1,720,964 research outputs found
OFET for gas sensing based on SuMBE grown pentacene films
No full textSupersonic molecular beam deposition (SuMBE) is a thin film growth method for organic semiconducting molecules that gives unprecedented control oil morphology and structure by tuning the kinetic energy of the impinging molecules. This is the key factor by which we could control the growth of high quality films showing state of the art electrical properties for pentacene films. We show that exploiting such ability to control structure and morphology of the films one could tailor the gas response of the organic thin film transistors. We envisage the potential of such devices in applications where the transistor configuration offers new strategic opportunities as in gas sensing and in microfluidics. (c) 2007 Elsevier Ltd. All rights reserved
Proton transfer reaction mass spectrometry: a new technique to assess post harvest quality of strawberries
No full textSupersonic molecular beams deposition of alpha-quaterthiophene: Enhanced growth control and devices performances
No full textThe alpha-quatertiophene is widely considered an interesting material for the realization of organic electronics and opto-electronics. Compared to other oligothiophenes, the performances of transistors based on this compound are limited by its kind of growth on the typical materials used for device realization. Here we show that via seeded supersonic beams we can lead to a nice improvement of both morphological and electrical properties of the film grown, through a better control of the initial state of the precursor in the vapor phase. Using the high kinetic energy achievable in the supersonic beams, we increase the dimensions of the grains and the coalescence of different islands, limiting the grain boundary formation, As consequence, the performance of the realized field effect transistors is enhanced of one order of magnitude. (C) 2009 Elsevier B.V. All rights reserved
Optimizing picene molecular assembling by supersonic molecular beam deposition
Full text linkHere we report an investigation of the growth of picene by supersonic molecular beam deposition on thermal silicon oxide and on a self-assembled monolayer of hexamethyldisiloxane (HMDS). In both cases film morphology shows a structure with very sharp island edges and well-separated islands which size and height depend on the deposition conditions. Picene films growth on bare silicon covered with hydrophobic HDMS shows islands characterized by large regular crystallites of several micrometers; on the other hand, films growth on silicon oxide shows smaller and thicker islands. We analyzed the details of the growth model and describe it as a balancing mechanism involving the weak interaction between molecules and surface and the strong picene-picene interaction that leads to a different Schwoebel-Ehrlich barrier in the first layer with respect to the successive one. Finally, we study the charge transport properties of these films by fabricating field-effect transistors devices in both top and bottom contact configuration. We notice that substrate influences the electrical properties of the device and we obtained a maximum mobility value of 1.2 cm2 V-1 s-1 measured on top contact devices in air. © 2012 American Chemical Society
Role of kinetic energy of impinging molecules in the alpha-sexithiophene growth
No full textWe report on the alpha-sexithiophene sub-monolayer growth with supersonic molecular beam deposition by investigating how the kinetic energy of the impinging molecules influences the growth on substrates with different surface wettabilities and temperatures. The results show that the energy of the impinging molecules affects the morphology of the molecular film increasing the coverage and the island size, and reducing the fractality of the sub-monolayer islands. The possibility of directing growth of more ordered islands could improve the performances of electronic devices, which are greatly affected by the structure of the first monolayers. (C) 2011 Elsevier B.V. All rights reserved
Solid state dye sensitized solar cells based on supersonic beam deposition of organic, inorganic cluster assembled, and nanohybrid materials
No full textThe growth of nanohybrids synthesized by supersonic beam codeposition of metal oxide clusters, produced by microplasma cluster source, and of aerodynamically accelerated molecules has been explored as a novel approach to the preparation of controlled dye sensitized materials for photovoltaic applications. The hybrid nanostructures are formed through deposition via supersonic expansion processes, controlling the kinetic energy of the precursors. With this approach, we developed prototype dye sensitized solar cells based on nanostructured TiO2 and CuPc with different architectures. To explore the viability of this approach, we compare cells made layer by layer with those where an intermediate codeposited layer is inserted between the two raw materials. This latter type of cells presents an enhancement of the photocurrent of a factor of 45 and of the efficiency of a factor of 40. This work opens a new viable perspective in the growth and in the control of the interfacial properties of nanohybrid materials, by direct codeposition of molecules and oxide nanostructures, with demonstrated useful applications in photovoltaic devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3501337
PTR-MS una diagnostica ad altissima sensibilità (PPT) di volatili organici per applicazioni agroalimentari: senescenza di bacche
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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