Materials Literature
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We present an exact expression for the frequency-dependent Kohn-Sham exact-exchange (EXX) kernel for periodic insulators, which can be employed for the calculation of electronic response properties within time-dependent (TD) density-functional theory. It is shown that the EXX kernel has a long-wavelength divergence be…
In1-xMnxAs diluted magnetic semiconductor (DMS) thin films have been grown using metalorganic vapor phase epitaxy (MOVPE). Tricarbonyl(methylcyclopentadienyl)manganese was used as the Mn source. Nominally single-phase, epitaxial films were achieved with Mn content as high as x=0.14 using growth temperatures Tg>475 C.…
The effect of grain size, easy magnetization axis and anisotropy constant distributions in the irreversible magnetic behavior of granular alloys is considered. A simulated granular alloy is used to provide a realistic grain structure for the Monte Carlo simulation of the ZFC-FC curves. The effect of annealing and exte…
The intermetallic compound SmMn$_2$Ge$_2$, displaying multiple magnetic phase transitions, is being investigated in detail for its magnetization behavior near the 145 K first order ferromagnetic to antiferromagnetic transition occuring on cooling, in particular for thermomagnetic history effects in the magnetization d…
The initial stages of growth of Ge and Si on the Ge(001) surface are studied and compared to growth on the Si(001) surface. Metastable rows of diluted ad-dimers exist on both surfaces as intermediate stages of epitaxial growth. Unexpectedly, for Ge(001) these rows are found exclusively in the <310> directions, whereas…
Electron-phonon scattering is studied within an effective-mass theory. A continuum model for acoustic phonons is introduced and electron-phonon interaction due to modification of band structure is derived as well as a normal deformation potential. In a metallic nanotube, the deformation potential does not participate…
Field emission energy distribution (FEED) has been measured for undergate-type triode carbon nanotube (CNT) field emitters where the gate electrodes are located underneath the cathode electrodes. The diode-type emission for these CNT emitters was found to follow the Fowler–Nordheim relation, whereas the triode-type em…
A model is proposed for the recent gate voltage VG modulation experiment of a kink-shaped carbon nanotube (NT) Schottky diode [Z. Yao, H. Postma, L. Balents, and C. Dekker, Nature (London) 402, 273 (1999)]. Since larger VG increases both the forward and the reverse turn-on voltages of the diode, we show that: (1) the…
Nanoporous-carbon (NPC) films are grown using physical processes such as low-power pulsed-laser deposition with attenuation of the ablated carbon species kinetic energy attained by using an inert background gas. With room-temperature growth and negligible residual stress, NPC can coat nearly any substrate to any desir…
Room-temperature micro-Raman scattering and temperature-dependent dielectric measurements were carried out on sol-gel-derived ferroelectric Pb1−xLaxTi1−x/4O3 (PLT x=0.05–0.30) thin films. Results indicate that the crystal structure and the electrical properties of PLT films were strongly influenced by the La contents.…
Two novel disc-shaped compounds (1, 2) with strong intramolecular hydrogen bonds were prepared and characterized; compound 2 showed a thermotropic mesophase as characterised by polarized optical microscopy, DSC and X-ray diffraction studies.
We performed piezoelectric force microscopy (PFM) measurements on arrays of poled nanosize domains in 150 nm thick 〈111〉 preferentially oriented Pb(Zr0.4Ti0.6)O3 films grown by chemical solution deposition. Each domain of arrays was characterized by dot, egg, and ring structures depending on the pulse width ranging fr…
To study the ion dynamics in an amorphous mixed alkali system, frequency-dependent conductivities of 0.3[xLi2O·(1 − x)Na2O]·0.7B2O3 glasses have been measured by impedance spectroscopy in a wide temperature range. The conductivities show a transition from their dc values into a dispersive regime where they increase co…
The phase transition behaviour and equilibrium phase relations in the fast-ion conductor system Na3PO4–Na2SO4 have been investigated using a combination of insitu XRD, neutron powder diffraction, and molecular dynamics simulation. The simulations predict that tetrahedrally-coordinated Na is relatively tightly bound wi…
Ground state ring opening/closing reactions of 1,3,3-trimethylspiro[indoline-2,3′-naphtho[2,1-b][1,4]oxazine] have been studied using DFT calculations. An extensive description of the ground state ring opening/closing and isomerization processes undergone by the eight open forms is proposed. The pathways for ring open…
With the help of spectroscopic data, we have characterized several isolated entities resulting from the reaction of lanthanide ions with a hexadentate Schiff base ligand obtained by reacting o-vanillin and 1,2-diaminoethane. This H2L ligand possesses two coordination sites, an N2O2 inner site and an O2O2 outer site. I…
We have used the lattice-mismatch epitaxial strain, induced by the constraint of epitaxy, to tune the metal–insulator (M–I) transition temperature of NdNiO3 films grown on Si(100) substrate. Films were integrated with the Si(100) substrate using several combinations of thin buffer layers. A systematic variation in the…
The dissipative particle dynamics technique has been used to study grafted polymer chains under shear in solvents of different quality. We show that width of the grafted polymer chains decreases with increasing shear rate for an adsorbed monolayer and bilayer in an athermal solvent but that the layer shrinks in a poor…
Bi-excess SrBi2Ta2O9 (SBT) thin films on Pt/Ti/SiO2/Si substrate were prepared by pulsed laser deposition technique. The SBT structure was characterized by x-ray diffraction studies. The ferroelectric properties were confirmed by P–E hysteresis loops at different applied electric fields. The dielectric constant and th…
ZnSe nanoparticles were synthesized by reacting vapors of (CH3)2Zn:N(C2H5)3 and H2Se, diluted in H2, in an opposed flow reactor operating at room temperature and 120 Torr. The particles were collected as random aggregates on silicon substrates and transmission electron microscopy (TEM) grids placed downstream of the r…