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201. Effect of moiré superlattice reconstruction in the electronic excitation spectrum of graphene-metal heterostructures

Author

Netherlands National Computing Facilities Foundation, European Commission, Ministerio de Economía y Competitividad (España), Politano, Antonio, Slotman, Guus J., Roldán, Rafael, Chiarello, Gennaro, Campi, Davide, Katsnelson, Mikhail I., Yuan, Shengjun, Netherlands National Computing Facilities Foundation, European Commission, Ministerio de Economía y Competitividad (España), Politano, Antonio, Slotman, Guus J., Roldán, Rafael, Chiarello, Gennaro, Campi, Davide, Katsnelson, Mikhail I., and Yuan, Shengjun

Abstract

We have studied the electronic excitation spectrum in periodically rippled graphene on Ru(0 0 0 1) and flat, commensurate graphene on Ni(1 1 1) by means of high-resolution electron energy loss spectroscopy and a combination of density functional theory and tight-binding approaches. We show that the periodic moiré superlattice originated by the lattice mismatch in graphene/Ru(0 0 0 1) induces the emergence of an extra mode, which is not present in graphene/Ni(1 1 1). Contrary to the ordinary intra-band plasmon of doped graphene, the extra mode is robust in charge-neutral graphene/metal contacts, having its origin in electron–hole inter-band transitions between van Hove singularities that emerge in the reconstructed band structure, due to the moiré pattern superlattice.

Published
2017

203. Interplay of surface and Dirac plasmons in topological insulators: the case of Bi2Se3

Author

Politano, Antonio, Silkin, Vm, Nechaev, Ia, Vitiello, Ms, Viti, L, Aliev, Zs, Babanly, Mb, Chiarello, G, Echenique, Pm, Chulkov, Ev, and Томский государственный университет Физический факультет Кафедра физики металлов

Subjects
селенид висмута, Physics::Optics, топологические изоляторы, Дирака фермионы
Abstract

We have investigated plasmonic excitations at the surface of Bi2Se3(0001) via high-resolution electron energy loss spectroscopy. For low parallel momentum transfer q∥, the loss spectrum shows a distinctive feature peaked at 104 meV. This mode varies weakly with q∥. The behavior of its intensity as a function of primary energy and scattering angle indicates that it is a surface plasmon. At larger momenta (q∥∼0.04 Å−1), an additional peak, attributed to the Dirac plasmon, becomes clearly defined in the loss spectrum. Momentum-resolved loss spectra provide evidence of the mutual interaction between the surface plasmon and the Dirac plasmon of Bi2Se3. The proposed theoretical model accounting for the coexistence of three-dimensional doping electrons and two-dimensional Dirac fermions accurately represents the experimental observations. The results reveal novel routes for engineering plasmonic devices based on topological insulators.

Published
2015

205. Interband plasmons in supported graphene on metal substrates: Theory and experiments

Author

Politano, Antonio, Radović, Ivan, Borka, Duško, Mišković, Z. L., Chiarello, G., Politano, Antonio, Radović, Ivan, Borka, Duško, Mišković, Z. L., and Chiarello, G.

Abstract

We present a theoretical modeling of the energy-loss spectroscopy data for monolayer graphene (MLG) supported by Pt(111), Ru(0001) and Ni(111) substrates. To reproduce the experimental loss function, we have used a two-dimensional, two-fluid hydrodynamic model for interband transitions of graphenes pi and sigma electrons and an empirical Drude-Lorentz model in the local approximation for metal substrates. The electronic response from the visible to the ultraviolet frequency range has been nicely reproduced for MLG/Pt(111) and MLG/Ru(0001). For graphene nanodomes on Ru(0001), the loss function of valleys shows an additional mode at 8-9 eV. By contrast, this models fails for the case of MLG/Ni(111), presumably due to the strong hybridization between the pi states of graphene and the d bands of Ni, which is not accounted for in the model. (C) 2015 Elsevier Ltd. All rights reserved.

Published
2016

210. Manipulating the Topological Interface by Molecular Adsorbates: Adsorption of Co-Phthalocyanine on Bi2Se3

Author

Caputo, Marco, primary, Panighel, Mirko, additional, Lisi, Simone, additional, Khalil, Lama, additional, Santo, Giovanni Di, additional, Papalazarou, Evangelos, additional, Hruban, Andrzej, additional, Konczykowski, Marcin, additional, Krusin-Elbaum, Lia, additional, Aliev, Ziya S., additional, Babanly, Mahammad B., additional, Otrokov, Mikhail M., additional, Politano, Antonio, additional, Chulkov, Evgueni V., additional, Arnau, Andrés, additional, Marinova, Vera, additional, Das, Pranab K., additional, Fujii, Jun, additional, Vobornik, Ivana, additional, Perfetti, Luca, additional, Mugarza, Aitor, additional, Goldoni, Andrea, additional, and Marsi, Marino, additional

Published
2016
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211. Unveiling the Mechanisms Leading to H2 Production Promoted by Water Decomposition on Epitaxial Graphene at Room Temperature

Author

Politano, Antonio, primary, Cattelan, Mattia, additional, Boukhvalov, Danil W., additional, Campi, Davide, additional, Cupolillo, Anna, additional, Agnoli, Stefano, additional, Apostol, Nicoleta G., additional, Lacovig, Paolo, additional, Lizzit, Silvano, additional, Farías, Daniel, additional, Chiarello, Gennaro, additional, Granozzi, Gaetano, additional, and Larciprete, Rosanna, additional

Published
2016
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213. Prospects of 2d Materials-Based Membranes in Water Desalination.

Author

Gugliuzza, Annarosa, Macedonio, Francesca, Politano, Antonio, and Drioli, Enrico

Subjects
SALINE water conversion, DISCONTINUOUS precipitation, ARTIFICIAL membranes, GRAPHENE, BISMUTH compounds, CRYSTALLIZATION
Abstract

This study discloses the role of graphene and bismuth chalcogenides in membranes designed to water desalination. Nanocomposite membranes were tailored and characterized from morphological and physicochemical point of views. Membrane distillation (MD) and membrane crystallization (MCr) experiments were implemented in order to evaluate how confined fillers can affect the final performance of membrane process in terms of flux, rejection, nucleation and growth rate of salts crystals. Chemisorption was envisaged as a crucial mechanism in assisting water diffusion and ion aggregation. This study provides new insightful indication about the powerful function of graphene and materials beyond graphene in membranes designed for scalable MD and MCr. Higher performances could make these membrane operations extremely challenging for future competitive water desalination processes. [ABSTRACT FROM AUTHOR]

Published
2019
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215. Tailoring the Surface Chemical Reactivity of Transition‐Metal Dichalcogenide PtTe2 Crystals.

Author

Politano, Antonio, Chiarello, Gennaro, Kuo, Chia‐nung, Lue, Chin Shan, Edla, Raju, Torelli, Piero, Pellegrini, Vittorio, and Boukhvalov, Danil W.

Subjects
*TRANSITION metals, *PLATINUM compounds, *HYDROGEN evolution reactions, *DENSITY functional theory, *ATOMIC spectroscopy, *FERMIONS, *OPTOELECTRONICS
Abstract

Abstract: PtTe2 is a novel transition‐metal dichalcogenide hosting type‐II Dirac fermions that displays application capabilities in optoelectronics and hydrogen evolution reaction. Here it is shown, by combining surface science experiments and density functional theory, that the pristine surface of PtTe2 is chemically inert toward the most common ambient gases (oxygen and water) and even in air. It is demonstrated that the creation of Te vacancies leads to the appearance of tellurium‐oxide phases upon exposing defected PtTe2 surfaces to oxygen or ambient atmosphere, which is detrimental for the ambient stability of uncapped PtTe2‐based devices. On the contrary, in PtTe2 surfaces modified by the joint presence of Te vacancies and substitutional carbon atoms, the stable adsorption of hydroxyl groups is observed, an essential step for water splitting and the water–gas shift reaction. These results thus pave the way toward the exploitation of this class of Dirac materials in catalysis. [ABSTRACT FROM AUTHOR]

Published
2018
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216. Spectroscopic characterization of graphene films grown on Pt(111) surface by chemical vapor deposition of ethylene

Author

Cazzanelli, Enzo, Caruso, Tommaso, Castriota, Marco, Marino, Antonio Raimondo, Politano, Antonio, Chiarello, Gennaro, Giarola, Marco, and Mariotto, Gino

Subjects
spectroscopic characterization, Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Graphene monolayers, CVD, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences
Abstract

This work reports the peculiar properties of a graphene film prepared by the chemical vapor deposition (CVD) of ethylene in high vacuum on a well oriented and carefully cleaned Pt(111) crystal surface maintained at high temperature. In-situ and ex-situ characterization techniques (low energy electron diffraction, high resolution electron energy loss spectroscopy, scanning electron microscopy and Raman micro-spectroscopy) used here indicate the prevalence of single layer regions and the presence of two different orientations of the graphene sheets with respect to the Pt(111) substrate. In most of the deposited area evidence is found of a compressive stress for the graphene lattice, as a net result of the growth process on a metal substrate. This graphene film grown on Pt(111) exhibits a lower degree of order and of homogeneity with respect to the exfoliated graphene on Si/SiO2, as it is found generally for graphene on metals, but several characterization techniques indicates a better quality than in previous deposition experiments on the same metal substrate., Comment: 18 pages, 5 figures, Journal of Raman spectroscopy 2013

Published
2013

218. Insight on Thermally Activated Hydrocarbon Dehydrogenation on the Pt3Ni(111) Surface: From Adsorbed Hydrocarbons up to Graphene Formation

Author

Politano, Antonio, Wang, Lin, and Chiarello, Gennaro

Abstract

The Pt3Ni(111) alloy is characterized by the presence of an outermost surface layer only composed by Pt atoms, that is, the so-called Pt skin, which is at the basis of its outstanding performances in oxygen reduction reaction. The growth of graphene on this alloy is further motivated by the realization of a charge-neutral Gr/metal gate, which can be replaced by a p-doped Gr/oxide/metal configuration upon heating in an oxygen environment. Herein, we have followed the complete reaction pathway starting with adsorbed hydrocarbons and ending with the large-scale growth of a graphene overlayer. Experiments using temperature-programmed X-ray photoelectron spectroscopy have been carried out for different conditions (C2H4dose and sample temperature). Submonolayer graphene (0.08 ML) is reached upon heating at T= 1000 K an ethene monolayer dosed at T= 80 K. Conversely, monolayer graphene domains are achieved for C2H4cracking at T= 800 K. We also find that carbon atoms dissolved into the bulk segregate toward the substrate during the cooling.

Published
2024
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225. Black Phosphorus Terahertz Photodetectors

Author

Viti, Leonardo, primary, Hu, Jin, additional, Coquillat, Dominique, additional, Knap, Wojciech, additional, Tredicucci, Alessandro, additional, Politano, Antonio, additional, and Vitiello, Miriam Serena, additional

Published
2015
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231. Proprietà elettroniche e vibrazionali di strati sottili adsorbiti su substrati metallici

Author

Politano, Antonio, Chiarello, Gennaro, and Falcone, Giovanni

Subjects
Proprietà fisica della materia, Elettronica molecolare
Abstract

Understanding the adsorption, catalytic, and electronic properties of metal/metal interfaces is one of the foremost aims of surface science. In fact, through the tailoring of the characteristics of the substrate it should be possible to obtain more selective catalysts and more effective electronic devices. This thesis is focused on the vibrational and electronic properties of various metal/metal systems, studied by high-resolution electron energy loss spectroscopy. Firstly, alkali adsorption and their coadsorption with CO, O, and OH on transition-metal and noble-metal surfaces have been investigated. Vibrational measurements demonstrated that alkalis adsorb as neutral and polarized adatoms on metal surfaces. The adsorption of CO induces alkali ionization. Short-range effects dominate in alkali coadsorption systems. Alkali oxidation is more readily achieved upon CO adsorption or dissociation than by direct exposures to oxygen. The stabilization of subsurface O was obtained on alkali-doped Cu(111), while on alkali-modified transition-metal catalysts O adatoms remain in on-surface sites. In the latter case a softening of the O-substrate bond occurs. Moreover, we studied chemical reactions at clean and alkali-doped bimetallic surfaces obtained by depositing monolayers of silver on Ni(111) and Cu(111). Important information on the metal surfaces and interfaces could be provided also by the analysis of collective electronic excitations. Surface plasmon dispersion was investigated in metal/metal systems exhibiting electron quantum confinement. Screening effects are enhanced by the presence of quantum well states and a direct correlation between the free-electron density of states of the system, the chemical reactivity, and dynamical screening processes exists. Measurements have been performed on both flat thin films and films nanostructured in islands in order to shed light on the influence of the growth mode on the electronic response of the system. The knowledge gained herein has far-reaching implications to the general understanding of processes at metal/metal interfaces. Keywords: chemisorption, alkali metals, carbon monoxide, oxygen, metallic thin films, silver, bimetallic surfaces, electronic excitations, electron energy loss spectroscopy, surface chemical reactivity, charge transfers, electron confinement. Dottorato di Ricerca in: Fisica, Ciclo XXI, SSD FIS/03 a.a. 2007-2008 Univerisità della Calabria

Published
2008

232. Spectroscopic Investigations of Phonons in Epitaxial Graphene.

Author

Politano, Antonio

Subjects
GRAPHENE, EPITAXY, SPECTRUM analysis, SUBSTRATES (Materials science), PHONONS, NANOTECHNOLOGY
Abstract

The interaction of graphene with metallic substrates reveals phenomena and properties of great relevance for applications in nanotechnology. In this article, the vibrational characterization by means of various inelastic scattering spectroscopies are surveyed for graphene epitaxially grown on metals and transition carbides. In particular, the manifestations of electron-phonon interaction, such as Kohn anomalies, the evaluation of elastic properties and the nanoscale control of phonon modes are presented and discussed. [ABSTRACT FROM PUBLISHER]

Published
2017
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239. Manipulating the Topological Interface by Molecular Adsorbates: Adsorption of Co-Phthalocyanine on Bi2Se3.

Author

Caputo, Marco, Panighel, Mirko, Lisi, Simone, Khalil, Lama, Di Santo, Giovanni, Papalazarou, Evangelos, Hruban, Andrzej, Konczykowski, Marcin, Krusin-Elbaum, Lia, Aliev, Ziya S., Babanly, Mahammad B., Otrokov, Mikhail M., Politano, Antonio, Chulkov, Evgueni V., Arnau, Andrés, Marinova, Vera, Das, Pranab K., Jun Fujii, Vobornik, Ivana, and Perfetti, Luca

Published
2016
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240. Nanoindentation of single-crystal Bi2Te3 topological insulators grown with the Bridgman-Stockbarger method.

Author

Lamuta, Caterina, Cupolillo, Anna, Politano, Antonio, Aliev, Ziya S., Babanly, Mahammad B., Chulkov, Evgueni V., Alfano, Marco, and Pagnotta, Leonardo

Subjects
NANOINDENTATION, SINGLE crystals, BISMUTH telluride, HARDNESS, POLYCRYSTALLINE semiconductors, TOPOLOGICAL insulators, YOUNG'S modulus, X-ray diffraction
Abstract

In this work, bismuth telluride (Bi2Te3) single crystals were grown from melted polycrystalline Bi-Te material using the Bridgman-Stockbarger method. Crystalline quality and surface chemistry were investigated through X-ray diffraction analysis and X-ray photoelectron spectroscopy. The mechanical properties were investigated by means of depth-sensing nanoindentation tests carried out using the continuous stiffness measurement (CSM) technique. In turn, the distribution of material hardness and Young's modulus in the depth direction (i.e., perpendicular to the single crystal basal plane) were resolved and quantitative comparisons with the available data extracted from previous literature works were drawn. It is shown that the obtained single crystals are free of contaminants and/or oxide phases and that the mechanical properties lie between those reported in recent literature for Bi2Te3 polycrystalline thin films and 2D nanosheets. [ABSTRACT FROM AUTHOR]

Published
2016
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