Materials Literature
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We determine dephasing times T2 in free standing porous silicon samples using nondegenerate four-wave mixing. Within the framework of an idealized inhomogeneously broadened two-level system, values of 20 fs for different porosities are obtained. Fast energy relaxation times are found in the range of 1.5–3.5 ps for 64%…
Surprisingly stable is the dinuclear complex cation [1CuCu]2+ with entwined ligand 1 (shown on the right; •, ○ = Cu+) that can be demetalated in a stepwise manner. The singly demetalated complex [1Cu]+ can be converted to give dissymmetrical heterodi-nuclear complexes [1CuAg]2+ and [1CuZn]3+ (○ = Ag+ and Zn2+, respect…
Completely new materials arise when semiconductor nanoparticles are periodically ordered in superlattices. First pioneering preparations of such superlattices were achieved by self-organization of ligand-stabilized CdSe and CdS nanoparticles. The block polymerization to give micelles in the presence of gold salts and…
We have fabricated erbium–oxygen-doped silicon light emitting diodes with molecular beam epitaxy by simultaneously evaporating erbium and silicon and providing a suitable background pressure of oxygen. In reverse bias, the diodes show intense room-temperature electroluminescence at λ=1.54 μm, originating from the intr…
Four bands, all belonging to the main thallium centres, have been detected in the emission spectra of CsCl:Tl and CsBr:Tl crystals. Their spectral, polarization and kinetic characteristics have been studied from 0.45 up to 360 K. It has been shown that the new model proposed by us recently for the relaxed excited stat…
The EPR spectra of in two transition metal fluoride glasses (PZG and PBI) have been extensively studied as functions of temperature, concentration and microwave frequency (S, X, K and Q bands). The marked changes observed in the EPR spectra with temperature and concentration imply the existence of pairs of ions. The s…
We present a stable simple cubic structure in the quaternary system (Al - Si) - Cu - Fe with the composition which corresponds to the p/q = 1/1 cubic approximant of the icosahedral Al - Cu - Fe phase. This cubic structure, with lattice parameter a = 12.330 Å and density , contains roughly 135 atoms per unit cell. Prel…
A strong reducing power in the excited state is just one of the features of the tetranuclear copper(I) complex 1. It contains an acetylide dianion bridging four copper atoms in both η1 and η2 bonding modes and exhibits long-lived luminescence. The central framework of the structure is shown on the right.
The kinetics of phase separation in thin polymer blend films of polystyrene and polybutadiene on a silicon substrate is examined by optical microscopy of the free film boundary. Our observations on 1000 and 200 \AA{} films are consistent with a crossover from three- to two-dimensional spinodal decomposition kinetics i…
As deduced from Nature, the principle of symmetry-driven self-assembly, based on incommensurate coordination numbers, is employed to design clusters using metal coordination as the driving force. The ten-component cluster on the right demonstrates the predicted cooperativity in cluster formation.
The kinetics of solid-solid phase transitions are explored using pressure-induced structural transformations in Si nanocrystals. In agreement with the predictions of homogeneous deformation theories, large elevations in phase transition pressure are observed in nanocrystals as compared to bulk Si, and high pressure x-…
Abstract Zwar steht der Entwicklung von nanometergroßen Strukturen prinzipiell nichts im Wege, doch setzt sich immer mehr die Auffassung durch, daß sich Strukturminiaturisierungen unter die gegenwärtig durch lithographische Techniken erreichbare 1‐μ‐Grenze als nicht mehr praktikabel erweisen werden. Es wurde daher deu…
The hydrolysis of tri-sec-butoxyaluminum in the presence of nonionic surfactants leads to mesoporous alumina molecular sieves with wormlike arrays of channels with uniform diameters in the range 2.4 – 4.7 nm, depending on the nature of the surfactant. Molecular sieves of this type are of interest as possible catalysts…
The transport properties of electrons and holes in poly(dialkoxy-p-phenylene vinylene) (PPV) are investigated by current–voltage measurements using Ca as an electron and indium-tin-oxide as a hole injecting contact. Both the electron and hole currents are dominated by the bulk conduction properties of the PPV, in cont…
Spun cast alloy HP50–Nb tubing retired from service in a steam reformer after approximately 8 years of service had stress rupture properties suggesting very short remaining life. Microstructural examination, however, indicated little or no creep damage (cavitation) but did reveal extensive microstructural modification…
An in situ method of monitoring the electron cyclotron resonance etching of III-V semiconductor heterostructures is discussed for in-plane lasers. Surface reflected and Fabry-Perot interference signals determine the etch depth, rate and surface quality. The etching accuracy is better than 500 /spl Aring/. The etch mon…
We have studied ion-beam-induced epitaxial crystallization and densification of sol-gel zirconia thin films on single-crystal yttria-stabilized zirconia (YSZ) substrates. The spin-coated sol-gel zirconia thin films (100 nm) on YSZ substrates were irradiated at 300 C with various ion beams (360 keV argon, 360 keV neon…
Abstract The spectral, polarization, and kinetic characteristics of luminescence are studied for In + and In 2+ ions associated with interstitials and vacancies in an X‐irradiated KCl: In crystal. It is shown that the 2.08 eV emission is caused by the electronic transitions from the tetragonal minima of the triplet re…
Abstract Molecules of the amphiphilic polyalcohol [9]‐10‐[9] arborol (molar mass M = 1053 g mol −1 ) dissolved in water form gels which are thermo‐reversible and shear sensitive. The gel formation sets in above a characteristic composition y gel of the solution and temperature T gel ( y gel = 7.5·10 −3 ; T gel ≈35°C;…
The results are presented of an investigation of radioluminescence and phosphorescence spectra, decay of phosphorescence at a constant temperature, and thermostimulated luminescence of transparent BeO:Li ceramics. The phosphorescence decay dependence on time suggests the appearance of tunnelling.