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The influences of external strain on diffusion properties of the bulk and subsurface oxygen vacancy (OV) in rutile TiO 2 are systematically studied using first-principle calculations. For OVs in bulk, we find that tensile (compressive) strain applied in the [001] direction or isotropically applied in the equivalent [110] and [ 1 1 ¯ 0 ] directions reduces (increases) the energy barriers of diffusion. Anisotropic strain applied in [110] and [ 1 1 ¯ 0 ] increases the energy barriers of diffusion in the two directions. Meanwhile it results in anisotropic diffusion behaviors. Between [110] and [ 1 1 ¯ 0 ] , the bulk OV prefers to diffuse along the one in which more compressive or less tensile strain is applied. From subsurface to surface, the most energetically favorable OV pathway is along the [110] rows terminated with the surface bridging oxygen atoms. The diffusion barrier of the OV in the first trilayer is much lower than that of a bulk OV. External in-plane tensile strain can further reduce the energy barrier of the subsurface OV diffusion, and thus help to improve the diffusion of OVs from bulk to surface.

We theoretically and experimentally reveal that the large resonant optical transmission (ROT) can be realized through a one-dimensional photonic crystal adjacent to a thin metal film, at a frequency in the original band-gap of the photonic crystal (PC). The influence of periodic number of PC and the thickness of the adjacent metal on the transmission frequency and intensity is studied in detail. An optimum design is given to reach the maximum transmission efficiency, meanwhile a mechanism underlining the ROT phenomenon is proposed. An effective admittance-matching theory is proposed to understand this effect and quantitatively determine the operating frequency, which matches very well with the simulated and measured results. The effects might be very useful to realize some optical filters and sensor devices since the structure is easy for mass production and is matured technically to be prepared in industry.

Spherical perovskite-type bismuth ferritic nanocrystals with diameters of 10–50 nm and hexagonal-shaped sillenite-type ones with sizes of 18–33 nm were synthesized at low temperatures by microwave hydrothermal process. Their structural, optical, and photocatalytic properties were investigated. The single-crystalline nature of the as-synthesized nanocrystals was confirmed by X-ray diffraction, selected area electron diffraction, and high-resolution transmission electron microscopy. X-ray photoelectron spectroscopy investigations show that Fe element exists as the Fe3+ valence state, as well as Bi element as Bi3+ in the as-prepared bismuth ferritic nanocrystals. The visible-light photocatalytic activities evaluated by the degradation of rhodamine B in aqueous solution show that the sillenite-type bismuth ferritic nanocrystals exhibit higher photocatalytic ability than the perovskite-type ones, which can be ascribed to their small mean particle size and the unique hexagonal-shape morphology, and also the structural characteristics of sillenite-type compound. The present results demonstrate that the hexagonal-shaped sillenite-type bismuth ferritic nanocrystals can be used as novel visible-light-responsive photocatalysts for degradation of organic compounds.

We study in this paper the atomic mechanisms of nanorod growth and propose the way of diameter selection of nanorod. A characteristic radius is demonstrated to be crucial in nanorod growth, which increases proportional to one fifth power of the ratio of the interlayer hopping rate of adatoms across the monolayer steps to the deposition rate. When the radius of the initial island is larger than this characteristic radius, the growth morphology evolves from a taper-like structure to a nanorod with radius equal to the characteristic radius after some transient layers. Otherwise the nanorod morphology can be maintained during the growth, with stable radius being limited by both the radius of the initial island and the three-dimensional Ehrlich-Schwoebel barrier. Therefore different growth modes and diameter of nanorod can be selected by tuning the characteristic radius. The theoretical predictions are in good agreement with experimental observations of ZnO growth., 7 pages, 4 figures, submitted to APS

Therefore,oneoftheimportantchallengesinfabricatingmetallicmicrostructures is to find an easy, repeatable, and controllablemethod to meet the increasing demands in optoelectronics andplasmonics.In this communication, we report a new template-assistedelectrochemical approach to fabricate arrays of metallic nano-wires. Unlike conventional template-assisted growth, where thegenerated wires are confined by the size of template, in ourcase the width of the metallic wires can be tuned by changing thecontrol parameters of electrodeposition. By imprinting polymerstripes ona silicon surface, the concave corner of polymerstripesandsiliconsubstrateprovidesapreferentialnucleationsitefortheformation of metal nanowires. The width of wires can be tunedfrom 25nm to a few hundred nanometers. Further, wedemonstrate that this method can be applied for fabricatingmore complicated structures rather than straight lines only.In our experiments, the metallic nanowires are electrodepo-sited with the help of polymer stripes embossed on siliconsurfaces. To form the patterned substrate, a thin film ofpoly(methylmethacrylate) (PMMA) (mr-I 7030E M

Perovskite pure BaTiO3 (BT) nanoparticles with spherical morphology and PX-phase PbTiO3 (PT) nanowires with acicular morphology, were synthesized by microwave–hydrothermal process, and their atomic-scale microstructures were characterized by electron microscopy. Both X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns demonstrated that the produced BT nanoparticles remained a cubic perovskite structure at room temperature. The BT nanoparticles exhibited a spherical morphology with a nearly uniform size of 50 nm. The PX-phase PT nanowires exhibited acicular morphology with diameter sizes of 40–60 nm and length up to several micrometers, and the aspect ratio was close to 90. They tended to grow into a regular structure with parallel arrangement along their long axis in the [001] direction. The extinction rule for the diffraction indexes (h, k, l ) in the XRD pattern is the sum of (h, k, l ) equal to odd number, similar to body-centered cubic crystal. In the SAED patterns of the PX-phase PT nanowires, both super electron diffraction spots with a threefold modulated periodicity along the [110] direction and the appearance of strong diffraction spot (008) but the forbidden (004) spot, were clearly observed, which indicated that the PX-phase PT has a threefold modulated periodicity along the [110] direction, and fourfold modulated periodicity in the [001] direction, respectively. This result was confirmed by high-resolution transmission electron microscopy images. The Raman bands centered near 146, 193, and 292 cm−1 observed in the nanowires at room temperature, could be assigned to the E(1LO), E(2TO), and E+B1 phonon modes of the tetragonal PT structure, respectively. However, no phonon modes of the tetragonal PT structure were responsible for the additional three Raman bands centered near 175, 548, and 832 cm−1, which are presumed to be resulted from the additional Raman modes of the PX-phase PT with a large and complex unit cell.

By using polyvinylpyrrolidone (PVP) as the nucleation promoter and directing agent, the shape-selective synthesis of ZnO has been realized at 35 °C. By simply modifying the amount of PVP or/and water, the product shape can be readily changed from one-dimensional structure via monolayer and semi-bilayer to bilayer structure with controlled aspect ratio (defined as monolayer thickness/edge length). As shown by both the photoluminescence and absorption spectra, the ZnO band gap can be modified by adjusting the sample shape. The low-temperature route reported here should open an effective and low-cost approach to the ZnO with tunable shapes and band gaps.

Nanocrystalline barium titanate (BaTiO3, BT) was synthesized hydrothermally at 220°C by reacting barium hydroxide with titanium dioxide. The resulting BT nanopowders were characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED), Raman spectrum, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM). The BT nanopowders have a cubic phase as revealed by the XRD and SAED results, whereas the Raman spectrum indicates that tetragonal phase BT exists in the produced nanopowders but is not the dominant phase because of the weak characteristic peak of the tetragonal structure at 305 cm−1. In the SEM and TEM images, many coarse-faceted cubic nanoparticles and a small amount of spherical particles are observed, indicating a developed bimodal size distribution of the BT powders. The variations of electron diffraction contrast across these particles in the TEM images indicate the presence of high strain in the BT nanoparticles, which is probably caused by the lattice defects like OH− ions and their compensation by cation vacancies. The HR-TEM image of a BT nanoparticle with a size of 24 nm and a spherical morphology demonstrates a uniform and perfect crystal structure. The surrounding edges of the particle are very smooth and no surface steps are observed. However, a terrace–ledge–kink (TLK) surface structure was frequently observed at the edges of the BT nanoparticles with rough surface morphology, and in most cases the terrace and ledge lie on the {100} planes. The observed TLK surface structure can be well interpreted by the theory of periodic bond chains. Small nucleated and triangular BT islands with three to four atomic layer thickness, and their outside surfaces faceted as (100) and (010) planes, are also observed in these particles. The rarely seen {110} surface in the BT nanoparticles was found to be reconstructed so that the surface was composed of corners bound by {100} minifaces like the triangular small islands. Microstructural defects such as antiphase boundaries were also observed near the edge of a BT nanoparticle, which were formed by the intersection of two crystalline parts with displacement deviation from each other by, as revealed by the HR-TEM images.

Interfacial structures of the Pt/SBT/Pt capacitors prepared by metallo-organic decomposition were examined by transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) as a function of the postannealed time at 750°C to investigate the interfacial evolution developed in the Pt/SBT/Pt capacitors. The results show that after postannealing at 750°C for a short time (e.g., 300 s), a thin amorphous layer was observed at the interfaces of the SBT/Pt-bottom and the SBT/Pt-top electrodes in the Pt/SBT/Pt capacitors, whereas after postannealing for a moderate time (e.g., 20 min), the interfaces of the SBT/Pt-bottom and the SBT/Pt-top electrodes became quite smooth and uniform, and almost free of the interfacial phase. However, after postannealing for a longer time (e.g., 60 min), an interfacial phase consisting of oval-shaped nanocrystallites was developed at both the SBT/Pt-bottom and the SBT/Pt-top electrode interfaces, which resulted in weakly bonded interfaces between the SBT films and Pt electrodes. This is the reason why a Pt electrode peeling phenomenon (similar to that reported in the Pt/SBT/Pt/capacitors annealed in the forming gas atmosphere) is frequently observed in the Pt/SBT/Pt capacitors postannealed for 60 min during the fabrication of cross-sectional TEM samples. Based on two-dimensional lattice fringes of the HRTEM images from the small nanocrystallites and the corresponding fast Fourier transform patterns, the oval-shaped nanocrystallites precipitated at both the SBT/Pt-bottom and the SBT/Pt-top electrode interfaces were determined to be a PtBi 2 phase with a cubic structure. The formation of the Pt-Bi-based interfaces in the Pt/SBT/Pt capacitors is due to the reaction of bismuth (out-diffused from the SBT films) with Pt electrodes during the postannealing process. The elliptical morphology of the interfacial PtBi 2 phase can be ascribed to its different growth rates in the parallel and vertical directions of the interface, and also the limited space for grain growth perpendicular to the interface.

Compositionally graded (Ba1−xSrx)TiO3 (BST) thin films (with 0.0 ⩽ x ⩽ 0.25) were grown by pulsed laser deposition on the (100)MgO single-crystal substrates covered with a conductive La0.5Sr0.5CoO3 (LSCO) layer as a bottom electrode. Their epitaxial growth, dielectric response, and microstructure were characterized. The epitaxial relationships between the BST, LSCO, and MgO can be determined as [001]BST//[001]LSCO//[001]MgO and (100)BST//(100)LSCO//(100)MgO, from the x-ray diffraction (rocking curve, ϕ scans) and electron-diffraction patterns. Dielectric data showed that the room temperature values of the dielectric constant and dielectric loss of the graded BST films were 630 and 0.017 at 100 kHz, respectively. Cross-sectional transmission electron microscopy (TEM) images reveal that both the BST films and the LSCO bottom electrode grow with a columnar structure, and they have flat interfaces and overall uniform thickness across the entire specimen. Cross-sectional high-resolution TEM images reveal that at the LSCO/MgO(100) interface, an interfacial reaction is not seen, whereas edge-type interfacial dislocations with their extra half-planes residing in the LSCO side are observed with an average interval of 2.20 nm, close to the theoretical value of 2.15 nm. At/near the LSCO/BST interface, the graded BST films grow perfectly and coherently on the LSCO lattice because they have the same type of crystal structure and almost same lattice constants, and no interfacial dislocations are observed. Planar TEM images show that the graded films exhibit granular and/or polyhedral morphologies with an average grain size of 50 nm, and the aligned rectangular-shaped voids were also observed. High-resolution TEM images show that the length sizes of voids vary from 8 to 15 nm, and with width of 5 to 10 nm along the 〈001〉 direction in the (100) plane.

A piezoelectric–piezomagnetic superlattice (PPS) is proposed to present the magneto-electric (ME) coupling wherein electric polarization induces magnetization or vice versa through the layer's coherent strain. We reveal that in PPS, the interaction of electromagnetic waves with the correspondent alternative piezoelectric and piezomagnetic superlattices through their vibrations excites the piezoelectric and the piezomagnetic phonon polaritons simultaneously. The polaritons couple with each other to give rise to a stop band, in which double negative permittivity and permeability can be realized, however negative refraction could not occur. The coupling also results in the huge dynamic ME effect which attributes to the large ME voltage coefficient in a BaTiO3–CoFe2O4 superlattice as large as 14.9 V cm−1 Oe−1.

Nanocrystalline BaTiO3 (BT) particles were synthesized via hydrothermal method, and their microstructure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution TEM (HRTEM). The results show that the BT nanoparticles remain a metastable cubic structure at room temperature, as revealed by XRD and SAED. Such an abnormal crystallographic phenomenon was caused by the lattice defects such as OH− defects and barium vacancies. The BT nanoparticles exhibit a spherical morphology with an average grain size of 70 nm, and narrow particle size distribution. HRTEM images of individual particles indicate that the BT nanoparticles have a good crystallinity and smooth surfaces. However, dark-field TEM images revealed high strains in BT nanoparticles, which were probably resulted from the surface defects. Anti-phase boundaries were also observed in some BT nanoparticles, which were formed by the intersection of two crystalline parts with a relative displacement from each other by 1 2 d 100 or 1 2 d 111 , as revealed by HRTEM images. Some local dark TEM contrast observed, near the pure edge dislocations with Burgers vector value of d110, was due to the existence of local strains around the pure edge dislocations.

Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) thin films with large remanent polarization and SrBi 2 Ta 2 O 9 (SBT) thin films with excellent fatigue-resisting characteristic have been widely studied for non-volatile random access memories, respectively. To combine these two advantages , bilayered Pb(Zr 0.52 Ti 0.48 )O 3 /SrBi 2 Ta 2 O 9 (PZT/SBT) thin films were fabricated on Pt/TiO 2 /SiO 2 /Si substrates by chemical solution deposition method. X-ray diffraction patterns revealed that the diffraction peaks of PZT/SBT thin films were completely composed of PZT and SBT, and no other secondary phase was observed. The electrical properties of the bilayered structure PZT/SBT films have been investigated in comparison with pure PZT and SBT films. PZT/SBT bilayered thin films showed larger remanent polarization (2 P r ) of 18.37 μC/cm 2 than pure SBT and less polarization fatigue up to 1 × 10 9 switching cycles than pure PZT. These results indicated that this bilayered structure of PZT/SBT is a promising material combination for ferroelectric memory applications.

A novel polyvinylpyrrolidone (PVP)-directed crystallization route is successfully developed for the shape-selective synthesis of ZnO particles with distinctive shapes, including monolayer, bilayer, and multilayer structures, gears, capped pots, hemispheres, and bowls, at temperatures as low as 32 °C. This route is based on exploiting a new water/PVP/n-pentanol system. In the system, PVP can greatly promote ZnO nucleation by binding water and direct ZnO growth by selectively capping the specific ZnO facets, which is confirmed by IR absorption spectra. The bandgap of the ZnO particles is readily tuned by modifying the product morphology by adjusting the PVP chain length, PVP amount, water volume, and reaction temperature. The remarkable ZnO structures and the biomimetic method demonstrated here not only expand the structures and applications of ZnO but also provide a new approach to explore the unusual structures for novel physicochemical properties and technological applications. Furthermore, the novel ZnO/Au/ZnO sandwich structure is successfully fabricated by inserting a Au plate into the bilayer ZnO structure.

Ferroelectric domain structures and their morphology evolution in the Bi- and Zn-modified (Pb0.985Bi0.01)(Ni1/4Zn1/12Nb2/3)x(ZrσTi1−σ)1−xO3 piezoelectric ceramics (0.20≤x≤0.60 and 0.10≤σ≤0.60) are investigated as a function of the relaxor Pb(Ni1/3Nb2/3)O3 content and the Zr/(Zr+Ti) ratio (σ) by transmission electron microscopy and selected area electron diffraction, and followed by a complete analysis of the nature of the domain walls based on the predicated twinning planes for the formation of domains in these piezoelectric ceramic systems. A systematic variation in the domain morphology was observed as the compositions move from the ferroelectric tetragonal (FT) to pseudocubic (Fpc) phases, and then to the rhombohedral (FR) phase. Wedged-shaped domains with misoriented {110} domain walls and mixed with herringbone-like configuration are the main features of the ferroelectric domains in the FT and Fpc phases, whereas in the compositions near the morphotropic phase boundary (MPB) between the Fpc and FR phases, the characteristic feature of the ferroelectric domains is an intricate domain structure exhibiting a fluctuating mottled contrast. However, the domain boundaries in the FR phase exhibit a wavy character. The domain feature for the compositions at/near the MPB between the FT and FR phases with high property coefficients is a 90° domain texture mixed with an intricate domain structure. The different domain configurations observed in the FT and FR phases are due to their different accommodations of local elastic strain fields. The piezoelectric soft behavior and a normal-relaxor ferroelectric behavior transition observed in this piezoelectric ceramic system are closely related to the above domain morphology evolution as increasing the PNN content or the Zr/(Zr+Ti) ratio.

The attachment of water molecules to poly(vinylpyrrolidone) (PVP) is used in conjunction with the region-selective distribution of PVP and water in a water/PVP/n-pentanol system to confine reactions along the surface of PVP, thus achieving the highly shape-selective synthesis of anisotropic Au nanostructures with controlled sizes and remarkable shapes such as regular octahedrons, triangles, rods, dumbbells, belts, and hexagons. The IR absorption spectra of the Au nanoparticles confirm that the nanoparticles are formed around PVP, and corroborate the adsorption of PVP on Au. The size, shape, and plasmon resonance of the Au nanoparticles can be readily tuned by modifying the adsorption behavior and/or the reducing ability of PVP by adjusting the relative amounts of PVP and water, directly adding gold seeds, or changing the stirring conditions in the reaction mixture. The obtained highly pure anisotropic Au nanostructures and the synthesis method demonstrated here enable us to study distinct nanostructures to search for novel physicochemical properties and technological applications. Our method is also successfully extended to prepare highly pure silica spheres, tubes, and needles with controlled aspect ratios.

A novel ethylene dichloride solvent-assisted route has been successfully developed to coat uniformly polystyrene colloids with Ag and prepare the corresponding hollow spheres. In this route, by corroding and swelling the PS colloid surface with ethylene dichloride, Ag seeds are synthesized directly in and on the surface layer of core, not only the surface functionalization is avoided, but also may enhance the combination of core and seeds. The ethylene dichloride concentration is crucial for the coating results. The coverage, thickness, and roughness of the Ag shell can be effectively controlled by varying the amount of HCHO during the seeding growth process, and the as-prepared composites can crystallize into ordered structure. This coating route is facile and versatile, and apt to coat PS colloids with other metal and prepare the corresponding hollow metal spheres.

We report in this article a mechanism to form regularly zigzag branch of CsCl crystallites on a flat glass substrate, in which the crystallographic orientation rotates continuously, and a pattern with long-range order on tens of micrometer scale is generated. Atomic force microscopy (AFM) indicates that this unusual crystallization behavior is associated with successive nucleation at the concave edge of crystallite facet and glass substrate, where interfacial tension underneath the nucleus is asymmetric. We suggest that these observations reveal a new lateral growth mode, and may help to understand a class of long-range ordering effect in crystallization.

This review paper reports the studies on ferroelectric domain inversion and inverse mechanism in ferroelectric and dielectric LiNbO 3 and LiTaO 3 single crystals by proton exchange followed by heat treatment. Secondary ion mass spectroscopy and numerical simulation of proton profile, differential scanning calorimetry, pyroelectric experiment and transmission electron microscopy were used to characterize the domain inversion. The inverse mechanism was discussed by means of an internal electric field model, which is based on the concentration gradient of proton and lithium deficiency.

A novel water/polyvinylpyrrolidone (PVP)/n-pentanol ternary system is successfully developed to realize the controlled growth and assembly of silver nanoprisms using a one-step synthesis for the first time. The highly shape-selective growth and assembly of nanoprisms is based on the unique water/PVP/n-pentanol interface. It is seen that the cooperative assembly of nanoprisms with PVP greatly affects the size-dependent nanoprism plasmon bands. The plasmon bands of the assemblies are closer to those of bulk silver than to those of nanoprisms. The method is simple and versatile, and is successfully extended to prepare Au and Pd nanoprisms, lamellar ZnO particles, and layered ZnO assemblies with high purity. The method may provide powerful technology for shape-selective synthesis and assembly of lamellar nanoparticles with novel structures and functions in nanotechnology.

Several kinds of azo-dye polymer films of the guest-host system were prepared by the spin-coating method. Four disperse red (DR) dyes of DR1, DR19, DR54 and DR73 were chosen as second order nonlinear optical active chromophores with polymer matrixes such as poly (methyl methacrylate) PMMA or polycarbonate (PC). The processing conditions such as heat-treatment, substrate, and film storage condition on all-optical poling characteristics of azopolymers have been investigated. It is found that the second harmonic generation intensity is very sensitive to the chromophores and processing parameters. Some explanations have been proposed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The silica@Ag–Cu alloy core-shell composite colloids have been successfully synthesized by an electroless plating approach to explore the possibility of modifying the plasmon resonance at the nanoshell surface by varying the metal nanoshell composition for the first time. The surface plasmon resonance of the composite colloids increases in intensity and shifts towards longer, then shorter wavelengths as the Cu/Ag ratio in the alloy shell is increased. The variations in intensity of the surface plasmon resonance with the Cu/Ag ratio obviously affect the Raman bands of the silica colloid core. The report here may supply a new technique to effectively modify the surface plasmon resonance.

A model is developed to deal with lateral growth of a crystalline layer on a foreign substrate, which is mediated by successive nucleation at the concave corner defined by the meeting of a crystal facet and the substrate. It is demonstrated that due to an imbalance of surface/interface tensions at the concave corner, once the embryo of a nucleus is formed, the crystallographic orientation of the nucleus is spontaneously twisted. By successive nucleation at the concave corner, the crystalline layer develops laterally on the substrate, with its crystallographic orientation continuously rotated. In this way, a regular spatial pattern with well-defined long-range order is eventually achieved. Our model provides a criterion to predict when such an effect becomes observable in the nucleation-mediated lateral growth. The theoretical expectations are consistent with the experimental observations.

Bi4Ti3O12 (BIT) films were prepared on Pt/TiO2/SiO2/Si substrates by the sol–gel method. A low electric field was in-situ applied to BIT films during rapid thermal annealing (RTA). It was first found that a bias electric field has great influence on the structure, orientation, and morphology of BIT films at proper temperatures. Under the electric field of very low V/cm, BIT films show highly c-axis-oriented growth with second phase of bismuth oxide at 600 and 650 °C. The possible origin is proposed. On one hand, the electrostatic energy provides an extra driving force and the co-interaction of the electrostatic energy and interface energy promotes the c-axis-oriented growth of the BIT grains. On the other hand, the second phase of bismuth oxide produced during RTA in an electric field also plays an important role in the control of film orientation.

Titanium oxide nanotubes were prepared by hydrothermal treatment of rutile titania powders in strong NaOH aqueous solution at 130°C for 36 hours. These nanotubes were used as Ti precursors to synthesize barium strontium titanate nanoparticles by reaction with Ba(OH)2 and Sr(OH)2 at 180 °C in hydrothermal conditions. The structure, composition and morphology of the obtained nanoparticles were characterized using transmission electron microscopy and energy dispersive spectroscopy. It is interesting to find that the morphology depends on (Ba + Sr)/Ti ratios. A strong photoluminescence centered at 575 nm was observed in these barium strontium titanate nanoparticles.

A double template-assisted fabrication method for making surface patterns with tunable lattice geometries on a polymer surface is reported. This technique is based on a locally nonuniform strain produced in a double-templated polymer film that has a strong modulation in thickness. It can produce all 2D primitive Bravais lattices as well as chains on the surface of a polymer. The lattice parameters are controllable with nanoprecision by varying the direction and amount of the applied strain.

A novel Zr/Ti mixed metal nitrate[Zr x Ti 1-x (N03)4] has been successfully developed as a single-source precursor to deposit multicomponent metal oxide films. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses confirm that Zr 0.65 Ti 0.35 O 2 films are successfully prepared from this anhydrous nitrate precursor using CVD. The basal dielectric properties of Zr 0.65 Ti 0.35 O 2 films are studied, and well-defined C-V curves with negligible hysteresis are achieved. Compared to pure TiO 2 and ZrO 2 films, the Zr 0.65 Ti 0.35 O 2 films exhibit a trade-off of dielectric properties with a moderate bandgap value of 4.3 eV and a value for k of 47. Zr x Ti 1-x O 2 is, therefore, a promising candidate for gate-dielectric application, and an anhydrous mixed-metal nitrate can be a potential single-source precursor for high-k materials derived from CVD.

Tailoring optical response using periodic nanostructures is one of the key issues in the current research on functional composite materials. The anomalous light transmission through metallic films that have a regular array of submicrometer holes has stimulated much interest. This interest stems from both the underlying physics and also the perceived potential for applications in nanophotonics, quantum-information processing, nanolithography, and surface-enhanced Raman scattering. Extraordinary transmission of light through an optically opaque metal film perforated with a 2D array of subwavelength holes was first reported by Ebbesen et al. This unusual phenomenon can be understood as a result of diffractive coupling to evanescent surface plasmon polaritons (SPPs) that leads to a strong concentration of light at the metal surface, which then weakly tunnels through the holes in the film, reradiating by the inverse process on the exit side. In order to explore the SPP properties of microstructured metal films, extensive efforts have been made to study their spectral response and dependence on geometrical parameters, such as the type of lattice symmetry, metal film thickness, and adjacent dielectric media. Recent studies show that the hole shape has a significant effect on the optical transmission. Nearly all the metallic films studied have been on a flat substrate and the hole arrays were made using focused ion-beam milling, and electron-beam lithography or interferometric lithography combined with reactive ion etching. Here we use nanosphere lithography as the sample production technique. This approach has several advantages over the conventional lithographic and machining techniques, including the relative ease of casting large, high-quality, ordered nanomaterials and the low cost of implementation. Ordered arrays of gold half shells and nanocaps have been constructed by controlled gold vapor deposition with thicknesses less than 20 nm by using a 2D colloidal crystal (CC) as a substrate. Baumberg’s group has fabricated metallic nanocavity arrays by electrodeposition within the pores of CC templates and observed the excitation of the SPPs in metallic cavities that led to rich features in reflectivity spectra. Very recently, Landstrom et al. have shown that the transmission spectra through a metal film formed on a 2D CC substrate are quite similar to those observed through subwavelength hole arrays in metal films. In this communication, we report a study on the infrared transmission properties of gold films patterned on 2D CCs. The fabricated metallodielectric structures have a strong surface corrugation as well as a 2D periodic pore array. We show that the SPPs on these curved surfaces display unusual dispersion properties, compared to those of metal films on flat substrates studied before. The dielectric property of the template spheres is also found to have a substantial effect on the transmission. More importantly, the transmission features vary dramatically as the gold film thickness is increased, with an apparent transition from the excitation of localized SPP resonance to extended SPP propagation at a critical metal film thickness. Our results will be useful for designing and fabricating new optical devices based on SPP excitation and this will stimulate further studies on the optical properties of metallic microstructures deposited on 2D CCs. The ordered metallic microstructures were prepared by sputtering a thin gold layer onto a monolayer of dielectric microspheres self-assembled onto a quartz chip. The 2D sphere arrays were crystallized by controlled evaporation from a colloidal solution within a channel formed using two quartz chips. The microbeads were hemispherically covered with metal and the resulting gold film consists of a hexagonally close-packed (HCP) array of gold half-shells with a size dictated by the template spheres. The diameters of these hemispherical shells can be conveniently controlled from 200 nm to several micrometers by choosing colloidal beads with different sizes. Figure 1 shows the scanning electron microscopy (SEM) image of a typical sample with a thin gold layer on a 2D silica CC substrate. In the center of the image, there is a vacancy C O M M U N IC A TI O N S

A general theory of heteroepitaxial lateral growth of nanocrystallites via successive nucleation at the concave comer of the nanocrystallite and the substrate was developed. The theory treats the existence of a rotational instability of crystallographic orientation induced by the imbalance of surface/interface energy. From the theory it can be concluded that the crystallographic orientation may rotate continuously, sustained either by consecutive changes of facets on the growth front or by periodic modulation of surface energy of the substrate.

We report here the electrodeposition of periodically structured single-crystalline zinc branches from an ultrathin aqueous electrolyte layer of ZnSO4. The main trunk and side branches of electrodeposits are regularly angled, and each branch is made of periodic bead-like structures. Layered morphology has been observed on each bead. During electrodeposition, spontaneous oscillation of electric current occurs when constant voltage is applied across the electrodes, and the oscillation leads to periodic patterns on deposit branches. According to electron diffraction of transmission electron microscopy (TEM), the whole branch of electrodeposits has the same crystallographic orientation despite the fact that the branch looks like an assembly of beads. We interpret this unique growth behavior to the epitaxial nucleation in the transport-limited growth system. Copyright © 2006 John Wiley & Sons, Ltd.

Faceted single-crystalline ZnO tubes were synthesized by a simple soft solution method at 65 ° C. These tubes are of several micrometers in length and several hundred nanometers in diameter, with bell-mouths on each end. Structural characterizations using electron spectroscopy revealed that these hexagonal ZnO tubes were along [0 0 0 1] direction and side-enclosed by { 01 1 ¯ 0 } facets. The growth of ZnO in hydrothermal condition and the formation of this unusual bell-mouthed structure were discussed on the basis of the observation of ring-shaped nano-crystallites upon decreasing the time for growth.

Monodisperse hollow Ag and Ag/Au submicrometer spheres have been synthesized by a facile colloidal templating method. In this method, the silver nanoparticle seeds are synthesized on the silica colloids surface through the electroless plating approach to avoid the complex surface functionalization, and the subsequent seeding growth and dissolving silica core are carried out simultaneously. The as-prepared hollow spheres remain mostly the fine monodispersity and spheric shape of the silica core, and can self-assemble directly into ordered structure, which is realized for the first time. The method is simple and versatile, and can be used to prepare other monodisperse hollow composite metallic or bimetallic spheres.

The formation of H2Ti3O7 nanotubes, nanofibers, nanowires, and nanobelts via alkali hydrothermal synthesis was studied in detail by TEM and HRTEM. The effects of preparation parameters, such as reaction temperature, duration, and cooling process, on the morphologies of the products are clarified. A universal formation mechanism is proposed based on the growth, split, wrapping, and thickening of Na2Ti3O7 nanointermediates, which links all kinds of morphologies observed for H2Ti3O7 nanoentities.

By using the method of eigenvalues and eigenstates, the emission and cavity-field spectra of a cascade three-level atom interacting with a single-mode electromagnetic field are studied in both intensity-dependent coupling (IDC) and intensity-independent coupling (IIC) cases. The photon statistics of the field on the spectra are investigated for the initial field in the pure number state, the coherent state and the thermal state. In the resonant case and the strong field limit, the pure-number-state emission spectrum exhibits six peaks and three peaks, respectively, for the IDC case and the IIC case. For a strong initial coherent state field or a strong thermal state field, the central structure of the emission spectrum at the field frequency is a doublet in the IDC case and a singlet in the IIC case. The cavity-field spectrum has three peaks in the IDC case and a single peak in the IIC case in the strong field limit for all of the three kinds of initial fields considered. Results indicate that in the emission spectrum merging of spectral peaks occurs for the IIC case as the initial field becomes stronger while it does not happen for the IDC case.

The microstructure of BaTiO 3 (BT) nanocrystals was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), and (high-resolution) transmission electron microscopy [(HR)TEM]. The BT nanocrystals have a cubic perovskite structure as revealed by XRD and SAED. They were prepared by a hydrothermal method using different starting materials: (i) Using as-prepared titanium hydroxide and barium hydroxide as starting materials, BT nanocrystals were obtained with a narrow size distribution and an average grain size of 65 nm, exhibiting a spherical particle morphology and smooth surfaces. These nanocrystals showed almost uniform contrast in TEM. HRTEM lattice fringe images indicate a rather uniform, perfect crystal structure. (ii) Using barium hydroxide and titanium dioxide (anatase) as starting materials, many coarse-faceted cubic nanocrystals and a small amount of spherical particle were observed, indicating a developed bimodal size distribution. Diffraction contrast variations across these particles indicate the presence of high strain in these BT particles. The strain is probably caused by the lattice defects like OH − ions and their compensation by cation vacancies. HRTEM images demonstrated that (1 0 0) and (1 1 0) surface facets are present on these particles. In addition they revealed the presence of very small-nucleated BT islands at the edges of the faceted particles.

The surface sol-gel (SSG), a solution-based and stepwise film growth technique, was developed to produce ultrathin zirconium oxide (ZrO2) films for high-k gate dielectric application. X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) measurements confirm the successful deposition of ultrathin polycrystalline ZrO2 films on Si substrate by the SSG method. Electrical measurements show that a large effective oxide thickness (EOT) of 2.4 nm with high leakage current was obtained, and a hysteresis in C-V curves and large fix charge density in ZrO2 films was observed, which related to the formation of substoichiometric silicon oxide in the interface. Surface nitridation of Si substrate by NH3 plasma can effectively reduce the leakage current and fixed or trapping charge density, as well as improve the interface properties. EOT of 2.21 nm with JA = 30.4 mA/cm2 at Vg = +1 V was demonstrated in ZrO2 films with a Si nitride barrier layer.