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Visible Wavelength (visible + wavelength)
Selected AbstractsBulk Photovoltaic Effect at Visible Wavelength in Epitaxial Ferroelectric BiFeO3 Thin FilmsADVANCED MATERIALS, Issue 15 2010Wei Ji Appreciable photovoltaic responses to visible light are observed in epitaxial ferroelectric BiFeO3 thin films by sputtering deposition. The photocurrent direction is opposite to the BiFeO3 polarization vector and can be switched by poling the films in different directions (see figure). The as-deposited films are strongly self-polarized, exhibiting significant photovoltaic response before any electrical poling process. [source] Log-Pile TiO2 Photonic Crystal for Light Control at Near-UV and Visible WavelengthsADVANCED MATERIALS, Issue 4 2010Ganapathi Subramania Three-dimensional photonic crystals with an omnidirectional bandgap at visible frequencies can have significant impact on solid-state lighting and solar-energy conversion. Using a procedure based on multistep electron-beam lithographic processing, a 9-layer log-pile photonic crystal is fabricated composed of 70-nm-wide titanium dioxide rods with 250-nm lattice spacing that exhibit a stacking direction bandgap between 400,nm and 500,nm (see image). [source] Multiple microscopy modalities applied to a sea urchin tooth fragmentJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2003S. R. Stock Two synchrotron X-ray microscopy methods, phase-contrast microradiography (the propagation method) and absorption microCT (high-resolution computed tomography or microtomography), and laser-scanning confocal microscopy (visible wavelength) were used to study a fragment of the keel of a tooth of the sea urchin Lytechinus variegatus. Stripes observed in the phase-contrast images of the fragment were also seen in confocal micrographs. MicroCT showed that the stripes were due to two parallel planar arrays of low-absorption channels within the bulk of the keel. In the phase microradiographs, maximum contrast stripes appear when a channel image from one row coincides with a channel image from the second row; otherwise, contrast is minimal. Long channels do not appear to have been observed previously in keels of sea urchin teeth. [source] UV-Curable Azobenzene Polymer Bearing Photo-Crosslinkable Moiety for Stabilization of Photo-Fabricated Surface Relief StructureMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2002Tatsumi Kimura Abstract In order to find a new class of photo-processable liquid crystalline (LC) aligning material, five kinds of new maleimide-based copolymers bearing both azobenzene and cinnamate moieties with different functionalization ratio have been synthesized. The properties of these five copolymers were compared regarding physical and chemical properties that are required for our aim. The photo-induced surface relief (PSR) gratings could be fabricated on the films of these copolymers using an Ar+ laser (,,=,488 nm), and were successfully immobilized and bleached by UV-light irradiation that causes photo-crosslinking of the cinnamate moiety and photo-degradation of the azobenzene moiety, respectively. The PSR inscription rate and the thermal stability have been investigated regarding the functionalization ratio between cinnamate and azobenzene side chain. The residual ratio of the PSR structure after UV-curing was increased with increasing photo-crosslinkable moiety. It was confirmed that the UV-cured PSR grating structure becomes transparent at visible wavelength and was able to align LC molecules parallel to the grating direction. Polarized optical microscope image of LC cell aligned by the PMPDC 21-18 film with UV-cured PSR structure (0°). [source] Crystalline ZnO/SrTiO3 transparent field effect transistorPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008E. Bellingeri Abstract We fabricated field effect transistors which are transparent at visible wavelength, by realizing epitaxial ZnO/SrTiO3 heterostructures. High crystalline quality ZnO layers were grown by pulsed laser deposition on 110 oriented strontium titanate single crystals. By conventional photolithographic techniques we realized micrometric sized devices in both bottom-gate stacked layers geometry and planar side-gate configuration. Our transistors show 80% light transmittance, on/off ratios up to 106 and field effect mobilities up to 30 cm2/Vs at 77 K. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fluorescence Modulation in Polymer Bilayers Containing Fluorescent and Photochromic Dopants,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2005M. Tomasulo Abstract We have identified viable operating principles for the modulation of optical signals under the influence of optical stimulations. They are based on the overlap between the emission bands of a fluorescent compound and the absorption bands of one of the two forms of a bistable photochromic switch. Under these conditions, the photoinduced interconversion of the two states of the photochrome modulates efficiently the emission intensity of the fluorophore. We have implemented this mechanism for intermolecular fluorescence modulation with multilayer structures. They consist of two quartz plates sandwiching two overlapping polymer layers. One of the polymers is doped with a fluorescent benzofurazan. The other contains a photochromic spiropyran. The multilayer assembly is operated with two light sources. One of them is centered at the excitation wavelength of the fluorophore, where neither of the two states of the photochrome absorbs. The other light source is switched between ultraviolet and visible wavelengths to induce the interconversion between the two states of the photochrome. The light emitted by the fluorescent component has to propagate through the photochromic layer before reaching a detector. It can do so efficiently for only one of the two states of the photochrome. It follows that a measurement of the light intensity reaching the detector can read the state of the photochromic switch, which in turn is written and erased with optical stimulations. Thus, our strategy for all-optical processing can be used to store and retrieve binary digits, as well as to implement optical inversion, with the aid of engineered molecule-based components. [source] Silicon-Based Near-Visible Logpile Photonic CrystalADVANCED MATERIALS, Issue 37 2010Ganapathi Subramania A nanocavity structure is embedded inside a silicon logpile photonic crystal that demonstrates tunable absorption behavior at near visible wavelengths well beyond the absorption edge of silicon. This is due to silicon's indirect bandgap resulting in a relatively slow increase in the absorption of silicon with decreasing wavelength. Our results open up the possibility of utilizing the wide, complete three dimensional photonic gap enabled by the large refractive index of silicon to create three dimensional photonic crystal based devices well into the visible regime. [source] Highly Bendable, Transparent Thin-Film Transistors That Use Carbon-Nanotube-Based Conductors and Semiconductors with Elastomeric Dielectrics,ADVANCED MATERIALS, Issue 3 2006Q. Cao Transparent flexible thin-film transistors (see Figure) have been made using single-walled carbon nanotube networks of high and moderate coverages as the conducting and semiconducting layers. Electrical (e.g., good performance on plastic), optical (e.g. transparency to visible wavelengths), and mechanical (e.g. extreme flexibility) characteristics that would be difficult, or impossible, to achieve with conventional materials are reported. [source] | ||||||||||