Showing papers on "Overlayer published in 2010"
TL;DR: In this paper, a double light-scattering layer ZnO (DL-ZnO) film was fabricated and studied as dye-sensitized solar-cell photoanodes.
Abstract: A novel double light-scattering-layer ZnO (DL-ZnO) film consisting of ZnO monodisperse aggregates (MA-ZnO) as underlayer and sub-micrometer-sized platelike ZnO (SP-ZnO) as overlayer was fabricated and studied as dye-sensitized solar-cell photoanodes. It was found that DL-ZnO could significantly improve the efficiency of dye-sensitized solar cells (DSSCs) owing to its relatively high surface area and enhanced light-scattering capability. The overall energy-conversion efficiency (η) of 3.44% was achieved by the formation of DL-ZnO film, which is 47% higher than that formed by MA-ZnO alone and far larger than that formed by SP-ZnO alone (η = 0.81%). Furthermore, the η decay measurements for DL-ZnO cell showed that no significant decrease of η occurred even when DL-ZnO cell was placed for 100 h at ambient temperature. The charge recombination behavior of cells was investigated by electrochemical impedance spectra (EIS), and the results showed that among MA-ZnO, SP-ZnO, and DL-ZnO based cells, DL-ZnO based cel...
174 citations
TL;DR: The growth and geometric structure of ultrathin zinc oxide films on Pd(111) have been studied by scanning tunneling microscopy, low-energy electron diffraction, and density functional theory calculations as mentioned in this paper.
Abstract: The growth and geometric structure of ultrathin zinc oxide films on Pd(111) has been studied by scanning tunneling microscopy, low-energy electron diffraction, and density functional theory calculations. For sub-monolayer coverages, depending on the oxygen pressure, two well-ordered zinc oxide phases with (4 × 4) and (6 × 6) coincidence structures form, which are attributed to H-terminated Zn6O5 and graphite-like Zn6O6 layers, respectively. The (6 × 6) phase exhibits a pronounced oxygen pressure dependence: at low p(O2) a well-ordered (6 × 6) two-dimensional array of O vacancies develops, yielding a layer with a formal Zn25O24 stoichiometry, while at high p(O2) the Zn6O6 monolayer transforms into bilayer islands. For oxide coverages up to 4 monolayers the graphite-like Zn6O6 structure is thermodynamically the most stable phase over a large range of oxygen chemical potentials, before it converges to the bulk-type wurtzite structure. Under oxygen-poor conditions a compressed overlayer of Zn adatoms can be s...
150 citations
Patent•
30 Aug 2010TL;DR: In this article, a method of removing photoresist beneath an overlayer includes estimating a rapid temperature change for a photoreflective layer to produce cracking in the overlayer.
Abstract: A method of removing photoresist beneath an overlayer includes estimating a rapid temperature change for a photoresist layer to produce cracking in the overlayer. The temperature chance is estimated so that the cracking of the overlayer is sufficient to allow a liftoff solution to penetrate below the overlayer during a liftoff step. The method further includes baking the photoresist layer and chilling the photoresist layer after baking to produce the rapid temperature change. The method then includes lifting off the photoresist layer using the liftoff solution.
131 citations
TL;DR: In this article, a bilayer-structured double-layer TiO2 (DL-TiO2) film was fabricated to improve the efficiency of dye-sensitized solar cells.
128 citations
TL;DR: In this article, as-grown and plasma-treated tin oxide (SnO2) nanowires were modified by Ar/O2 plasma treatment through preferential etching of the lattice oxygen atoms, which produced nonstoichiometric surface compositions that imparted a manyfold higher sensitivity toward gas absorption on such surfaces.
Abstract: Tin oxide (SnO2) nanowires grown by chemical vapor deposition were modified by Ar/O2 plasma treatment through preferential etching of the lattice oxygen atoms, which produced nonstoichiometric surface compositions that imparted a manyfold higher sensitivity toward gas absorption on such surfaces. Microstructures of as-grown and plasma-treated SnO2 nanowires confirmed the gradual change in the chemical composition and morphologies. Surficial disorder caused by the bombardment of argon and oxygen ions present in the plasma was visible as a disordered overlayer in high-resolution TEM micrographs, when compared to single crystalline as-grown SnO2 nanowires. Gas-sensing experiments on modified SnO2 nanostructures showed higher sensitivity for ethanol gas at lower operating temperatures and exhibited an improved transduction response toward changing gas atmospheres, attributed to the increased concentration of oxygen vacancies on the surface of SnO2 nanowires. Modulation of surface chemistry was also supported ...
115 citations
TL;DR: In this article, the magnetic anisotropy energy (MAE) derived from the magnetization curves of the Fe and Co films is one order of magnitude larger than the respective bulk values.
Abstract: We report on a combined experimental and theoretical investigation of the magnetic anisotropy of Fe and Co ultrathin layers on strongly polarizable metal substrates. Monolayer (ML) films of Co and Fe on Rh(111) have been investigated in situ by x-ray magnetic circular dichroism (XMCD), magneto-optic Kerr effect, and scanning tunneling microscopy. The experiments show that both magnetic adlayers exhibit ferromagnetic order and enhanced spin and orbital moments compared to the bulk metals. The easy magnetization axis of 1 ML Co was found to be in plane, in contrast to Co/Pt(111), and that of 1 ML Fe out of plane. The magnetic anisotropy energy (MAE) derived from the magnetization curves of the Fe and Co films is one order of magnitude larger than the respective bulk values. XMCD spectra measured at the Rh M2,3 edges evidence significant magnetic polarization of the Rh(111) surface with the induced magnetization closely following that of the overlayer during the reversal process. The easy axis of 1–3 ML Co/Rh(111) shows an oscillatory in-plane/out-of-plane behavior due to the competition between dipolar and crystalline MAE. We present a comprehensive theoretical treatment of the magnetic anisotropy of Fe and Co layers on Rh(111) and Pt(111) substrates. For free-standing hexagonally close-packed monolayers the MAE is in plane for Co and out of plane for Fe. The interaction with the substrate inverts the sign of the electronic contribution to the MAE, except for Fe/Rh(111), where the MAE is only strongly reduced. For Co/Rh(111), the dipolar contribution outweighs the band contribution, resulting in an in-plane MAE in agreement with experiment while for Co/Pt(111) the larger band contribution dominates, resulting in an out-of-plane MAE. For Fe films however, the calculations predict for both substrates an in-plane anisotropy in contradiction to the experiment. At least for Fe/Pt(111) comparison of theory and experiment suggests that the magnetic structure of the adlayer is more complex than the homogenous ferromagnetic order assumed in the calculations. The angular momentum and layer-resolved contributions of the overlayer and substrate to the MAE and orbital moment anisotropy are discussed with respect to the anisotropic hybridization of the 3d, 4d, and 5d electron states and vertical relaxation. The role of technically relevant parameters such as the thickness of the surface slab, density of k points in the Brillouin zone, and electron-density functionals is carefully analyzed.
96 citations
TL;DR: In this paper, a characterization of the graphitic overlayer that forms on 4H-SiC ( 0 0 0 1 ¯ ) substrates heated for ten minutes to temperatures T < 1350°C under vacuum conditions has been performed.
92 citations
TL;DR: This work follows the formation of boron nitride layers on Rh(111) with scanning tunneling microscopy (STM) under realistic growth conditions, up to 1200 K, and arrives at the optimal recipe for a high-quality overlayer.
Abstract: Boron nitride forms nearly perfectly regular films with a thickness of precisely one atom on various metal surfaces. Here, we follow the formation of boron nitride layers on Rh(111) with scanning tunneling microscopy (STM) under realistic growth conditions, up to 1200 K. Our STM movies demonstrate in detail how the structure grows and how defects are introduced. Based on these observations we arrive at the optimal recipe for a high-quality overlayer.
75 citations
TL;DR: In this article, a dielectric overlayer on top of Au/Co/Au multilayer films can significantly enhance the magnetic field induced modulation of the surface plasmon polariton (SPP) wave vector.
Abstract: The deposition of a dielectric overlayer on top of Au/Co/Au multilayer films can significantly enhance the magnetic field induced modulation of the surface plasmon polariton (SPP) wave vector. This enhancement is analyzed as a function of the thickness of the dielectric overlayer and the associated SPP electromagnetic field confinement and redistribution. The decrease in SPP propagation distance is taken into account by analyzing an adequate figure of merit.
71 citations
TL;DR: In this paper, the effect of oxygen partial pressure in the reactive gas mixture and film thickness on the photoconductivity transients was studied and a different photodetector configuration comprising ZnO thin film with an ultrathin overlayer of metals like Cu, Al, Sn, Au, Cr, and Te was designed and tested.
Abstract: Ultraviolet photoconductivity relaxation in ZnO thin films deposited by rf magnetron sputtering are investigated. Effect of oxygen partial pressure in the reactive gas mixture and film thickness on the photoconductivity transients is studied. A different photodetector configuration comprising ZnO thin film with an ultrathin overlayer of metals like Cu, Al, Sn, Au, Cr, and Te was designed and tested. Photoresponse signal were found to be stronger (four to seven times) in these configurations than the pure ZnO thin films. Sn(30 nm)/ZnO sample exhibits highest responsivity of ∼8.57 kV/W whereas Te(20 nm)/ZnO structure presents highest sensitivity of ∼31.3×103 compared to unloaded ZnO thin film. Enhancement in the photoresponse of ZnO thin films is attributed to the change in surface conductivity due to induced charge carriers at the interface because of the difference in work function and oxygen affinity values of metal overlayer with the underlying semiconducting layer. Charge carrier transfer from the meta...
68 citations
TL;DR: In this article, the fabrication of hybrid conjugated polymer/ZnO photovoltaic devices using ZnO nanorod structures prepared by electrodeposition and study the effect of introducing a second metal oxide overlayer using a TiCl4 post-treatment.
Abstract: We report herein the fabrication of hybrid conjugated polymer/ZnO photovoltaic devices using ZnO nanorod structures prepared by electrodeposition and study the effect of introducing a second metal oxide overlayer using a TiCl4 post-treatment. We use transient absorption spectroscopy, scanning electron microscopy, and photovoltaic device measurements to study the microstructure and charge generation properties of the hybrid films and the performance of the resulting devices. We show how the ZnO nanostructure can be controlled via the nanorod growth conditions and demonstrate that photovoltaic device performance can be optimized by controlling the nanostructure in this way. Moreover, we show that a large increase in photocurrent generation can be achieved by coating the ZnO surface with a thin layer of titanium oxide by treating the ZnO nanostructure with a TiCl4 solution.
TL;DR: In this paper, it is revealed from first-principles calculations that polarization-induced asymmetric distribution of oxygen vacancies plays an important role in the insulating behavior at p-type LaAlO3/SrTiO3 interface.
Abstract: It is revealed from first-principles calculations that polarization-induced asymmetric distribution of oxygen vacancies plays an important role in the insulating behavior at p-type LaAlO3/SrTiO3 interface. The formation energy of the oxygen vacancy (V-O) is much smaller than that at the surface of the LaAlO3 overlayer, causing all the carriers to be compensated by the spontaneously formed V-O's at the interface. In contrast, at an n-type interface, the formation energy of V-O is much higher than that at the surface, and the V-O's formed at the surface enhance the carrier density at the interface. This explains the puzzling behavior of why the p-type interface is always insulating but the n-type interface can be conducting.
TL;DR: In this paper, the effect of charge carriers induced at the ZnO-metal interface by the tin metal overlayer compensates the surface lying trap centers and leads to the enhanced photoresponse.
Abstract: Photoconductivity relaxation in rf magnetron sputtered ZnO thin films integrated with ultrathin tin metal overlayer is investigated. Charge carriers induced at the ZnO-metal interface by the tin metal overlayer compensates the surface lying trap centers and leads to the enhanced photoresponse. On termination of ultraviolet radiation, recombination of the photoexcited electrons with the valence band holes leaves the excess carriers deeply trapped at the recombination center and holds the dark conductivity level at a higher value. Equilibrium between the recombination centers and valence band, due to trapped charges, eventually stimulates the persistent photoconductivity in the Sn/ZnO photodetectors.
TL;DR: In this paper, the formation of an ordered H-Zn overlayer on the ZnO(0001) surface and its unexpected evolution toward a disordered layer was investigated.
Abstract: Total energy calculations for the adsorption of hydrogen on the polar Zn-ended ZnO(0001) surface predict that a metal-insulator transition and the reversible switch of surface magnetism can be achieved by varying the hydrogen density on the surface. An on top $\text{H}(1\ifmmode\times\else\texttimes\fi{}1)$ ordered overlayer with genuine H-Zn chemical bonds is shown to be energetically favorable. The $\text{H}(1\ifmmode\times\else\texttimes\fi{}1)$ covered surface is metallic and spin polarized. Lower hydrogen coverages lead to a nonmagnetic insulating surface, with strengthened H-Zn bonds and corrugation of the topmost layers. Our results explain the experimental observation of formation of an ordered $\text{H}(1\ifmmode\times\else\texttimes\fi{}1)$ overlayer on the ZnO(0001) surface and its unexpected evolution toward a disordered layer. Furthermore, we identify a mechanism which can contribute to the room-temperature ferromagnetism measured in ZnO thin films and nanoparticles.
TL;DR: In this article, the mesoporous material inside a polystyrene bead assembly has been demonstrated with using TEM, grazing incidence X-ray diffraction (GIXD), and Krypton sorption isotherm.
Abstract: Thin films with combined macropores (∼100 nm) and mesopores (∼3 nm) can be prepared by the electro-assisted deposition of a mesoporous silica material inside a polystyrene bead assembly The filling of voids between the polystyrene beads template strongly depends on the deposition time, as demonstrated by systematic SEM analysis Low deposition time leads only to very thin silica layers on the PS beads Longer deposition time leads to the complete filling of the macroporous texture and to the growth of an additional overlayer with very well oriented pores normal to the electrode surface The presence of mesopores into the film has been evidenced with using TEM, grazing incidence X-ray diffraction (GIXD), and Krypton sorption isotherm The electrochemical characterization demonstrates that the hierarchical material is highly permeable to external reagents, being thereby promising for various applications involving such mass transport processes
TL;DR: In this article, a two-stage magnetron sputtering process was used to fabricate high-surface-textured ZnO:Al (AZO) thin films with a very low square resistance of 0.66 Ω/sq.
Abstract: Highly surface-textured ZnO:Al (AZO) thin films have been fabricated at room temperature by a two-step magnetron sputtering process and using an oxygen-deficient ZnO target with small grain sizes. The as-deposited AZO films are composed of a highly oriented seed layer and a closely packed columnar overlayer with pyramidal growth fronts, supporting a two-step mechanism of crystallite nucleation and grain growth. The structural, optical, and electrical properties of the AZO films can be tuned by the deposition conditions. The optimal two-step AZO film with a maximum root-mean-square roughness of 40.2 nm reaches a very low square resistance of 0.66 Ω/sq (ρ = 1.32 × 10−4 Ω·cm) with an average transparency of 87.9% in the range of 400−1100 nm. The maximum haze factor of the as-deposited film is 60.7% at 360 nm, and the average haze factor is 14.8%. These properties are comparable to or exceed the reported values of surface-textured SnO2- and ZnO-based transparent conducting oxide films, making our films suitab...
TL;DR: In this paper, the authors demonstrate the high-quality passivation of the silicon (100) surface using an organic molecule (9,10-phenanthrenequinone, PQ), which reacts with the dangling bonds, thus providing a bridge between organic semiconductors and silicon.
Abstract: Merged organic-silicon heterojunction devices require the passivation of dangling bonds at the silicon surface, preferably with a low-temperature process. In this paper, we demonstrate the high-quality passivation of the silicon (100) surface using an organic molecule (9,10-phenanthrenequinone, PQ). PQ reacts with the dangling bonds, thus providing a bridge between organic semiconductors and silicon. We measure low recombination velocities (∼150 cm/s) at the PQ-silicon interface. Metal/organic-insulator/silicon capacitors and transistors prove that at PQ-silicon interface, the Fermi level can be modulated. The formation of an inversion layer with electron mobility of 600 cm2/V∙s further demonstrates the passivation quality of PQ.
TL;DR: It is shown that the delicate, temperature-dependent balance between the vertical and lateral forces is the key to understanding this unconventional phase transition, and shown that inverse disordering also occurs in two dimensions.
Abstract: Inverse melting or disordering, in which the disordered phase forms upon cooling, is known for a few cases in bulk systems under high pressure. We show that inverse disordering also occurs in two dimensions: For a monolayer of 1,4,5,8-naphthalene-tetracarboxylic dianhydride on Ag(111), a completely reversible order-disorder transition appears upon cooling. The transition is driven by strongly anisotropic interactions within the layer versus with the metal substrate. Spectroscopic data reveal changes in the electronic structure of the system corresponding to a strengthening of the interface bonding at low temperatures. We demonstrate that the delicate, temperature-dependent balance between the vertical and lateral forces is the key to understanding this unconventional phase transition.
TL;DR: In this paper, the authors overviewed the recent progress in the development of insulator coating for liquid Li blanket with V-alloy structures and proposed a two-layer coating with metallic overlayer.
TL;DR: The dependence of thin-film detection sensitivity on the optical geometrical parameters of tubes, different thicknesses and tube wall refractive indices, and on different resonant frequencies is experimentally studied.
Abstract: A simple dielectric hollow-tube has been experimentally demonstrated at terahertz range for bio-molecular layer sensing based on the anti-resonant reflecting wave-guidance mechanism. We experimentally study the dependence of thin-film detection sensitivity on the optical geometrical parameters of tubes, different thicknesses and tube wall refractive indices, and on different resonant frequencies. A polypropylene hollow-tube with optimized sensitivity of 0.003 mm/μm is used to sense a subwavelength-thick (λ/225) carboxypolymethylene molecular overlayer on the tube's inner surface, and the minimum detectable quantity of molecules could be down to 1.22 picomole/mm(2). A double-layered Fabry-Perot model is proposed for calculating the overlayer thicknesses, which agrees well with the experimental results.
TL;DR: In this paper, the authors fabricated highly adherent and electrically conductive micropatterns on SU-8 by supersonic cluster beam deposition (SCBD), which is based on the acceleration of neutral metallic nanoparticles produced in the gas phase.
Abstract: We fabricated highly adherent and electrically conductive micropatterns on SU-8 by supersonic cluster beam deposition (SCBD). This technique is based on the acceleration of neutral metallic nanoparticles produced in the gas phase. The kinetic energy acquired by the nanoparticles allows implantation in a SU-8 layer, thus producing a metal-polymer nanocomposite thin layer. The nanocomposite shows ohmic electrical conduction and it can also be used as an adhesion layer for further metallization with a metallic overlayer. We characterized the electrical conduction, adhesion and biocompatibility of microdevices obtained by SCBD on SU-8 demonstrating the compatibility of our approach with standard lift off technology on 4" wafer. A self-standing and flexible Micro Electrode Array has been produced. Cytological tests with neuronal cell lines demonstrated an improved cell growth and a spontaneous confinement of cells on the nanocomposite layer.
TL;DR: In this article, simple reaction kinetic models for photocatalyzed removal of carbonaceous and sulfur films were developed and demonstrated their applicability to a common range of deposited film-catalyst configurations studied in the photocatalyst literature.
Abstract: We develop simple reaction kinetic models for photocatalyzed removal of carbonaceous and sulfur films, and demonstrate their applicability to a common range of deposited film-catalyst configurations studied in the photocatalyst literature: 1. Non-porous photocatalyst, non-porous transparent organic overlayer (stearic, palmitic acids). 2. Porous photocatalyst: transparent organic (stearic acid) in catalyst void volume. 3. Non-porous photocatalyst, non-transparent porous overlayer (sulfur). 4. Non-porous photocatalyst, adjacent organic layer (soot). In each case, we consider a simple film-catalyst configuration, propose a corresponding one-dimensional physical model for reaction, and compare model results with literature data to evaluate the correspondence between model and experiment. These examples cover both direct and lateral oxidation by photocatalysis. The respective physical and chemical phenomena which determine these rates of film removal include intrinsic catalyst kinetics (1), simultaneous reaction and light attenuation (2), reaction with light absorption by non-transparent organic film (3), and oxidant lateral transport (surface diffusion) (4). In each case, a simple model suffices to represent the key kinetic phenomena. In all cases, the true kinetic order is zero, but the apparent order may be influenced by light absorption (case 2). The apparent rate constant may be influenced by catalyst light absorption (case 2) or overlayer (case 3), or by catalyst–reactant separation (case 4).
TL;DR: By means of the "swelling−diffusion−interfacial polymerization method" (SDIPM), the authors successfully coated polyaniline (PANi) onto the positively charged polystyrene (PS) particles, which electrostatically repulse each other.
Abstract: By means of the “swelling−diffusion−interfacial polymerization method” (SDIPM), we successfully coated polyaniline (PANi) onto the positively charged polystyrene (PS) particles, which electrostatically repulse each other. After initially forming aniline-swollen PS particles, diffusion of the monomer toward the aqueous phase was controlled through a slow addition of hydrochloric acid, eventually leading to its polymerization on the particle surface. It is an unique, facile, and efficient approach based on raw substrate particles with cationic surface, in comparison with the previous efforts focusing on laborious surface modification or customized design of the substrate particles. The synthesized composite particles have been extensively characterized using scanning electron microscope, transmission electron microscope, Fourier transform infrared, Raman spectroscopy, and thermogravimetry. The resultant PS/PANi core/shell conductive composites possessed a uniform, intact PANi overlayer, and furthermore, the...
TL;DR: In this paper, the binding energy shifts in molecular orbitals at metal/organic interfaces vary as a function of the organic overlayer thickness, and it is shown that electrostatic screening can have a significant effect on the final-state relaxation energy.
Abstract: Photoemission spectra of very thin organic films differ from that of thicker bulklike films. In particular, the binding-energy shifts in molecular orbitals at metal/organic interfaces vary as a function of the organic overlayer thickness. Using a simple image-charge model it is found that electrostatic screening can have a significant effect on the final-state relaxation energy. Good agreement between experimental results and theoretical calculations for a variety of dielectric substrates indicate that reported thickness dependent energy-level shifts in organic overlayer spectra can be accounted for by electrostatic screening. Models of organic interfaces based on photoemission spectra of organic thin films should therefore be re-examined.
TL;DR: In this paper, the authors used low temperature scanning tunneling microscope (LT-STM) and low energy electron diffraction (LEED) to study the adaption-induced structures of naphthalene on Cu(111) and found that three kinds of long-range ordered superstructures, namely (5√3 × 5 √3)R30°, (2√ 3 × 3)rect-1C10H8, and (−411−4) are observed depending on the molecular concentrations and the substrate temperatures during molecular adsorption
Abstract: Adsorbed structures of naphthalene on Cu(111) have been studied using low temperature scanning tunneling microscope (LT-STM) and low energy electron diffraction (LEED). Starting from single molecules, three kinds of long-range ordered superstructures, (5√3 × 5√3)R30°, (2√3 × 3)rect-1C10H8, and (−411−4) are observed depending on the molecular concentrations and the substrate temperatures during molecular adsorption. One of the self-assembled ordered phases with a (5√3 × 5√3) R30° periodicity is chiral in adsorption-induced arrangement though a single naphthalene molecule itself has no inherent chirality. In STM images, isolated single molecules appear as depressions whereas the molecules are seen as protrusions in self-assembled layers. Coverage dependent two-photon photoemission (2PPE) spectra show that the adsorption-induced occupied states is formed at around Cu 3d bands, and this results in the enhanced tunneling of occupied state images in assembled layers.
TL;DR: In this article, the coating systems of a NiCrAlYSi overlayer with or without a diffusion barrier (DB) were deposited by one-step arc ion plating (AIP), and isothermal and cyclic oxidations were performed at 1050 degrees C for 100 h and 100 cycles, respectively.
TL;DR: In this paper, the authors present dye-sensitized solar cells (DSSCs) employing a thermally and chemically stable Nb-doped TiO2 (NTO)/Aldoped ZnO (AZO) multilayer transparent conducting oxide (TCO) thin film.
Abstract: We present dye-sensitized solar cells (DSSCs) employing a thermally and chemically stable Nb-doped TiO2 (NTO)/Al-doped ZnO (AZO) multilayer transparent conducting oxide (TCO) thin film. The NTO overlayer was found to block oxygen diffusion into AZO during the air-annealing process for the fabrication process of the DSSCs, thereby exhibiting good thermal stability in electrical conductivity of the multilayer TCO. Moreover, the NTO overlayer suppressed the formation of Zn2+-dye aggregates at the surface of the AZO. The DSSC employing this multilayer TCO showed a photon to electron conversion efficiency of 3.8% compared to 1.9% for the cell employing the AZO single layer. The optical transmittance and charge transport properties that were measured using electrochemical impedance spectroscopy demonstrate that NTO/AZO is a promising TCO for large scale DSSCs.
TL;DR: A lattice Monte Carlo model was proposed with the aim of understanding the factors affecting the chiral self-assembly of tripod-shaped molecules in two dimensions and demonstrated a spontaneous self- assembly into extended chiral networks with hexagonal cavities.
Abstract: A lattice Monte Carlo (MC) model was proposed with the aim of understanding the factors affecting the chiral self-assembly of tripod-shaped molecules in two dimensions. To that end a system of flat symmetric molecules adsorbed on a triangular lattice was simulated by using the canonical ensemble method. Special attention was paid to the influence of size and composition of the building block on the morphology of the adsorbed overlayer. The obtained results demonstrated a spontaneous self-assembly into extended chiral networks with hexagonal cavities, highlighting the ability of the model to reproduce basic structural features of the corresponding experimental systems. The simulated assemblies were analyzed with respect to their structural and energetic properties resulting in quantitative estimates of the unit cell parameters and mean potential energy of the adsorbed layer. The predictive potential of the model was additionally illustrated by comparison of the obtained superstructures with the recent STM images that have been recorded for different organic tripod-shaped molecules adsorbed at the liquid/pyrolytic graphite interface.
TL;DR: In this article, the authors investigated the nature and localization of the TiO2 overlayer and found that there was formation of very small (UV-visible, EXAFS, XANES), ca. 2 nm or smaller (XRD and TEM) domains that cover only partially the silica surface (CO adsorption).
Abstract: Titania-coated SBA-15 materials (Ti-SBA-n with n = 1–4) were synthesized by successive grafting of titanium isopropoxide in iso-propanol. The investigation of the nature and localization of the TiO2 overlayer allowed us to conclude that there was formation of very small (UV-visible, EXAFS, XANES), ca. 2 nm or smaller (XRD and TEM) TiO2 domains that cover only partially the silica surface (CO adsorption). These nano TiO2 domains are located on or close to the mesopore surface (EELS, XRD and N2-sorption) rather than in the micropores as previously reported.
TL;DR: The growth of cubic Sr(Ti,Fe)O(3) (STF) films with an unusual self-assembled nanocomposite microstructure consisting of (100) and (110)-oriented crystals are demonstrated, offering the potential for the implementation of self-organized optical/ferromagnetic or ferromagnetic/ferroelectric hybrid nanostructures integrated on technologically important Si substrates with applications in magnetooptical or spintronic devices.
Abstract: Thin films of perovskite-structured oxides with general formula ABO3 have great potential in electronic devices because of their unique properties, which include the high dielectric constant of titanates,(1) high-TC superconductivity in cuprates,(2) and colossal magnetoresistance in manganites.(3) These properties are intimately dependent on, and can therefore be tailored by, the microstructure, orientation, and strain state of the film. Here, we demonstrate the growth of cubic Sr(Ti,Fe)O3 (STF) films with an unusual self-assembled nanocomposite microstructure consisting of (100) and (110)-oriented crystals, both of which grow epitaxially with respect to the Si substrate and which are therefore homoepitaxial with each other. These structures differ from previously reported self-assembled oxide nanocomposites, which consist either of two different materials(4-7) or of single-phase distorted-cubic materials that exhibit two or more variants.(8-12) Moreover, an epitaxial nanocomposite SrTiO3 overlayer can be...