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The morphology and microstructure of all-epitaxial (Bi,La)4Ti3O12/Pb(Zr0.4Ti0.6)O3/(Bi,La)4Ti3O12 (BLT/PZT/BLT) tri-layered ferroelectric films, grown on (011)-oriented SrTiO3 (STO) substrates by pulsed laser deposition, are investigated by transmission electron microscopy (TEM). X-ray diffraction and electron diffraction patterns demonstrate that the epitaxial relationship between BLT, PZT and STO can be described as;. Cross-sectional TEM images show that the growth rate of BLT is nearly two times that for PZT at the same growth conditions, and 90° ferroelectric domain boundaries lying on {110} planes are observed in the PZT layer. The 90° ferroelectric domains in the PZT layer extend up to 600 nm in length. Long domains penetrate into the neighboring columnar grain through the columnar grain boundary, whereas others are nucleating at the columnar grain boundaries. The roughness of the PZT/BLT interfaces appears to depend on the viewing direction, i.e., it is different for different azimuthal directions. Planar TEM investigations show that the grains in the top BLT layer have a rod-like morphology, preferentially growing along the [110]BLT direction. The grain width is rather constant at about 90 nm, whereas the length of the grains varies from 150 to 625 nm. These morphological details point to the important role the crystal anisotropy of BLT plays for the growth and structure of the tri-layered films. [ABSTRACT FROM AUTHOR]

Compositionally graded (Ba1-xSrx)TiO3 (BST) thin films, with x decreasing from 0.25 to 0.0, were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by pulsed-laser ablation at 600 °C and under ambient oxygen pressures ranging from 50 to 400 mTorr. The influence of the ambient gas pressure on the preferred orientation, microstructures, and dielectric properties of compositionally graded BST films was investigated by X-ray diffraction, scanning electron microscopy, and dielectric frequency spectra, respectively. As the ambient oxygen pressure was increased, the preferred orientation evolved in the order: (100)+(110)?(110)+(111)? random orientation, and the surface roughness of the graded BST films also increased. The graded BST films deposited at high ambient oxygen pressures (300~400 mTorr) exhibited a grainy structure with polycrystalline grains throughout the film thickness, whereas the graded films deposited at low ambient oxygen pressures (50~200 mTorr) possessed a columnar structure. The evolution of the microstructure was ascribed to the different physical and chemical properties of the species that were incident onto the substrates at the various oxygen pressures. The dielectric properties of the graded BST films were dependent upon the ambient oxygen pressures. The graded BST films deposited at 200 mTorr exhibited the highest dielectric constant. [ABSTRACT FROM AUTHOR]

Rutile TiO2 nanorods have been successfully prepared by a sonochemical method. The microstructures of TiO2 nanorods were investigated in detail by transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HREM). Probable mechanisms for the sonochemical formation of TiO2 nanorods are proposed. [ABSTRACT FROM AUTHOR]

The surfactants of hexadecyl-pyridinium chloride and dodecylbenzenesulfonic acid are recovered from the aqueous systems by solvent sublation into organic solvent. The mathematical model of surfactants by solvent sublation is built and many parameters are analyzed in details. The simulation of the mathematical and experimental data is completed with perfect results. [Copyright &y& Elsevier]

High permittivity Bi24Fe2O39 (BFO) thin films have been deposited on platinized silicon substrates by a low temperature process combining rf magnetron sputtering at room temperature and postdeposition annealing at 450 °C. A nearly pure tetragonal crystal structure with highly (201)-preferred orientation, determined by x-ray diffraction, was formed in the BFO thin film. The BFO film not only exhibits high dielectric permittivity ([variant_greek_epsilon]r=113) and relatively low loss tangent (tan δ=0.012), but also shows a fairly small quadratic voltage coefficient of capacitance (α∼800 ppm/V2) and a small temperature coefficient of capacitance (αT∼790 ppm/°C). Moreover, the leakage current density, obeying the Fowler-Nordheim tunneling mechanism, remains at a reasonably low level with the increase in applied electric field (J∼10-6-10-4 A/cm2 under E=400 kV/cm). These attractive dielectric and electrical properties make the low temperature processed Bi24Fe2O39 thin film a promising candidate for high-k dielectric applications in silicon-based integrated circuits. [ABSTRACT FROM AUTHOR]

In this paper, the micro-structure and laser damage threshold of nano-ZrO2 thin films were investigated. High-purity nano-ZrO2 particles as the coating materials of samples were prepared by electron beam evaporation. The crystallitic size and surfaces’ roughness of the samples were analyzed. The laser damage threshold test used a 1064 nm, 10 ns, 3 Hz Nd:YAG laser. The experimental results showed that oxygen partial pressure has an important influence on the micro-structure of nano-ZrO2 films, and also we found that the laser damage threshold was dependent on the micro-structure. [ABSTRACT FROM AUTHOR]

Self-organized (Ba0.7,Sr0.3) TiO3 (BST) thin film nanocomposites with spherical inclusions have been fabricated. The composite structures were built up from initial amorphous BST films, thanks to an adequate thermal treatment. Microstructural and electrical analyses are reported as a function of crystallization ratio q. Our experimental results agree with recently developed models of composite materials. The main conclusion of the study is that high dielectric performances can be obtained with a half-crystallized material. For a 630 °C annealing temperature (q-ratio equal to 0.47), Vendik commutation quality factor reaches 1500, which is two times greater than a fully crystallized sample annealed at 700 °C. [ABSTRACT FROM AUTHOR]

(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMNT) (with x=0.1) thin films were prepared on Pt-coated silicon substrates by radio-frequency magnetron sputtering and postdeposition annealing method. A well-crystallized pyrochlore phase structure, which started to nucleate and grow at 450–500 °C, was formed in the PMNT thin films. These pyrochlore-structured PMNT thin films show ultralow dielectric losses with a typical loss tangent as low as 0.001, accompanied by a relatively high dielectric constant ([variant_greek_epsilon]r=176). Such an extremely low dielectric loss, having never been obtained in thin films of perovskite PMNT, is probably ascribed to the specific structural feature of pyrochlore phase, chemically different from its perovskite counterpart, and ascribed to the avoidance of the polar domain-related losses. [ABSTRACT FROM AUTHOR]

Thickness dependence of structural and electrical properties of multiferroic Mn-doped BiFeO3 (BFMO) thin films, grown on SrTiO3 (001) substrates with a bottom electrode of SrRuO3, was investigated. Very good ferroelectric properties were obtained in the thicker BFMO films with a typical remanent polarization of ∼65 μC/cm2, while ferroelectric polarization switching was too difficult to detect using a conventional technique in the thinnest BFMO films due to a much higher coercive field and an increase in the tunneling current. Their ferroelectric nature, however, was demonstrated by piezoresponse force microscopy, and excellent insulating properties and homogeneity were achieved in the films. [ABSTRACT FROM AUTHOR]

BiFeO3 thin films deposited on (111)-SrTiO3 substrates present both structural (rhombohedral) and multiferroic properties similar to bulk. The structural relaxation occurring when thickness increases and the low critical thickness possibly indicate different defect types and distribution as compared to (001)-BiFeO3, which may influence multiferroic domain dynamics. The same G-type antiferromagnetic order as in bulk is observed by neutron diffraction, with a superimposed weak ferromagnetic moment (10 emu/cm3) showing a planar anisotropy of 5 kJ/m3. When doped with 5% Mn these films also exhibit a polarization of 95 μC/cm2 along the [111] direction at room temperature, similar to high-quality BiFeO3 single crystals. [ABSTRACT FROM AUTHOR]

High quality Ba(Zr0.2Ti0.8)O3 (BZT) thin films were epitaxially grown on MgO single-crystal substrates. No structural phase transition took place in the temperature range of 80–300 K, and the films displayed a typical behavior of relaxor ferroelectrics, which was demonstrated by micro-Raman spectroscopy. Frequency and temperature dependence of dielectric properties was systematically investigated for the BZT thin films. It was found that enhanced dielectric properties could be obtained over a wide frequency and temperature range. This is of great importance for practical microelectronic device applications. At room temperature, a high dielectric tunability of nearly 50% was achieved over the whole measurement frequency range of 10 kHz–1 MHz by applying an electric field with intensity as low as 40 kV/cm; meanwhile, a relatively low dielectric loss was obtained and the value could be further reduced significantly with the applied dc electric field, indicating an excellent figure of merit and promising applications in tunable microwave devices for the BZT films. [ABSTRACT FROM AUTHOR]

La2/3Ca1/3MnO3 thin films have been grown on yttria-stabilized zirconia (YSZ) buffered silicon-on-insulator (SOI) substrates by the pulsed laser deposition technique. While full cube-on-cube epitaxy was achieved for the YSZ layer, the top manganite layer was multioriented in plane, with a coexistence of cube-on-cube and cube-on-diagonal epitaxial structures. Due to a combined influence from the magnetocrystalline, shape, and stain-induced magnetic anisotropy, in zero field and low temperatures the local spin orientation varies across the large-angle grain boundaries. As a result, a quite large low-field magnetoresistance (LFMR) based on spin-dependent tunneling was observed. The film shows a resistance change of ∼20% in a magnetic field <1000 Oe at 50 K, which is promising for real applications. [ABSTRACT FROM AUTHOR]

Structural planar defects in the SrBi[sub 2]Ta[sub 2]O[sub 9] (SBT) films with 10 mol % excess Bi grown in Pt/TiO[sub 2]/SiO[sub 2]/Si substrates by metalorganic deposition have been observed by high-resolution electron microscopy. It was found that these stacking defects were planar defects with extra Bi-O planes normal to the c axis. These structural defects are expected to effectively improve the ferroelectric response and fatigue-resistance characteristics of SBT films because of the extra Bi-O planes having higher strucutral flexibility and alleviating the mechanical stresses and strains as well as injected-charge problems. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A simple and successful design for an adaptive radar phase-coded waveform is presented. The optimised phase-coded waveform is designed by the phase-only conjugate gradient method. The signal-to-interference-plus-noise ratio of the optimised phase-coded waveform is compared with an optimal waveform and good approximation is achieved. [ABSTRACT FROM AUTHOR]

This paper presents a Raman spectroscopic study of compositional-change-induced structure variation and of the related mechanism of Mg doping in LiSbO3 (LS)-modified (K0.5Na0.5)NbO3 (KNN) ceramics. With increasing LS content from 0 to 0.06, a discontinuous shift towards higher wavenumbers was found for the band position of the A1g(v1) stretching mode of KNN, accompanied by a clearly nonlinear broadening of this band and a decrease in its intensity. Such morphological changes in the Raman spectrum result from two factors: (i) changes in polarizability/binding strength of the O-Nb-O vibration upon incorporation of Li ions in the KNN perovskitic structure and (ii) a polymorphic phase transition (PPT) from orthorhombic to tetragonal (O - T) phase at x > 0.04. Upon increasing the amount, w, of Mg dopant incorporated into the (1-x)KNN-xLS ceramic structure, the intensity of the Raman bands are enhanced, while the peak position and the full width at half maximum of the A1g(v1) mode was found to experience a clear dependence on both w and x. Raman characterization revealed that the mechanism of Mg doping is strongly correlated with the concentration of Li in the perovskite structure: Mg2+ ions will preferentially replace Li+ ions for low Mg doping while replace K/Na ions for higher doping of Mg. The PPT O - T was also found to be altered by the introduction of Mg and the critical value of LS concentration, xO[?]T, for incipient O - T transition in the KNN-xLS-wMT system was strongly dependent on Mg content, with xO - T being roughly equal to 0.04 + 2w, for the case of dilute Mg alloying. [ABSTRACT FROM AUTHOR]

First principles study of the structural, electronic and optical properties of Al-doped γ-Ge3N4 with different concentration has been reported using the pseudo-potential plane wave method within the generalized gradient approximation (GGA). The binding energy and the formation energy suggest that Aluminum (Al) impurities prefer to substitute at octahedral sites. Different doping concentrations are considered and the corresponding density of states (DOS) are analyzed. Calculated DOS indicates that there are holes in the top of the valance band after doping, meaning a p-type doping. We study the complex dielectric function, the absorption coefficient, and the electron energy loss spectra. It is demonstrated that for the low Al concentration, the material exhibits the dielectric behavior and for the high Al concentration, the material has possibilities to exhibit some metallic behavior. The γ-Ge3N4 doped with Al has a much higher static dielectric constant than undoped γ-3N4, implying its potential applications in electronics and optics. [ABSTRACT FROM AUTHOR]

Objective The aim of this work was to report the treatment effectiveness of central serous chorioretinopathy (CSCR) in a renal transplant recipient who received conventional therapy with little effect, and then reducing corticoid successively and with a better outcome later. Methods We performed a retrospective comparison of best-corrected visual acuity (BCVA) and spectral-domain optical coherence tomography (SD-OCT) of a 57-year-old renal transplant recipient who received conventional therapy and reducing corticoid successively after he was diagnosed as CSCR in the left eye. Results The BCVA of the left eye stayed at 20/200 after 3 months' conventional therapy, but rapidly improved to 20/25 after reducing corticoid by one-half. At the same time, SD-OCT showed much more obvious absorption of retinal liquid in the left eye from reducing corticoid than from conventional therapy. Despite the reducing of corticoid by one-half, the patient did not show any signs of rejection of the renal transplant. Conclusions CSCR may be a sign in renal transplant recipients for reducing corticoid, and reducing corticoid might be a more reliable and safer treatment for such patients. [ABSTRACT FROM AUTHOR]

The sign of Leser–Trélat (LT) is defined as the sudden eruption of multiple seborrhoeic keratoses (SKs), or increase in the number and size of existing SKs, associated with an underlying malignancy. A 75-year-old man was admitted to our hospital with dyspnoea and multiple verrucous papules that had been developing gradually over the previous 30 years. During the 3 months before presentation, the number of SKs on his chest and back had increased rapidly. A diagnosis of nasopharyngeal carcinoma was made based on results of computed tomography, endoscopy and biopsy examinations. The patient is receiving radiotherapy at present. To our knowledge, this is the first case of the Leser–Trélat sign associated with nasopharyngeal carcinoma. [ABSTRACT FROM AUTHOR]