Materials Literature
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A combination of SiO vapor-deposition and direct wafer bonding is used to produce buried layers of SiOx. By thermally induced decomposition, Si nanocrystals embedded in SiO2 are obtained. Decomposition of the silicon suboxide is observed by studying the Si-O-Si stretching vibration in the infrared range. This phase se…
In this letter, we report on the influence of lead content on thin-film ferroelectric properties of lead niobium zirconate titanate. These films were prepared by the sol-gel technique and deposited on (La,Sr)CoO3 electrodes. It was determined that 7% excess lead in the sol was required to obtain nominally stoichiometr…
We have observed the ferroelectricity at room temperature in YMnO3 thin films prepared via solution. Precursor films of YMnO3 on Pt/sapphire or Y2O3/Si substrates were heat treated in vacuum or in air for controlling the crystallinity. X-ray diffraction measurements indicated that each film was a single phase of hexag…
Full chemical control of magnetic anisotropy in hexairon(III) rings can be achieved by varying the size of the guest alkali metal ion. Dramatically different anisotropies characterize the Li(I) and Na(I) complexes of [Fe(6)(OMe)(12)(L)(6)] (L=1,3-propanedione derivatives; a schematic representation of the Li(I) comple…
We positioned semiconducting multiwalled carbon nanotube, using an atomic force microscope, between two gold electrodes at SiO2 surface. Transport measurements exhibit single-electron effects with a charging energy of 24 K. Using the Coulomb staircase model, the capacitances and resistances between the tube and the el…
Mesoporous thin films based on neutral, porphyrin-bridged, tetrarhenium "square" compounds (metallacycles) display permeability to molecules smaller than the dimensions of an individual square cavity, but blocking behavior toward larger species (see schematic representation). The characteristic permeant size cutoff ca…
<div class="htmlview paragraph">Advanced thermoelectric microdevices integrated into thermal management packages and low power, electrical power source systems are of interest for a variety of space and terrestrial applications. By making use of macroscopic film technology, microgenerators operating across relat…
The dielectric susceptibility, = ´ - i ´´ , of nominally pure strontium titanate is measured between 4 and 70 K as a function of an external bias field. Static scaling analysis of the susceptibility reveals a very good scaling behaviour with a quasi-critical exponent a = /( - 1) = 2.00 ± 0.02 extracted consistently fr…
The ferroelectric SrBi2Ta2O9 (SBT) and YMnO3 buffer layers for the metal/ferroelectric/ insulator/semiconductor (MFIS) structure were deposited using pulsed-laser ablation and metalorganic chemical vapor deposition, respectively. Memory windows of the MFIS structure were in the range of 0.3–1.5 V when the gate voltage…
We study two expanded phases of Ge crystals, type-I (Ge 46 ) and type-II (Ge 136 ) clathrates, using an ab initio density functional planewave pseudopotential method. The equation of state, electronic structure and vibrational modes have been determined. These expanded Ge phases are shown to be only slightly higher in…
Building blocks for conducting polymers or NLO materials are the linear, unsaturated carbon chain bridged manganese complexes 1(n+) (n=0-2). All oxidation states were investigated spectroscopically and by X-ray structure determinations. The analytical data confirm a communication of the electrons over the C(4) chain-a…
Chromium dioxide (CrO2) films have been grown epitaxially on (100) TiO2 substrates using chemical vapor deposition and their magnetic properties were studied as a function of film thickness (500 Å–1.2 μm). Because of the lattice mismatch with the substrate, the films are strained as evidenced by x-ray diffraction meas…
Single-walled carbon nanotubes are synthesized by chemical vapor deposition of methane at controlled locations on a substrate using patterned catalytic islands. The combined synthesis and microfabrication technique presented here allows a large number of ohmically contacted nanotube devices with controllable length to…
<div class="section abstract"><div class="htmlview paragraph">The daily variation in air temperature is large compared with the temperature changes a short distance below the surface of the ground. In theory, a heat engine can be arranged to produce electricity from this temperature difference. In practice…
We have performed an angle-resolved photoemission study on untwinned PrBa$_2$Cu$_3$O$_7$, which has low resistivity but does not show superconductivity. We have observed a dispersive feature with a band maximum around ($π$/2,$π$/2), indicating that this band is derived from the undoped CuO$_2$ plane. We have observed…
We have studied the chemical potential shift in La$_{2-x}$Sr$_x$NiO$_4$ and the charge ordering transition in La$_{1.67}$Sr$_{0.33}$NiO$_4$ by photoemission spectroscopy. The result shows a large ($\sim$ 1 eV/hole) downward shift of the chemical potential with hole doping in the high-doping regime ($δ\gtrsim$ 0.33) wh…
The dielectric response of many materials exhibits universal behavior in the form of a power law frequency dependence of the ac conductivity. This response is seen in all types of structures both crystalline and amorphous and for all types of polarizing species including dipoles and ions. Here I demonstrate that for i…
Abstract Disordered or ‘glassy’ materials are of significant technological value. Their structure can be investigated by diffraction (neutron, X-ray, electron) techniques. When the available volume is very small (eg thin films, non-homogeneous structures) only electrons are suitable. Cockayne and McKenzie developed a…
In narrow-band conductors a weakly screened Coulomb interelectron repulsion can supress narrow-band electrons’ hopping, resulting in formation of a “frozen” electron phase which differs principally from any known macroscopic self-localized electron state including the Wigner crystal. In a zero-band-width limit the “fr…
A discontinuity wall in smectic A liquid crystals was discussed in M. Kléman, Points, Lines and Walls in Liquid Crystals, Magnetic Systems and Various Ordered Media (J. Wiley. Chichester 1983). Possible solutions describing a twist disclination which terminates the discontinuity wall in an infinite smectic A liquid cr…