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Materials, Volume 3, Issue 11 (November 2010), Pages 4860-5006

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Research

Jump to: Review

Open AccessArticle Mapping Disorder in Polycrystalline Relaxors: A Piezoresponse Force Microscopy Approach
Materials 2010, 3(11), 4860-4870; doi:10.3390/ma3114860
Received: 12 September 2010 / Accepted: 22 October 2010 / Published: 28 October 2010
Cited by 10 | PDF Full-text (581 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Advances in Ferroelectric & Piezoelectric Materials)
Open AccessArticle Transparent Conducting Oxides for Photovoltaics: Manipulation of Fermi Level, Work Function and Energy Band Alignment
Materials 2010, 3(11), 4892-4914; doi:10.3390/ma3114892
Received: 25 September 2010 / Accepted: 25 October 2010 / Published: 2 November 2010
Cited by 98 | PDF Full-text (190 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Solar Energy Materials)
Open AccessArticle Photovoltaic Properties in Interpenetrating Heterojunction Organic Solar Cells Utilizing MoO3 and ZnO Charge Transport Buffer Layers
Materials 2010, 3(11), 4915-4921; doi:10.3390/ma3114915
Received: 19 October 2010 / Accepted: 2 November 2010 / Published: 8 November 2010
Cited by 11 | PDF Full-text (246 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Solar Energy Materials)
Open AccessArticle Solvent Vapor Treatment Effects on Poly(3-hexylthiophene) Thin Films and its Application for Interpenetrating Heterojunction Organic Solar Cells
Materials 2010, 3(11), 4939-4949; doi:10.3390/ma3114939
Received: 22 October 2010 / Revised: 8 November 2010 / Accepted: 12 November 2010 / Published: 15 November 2010
Cited by 6 | PDF Full-text (602 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Solar Energy Materials)
Open AccessArticle Mechanisms of Texture Development in Lead-Free Piezoelectric Ceramics with Perovskite Structure Made by the Templated Grain Growth Process
Materials 2010, 3(11), 4965-4978; doi:10.3390/ma3114965
Received: 1 October 2010 / Revised: 10 November 2010 / Accepted: 19 November 2010 / Published: 22 November 2010
Cited by 7 | PDF Full-text (2113 KB) | HTML Full-text | XML Full-text
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 Bi0.5(Na,K)0.5TiO3. The dominant mechanism was different in [...] Read more.
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 Bi0.5(Na,K)0.5TiO3. The dominant mechanism was different in each material; grain boundary migration in BaTiO3, solid state spreading in Bi0.5(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. Full article
Open AccessArticle SAXS Studies of TiO2 Nanoparticles in Polymer Electrolytes and in Nanostructured Films
Materials 2010, 3(11), 4979-4993; doi:10.3390/ma3114979
Received: 11 October 2010 / Revised: 10 November 2010 / Accepted: 17 November 2010 / Published: 22 November 2010
Cited by 3 | PDF Full-text (2445 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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. Full article
Open AccessArticle Neural Stem Cell Spreading on Lipid Based Artificial Cell Surfaces, Characterized by Combined X-ray and Neutron Reflectometry
Materials 2010, 3(11), 4994-5006; doi:10.3390/ma3114994
Received: 25 October 2010 / Accepted: 9 November 2010 / Published: 22 November 2010
Cited by 1 | PDF Full-text (552 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Supported Lipid Membrane Surface Modifications and Applications)
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Review

Jump to: Research

Open AccessReview Catalytic CVD Synthesis of Carbon Nanotubes: Towards High Yield and Low Temperature Growth
Materials 2010, 3(11), 4871-4891; doi:10.3390/ma3114871
Received: 12 October 2010 / Accepted: 25 October 2010 / Published: 1 November 2010
Cited by 36 | PDF Full-text (672 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Progress in Nanomaterials Preparation)
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Open AccessReview Review of the Two-Step H2O/CO2-Splitting Solar Thermochemical Cycle Based on Zn/ZnO Redox Reactions
Materials 2010, 3(11), 4922-4938; doi:10.3390/ma3114922
Received: 8 October 2010 / Revised: 4 November 2010 / Accepted: 8 November 2010 / Published: 12 November 2010
Cited by 52 | PDF Full-text (396 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Solar Energy Materials)
Open AccessReview Recent Progress of Ferroelectric-Gate Field-Effect Transistors and Applications to Nonvolatile Logic and FeNAND Flash Memory
Materials 2010, 3(11), 4950-4964; doi:10.3390/ma3114950
Received: 18 October 2010 / Revised: 12 November 2010 / Accepted: 16 November 2010 / Published: 18 November 2010
Cited by 20 | PDF Full-text (1588 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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 (Vth) distribution. The Vth 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. Full article
(This article belongs to the Special Issue Advances in Ferroelectric & Piezoelectric Materials)

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