37 results on '"Dikonimos, T."'
Search Results
2. Taguchi optimized synthesis of graphene films by copper catalyzed ethanol decomposition
- Author
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Santangelo, S., Messina, G., Malara, A., Lisi, N., Dikonimos, T., Capasso, A., Ortolani, L., Morandi, V., and Faggio, G.
- Published
- 2014
- Full Text
- View/download PDF
3. Annealing Free, High Quality CVD Graphene Growth and Transfer
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Brajpuriya, R., primary, Dikonimos, T., additional, Buonocore, F., additional, and Lisi, N., additional
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- 2016
- Full Text
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4. Carbon nanowall growth on carbon paper by hot filament chemical vapour deposition and its microstructure
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Lisi, N., Giorgi, R., Re, M., Dikonimos, T., Giorgi, L., Salernitano, E., Gagliardi, S., and Tatti, F.
- Published
- 2011
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5. Graphene-based derivative as interfacial layer in graphene/n-Si Schottky barrier solar cells
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Lisi, N., Dikonimos, T., Veneri, P.D., Bobeico, E., Lancellotti, L., Lisi, N., Dikonimos, T., Veneri, P. D., Bobeico, E., and Lancellotti, L.
- Subjects
Photovoltaics ,Graphene-based derivative ,CVD graphene ,Raman spectroscopy ,Solar cell ,Photovoltaic - Abstract
In Schottky barrier solar cell (SBSC), the interface between absorber and front electrode plays a vital role for reducing the dark current, blocking the majority carriers injected into the electrode at forward bias, reducing surface recombination and passivating the silicon surface. In this respect, the addition of interfacial layer between the semiconductor absorber and the metal electrode can reflect into an improvement of the device performance. Here we combine n-type crystalline silicon with stacks of graphene and graphene-based derivative (GBD) layers with different properties, in order to realize efficient SBSCs. Graphene layers with different structure, work function and electrical conductivity, were obtained by varying the chemical vapor deposition (CVD) parameters: conductive graphene films were grown at 1070 °C, GBD interfacial layers at 790 °C. The stacked structures were fabricated by the multiple transfer of these films. The films and the stacks were characterized by Raman spectroscopy. The device with the GBD interlayer (acting as hole transport layer) exhibits promising performances in terms of external quantum efficiency (EQE) and power conversion efficiency (PCE, ~5 %). Doping treatments with nitric acid vapor was performed and improved the cell PCE up to 6.7 %. © 2018 AMSE Press. All rights reserved.
- Published
- 2018
6. Graphene -Gold Electrodes for Flexible Nanogenerators Based on Porous Piezoelectric PVDF Films
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Fortunato, M., primary, Rinaldi, A., additional, Tamburrano, A., additional, De Bellis, G., additional, Dikonimos, T., additional, Lisi, N., additional, and Sarto, M.S., additional
- Published
- 2018
- Full Text
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7. Effects of HNO3 molecular doping in graphene/Si Schottky barrier solar cells
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Delli Veneri, P., Lisi, N., Dikonimos, T., Della Noce, M., Capasso, A., Bobeico, E., Lancellotti, L., Delli Veneri, P., Lisi, N., Dikonimos, T., Della Noce, M., Capasso, A.,, Bobeico, E., and Lancellotti, L.
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Solar cell ,Graphene ,Chemical doping ,Schottky barrier - Abstract
Schottky barrier solar cells based on graphene/n-silicon heterojunction have been fabricated and characterized and the effect of graphene molecular doping by HNO3 on the solar cells performances have been analyzed. Different doping conditions and thermal annealing processes have been tested to asses and optimize the stability of the devices. The PCE of the cells increases after the treatment by HNO3 and reaches 5% in devices treated at 200 °C immediately before the exposition to the oxidant. Up to now our devices retain about 80% of efficiency over a period of two weeks, which represents a good stability result for similar devices. © 2014 AEIT.
- Published
- 2014
8. Improving the cleanliness of graphene grown on copper by chemical vapor deposition for biosensing applications
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Pittori, M., Brajpuriya, R., Leoni, E., Capasso, A., Dikonimos, T., Buonocore, F., Mazzaro, R., Morandi, V., Rizzoli, R., Santonicola, M. G., and Lisi, N.
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graphene ,SEM ,chemical vapor deposition ,biosensors - Published
- 2016
9. Electrocatalysts for Methanol Oxidation Based on Platinum/Carbon Nanofibers Nanocomposite
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S. Gagliardi, Luca Giorgi, Rossella Giorgi, E. Salernitano, Martina, Nicola Lisi, Dikonimos T, and De Riccardis F
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Materials science ,Nanocomposite ,Graphene ,Carbon nanofiber ,Biomedical Engineering ,chemistry.chemical_element ,Bioengineering ,General Chemistry ,Carbon nanotube ,Carbon black ,Condensed Matter Physics ,law.invention ,chemistry ,Chemical engineering ,law ,Nanofiber ,General Materials Science ,Cyclic voltammetry ,Carbon - Abstract
New carbon nanomaterials, i.e., carbon nanotubes and nanofibers, with special physico-chemical properties, are recently studied as support for methanol oxidation reaction electrocatalysts replacing the most widely used carbon black. Particularly, carbon fibrous structures with high surface area and available open edges are thought to be promising. Platelet type carbon nanofibers, which have the graphene layers oriented perpendicularly to the fiber axis, exhibit a high ratio of edge to basal atoms. Different types of carbon nanofibers (tubular and platelet) were grown by plasma enhanced chemical vapour deposition on carbon paper substrates. The process was controlled and optimised in term of growth pressure and temperature. Carbon nanofibers were characterised by high resolution scanning electron microscopy and X-ray photoelectron spectroscopy to assess the morphological properties. Then carbon nanofibers of both morphologies were used as substrates for Pt electrodeposition. High resolution scanning electron microscopy images showed that the Pt nanoparticles distribution was well controlled and the particles size went down to few nanometers. Pt/carbon nanofibers nanocomposites were tested as electrocatalysts for methanol oxidation reaction. Cyclic voltammetry in H2SO4 revealed a catalyst with a high surface area. Cyclic voltammetry in presence of methanol indicated a high electrochemical activity for methanol oxidation reaction and a good long time stability compared to a carbon black supported Pt catalyst.
- Published
- 2011
10. High frequency performance limits of nanointerconnects based on CVD-grown graphene films transferred on SiO2-substrate
- Author
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Giorgi, R., Dikonimos, T., Lisi, N., Giorgi, R., Dikonimos, T., and Lisi, N.
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nanotechnology ,transmission lines ,sheet resistance measurements ,signal propagation ,Graphene ,nanointerconnect ,transmission line ,ignal propagation ,heet resistance measurement - Abstract
Graphene films are grown by chemical vapour deposition on copper layer and then transferred onto a silicon substrate, coated with silicon dioxide. The topological characterization of the produced film is performed by atomic force microscopy, and the sheet resistance is measured by applying the four-probe test method. The equivalent single conductor model is then used in order to analyze the signal propagation along a nanointerconnect made with multilayer graphene over silicon dioxide, in a wide frequency range, up to 100 GHz. The comparison of the radio-frequency performances of the nanointerconnect, modeled by using either the measured value of effective resistivity or a theoretical estimation of the p.u.l. resistance, suggests that graphene films grown by chemical vapor deposition are more suitable for application as low frequency electrical interconnections in flexible electronics, than in high-speed integrated circuits. © 2013 IEEE.
- Published
- 2013
11. Effect of growth parameters on the properties of RF-sputtered highly conductive and transparent p-type NiOxfilms
- Author
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Grilli, M L, primary, Menchini, F, additional, Dikonimos, T, additional, Nunziante, P, additional, Pilloni, L, additional, Yilmaz, M, additional, Piegari, A, additional, and Mittiga, A, additional
- Published
- 2016
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12. Graphene/Silicon Heterojunction for Photovoltaic Applications
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Lancellotti, L., Bobeico, E., Capasso, A., Della Noce, M., Delli Veneri, P., Del Sorbo, S., Dikonimos, T., Di Francia, G., Lisi, N., Mittiga, A., Polichetti, T., and Ricciardella, F.
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MATERIAL STUDIES, NEW CONCEPTS, ULTRA-HIGH EFFICIENCY AND SPACE TECHNOLOGY ,New Materials and Concepts for Cells - Abstract
28th European Photovoltaic Solar Energy Conference and Exhibition; 340-343, One of the most reputable applications of graphene is in the field of solar cells because of its notable performances as transparent electrode and active layer for electron-hole separation in photovoltaic devices. In the present paper we fabricate and characterize graphene/n-crystalline-silicon heterojunctions with simple planar thin-film geometry. The rectifying behaviour of the devices is verified through the acquisition of dark current-voltage curves. External quantum efficiencies (EQE) have also been measured to evaluate the charge separation and collection, as a result of the Schottky barrier formed at the interface between graphene and silicon. Our devices show EQE values over 50% for wavelengths in the range 400 nm<
- Published
- 2013
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13. The Italian FIRB project on EUV lithography
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Reale, A, Baldacchini, G, Baldesi, A, Bellecci, C, Bollanti, S, Bonfigli, F, Clementi, G, Conti, A, Dikonimos, T, Di Lazzaro, P, Flora, F, Francucci, F, Gaudio, P, Gerardino, A, Giorgi, R, Krasilnikova, A, Letardi, T, Lisi, N, Marolo, T, Martellucci, S, Mattarello, V, Mezi, L, Montereali, R, Murra, D, Nichelatti, E, Nicolosi, P, Nocerino, G, Palladino, L, Patelli, A, Pelizzo, M, Piegari, A, Richetta, M, Rigato, V, Ritucci, A, Rydzy, A, Santoni, A, Sarto, F, Scaramuzzi, F, Tefouet Kana, E, Tomassetti, G, Torre, A, and Zheng, C
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Settore FIS/01 - Fisica Sperimentale - Published
- 2006
14. Cyclododecane as support material for clean and facile transfer of large-area few-layer graphene
- Author
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Capasso, A., primary, De Francesco, M., additional, Leoni, E., additional, Dikonimos, T., additional, Buonocore, F., additional, Lancellotti, L., additional, Bobeico, E., additional, Sarto, M. S., additional, Tamburrano, A., additional, De Bellis, G., additional, and Lisi, N., additional
- Published
- 2014
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15. Effects of HNO3 molecular doping in graphene/Si Schottky barrier solar cells
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Lancellotti, L., primary, Bobeico, E., additional, Capasso, A., additional, Della Noce, M., additional, Dikonimos, T., additional, Lisi, N., additional, and Delli Veneri, P., additional
- Published
- 2014
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16. High frequency performance limits of nanointerconnects based on CVD-grown graphene films transferred on SiO2-substrate
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D'Aloia, A.G., primary, Tamburrano, A., additional, Lisi, N., additional, Dikonimos, T., additional, De Bellis, G., additional, Giorgi, R., additional, D'Amore, M., additional, and Sarto, M.S., additional
- Published
- 2013
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17. Role of iron catalyst particles density in the growth of forest-like carbon nanotubes
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Signore, M.A., primary, Rizzo, A., additional, Rossi, R., additional, Piscopiello, E., additional, Di Luccio, T., additional, Capodieci, L., additional, Dikonimos, T., additional, and Giorgi, R., additional
- Published
- 2008
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18. Effect of Fe catalyst thickness and C2H2/H2 flow rate ratio on the vertical alignment of carbon nanotubes grown by chemical vapour deposition
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Rizzo, A., primary, Rossi, R., additional, Signore, M.A., additional, Piscopiello, E., additional, Capodieci, L., additional, Pentassuglia, R., additional, Dikonimos, T., additional, and Giorgi, R., additional
- Published
- 2008
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19. Fabrication of 3D monolithic graphene foam/polycaprolactone porous nanocomposites for bioapplications
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Theodoros Dikonimos, Giacomo Messina, Annalisa Aurora, Giuliana Faggio, Alessio Tamburrano, Hamidreza Salimijazi, Nicola Lisi, Neda Bahremandi Tolou, Bahremandi Tolou, N., Salimijazi, H., Dikonimos, T., Faggio, G., Messina, G., Tamburrano, A., Aurora, A., and Lisi, N.
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Materials science ,Fabrication ,02 engineering and technology ,Chemical vapor deposition ,engineering.material ,010402 general chemistry ,cvd ,01 natural sciences ,law.invention ,graphene ,foam ,nanocomposite ,polycaprolactone ,nickel ,bioapplications ,chemistry.chemical_compound ,Coating ,Electrical resistance and conductance ,law ,General Materials Science ,Composite material ,Nanocomposite ,Graphene ,Mechanical Engineering ,Graphene foam ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Mechanics of Materials ,Polycaprolactone ,engineering ,0210 nano-technology - Abstract
Abstract Aiming at the production of light, porous, conductive, biosafe composites, in this paper we are presenting a novel fabrication method for monolithic, three-dimensional (3D) graphene foam (GF)/porous polymer composites. The synthesis adopts a novel process architecture by using Ni foam templates in an inductive heating chemical vapor deposition growth process, and by removing Ni chemically while retaining graphene integrity by the reversible application of cyclododecane (CD); finally, nondestructive coating procedures with polycaprolactone (PCL) solutions have been developed. The composites can be optimized to enhance electrical conduction, flexibility and mechanical properties, while mixing PCL and CD allows to coat the GF with a novel mesoporous polymer coating. By tuning the GF properties, the typical electrical resistance of the 3D forms can be reduced to a few 10 s of Ohms, values that are maintained after the PCL coatings. The current study achieved a GF fraction ranging between 1 and 7.3 wt%, with even the lower graphene content composites showing acceptable electrical and mechanical properties. The properties of these conductive 3D-GF/PCL composites are in line with the requirements for applications in the field of nerve tissue engineering. Graphical abstract
- Published
- 2020
20. Effect of Fe catalyst thickness and C2H2/H2 flow rate ratio on the vertical alignment of carbon nanotubes grown by chemical vapour deposition
- Author
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Rizzo, A., Rossi, R., Signore, M.A., Piscopiello, E., Capodieci, L., Pentassuglia, R., Dikonimos, T., and Giorgi, R.
- Subjects
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CARBON nanotubes , *VAPOR-plating , *ELECTRON microscopy , *ATOMIC force microscopy - Abstract
Abstract: Carbon nanotubes (CNTs) were fabricated by Chemical Vapour Depositon using a C2H2/H2 mixture. They were grown on Si/SiO2 substrate with Fe film as catalyst, deposited using thermal evaporation technique. The aim of this work is to emphasize the role of the Fe catalyst thickness and the C2H2/H2 flow rate ratio to grow vertically aligned CNTs by thermal CVD. In order to investigate these aspects, four Fe metal films with thickness of 2.5, 3.5, 7.5 and 16 nm were deposited on Si/SiO2 substrate and CNTs were grown with different C2H2/H2 flow rate ratios, from 5/95 to 30/70 by thermal CVD at 750 °C. Results showed that CNTs were not vertically aligned with 16 nm catalyst thickness for all flow rate ratios, while CNTs were always vertically aligned for iron thickness less than 3.5 nm and vertically aligned only for a C2H2/H2 flow rate ratio greater than 20/70 for the 7.5 nm catalyst thickness. Morphology and structural information about CNTs and Fe metal clusters were provided by field emission gun-scanning electron microscopy (FEG-SEM), atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). Our results also indicate that for each flow rate ratio exists a critical thickness of iron catalyst under which vertically aligned CNTs are obtained. [Copyright &y& Elsevier]
- Published
- 2008
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21. Characteristics of Ultrathin Ni Films
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Ludvik Martinu, Richard Vernhes, Maria Luisa Grilli, Theodoros Dikonimos, Guohang Hu, Anna Sytchkova, Hongbo He, Angela Piegari, Ilaria Di Sarcina, Grilli, M. L., Vernhes, R., Hu, G., Di Sarcina, I., Dikonimos, T., Sytchkova, A., Martinu, L., He, H., and Piegari, A.
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Materials science ,transparent conductive films ,business.industry ,Optical measurements ,Surfaces and Interfaces ,transparent conductive film ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ni films ,optical measurements ,ultrathin films ,Materials Chemistry ,Ni film ,Optoelectronics ,optical measurement ,Electrical and Electronic Engineering ,business - Abstract
Conductive and transparent ultra-thin Nickel films are grown by RF sputtering on fused silica substrates. The characteristics of Ni films (thickness, refractive index, and extinction coefficient) are obtained by fitting multi-angle spectrophotometric and ellipsometric data. Films thickness inferred by X ray reflection (XRR) measurements is in good accordance with ellipsometric results. XPS analysis reveals that Ni metal phase is present in the film surface together with Ni mixed oxide phases, which explains the high electrical stability of such films.
- Published
- 2019
22. The Role of Graphene-Based Derivative as Interfacial Layer in Graphene/n-Si Schottky Barrier Solar Cells
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Giuliana Faggio, Riccardo Carotenuto, Laura Lancellotti, Andrea Capasso, Eugenia Bobeico, Theodoros Dikonimos, Andrea Gnisci, Paola Delli Veneri, Nicola Lisi, Giacomo Messina, Gnisci, A., Faggio, G., Lancellotti, L., Messina, G., Carotenuto, R., Bobeico, E., Delli Veneri, P., Capasso, A., Dikonimos, T., and Lisi, N.
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Materials science ,CVD graphene ,graphene-based derivative ,photovoltaics ,solar cell ,Schottky barrier ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,law.invention ,photovoltaic ,chemistry.chemical_compound ,law ,Photovoltaics ,Solar cell ,Materials Chemistry ,Electrical and Electronic Engineering ,Cvd graphene ,Graphene ,business.industry ,Surfaces and Interfaces ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Optoelectronics ,0210 nano-technology ,business ,Layer (electronics) ,Derivative (chemistry) - Abstract
Schottky-barrier solar cells (SBSCs) represent low-cost candidates for photovoltaics applications. The engineering of the interface between absorber and front electrode is crucial for reducing the dark current, blocking the majority carriers injected into the electrode, and reducing surface recombination. The presence of tailored interfacial layers between the metal electrode and the semiconductor absorber can improve the cell performance. In this work, the interface of a graphene/n-type Si SBSC by introducing a graphene-based derivative (GBD) layer meant to reduce the Schottky-barrier height (SBH) and ease the charge collection are engineered. The chemical vapor deposition (CVD) parameters are tuned to obtain the two graphene films with different structure and electrical properties: few-layer graphene (FLG) working as transparent conductive electrode and GBD layer with electron-blocking and hole-transporting properties. Test SBSCs are fabricated to evaluate the effect of the introduction of GBD as interlayer into the FLG/n-Si junction. The GBD layer reduces the recombination at the interface between graphene and n-Si, and improves the external quantum efficiency (EQE) with optical bias from 50 to 60%. The FLG/GBD/n-Si cell attains a power conversion efficiency (PCE) of ≈5%, which increase to 6.7% after a doping treatment by nitric acid vapor.
- Published
- 2019
23. Ethanol-CVD Growth of Sub-mm Single-Crystal Graphene on Flat Cu Surfaces
- Author
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Jong-Young Lee, Nicola Lisi, Junyoung Kwon, Giuliana Faggio, Andrea Gnisci, Andrea Capasso, Theodoros Dikonimos, Gwan Hyoung Lee, Giacomo Messina, Lisi, N., and Dikonimos, T.
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Ethanol ,Materials science ,Scale (ratio) ,Graphene ,food and beverages ,02 engineering and technology ,Chemical vapor deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Methane ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,General Energy ,Chemical engineering ,chemistry ,law ,Carbon source ,Physical and Theoretical Chemistry ,0210 nano-technology ,Single crystal - Abstract
High-quality graphene can be produced in large scale by chemical vapor deposition (CVD). Ethanol is emerging as a versatile carbon source alternative to methane for the growth of graphene on a copper (Cu) foil catalyst. To date, rigorous studies of the ethanol-based process still lack, especially concerning the first stages of the growth, which ultimately determines graphene's properties, such as defect density and crystal size, and performance, such as electrical conductance and mechanical strength. In particular, so far the growth of isolated graphene grains by ethanol-CVD has been achieved only on preoxidized Cu foils folded in enclosures, in an attempt to limit the partial pressure of the precursor, and thus the nucleation rate. We systematically explored the process parameters of ethanol-CVD to obtain full control over the nucleation rate, grain size, and crystallinity of graphene on flat Cu foils, which are of interest for any realistic production in large scale. To limit the nucleation density and increase the grain size, preoxidized Cu foils (250 °C in air) were used as substrates, and the process parameters were thoroughly investigated and tuned. Ultimately, at an ethanol vapor flow of 1.5 × 10-3 sccm the nucleation density reduced to less than 3 nuclei/mm2 and isolated single-crystal grains grew with a lateral size above 500 μm. When transferred onto Si/SiO2 substrates, these grains showed field-effect mobility beyond 1300 cm2/(V s). Our results provide a step closer towards an affordable commercialization of electronic-grade, large-area graphene. © 2018 American Chemical Society.
- Published
- 2018
24. Plasma enhanced hot filament CVD growth of thick carbon nanowall layers
- Author
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Theodoros Dikonimos, Nicola Lisi, Daniele Passeri, Marco Rossi, Marco Natali, Lisi, N., and Dikonimos, T.
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Physics and Astronomy (all) ,Materials science ,Electrical resistance and conductance ,Graphene ,law ,Carbon nanofiber ,Electrode ,Refractory metals ,Nanotechnology ,Porosity ,Electrochemistry ,Nanoscopic scale ,law.invention - Abstract
Carbon nanowalls are carbon nanostructures consisting of arrays of graphitic carbon plates which are mainly positioned perpendicularly to the growth surface. Carbon nanowalls have received considerable interest in recent years, since they are closely related to graphene from the structural point of view, while maintaining an open honeycomb lattice on the nanoscale. They are thus believed to be an interesting electrode material for many applications since they offer high chemical resistance, low electrical resistance and high surface area. In this paper we are presenting a method that allows the growth of thick layers of carbon nanowalls onto flat and porous substrates, both carbon and refractory metal based. Such methods are promising for making electrodes for use in electrochemical devices. © 2017 Author(s).
- Published
- 2017
25. Contamination-free graphene by chemical vapor deposition in quartz furnaces
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Martina Pittori, Nicola Lisi, Andrea Capasso, Sergio Marras, Rita Rizzoli, Theodoros Dikonimos, Francesco Buonocore, Raffaello Mazzaro, Lisi, Nicola, Dikonimos, Theodoro, Buonocore, Francesco, Pittori, Martina, Mazzaro, Raffaello, Rizzoli, Rita, Marras, Sergio, Capasso, Andrea, Buonocore, F., Dikonimos, T., and Lisi, N.
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Materials science ,nucleation ,lcsh:Medicine ,Transport ,Nanotechnology ,Context (language use) ,02 engineering and technology ,Chemical vapor deposition ,010402 general chemistry ,01 natural sciences ,Article ,law.invention ,Crystallinity ,law ,CVD Growth ,lcsh:Science ,Quartz ,Multidisciplinary ,Graphene ,Industrial scale ,lcsh:R ,Contamination ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,SCALE-UP ,lcsh:Q ,C diffusion ,0210 nano-technology - Abstract
Although the growth of graphene by chemical vapor deposition is a production technique that guarantees high crystallinity and superior electronic properties on large areas, it is still a challenge for manufacturers to efficiently scale up the production to the industrial scale. In this context, issues related to the purity and reproducibility of the graphene batches exist and need to be tackled. When graphene is grown in quartz furnaces, in particular, it is common to end up with samples contaminated by heterogeneous particles, which alter the growth mechanism and affect graphene’s properties. In this paper, we fully unveil the source of such contaminations and explain how they create during the growth process. We further propose a modification of the widely used quartz furnace configuration to fully suppress the sample contamination and obtain identical and clean graphene batches on large areas.
- Published
- 2017
26. Morphology and electrochemical properties of Pd-based catalysts deposited by different thin-film techniques
- Author
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Luca Giorgi, M. De Francesco, Mirko Sansovini, V. Violante, E. Castagna, Francesca Sarto, Theodoros Dikonimos, S. Lecci, Violante, V., Sansovini, M., Lecci, S., Dikonimos, T. M., De Francesco, M., Castagna, E., and Sarto, F.
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Cyclic voltammetry ,Nanostructure ,Materials science ,Renewable Energy, Sustainability and the Environment ,Hydride ,Scanning electron microscope ,Analytical chemistry ,Sputtering ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Electrocatalysts ,Condensed Matter Physics ,Microstructure ,Nanostructures ,Fuel Technology ,Electrodeposition ,chemistry ,Electrode ,Palladium ,Thin film - Abstract
Pd/C-based electrodes for fuel cells applications were prepared by galvanostatic electrodeposition and DC sputtering of palladium on gas diffusion layers. Different sets of samples were realized by varying the Pd load, for each technique. The surface morphology of the deposits was investigated by scanning electron microscopy. Cyclic voltammetry in acidic solution was applied to study the catalytic behavior of the freshly deposited samples and to follow their evolution with increasing cycle numbers. The results showed that, depending on the sputtering or electrochemical technique and metal load, samples grew with different morphologies and showed different electrochemical behaviors, with electroactive surface values ranging between a few tens to some hundreds m 2/g. Sputtered films were characterized by a microstructure made of sub-micrometric cauliflower-shaped clusters and showed the highest electroactive surface values after prolonged voltammetric scanning. Pd hydride formation with both α and β phases and high hydrogen absorption capability were observed in some of the electrodeposited samples, in association to flower-like micrometric-size clustered structure and hydrogen codeposition during the electrochemical growth process. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
- Published
- 2014
27. Chemical Vapor Deposited Graphene-Based Derivative As High-Performance Hole Transport Material for Organic Photovoltaics
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Francesco Buonocore, Nicola Lisi, Luigi Salamandra, Luca Ortolani, Theodoros Dikonimos, Andrea Capasso, Giuliana Faggio, Vittorio Morandi, Lisi, N., Buonocore, F., Dikonimos, T., and Capasso, A.
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Fabrication ,Materials science ,Organic solar cell ,02 engineering and technology ,Chemical vapor deposition ,010402 general chemistry ,hole transport layer ,01 natural sciences ,law.invention ,PEDOT:PSS ,law ,General Materials Science ,Work function ,functionalized graphene film ,business.industry ,Graphene ,graphene ,Energy conversion efficiency ,graphene-based derivative ,CVD ,021001 nanoscience & nanotechnology ,phtovoltaic ,0104 chemical sciences ,Indium tin oxide ,ethanol CVD ,organic photovoltaics ,Optoelectronics ,0210 nano-technology ,business - Abstract
The development of efficient charge transport layers is a key requirement for the fabrication of efficient and stable organic solar cells. A graphene-based derivative with planar resistivity exceeding 105 Ω/S and work function of 4.9 eV is here produced by finely tuning the parameters of the chemical vapor deposition process on copper. After the growth, the film is transferred to glass/indium tin oxide and used as hole transport layer in organic solar cells based on a PBDTTT-C-T:[70]PCBM blend. The cells attained a maximum power conversion efficiency of 5%, matching reference cells made with state-of-the-art PEDOT:PSS as the hole transport layer. Our results indicate that functionalized graphene could represent an effective alternative to PEDOT:PSS as hole transport/electron blocking layer in solution-processed organic photovoltaics. © 2016 American Chemical Society.
- Published
- 2016
28. Application of NiOx thin films as p-type emitter layer in heterojunction solar cells
- Author
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Francesca Menchini, Alberto Mittiga, Rosa Chierchia, Luca Serenelli, E. Salza, Mario Tucci, Maria Luisa Grilli, Theodoros Dikonimos, Menchini, F., Grilli, M. L., Dikonimos, T., Mittiga, A., Serenelli, L., Salza, E., Chierchia, R., and Tucci, M.
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Materials science ,Passivation ,Silicon ,Oxide ,chemistry.chemical_element ,nickel oxide ,02 engineering and technology ,01 natural sciences ,interface defects ,chemistry.chemical_compound ,0103 physical sciences ,Thin film ,Common emitter ,010302 applied physics ,business.industry ,Nickel oxide ,silicon heterojunction solar cell ,Heterojunction ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,chemistry ,Optoelectronics ,0210 nano-technology ,business ,Layer (electronics) ,electron blocking layer - Abstract
Non-stoichiometric nickel oxide (NiOx) is attracting growing attention due to its characteristics of p-type transparent conductive layer and to the possibility to tailor its optical and electrical properties. NiOx could also be employed as the electron blocking layer in silicon-based heterojunction solar cells. However, at present not much work has been done in this direction. In this paper we investigate the optoelectronic characteristics of NiOx thin films and demonstrate the usability of NiOx as emitter layer in silicon based heterostructure solar cells due to its hole collection selectivity. Test heterojunctions show a rectifying behaviour, even if their characteristics are still limited by the density of defects at the c-Si/NiOx interface, as deduced by comparing the experimental results with numerical simulations. This suggests that the quality of the interface between NiOx and c-Si needs to be improved, either by optimizing the deposition process of NiOx or by depositing a buffer layer able to carefully passivate the silicon surface and helpfully allow the growth of oxide layer. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).
- Published
- 2016
29. Effect of growth parameters on the properties of RF-sputtered highly conductive and transparent p-type NiOx films
- Author
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Angela Piegari, Mehmet Yilmaz, Maria Luisa Grilli, Alberto Mittiga, Luciano Pilloni, P. Nunziante, Francesca Menchini, Theodoros Dikonimos, Piegari, A., Pilloni, L., Dikonimos, T., Menchini, F., Grilli, M. L., and Mittiga, A.
- Subjects
optical properties ,Materials science ,radio frequency sputtering ,Analytical chemistry ,chemistry.chemical_element ,nickel oxide ,02 engineering and technology ,01 natural sciences ,Oxygen ,X-ray photoelectron spectroscopy ,Electrical resistivity and conductivity ,Sputtering ,0103 physical sciences ,Materials Chemistry ,Transmittance ,Electrical and Electronic Engineering ,Total pressure ,010302 applied physics ,Partial pressure ,Atmospheric temperature range ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,optical propertie ,chemistry ,p-type transparent conductive oxide ,electrical properties ,0210 nano-technology - Abstract
Highly conductive and transparent NiOx films can be very useful as buffer layers for the optimization of the p-type contacts of optoelectronic devices. Thin NiOx films were fabricated by reactive radio frequency (RF) sputtering at room temperature starting from a Ni target. A systematic study of the influence of oxygen partial pressure, RF power and sputtering gas pressure on the films' properties was carried out. The structural, microstructural, optical and electrical properties were affected differently by the sputtering parameters. Resistivity decreased by increasing the oxygen partial pressure and the sputtering total pressure and by decreasing the RF power, while transmittance increased by decreasing the oxygen partial pressure and by increasing the RF power and sputtering pressure. Minimum resistivity of 1.6 × 10-2 Ωcm and a visible transmittance of 40% were achieved for a film grown in a pure oxygen atmosphere, while a higher transmittance of 54% and a resistivity of ρ = 1.1×10-1 Ωcm were obtained for a film grown at 30% oxygen partial pressure. The trends of transmittance and resistivity as a function of the oxygen pressure during the sputtering process can be explained in terms of the amount of Ni3+ defects deduced by x-ray photoelectron spectroscopy (XPS) measurements. The full interpretation of the other results is less straightforward and highlights the relevance of the samples' structural properties. © 2016 IOP Publishing Ltd.
- Published
- 2016
30. Electrochemical synthesis of self-organized TiO2crystalline nanotubes without annealing
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L. Giorgi, Rossella Giorgi, Giacomo Messina, Francesco Buonocore, Nicola Lisi, Giuliana Faggio, Theodoros Dikonimos, Lisi, N., Buonocore, F., and Dikonimos, T.
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Nanotube ,Materials science ,crystallization ,Bioengineering ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Condensed Matter::Materials Science ,symbols.namesake ,Crystallinity ,X-ray photoelectron spectroscopy ,General Materials Science ,Electrical and Electronic Engineering ,Nanotubular structure ,Mechanical Engineering ,Titanium dioxide ,Anodization ,electronic structure ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Amorphous solid ,Dielectric spectroscopy ,Condensed Matter::Soft Condensed Matter ,Field electron emission ,Chemical engineering ,Mechanics of Materials ,symbols ,0210 nano-technology ,Raman spectroscopy ,Ultraviolet photoelectron spectroscopy - Abstract
This work demonstrates that upon anodic polarization in an aqueous fluoride-containing electrolyte, TiO2 nanotube array films can be formed with a well-defined crystalline phase, rather than an amorphous one. The crystalline phase was obtained avoiding any high temperature annealing. We studied the formation of nanotubes in an HF/H2O medium and the development of crystalline grains on the nanotube wall, and we found a facile way to achieve crystalline TiO2 nanotube arrays through a one-step anodization. The crystallinity of the film was influenced by the synthesis parameters, and the optimization of the electrolyte composition and anodization conditions (applied voltage and time) were carried out. For comparison purposes, crystalline anatase TiO2 nanotubes were also prepared by thermal treatment of amorphous nanotubes grown in an organic bath (ethylene glycol/NH4F/H2O). The morphology and the crystallinity of the nanotubes were studied by field emission gun-scanning electron microscopy (FEG-SEM) and Raman spectroscopy, whereas the electrochemical and semiconducting properties were analyzed by means of linear sweep voltammetry, impedance spectroscopy, and Mott-Schottky plots. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) allowed us to determine the surface composition and the electronic structure of the samples and to correlate them with the electrochemical data. The optimal conditions to achieve a crystalline phase with high donor concentration are defined. © 2018 IOP Publishing Ltd.
- Published
- 2018
31. Fast growth of polycrystalline graphene by chemical vapor deposition of ethanol on copper
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Theodoros Dikonimos, Andrea Capasso, Nicola Lisi, Enrico Leoni, Angela Malara, Maria Arcangela Nigro, Giacomo Messina, Francesco Buonocore, Giuliana Faggio, Saveria Santangelo, Faggio, G., Capasso, A., Malara, A., Leoni, E., Nigro, M. A., Santangelo, S., Messina, G., Dikonimos, T., Buonocore, F., and Lisi, N.
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Materials science ,Graphene ,electropolished Cu ,graphene ,Graphene foam ,chemistry.chemical_element ,Nanotechnology ,Chemical vapor deposition ,ethanol ,chemical vapor deposition ,Copper ,law.invention ,Carbon film ,Chemical engineering ,chemistry ,law ,Graphene nanoribbons ,Graphene oxide paper ,Transparent conducting film - Abstract
High conductive graphene films can be grown on metal foils by chemical vapor deposition (CVD). We here analyzed the use of ethanol, an economic precursor, which results also safer than commonly-used methane. A comprehensive range of process parameters were explored in order to obtain graphene films with optimal characteristics in view of their use in optoelectronics and photovoltaics. Commercially-available and electro-polished copper foils were used as substrates. By finely tuning the CVD conditions, we obtained few-layer (2-4) graphene films with good conductivity (∼500 Ohm/sq) and optical transmittance around 92-94% at 550 nm on unpolished copper foils. The growth on electro-polished copper provides instead predominantly mono-layer films with lower conductivity (≥1000 Ohm/sq) and with a transmittance of 97.4% at 550 nm. As for the device properties, graphene with optimal properties as transparent conductive film were produced by CVD on standard copper with specific process conditions.
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- 2014
32. Rapid and highly efficient growth of graphene on copper by chemical vapor deposition of ethanol
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Enrico Leoni, Francesco Buonocore, Vittorio Morandi, Giuliana Faggio, Giacomo Messina, Luca Ortolani, Andrea Capasso, Nicola Lisi, Theodoros Dikonimos, Capasso, A., Leoni, E., Dikonimos, T., Buonocore, F., and Lisi, N.
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Materials science ,Inorganic chemistry ,chemistry.chemical_element ,Chemical vapor deposition ,law.invention ,symbols.namesake ,Liquid precursor ,law ,Materials Chemistry ,Catalyst ,Graphene ,Rapid growth ,Ethanol ,Copper ,Hybrid physical-chemical vapor deposition ,Metals and Alloys ,Substrate (chemistry) ,Surfaces and Interfaces ,Combustion chemical vapor deposition ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,symbols ,Raman spectroscopy ,Carbon - Abstract
The growth of graphene by chemical vapor deposition on metal foils is a promising technique to deliver large-area films with high electron mobility. Nowadays, the chemical vapor deposition of hydrocarbons on copper is the most investigated synthesis method, although many other carbon precursors and metal substrates are used too. Among these, ethanol is a safe and inexpensive precursor that seems to offer favorable synthesis kinetics. We explored the growth of graphene on copper from ethanol, focusing on processes of short duration (up to one min). We investigated the produced films by electron microscopy, Raman and X-ray photoemission spectroscopy. A graphene film with high crystalline quality was found to cover the entire copper catalyst substrate in just 20 s, making ethanol appear as a more efficient carbon feedstock than methane and other commonly used precursors. (C) 2014 Elsevier B.V. All rights reserved.
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- 2014
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33. Electrochemical synthesis of self-organized TiO 2 crystalline nanotubes without annealing.
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Giorgi L, Dikonimos T, Giorgi R, Buonocore F, Faggio G, Messina G, and Lisi N
- Abstract
This work demonstrates that upon anodic polarization in an aqueous fluoride-containing electrolyte, TiO
2 nanotube array films can be formed with a well-defined crystalline phase, rather than an amorphous one. The crystalline phase was obtained avoiding any high temperature annealing. We studied the formation of nanotubes in an HF/H2 O medium and the development of crystalline grains on the nanotube wall, and we found a facile way to achieve crystalline TiO2 nanotube arrays through a one-step anodization. The crystallinity of the film was influenced by the synthesis parameters, and the optimization of the electrolyte composition and anodization conditions (applied voltage and time) were carried out. For comparison purposes, crystalline anatase TiO2 nanotubes were also prepared by thermal treatment of amorphous nanotubes grown in an organic bath (ethylene glycol/NH4 F/H2 O). The morphology and the crystallinity of the nanotubes were studied by field emission gun-scanning electron microscopy (FEG-SEM) and Raman spectroscopy, whereas the electrochemical and semiconducting properties were analyzed by means of linear sweep voltammetry, impedance spectroscopy, and Mott-Schottky plots. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) allowed us to determine the surface composition and the electronic structure of the samples and to correlate them with the electrochemical data. The optimal conditions to achieve a crystalline phase with high donor concentration are defined.- Published
- 2018
- Full Text
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34. Contamination-free graphene by chemical vapor deposition in quartz furnaces.
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Lisi N, Dikonimos T, Buonocore F, Pittori M, Mazzaro R, Rizzoli R, Marras S, and Capasso A
- Abstract
Although the growth of graphene by chemical vapor deposition is a production technique that guarantees high crystallinity and superior electronic properties on large areas, it is still a challenge for manufacturers to efficiently scale up the production to the industrial scale. In this context, issues related to the purity and reproducibility of the graphene batches exist and need to be tackled. When graphene is grown in quartz furnaces, in particular, it is common to end up with samples contaminated by heterogeneous particles, which alter the growth mechanism and affect graphene's properties. In this paper, we fully unveil the source of such contaminations and explain how they create during the growth process. We further propose a modification of the widely used quartz furnace configuration to fully suppress the sample contamination and obtain identical and clean graphene batches on large areas.
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- 2017
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35. Chemical Vapor Deposited Graphene-Based Derivative As High-Performance Hole Transport Material for Organic Photovoltaics.
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Capasso A, Salamandra L, Faggio G, Dikonimos T, Buonocore F, Morandi V, Ortolani L, and Lisi N
- Abstract
The development of efficient charge transport layers is a key requirement for the fabrication of efficient and stable organic solar cells. A graphene-based derivative with planar resistivity exceeding 10(5) Ω/□ and work function of 4.9 eV is here produced by finely tuning the parameters of the chemical vapor deposition process on copper. After the growth, the film is transferred to glass/indium tin oxide and used as hole transport layer in organic solar cells based on a PBDTTT-C-T:[70]PCBM blend. The cells attained a maximum power conversion efficiency of 5%, matching reference cells made with state-of-the-art, Pedot: PSS as the hole transport layer. Our results indicate that functionalized graphene could represent an effective alternative to, Pedot: PSS as hole transport/electron blocking layer in solution-processed organic photovoltaics.
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- 2016
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36. Nitrogen-doped graphene films from chemical vapor deposition of pyridine: influence of process parameters on the electrical and optical properties.
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Capasso A, Dikonimos T, Sarto F, Tamburrano A, De Bellis G, Sarto MS, Faggio G, Malara A, Messina G, and Lisi N
- Abstract
Graphene films were produced by chemical vapor deposition (CVD) of pyridine on copper substrates. Pyridine-CVD is expected to lead to doped graphene by the insertion of nitrogen atoms in the growing sp(2) carbon lattice, possibly improving the properties of graphene as a transparent conductive film. We here report on the influence that the CVD parameters (i.e., temperature and gas flow) have on the morphology, transmittance, and electrical conductivity of the graphene films grown with pyridine. A temperature range between 930 and 1070 °C was explored and the results were compared to those of pristine graphene grown by ethanol-CVD under the same process conditions. The films were characterized by atomic force microscopy, Raman and X-ray photoemission spectroscopy. The optical transmittance and electrical conductivity of the films were measured to evaluate their performance as transparent conductive electrodes. Graphene films grown by pyridine reached an electrical conductivity of 14.3 × 10(5) S/m. Such a high conductivity seems to be associated with the electronic doping induced by substitutional nitrogen atoms. In particular, at 930 °C the nitrogen/carbon ratio of pyridine-grown graphene reaches 3%, and its electrical conductivity is 40% higher than that of pristine graphene grown from ethanol-CVD.
- Published
- 2015
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37. Electrocatalysts for methanol oxidation based on platinum/carbon nanofibers nanocomposite.
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Giorgi L, Salernitano E, Gagliardi S, Dikonimos T, Giorgi R, Lisi N, De Riccardis F, and Martina V
- Abstract
New carbon nanomaterials, i.e., carbon nanotubes and nanofibers, with special physico-chemical properties, are recently studied as support for methanol oxidation reaction electrocatalysts replacing the most widely used carbon black. Particularly, carbon fibrous structures with high surface area and available open edges are thought to be promising. Platelet type carbon nanofibers, which have the graphene layers oriented perpendicularly to the fiber axis, exhibit a high ratio of edge to basal atoms. Different types of carbon nanofibers (tubular and platelet) were grown by plasma enhanced chemical vapour deposition on carbon paper substrates. The process was controlled and optimised in term of growth pressure and temperature. Carbon nanofibers were characterised by high resolution scanning electron microscopy and X-ray photoelectron spectroscopy to assess the morphological properties. Then carbon nanofibers of both morphologies were used as substrates for Pt electrodeposition. High resolution scanning electron microscopy images showed that the Pt nanoparticles distribution was well controlled and the particles size went down to few nanometers. Pt/carbon nanofibers nanocomposites were tested as electrocatalysts for methanol oxidation reaction. Cyclic voltammetry in H2SO4 revealed a catalyst with a high surface area. Cyclic voltammetry in presence of methanol indicated a high electrochemical activity for methanol oxidation reaction and a good long time stability compared to a carbon black supported Pt catalyst.
- Published
- 2011
- Full Text
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