Materials Literature
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C 60 molecules were chemically coupled in the pores of porous Si through a coupling agent and then coated with a layer of Si, and followed by N2 annealing. X-ray diffraction results indicate that the fabricated samples contain β-SiC particles which may exist in the pores, in addition to Si, SiO2, and graphite. The pho…
Neodymium-doped polyimide waveguides were studied for optical amplifier applications. Photoluminescence at 890 nm, 1.06 μm, and 1.33 μm from neodymium ions in the polymer matrix was observed. Optical gain of about 8 dB was measured at 1.06 μm in a 5-cm-long multimode channel waveguide. Phase separation was observed in…
Theoretical investigations (density-functional tight binding) about the changes of the properties of single-wall carbon nanotubes (SWNTs) by fluorination are reported. It is shown that a sidewall functionalization of SWNTs may lead to tubes with a wide variety of electronic properties, ranging from insulating over sem…
The local atomic order of semiconducting liquid GeTe is studied using first-principles molecular-dynamics simulations. Our work points out a high degree of alternating chemical order in the liquid and demonstrates the presence of a Peierls distortion close above the melting temperature. This distortion, absent in the…
Rare-earth intermetallic compounds (Tb1−xGdx)Al2, have been successfully fabricated and characterized. Large magnetic entropy change, ΔSM, was observed in these alloys. The maximum −ΔSM(=14.3 J/kg K) is achieved in the TbAl2 alloy at its Curie temperature, TC=105 K, with a 5 T magnetic field change. It is shown that t…
Ultrafast spin dynamics in ferromagnetic half-metallic compound Sr2FeMoO6 is investigated by pump-probe measurements of the magneto-optical Kerr effect. The half-metallic nature of this material gives rise to anomalous thermal insulation between spins and electrons and allows us to pursue the spin dynamics from a few…
The dynamic susceptibility study of photoinduced magnetism in a molecule-based magnet, ${\mathrm{K}}_{1\ensuremath{-}2x}{\mathrm{Co}}_{1+x}[\mathrm{Fe}(\mathrm{CN}{)}_{6}]\ifmmode \dot{}\else \.{}\fi{}y{\mathrm{H}}_{2}\mathrm{O}$ $(0.2\ensuremath{\le}x\ensuremath{\le}0.4,y\ensuremath{\sim}5)$, is reported. Upon excita…
In weakest link models the failure of a single microscopic element of a brittle material causes the failure of an entire macroscopic specimen, just as a chain fails if one link fails. Pristine samples of glass, such as optical communications fiber, approach their ideal strength, and their brittle tensile failure has b…
We study by numerical simulations the scattering of $s$-polarized light from a rough dielectric film deposited on the planar surface of a semi-infinite perfect conductor. The dielectric film is allowed to be either active or passive, situations that we model by assigning negative and positive values, respectively, to…
An eight-potential-well order-disorder ferroelectric model was presented and the phase transition was studied under the mean-field approximation. It was shown that the two-body interactions are able to account for the first-order and the second order phase transitions. With increasing the random fields in the system,…
We present a model to find analytically the electronic states in self-assembled quantum dots with a truncated spherical cap (`lens') geometry. A conformal analytical image is designed to map the quantum dot boundary into a dot with semi-spherical shape. The Hamiltonian for a carrier confined in the quantum lens is cor…
Holographic techniques significantly extend the capabilities of laser tweezing, making possible extended trapping patterns for manipulating large numbers of particles and volumes of soft matter. We describe practical methods for creating arbitrary configurations of optical tweezers using computer-generated diffractive…
We study a recently proposed nonlinear evolution equation describing the collective step meander on a vicinal surface subject to the Bales-Zangwill growth instability [O. Pierre-Louis et al., Phys. Rev. Lett. (80), 4221 (1998)]. A careful numerical analysis shows that the dynamically selected step profile consists of…
The decay properties of the one-particle Green function in real space and imaginary time are systematically studied for solids. I present an analytic solution for the homogeneous electron gas at finite and at zero temperature as well as asymptotic formulas for real metals and insulators that allow an analytic treatmen…
We use an atom-atom potential between carbon atoms to obtain an interaction potential between nanotubes (assumed rigid), thereby calculating the cohesive energy of a bunch of nanotubes in hexagonal two dimensional packing. The model proposed is quite similar to our earlier work on fullerenes and organic molecular crys…
Transparent films of CuScO2+x have been prepared which show p-type electrical conductivity. The temperature dependence of the conductivity indicates semiconducting behavior with an apparent room temperature activation energy of 0.11 eV. The highest room temperature conductivity observed was 30 S cm−1. Films 110 nm thi…
Single-walled carbon nanotubes show linear elasticity under hydrostatic pressure up to 1.5 GPa at room temperature. The volume compressibility, measured by in situ synchrotron x-ray diffraction, has been determined to be 0.024 GPa (-1). Theoretical calculations suggest that single-walled carbon nanotubes are polygoniz…
The oxygen-binding behaviors of five cobalt(II) meso -tetrakis(substituted phenyl)porphyrin complexes [CoTPP, CoT(2-Cl)PP, CoT(4-Cl)PP, CoT(4-MeO)PP, and CoT(2,4-2MeO)PP] in chloroform solution were investigated using a UV−visible spectrophotometer. It shows that the substituents and the fifth ligand in the cobalt(II)…
Unusually rigid π-stacked porphyrin−spacer−quinone systems have been synthesized using an approach that enables extensive control over the nature of electronic interactions between donor, aromatic spacer, and acceptor. This new class of porphyrin-based structures is distinct from related assemblies designed to probe e…
Bis-benzamidines were studied as linkers for the formation of gold nanoparticle assemblies on planar gold surfaces modified with ω-mercaptohexadecanoic acid. In situ ellipsometry, external reflection Fourier transform spectroscopy, and atomic force microscopy showed that the packing density and order of the bis-benzam…