Materials Literature
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The saturation magnetic moment Ms and the Curie temperature TC of the half-metal-type Co2CrGa Heusler alloy have been investigated. The value of Ms at 4.2K for the L21-type Co2CrGa alloy is 3.01μB∕f.u., in agreement with the generalized Slater-Pauling line and the theoretical calculation. The Curie temperature TC and…
Abstract Much research related to the use of natural fibers in polymeric matrix composites has been developed. The presence of OH groups in the chemical components of the natural fibers generates an important hydrophylic tendency that produces adhesion lacks with hydrophobic polymeric matrices. In this work natural f…
Single ZnO nanorods with diameters of ∼130nm were grown on Au-coated Al2O3 substrates by catalyst-driven molecular beam epitaxy. Individual nanorods were removed from the substrate and placed between Ohmic contact pads and the current–voltage characteristics measured as a function of temperature and gas ambient. In th…
We report photoconductivity at infrared wavelengths, 975–1300nm, from a polymer∕nanocrystal quantum dot composite. Biased films of the conjugated polymer poly[2-methoxy-5-(2′-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) sensitized with PbS nanocrystals (∼5nm diameter) demonstrate photocurrent at wavelengths beyond th…
The dielectric response function of single-walled carbon nanotubes is calculated within tight-binding models with different levels of complexity. First, the effects of the orbital basis set of the model, the orbitals overlap, and the structural optimization on the electronic band structure and the dielectric function…
Self-assembled BaTiO3–CoFe2O4 complex oxide nanostructures have been synthesized by pulsed laser deposition. A single ceramic target with a molar ratio of 0.62BaTiO3–0.38CoFe2O4 was used. Spinel CoFe2O4 and perovskite BaTiO3 phases spontaneously separated during heteroepitaxial growth on a single-crystal SrTiO3(001) s…
Thin films of Ti1-xCoxO2 (x=0 and 0.03) have been prepared on sapphire substrates by spin-on technique starting from metalorganic precursors. When heat treated in air at 550 and 700 C respectively, these films present pure anatase and rutile structures as shown both by X-ray diffraction and Raman spectroscopy. Optical…
We study a minimal stochastic model of step bunching during growth on a one-dimensional vicinal surface. The formation of bunches is controlled by the preferential attachment of atoms to descending steps (inverse Ehrlich-Schwoebel effect) and the ratio $d$ of the attachment rate to the terrace diffusion coefficient. F…
The relation between tunnel magnetoresistance (TMR) and spin polarization is explored for GaMnAs∕GaAlAs∕GaMnAs structures where the carriers experience strong spin–orbit interactions. TMR is calculated using the Landauer approach. The materials are described in the 6 band k∙p model which includes spin–orbit interactio…
We have carried out time-domain electrostatic force spectroscopy on two different ion-conducting glasses using an atomic force microscope. We compare the electrostatic force spectroscopic data obtained at different temperatures with macroscopic electrical data of the glasses. The overall consistency of the data shows…
Thin films of thermochromic VO2, V1−xWxO2 and V1−x−yWxTiyO2 (x=0.014, and y=0.12) were synthesized onto quartz substrates using a reactive pulsed laser deposition technique. The films were then characterized by x-ray diffraction and x-ray photoelectron spectroscopy. The W and Ti dopant effects on the semiconductor-to-…
A thermodynamic analysis has been carried out to investigate the role of dislocations in ferroelectric materials. Due to the coupling of the stress field of the dislocation and the polarization, there is a drastic variation in the polarization near the dislocation. These polarization gradients result in strong depolar…
We propose an efficient approach within the density-functional theory to determine the phonon structure of infinite solids under finite electric fields. We apply this approach to technological SrTiO$_3$, predicting many unusual properties--including a giant frequency shift, anomalous piezoelectric response, as well as…
The electronic, structural and vibrational properties of small carbon interstitial and antisite clusters are investigated by ab initio methods in 3C and 4H-SiC. The defects possess sizable dissociation energies and may be formed via condensation of carbon interstitials, e.g. generated in the course of ion implantation…
The pi-stacking of oxidized thiophene oligomers is investigated using ab-initio quantum chemistry methods. Dimers of singly-charged oligothiophenes are found to be unstable in the gas phase, but can be stabilized as bound dications in the singlet state by a polarizable solvent such as acetonitrile. Our calculations pr…
Lattice variations and bonding characteristics in rutile TiO2 nanocrystals were examined by x-ray diffraction and x-ray photoelectron spectroscopy. With a reduction in the physical dimensions, rutile TiO2 nanocrystals show a linear lattice expansion and an anomalous covalency enhancement in apparent contradiction to t…
We have investigated carrier transport in a crystalline oxide semiconductor InGaO3(ZnO)5 using single-crystalline thin films. When carrier concentration is less than 2×1018cm−3, logarithm of electrical conductivity decreases in proportion to T−1∕4 and room-temperature Hall mobility was as low as ∼1cm2(Vs)−1. When carr…
Abstract Summary: A feasible method for the preparation of antimicrobial ultrafine fibers with silver nanoparticles was developed by direct electrospinning of a cellulose acetate (CA) solution with small amounts of silver nitrate followed by photoreduction. Silver nanoparticles in ultrafine CA fibers were stabilized b…
Unlike La0.7Ca0.3CoO2.97, Pr0.7Ca0.3CoO3 and Nd0.7Ca0.3CoO2.95 do not show distinct ferromagnetic transitions, but instead they exhibit very low magnetic moments down to 50 K. A detail study of magnetic properties of Pr0.7Ca0.3CoO3 and Nd0.7Ca0.3CoO2.95 shows that the materials are inhomogeneous, exhibiting properties…
We studied the exchange coupling and decoupling occurring in a nanocomposite spin system based on a 3D Heisenberg model by means of Monte Carlo numerical computation simulation. Different from conventional micromagnetism approach which usually adopts finite elements method to compute, in a top-down way, the magnetic p…