Table of Contents

Abstract: Relaxors constitute a large class of ferroelectrics where disorder is introduced by doping with ions of different size and valence, in order to maximize their useful properties in a broad temperature range. Polarization disorder in relaxors is typically studied by dielectric and scattering techniques that do not allow direct mapping of relaxor parameters, such as correlation length or width of the relaxation time spectrum. In this paper, we introduce a novel method based on measurements of local vibrations by Piezoresponse Force Microscopy (PFM) that detects nanoscale polarization on the relaxor surface. Random polarization patterns are then analyzed via local Fast Fourier Transform (FFT) and the FFT PFM parameters, such as amplitude, correlation radius and width of the spectrum of spatial correlations, are mapped along with the conventional topography. The results are tested with transparent (Pb, La) (Zr, Ti)O₃ ceramics where local disorder is due to doping with La³⁺. The conclusions are made about the distribution of the defects responsible for relaxor behavior and the role of the grain boundaries in the macroscopic response.

Abstract: The catalytic chemical vapor deposition (CCVD) is currently the most flexible and economically attractive method for the growth of carbon nanotubes. Although its principle is simple, the precisely controlled growth of carbon nanotubes remains very complex because many different parameters influence the growth process. In this article, we review our recent results obtained on the synthesis of carbon nanotubes via CCVD. We discuss the role of the catalyst and the catalyst support. Our recent results obtained from the water assisted growth and the equimolar C₂H₂-CO₂ reaction are also discussed. Both procedures lead to significantly enhanced carbon nanotube growth. In particular, the latter allows growing carbon nanotubes on diverse substrate materials at low temperatures.

Abstract: Doping limits, band gaps, work functions and energy band alignments of undoped and donor-doped transparent conducting oxides Zn₀, In₂O₃, and SnO₂ as accessed by X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS) are summarized and compared. The presented collection provides an extensive data set of technologically relevant electronic properties of photovoltaic transparent electrode materials and illustrates how these relate to the underlying defect chemistry, the dependence of surface dipoles on crystallographic orientation and/or surface termination, and Fermi level pinning.

Abstract: Organic thin-film solar cells with a conducting polymer (CP)/fullerene (C₆₀) interpenetrating heterojunction structure, fabricated by spin-coating a CP onto a C₆₀ deposit thin film, have been investigated and demonstrated to have high efficiency. The photovoltaic properties of solar cells with a structure of indium-tin-oxide/C₆₀/ poly(3-hexylthiophene) (PAT6)/Au have been improved by the insertion of molybdenum trioxide (VI) (MoO₃) and zinc oxide charge transport buffer layers. The enhanced photovoltaic properties have been discussed, taking into consideration the ground-state charge transfer between PAT6 and MoO₃ by measurement of the differential absorption spectra and the suppressed contact resistance at the interface between the organic and buffer layers.

Abstract: This article provides a comprehensive overview of the work to date on the two‑step solar H₂O and/or CO₂ splitting thermochemical cycles with Zn/ZnO redox reactions to produce H₂ and/or CO, i.e., synthesis gas—the precursor to renewable liquid hydrocarbon fuels. The two-step cycle encompasses: (1) The endothermic dissociation of ZnO to Zn and O₂ using concentrated solar energy as the source for high-temperature process heat; and (2) the non-solar exothermic oxidation of Zn with H₂O/CO₂ to generate H₂/CO, respectively; the resulting ZnO is then recycled to the first step. An outline of the underlying science and the technological advances in solar reactor engineering is provided along with life cycle and economic analyses.

Abstract: The solvent vapor treatment (SVT) for poly(3-hexylthiophene) (PAT6) films and its application to interpenetrating heterojunction organic solar cells have been studied. It was found that SVT could improve the crystallinity and electrical characteristics of the PAT6 films. We fabricated organic solar cells with an interpenetrating structure of PAT6 and fullerenes utilizing the SVT process, and discuss the improved performance of the solar cells by taking the film crystallinity, optical properties, and morphology into consideration.

Abstract: We have investigated ferroelectric-gate field-effect transistors (FeFETs) with Pt/SrBi₂Ta₂O₉/(HfO₂)_x(Al₂O₃)_1−x (Hf-Al-O) and Pt/SrBi₂Ta₂O₉/HfO₂ gate stacks. The fabricated FeFETs have excellent data retention characteristics: The drain current ratio between the on- and off-states of a FeFET was more than 2 × 10⁶ after 12 days, and the decreasing rate of this ratio was so small that the extrapolated drain current ratio after 10 years is larger than 1 × 10⁵. A fabricated self-aligned gate Pt/SrBi₂Ta₂O₉/Hf-Al-O/Si FET revealed a sufficiently large drain current ratio of 2.4 × 10⁵ after 33.5 day, which is 6.5 × 10⁴ after 10 years by extrapolation. The developed FeFETs also revealed stable retention characteristics at an elevated temperature up to 120 °C and had small transistor threshold voltage (V_th) distribution. The V_th can be adjusted by controlling channel impurity densities for both n-channel and p-channel FeFETs. These performances are now suitable to integrated circuit application with nonvolatile functions. Fundamental properties for the applications to ferroelectric-CMOS nonvolatile logic-circuits and to ferroelectric-NAND flash memories are demonstrated.

Abstract: The mechanisms of texture development were examined for BaTiO₃ and a (K,Na,Li)(Nb,Ta)O₃ solid solution made by the templated grain growth method, and compared with the mechanism in Bi_0.5(Na,K)_0.5TiO₃. The dominant mechanism was different in each material; grain boundary migration in BaTiO₃, solid state spreading in Bi_0.5(Na,K)_0.5TiO₃, and abnormal grain growth in the (K,Na,Li)(Nb,Ta)O₃ solid solution. The factor determining the dominant mechanism is the degree of smoothness of surface structure at an atomic level.

Abstract: Polymer electrolytes as nanostructured materials are very attractive components for batteries and opto-electronic devices. (PEO)₈ZnCl₂ polymer electrolytes were prepared from PEO and ZnCl₂. The nanocomposites (PEO)₈ZnCl₂/TiO₂ themselves contained TiO₂ nanograins. In this work, the influence of the TiO₂ nanograins on the morphology and ionic conductivity of the nanocomposite was systematically studied by transmission small-angle X-ray scattering (SAXS) simultaneously recorded with wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) at the synchrotron ELETTRA. Films containing nanosized grains of titanium dioxide (TiO₂) are widely used in the research of optical and photovoltaic devices. The TiO₂ films, prepared by chemical vapor deposition and e-beam epitaxy, were annealed in hydrogen atmospheres in the temperature range between 20 °C and 900 °C in order to study anatase-rutile phase transition at 740 °C. Also, grazing-incidence small angle X-ray scattering (GISAXS) spectra for each TiO₂ film were measured in reflection geometry at different grazing incident angles. Environmentally friendly galvanic cells, as well as solar cells of the second generation, are to be constructed with TiO₂ film as working electrode, and nanocomposite polymer as electrolyte.

Abstract: We developed a bioadhesive coating based on a synthetic peptide-conjugate (AK-cyclo[RGDfC]) which contains multiples of the arginyl-glycyl-aspartic acid (RGD) amino acid sequence. Biotinylated AK-cyclo[RGDfC] is bound to a supported lipid bilayer via a streptavidin interlayer. Layering, hydration and packing of the coating is quantified by X-ray and neutron reflectometry experiments. AK-cyclo[RGDfC] binds to the streptavidin interlayer in a stretched-out on edge configuration. The highly packed configuration with only 12% water content maximizes the number of accessible adhesion sites. Enhanced cell spreading of neural stem cells was observed for AK-cyclo[RGDfC] functionalized bilayers. Due to the large variety of surfaces which can be coated by physisorption of lipid bilayers, this approach is of general interest for the fabrication of biocompatible surfaces.