike Ta displacements al…
Nanotubes like feather boas were synthesised by the decomposition of methane in a nitrogen atmosphere using a bias-enhanced hot-filament chemical vapour deposition technique. This new type of slightly nitrogenated carbon (C:N) nanotubes exhibits a vermicular shape. Graphitic thin foils growing perpendicular to the tub…
The magnetic properties and microstructural evolution of Zr-doped FePt alloy films prepared by dc-magnetron sputtering were investigated. Compared to an undoped Fe59Pt41 binary film, Zr-doped FePt alloy films showed accelerated ordering transformation kinetics accompanying smaller grains: we were able to fabricate a Z…
Transparent glasses in the system (100–x) Li2B4O7–xSrBi2Ta2O9 (0⩽x⩽20) were fabricated via a splat-quenching technique. The glassy nature of the as-quenched samples was established by differential thermal analyses. X-ray powder diffraction and transmission electron microscopic studies confirmed the amorphous nature of…
The first experimental evidence for triclinic symmetry of bulk smectic liquid-crystal samples of achiral banana-shaped molecules is presented. This phase corresponds to the so-called Sm-CG phase consisting of biaxial molecules and characterized by two tilt directions with respect to the layer normal: tilt of the molec…
We report experimental and theoretical results on the effect of electromagnetic coupling between metal particles in surface-enhanced Raman scattering (SERS). Model calculations of the near-field optical properties of Ag and Au nanoparticle-aggregates show that the electromagnetic surface-enhancement factor can reach 1…
By studying the structures of clusters bound by a model potential that favors polytetrahedral order, we find a previously unknown series of "magic numbers" (i.e., sizes of special stability) whose polytetrahedral structures are characterized by disclination networks that are analogous to hydrocarbons.
In this letter, we show that normal-incidence spectroscopic ellipsometry can be used for high-accuracy topography measurements on surface relief gratings. We present both experimental and theoretical results which show that spectroscopic ellipsometry or reflectance-difference spectroscopy at near-normal incidence coup…
Grafting of a ferrocene-containing liquid-crystalline malonate derivative to C60 led to the mixed fullerene-ferrocene material 1 which gave rise to a smectic A phase. Cholesterol was used as liquid-crystalline promoter. X-ray diffraction experiments and volumetric measurements indicated that 1 is organized in double l…
Rare organometallic complexes can be stabilized by using an N-confused system as a carbon ligand. A stable organocopper(II) compound of N-confused calix[4]phyrin has been characterized by X-ray crystallography. Complete π conjugation was found not to be a prerequisite for the formation of the metal-carbon bond.
A method for calculating the anisotropic elastic energy of a dislocation dipole in a periodic cell is derived in which the infinite image summation is absolutely convergent. The core energy of a screw dislocation in Si, extracted from atomistic simulation, is shown to be manifestly system size invariant. Existence of…
Enhanced surface reaction efficiency has been demonstrated in the photocatalysis of obliquely deposited TiO2 thin films with variously shaped columns such as zigzag, cylinder, and helix. The columnar thickness and spacing play an important role in the enhancement of the effective surface area, while the columnar shape…
We have designed high-efficiency finite-aperture diffractive optical elements (DOE's) with features on the order of or smaller than the wave-length of the incident illumination. The use of scalar diffraction theory is generally not considered valid for the design of DOE's with such features. However, we have found sev…
We present the observation of ferroelastoelectric switching in a ferroelectric material. It is achieved in barium titanate thin film by simultaneously applying electric field and compressive stress with the tip of a scanning force microscope. For low compressive stresses, the presented measurements reveal classical fe…
The Mo≡N bond is conjugated with the organic segment in the novel molecular organic-inorganic hybrid materials that have been obtained by Pd-catalyzed coupling of an iodo-functionalized hexamolybdate anion and an alkyne (see scheme; Ar=4-methylphenyl,3-5-di(tert-butyl)phenyl). The interaction between the polyoxometala…
Surface pattern formation in diblock copolymer films is investigated as a function of film thickness h and molecular mass M. Smooth films are observed for certain h ranges centered about multiples of the lamellar thickness L0, and we attribute this effect to an increase in the surface chain density with h in the outer…
Computer simulations of bubble oscillations are performed under conditions of sonoluminescence (SL) in water for various liquid temperatures. It is clarified that at almost all acoustic amplitudes, the bubble temperature at the collapse is higher in a colder liquid because a lesser amount of water vapor is trapped ins…
Current imaging scanning tunneling microscopy is used to observe the electronic wave functions in InAs/ZnSe core/shell nanocrystals. Images taken at a bias corresponding to the s conduction band state show that it is localized in the central core region, while images at higher bias probing the p state reveal that it e…
) shows induced circular dichroism, which is indicative of a chiral environment.
Extremely small colloidal InP quantum dots (QDs) with diameters ranging from 15 to 23 Å were synthesized, and the optical properties of close-packed arrays of these dots were studied. The isolated QDs in dilute colloidal solution exhibit pronounced discrete absorption spectra, indicating a narrow size distribution. Th…