Materials Literature
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Sb nanocrystals were formed in thin, thermally grown SiO2 layers using low-energy ion implantation followed by thermal annealing. These Sb nanocrystals have good size and position uniformity. Both the narrow as-implanted profile and the compressive strain that exists near the SiO2/Si interface supposedly contribute to…
The magnetoresistance of mechanically induced grain boundaries in La0.7Ca0.3MnO3 thin films is investigated. The grain boundaries are fabricated by a mechanical deformation of the LaAlO3 substrate prior to film deposition. During film deposition, the deformed substrate region induces some growth disorder in the film l…
High-quality (001) thin film La0.5Sr0.5CoO3−x (LSCO) has been prepared on (001) SrTiO3 substrates by pulsed laser deposition under different oxygen pressures with and without postannealing. C-axis expansion of the LSCO with reducing oxygen pressure was revealed. The electrical resistivity increased over five orders of…
A novel principle for cooling by adiabatic pressure application in the mixed crystalline compound Pr1−xLaxNiO3 is described and experimentally verified. Cooling occurs in the vicinity of the structural phase transition where the electronic ground state of the Pr3+ ions changes from a singlet to a doublet state. By pro…
Porous silicon (PS) with nondegrading photoluminescence (PL) was prepared by a novel method. For fresh samples, the PL peak intensity is 2--2.5 times stronger than that in normal PS. Upon exposing PS to ambient air, the PL intensity increases during the first four months and then saturates. No PL degradation is observ…
single crystals were grown by the laser floating zone method. Polarized Raman spectra were measured and interpreted consistently with the Pcmn crystal space group. Up to 16 Raman modes were identified and their symmetry assigned. The infrared optical constants of were determined from the analysis of the reflectance sp…
Reactions on surfaces play an important role in many technological applications. Since these processes are often rather complex, one tries to understand single steps of these complicated reactions by investigating simpler system. In particular the hydrogen dissociation on surfaces serves as such a model system. There…
Density functional theory (DFT) primarily provides a good description of the electronic structure. Thus, DFT primarily deals with length scales as those of a chemical bond, i.e. 10^-10 meter, and with time scales of the order of atomic vibrations, i.e. 10^-13 seconds. However, several interesting phenomena happen and/…
Knowledge of the atomic geometry of a surface is a prerequisite for any detailed understanding of the surface's electronic structure and chemical properties. Previous studies have convincingly demonstrated that density functional theory (DFT) yields accurate surface atomic geometries and that reliable predictions conc…
The electronic structure of finite-length armchair carbon nanotubes has been studied using several ab-initio and semi-empirical quantum computational techniques. The additional confinement of the electrons along the tube axis leads to the opening of a band-gap in short armchair tubes. The value of the band-gap decreas…
The lowest energy structures of ${\mathrm{Au}}_{n}$ ( $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}38,55,75$) nanoclusters are obtained by unconstrained dynamical and genetic-symbiotic optimization methods, using a Gupta $n$-body potential. A set of amorphous structures, nearly degenerate in energy, are found…
Experimental observations of various deformation and fracture modes under compression of single multiwalled carbon nanotubes, obtained as a result of embedment within a polymeric film, are reported. Based on a combination of experimental measurements and the theory of elastic stability, the compressive strengths of th…
The emission spectrum of high quality ZnO epilayers is studied from room temperature up to 550 K. At room temperature and low excitation power a single emission peak is observed which may be identified with the free exciton from its peak energy and dependence on temperature. However, when excitation intensities exceed…
Surfactant micellar templates used for synthesis of MCM-41 mesoporous oxides are revealed to serve as a hydrophobic carrier for bringing nonpolar inorganic precursors selectively into the one-dimensional channels of MCM-41. Stepwise calcination of MCM-41 incorporating ferrocene thereby gives rise to a sharp and intens…
In this research, oligomeric polyalkyl phosphate-type polyols (P% = 14–17) were synthesized from ethylene glycol or 1,4-butanediol (PBE or PBB) by means of butyl phosphorodichloridate, which was prepared from phosphorus oxychloride and butanol. These polyols were then reacted with isocyanate to form the corresponding…
The room-temperature resonance Raman (RR) spectra of nickel(II) porphine have been simulated for excitation within the Q-band optical transition, taking into account both coordinate-independent (Condon) as well as coordinate-dependent (non-Condon) contributions to the Raman scattering amplitude of each vibration. Comp…
A latex of poly(β-hydroxyoctanoate) was obtained from Pseudomonas oleovorans grown at high cell density on sodium octanoate. A fermentation using a pH-stat control of octanoate concentration as well as the purification steps using sodium hypochlorite were described. It was observed that latex stabilization occurred sp…
We have prepared and characterized a mesoporous material where the framework, of both the as-synthesized and calcined materials, is composed of ZrO 2 -doped 25-Å TiO 2 anatase crystallites. The nanocrystalline framework is structured about a surfactant-templated, disordered porous network with a uniform pore diameter…
Low-dimensional metals exhibit a wealth of interesting phenomena associated with the special topology of their Fermi surfaces. These Fermi surfaces contain a very rich information concerning not only the dimensionality of the conductivity but also the possibility of different metal-to-insulator or metal-to-metal trans…
The syntheses and characterization of [2,3,7,8,12,13,17,18-octafluoro-5,10,15,20-tetraphenylporphinato]cobalt, Co(F(8)TPP), and [2,3,7,8,12,13,17,18-octafluoro-5,10,15,20-tetrakis(pentafluorophenyl)porphinato]cobalt, Co(F(28)TPP), are reported. Co(F(28)TPP).2tol (tol = toluene) crystallizes in the monoclinic space gro…