Materials Literature
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Taking into account the bilinear coupling between the tunneling protons and the displacements of the electron shells of the surrounding ${\mathrm{PO}}_{4}$ groups, we present a new model of hydrogen-bonded ferroelectrics. The model is an extension of both the tunneling model and the nonlinear polarizability model and…
We have made ferroelectric memory capacitors by depositing a SrBi2Ta2O9 thin film on a Si substrate separated by an ultrathin buffer layer of silicon nitride film. The hysteresis in the capacitance–voltage curves suggests a sizable memory window of 2 V with a programming voltage swing of ±7 V. The switching time is es…
Using first principles variable cell shape molecular dynamics, we predict a new structure for silica. This structure results from annealing $\ensuremath{\alpha}$-quartz at pressures near a major phonon instability. The new phase is obtained by rotations of ${\mathrm{SiO}}_{4}$ tetrahedra producing edge-sharing ${\math…
We extended the sensitivity of fluorescence polarization anisotropy measurements to the single molecule level by studying the polarization response of single fluorophores rapidly rotating in liquid. Comparison with a simple model calculation allows us to obtain information on the hindered motion as well as on the rota…
Computer simulations suggest that ultrathin metal wires should develop exotic, non-crystalline stable atomic structures, once their diameter decreases below a critical size of the order of a few atomic spacings. The new structures, whose details depend upon the material and the wire thickness, may be dominated by icos…
Photocrystallization of amorphous selenium (a-Se) films under illumination by polarized light with 632.8 or 647.1 nm wavelength has been studied by Raman spectroscopy. Preferential orientation of trigonal crystalline, selenium (t-Se) obtained as a result of photocrystallization has been observed, threefold c axis of t…
The magnetoresistance (MR) associated with domain boundaries has been investigated in microfabricated bcc Fe (0.65 to 20 $μ$m linewidth) wires with controlled stripe domains. Domain configurations have been characterized using magnetic force microscopy. MR measurements as a function of field angle, temperature and dom…
The effect of domain walls on electron transport has been investigated in microfabricated Fe wires (0.65 to 20 $μm$ linewidths) with controlled stripe domains. Magnetoresistance (MR) measurements as a function of domain wall density, temperature and the angle of the applied field are used to determine the low field MR…
Long-range magnetic ordering in R_2 Ba Ni O_5 (R=magnetic rare earth) quasi-1-dimensional mixed-spin antiferromagnets is described by a simple mean-field model that is based on the intrinsic staggered magnetization function of isolated Haldane spin chains for the Ni-subsystem, and single-ion magnetization functions fo…
Linear-chain nickelates with the composition (Nd_x Y_{1-x})_2 Ba Ni O_5 (x=1, x=0.75, x=0.5, and x=0.25) are studied in a series of neutron scattering experiments. Powder diffraction is used to determine the temperature dependence of the magnetic structure in all four systems. Single-crystal inelastic neutron scatteri…
Numerical simulations were performed to predict the performance of microwave plasma reactors with various reactor geometries. The simulations include the calculation of the electric field distribution using the finite integration theory and the determination of the plasma density distribution based on a breakdown fiel…
The conditions for the self-organized formation of ordered hexagonal structures in anodic alumina were investigated for both oxalic and sulfuric acid as an electrolyte. Highly ordered pore arrays were obtained for oxidation in both acids. The size of the ordered domains depends strongly on the anodizing voltage. This…
The heat capacities of (NH4)2PbCl6 and (ND4)2PbCl6 were measured at temperatures between 13 K and 300 K. A gradual phase transition was found at 77.8±0.3 K for (NH4)2PbCl6 with an associated transition entropy of 3.0 J K−1 mol−1. The transition temperature shifted to 81.0±0.3 K in (ND4)2PbCl6. A sharp first order tran…
We report an experimental result of the thermally induced morphological transition from lamellar to gyroid phase in a binary blend of polystyrene-block-polyisoprene (SI) diblock copolymers. Two SI copolymers employed in this study have almost the same molecular weights but different volume fractions of polystyrene (PS…
A theoretical description of the six-wave mixing spectroscopy is presented. The six-wave mixing spectroscopic signals in time and frequency domains are expressed in terms of the fifth-order nonlinear response functions. Particularly, the resonant coherent hyper-Raman scattering with wave vector of 4k1−k2 and frequency…
We report on a deuteron NMR study of quadrupolar splittings and spin-lattice relaxation times T1Q and T1Z as a function of temperature and at two different Larmor frequencies in the columnar phase of hexakis(n-hexyloxy)triphenylene (HAT6). The additive potential method is used to model the quadrupolar splittings, from…
Electrical property derivative expressions are presented for the nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties. For CF4 and SF6, as opposed to HF and CH4, a term that is quadratic in the vibrational anharmonicity (and not previously evaluated for…
The absorption band (band A) due to the aggregate effect of nanoscale silver particles in silver sol prepared by a modification of the procedure of the original silver sol used in surface-enhanced Raman scattering (SERS) was observed near 435 nm without the presence of any foreign molecules. This band eventually stabi…
We study the magnetic circular dichroism (MCD) of exciton states near the band edge of CdSe nanocrystallites (quantum dots). The experiment probes the difference between left and right circularly polarized transitions in the presence of an external magnetic field. Analysis of the MCD signal determines the sign and mag…
The gas-phase hydrolysis of TiCl 4 has been studied with several laboratory reactors. Unexpectedly, the reaction is clearly split in two steps, an almost instantaneous partial hydrolysis which produces 2 mol of HCl/mol of TiCl 4 together with a salt, identified as Ti(OH) 2 Cl 2 . The latter forms a very fine dust whic…