Materials Literature
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We prepared for Mott–Hubbard-type perovskite La0.5Sr0.5TiO3+δ thin films under an oxygen reduced environment, 5% H2/Ar. Control of the partial pressure during deposition could change the conductivity of the films, and induces a metal–insulator transition. In addition, we observed an excellent transparency at visible l…
Auch ohne π-Konjugation gelingen Energiewanderung und -transfer über große Entfernungen: Schnell (kENT=1.04×109 s−1) und effizient (ΦEXT=71 %) ist der Energietransfer von den 28 photoangeregten Zinkporphyrin-Einheiten auf die zentrale freie Porphyrinbase in einer großen, sternenförmigen dendritischen Multiporphyrin-An…
The temporal evolution of an anisotropic reflection grating produced in a holographic polymer-dispersed liquid crystal film is investigated. We find that this type of grating is preceded in time by an isotropic concentration grating, and that the development of the anisotropic grating can be delayed until several seco…
We present results of first-principles calculations of the elastic constants and other mechanical properties of Ti3SiC2. This knowledge is important from a technological point of view, since the material shows promising characteristics, such as a combined metallic and ceramic appearance. We also confirm a recent exper…
The synthesis, characterization, and two-dimensional second-order nonlinear optical (NLO) response of a dipolar NiII donor- acceptor Schiff base complex and the related ligand are reported. Electric-field-induced second-harmonic generation and harmonic light (hyper-Rayleigh) scattering techniques, in combination with…
N-Acyl amino acids RCONH(CH2)nCOOR1 represent a new family of organogelators that can be obtained in a combinatorial approach from libraries of activated acids and amino acids. The amounts required for gel formation (see picture) in solvents such as DMF are less than 1 mg mL−1 and the gels formed are very stable. n=5,…
Very different types of straight and long multiwalled carbon nanotubes, ranging from semi-crystalline to highly crystalline, are obtained using a floating reactant method, by merely changing the flow rate of the carrier gas. Graphitization behaviors of these nanotubes are studied comparatively in terms of their micros…
Aligned carbon nitride (C–N) nanobells in polymer form, prepared by microwave plasma-assisted chemical vapor deposition, were used as hydrogen adsorbent. A hydrogen storage capacity up to 8 wt % was achieved reproducibly under ambient pressure and at temperature of 300 °C. The high hydrogen storage capacity under the…
We have observed the growth mode transition from two-dimensional (2D) layer-by-layer to step-flow in the earliest stage growth of heteroepitaxial SrRuO3 thin films on TiO2-terminated (001) SrTiO3 substrates by in situ high pressure reflective high energy electron diffraction (RHEED) and atomic-force microscopy. There…
Electrical resistivity (ρ) and thermoelectric power (S) were measured for NaxCo2O4 samples with various Na contents (x). A highly precise control of Na nonstoichiometry was facilitated by optimizing the synthesis procedure. With increasing x, the absolute value of ρ monotonically decreased, while the value of S increa…
π-Electronic conjugation is not necessary to facilitate long-range energy migration and transfer: A rapid (kENT=1.04×109 s−1) and efficient (ΦEXT=71 %) energy transfer from the 28 photoexcited zinc porphyrin units to the focal free-base porphyrin unit occurs in a large, star-shaped dendritic multiporphyrin array in wh…
Crystallizing walls: Following the templated solid-state secondary crystallization of an amorphous mesoporous material the amorphous pore walls of the mesoporous precursor are partially reorganized into a crystalline material, the zeolite ZSM-5, as indicated by the dark-field transmission electron micrograph image sho…
The significance of thermal fluctuations on nucleation in structural first-order phase transitions has been examined. The prototype case of martensitic transitions has been experimentally investigated by means of acoustic emission techniques. We propose a model based on the mean first-passage time to account for the e…
The thermal properties of bulk copper are investigated by performing ab initio DFT and DFPT calculations and using the quasiharmonic approximation for the free energy. Using both the LDA and the GGA for the exchange-correlation potential, we compute the temperature dependence of the lattice constant, coefficient of th…
We present results of a numerical mean field treatment of interacting spins and carriers in doped diluted magnetic semiconductors, which takes into account the positional disorder present in these alloy systems. Disorder is found to enhance the ferromagnetic transition temperature significantly for metallic densities…
We have studied the evolution of the magnetic, electronic, and structural properties of annealed epilayers of Ga1−xMnxAs grown by low temperature molecular beam epitaxy. Annealing at the optimal temperature of 250 °C for less than 2 h significantly enhances the conductivity and ferromagnetism, but continuing the annea…
In order to utilize the unique properties of carbon nanotubes in microelectronic devices, it is necessary to develop a technology which enables high yield, uniform, and preferential growth of perfectly aligned nanotubes. We demonstrate such a technology by using plasma-enhanced chemical-vapor deposition (PECVD) of car…
Ultrananocrystalline diamond (UNCD) films with up to 0.2% total nitrogen content were synthesized by a microwave plasma-enhanced chemical-vapor-deposition method using a CH4(1%)/Ar gas mixture and 1%–20% nitrogen gas added. The electrical conductivity of the nitrogen-doped UNCD films increases by five orders of magnit…
Sputter deposition of ZnO on Si specimens with surface metallization of copper was performed using a radio frequency sputter deposition technique using various deposition temperatures and ratio of O2/Ar. Copper metallization was carried out using an ion beam sputter deposition technique at different temperatures. Spec…
A series of new compounds has been synthesized by insertion of alkali or alkaline earth-metals in chalcopyrite, CuFeS2. Their crystal structures vary from layered arrangements of tetrahedra in a trigonal (LiCuFeS2, NaCuFeS2) or a tetragonal symmetry (KCuFeS2, CsCuFeS2), to three-dimensional cubic framework (Ba6Cu12Fe1…