1,720,987 research outputs found
Epidemia di scabbia in una residenza protetta per anziani
No full textviene descritta la gestione di un' epidemia di scabbia in una casa protett
All-inkjet printed organic transistors: Dielectric surface passivation techniques for improved operational stability and lifetime
No full textWe report about the use of a printed pentafluorothiophenol layer on top of the dielectric surface as a passivation coating to improve the operational stability of all-ink-jet printed transistors. Transistors with bottom-gate structure were fabricated using cross-linked poly-4-vinylphenol (c-PVP) as dielectric layer and an ink formulation of an amorphous triarylamine polymer as semiconductor. The resulting TFTs had low turn-on voltage (Vth < |5 V|) and a mobility ≈0.1 cm2/(V s). A comparison of identically fabricated transistors shows that devices with coated dielectric have a higher operational stability than those using bare c-PVP. This conclusion is supported by a quantitative study of the threshold voltage shift with time under continuous operation. Long exposure to the ambient atmosphere causes an increase in the threshold voltage strongly dependent on the used semiconducting ink formulation. © 2015 Elsevier Ltd
Analysis of the persistent photoresponse of C8BTBT transistors in the near-bandgap spectral region
No full textThe variations in physical parameters of an organic field-effect transistor having dioctylbenzothieno[2,3-b]benzothiophene (C8BTBT) as the channel semiconductor were investigated under different light irradiation conditions at wavelengths of 350 nm, 370 nm, 400 nm and by increasing exposure doses. The progress of the electro-optical history of the transistor was evaluated by repeating I-V scan cycles both in the dark and under light exposure. The information recorded upon different exposure times was used to detect the photoactivated charge-trapping effects. The device showed a stable I-V response in the dark bias (VDS = -10 V, -10 V ≤ VGS ≤ +10 V) conditions and a persistent threshold voltage (VT) shift under illumination at all irradiation wavelengths. We suggested that the observed dose-dependent VT drifts were due to charge retention in trap sites within the organic semiconductor. The threshold voltage was recognized as the main parameter affected by charge retention. VT variations were modelled versus time through a single exponential revealing a maximum in charge relaxation times for irradiations at wavelengths of 370 nm, in proximity of the C8BTBT bandgap energy. Furthermore, bias-stress effects and persistent photoinduced VT drifts were found to depend on comparable characteristic times. Therefore, a common nature for both the bias-stress decay and relaxation from photoexcitation mechanisms is likely. © 2015 Elsevier B.V. All rights reserved
Photosensing properties of pentacene OFETs based on a novel PMMA copolymer gate dielectric
No full textIn the present work, bottom-gate top-contact organic field effect transistors (OFETs) were fabricated by evaporating a pentacene semiconductor film on top of a new insulating poly(methyl methacrylate) (PMMA) copolymer containing methacrylate units. The PMMA copolymer was synthesized in order to combine the well-known insulating properties of PMMA with the possibility to be efficiently photocured enabling photopatterning-based organic circuitry integration processes. The properties of the pentacene layer deposited on ITO/PMMA copolymer stack were studied through morphological and structural analyses. Device photoresponses and photoexcitated transients were investigated and compared to reference devices based on standard PMMA gate dielectric. © 2015 IEEE
Tube expansion deformation enables in situ synchrotron X-ray scattering measurements during extensional flow-induced crystallization of Poly L-lactide near the glass transition
No full textCoronary Heart Disease (CHD) is one of the leading causes of death worldwide, claiming over seven million lives each year. Permanent metal stents, the current standard of care for CHD, inhibit arterial vasomotion and induce serious complications such as late stent thrombosis. Bioresorbable vascular scaffolds (BVSs) made from poly L-lactide (PLLA) overcome these complications by supporting the occluded artery for 3-6 months and then being completely resorbed in 2-3 years, leaving behind a healthy artery. The BVS that recently received clinical approval is, however, relatively thick (~150 μm, approximately twice as thick as metal stents ~80 μm). Thinner scaffolds would facilitate implantation and enable treatment of smaller arteries. The key to a thinner scaffold is careful control of the PLLA microstructure during processing to confer greater strength in a thinner profile. However, the rapid time scales of processing (~1 s) defy prediction due to a lack of structural information. Here, we present a custom-designed instrument that connects the strain-field imposed on PLLA during processing to in situ development of microstructure observed using synchrotron X-ray scattering. The connection between deformation, structure and strength enables processing-structure-property relationships to guide the design of thinner yet stronger BVSs. © 2018 by the authors
Gravure Printing for PVDF Thin-Film Pyroelectric Device Manufacture
No full textPyroelectric energy harvesting is one of the more recent and promising solid-state approaches for directly converting time-dependent temperature fluctuations into electric energy. Conventional printing technologies can offer many advantages for the production of pyroelectric thin-film-based devices, such as low cost, low temperature, the use of flexible substrates and shaping at the same time as deposition. Nevertheless, some issues related to low printed thickness and film-forming microstructure control need to be addressed. In this exploratory study, the possibility of exploiting the highly attractive gravure printing process for the potential industrial manufacture of flexible polyvinylidene fluoride (PVDF) thin-film pyroelectric devices was investigated. By the use of corona pre-treatment of the printing substrate and low-temperature polar solvent evaporation, multilayer gravure-printed PVDF pyroelectric devices were successfully manufactured for the first time, achieving a maximum generated current of 0.1 nA at 2.5 K/s from a device with an active area of 1 cm2. Considering the very low thermal inertia and performance scaling by the area expected for pyroelectric thin-film-based devices, combined with the upscaling potential of roll-to-roll gravure printing, our results provide new opportunities for on-demand, low-cost pyroelectric device manufacture and their integration in hybrid harvesters
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