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Taleb AA, Schiller F, Vyalikh DV, María Pérez J, Auras SV, Farías D, Ortega JE. Simulating high-pressure surface reactions with molecular beams. Phys Chem Chem Phys 2024; 26:1770-1776. [PMID: 38168970 DOI: 10.1039/d3cp05071h] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Using a reactive molecular beam with high kinetic energy (Ekin), it is possible to speed gas-surface reactions involving high activation barriers (Eact), which would require elevated pressures (P0) if a random gas with a Maxwell-Boltzmann distribution is used. By simply computing the number of molecules that overcome the activation barrier in a random gas at P0 and in a molecular beam at Ekin = Eact, we establish an Ekin-P0 equivalence curve, through which we postulate that molecular beams are ideal tools to investigate gas-surface reactions that involve high activation energies. In particular, we foresee the use of molecular beams to simulate gas surface reactions within the industrial-range (>10 bar) using surface-sensitive ultra-high vacuum (UHV) techniques, such as X-ray photoemission spectroscopy (XPS). To test this idea, we revisit the oxidation of the Cu(111) surface combining O2 molecular beams and XPS experiments. By tuning the kinetic energy of the O2 beam in the range of 0.24-1 eV, we achieve the same sequence of surface oxides obtained in ambient pressure photoemission (AP-XPS) experiments, in which the Cu(111) surface was exposed to a random O2 gas up to 1 mbar. We observe the same surface oxidation kinetics as in the random gas, but with a much lower dose, close to the expected value derived from the equivalence curve.
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Affiliation(s)
- Amjad Al Taleb
- Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Cantoblanco Madrid, Spain
| | - Frederik Schiller
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018 San Sebastián, Spain.
| | - Denis V Vyalikh
- Donostia International Physics Center, E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Spain
| | - José María Pérez
- Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Cantoblanco Madrid, Spain
| | - Sabine V Auras
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018 San Sebastián, Spain.
- Universidad del País Vasco, Dpto. Física Aplicada, E-20018 San Sebastián, Spain
| | - Daniel Farías
- Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Cantoblanco Madrid, Spain
- Instituto "Nicolás Cabrera", Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - J Enrique Ortega
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018 San Sebastián, Spain.
- Donostia International Physics Center, E-20018 Donostia-San Sebastián, Spain
- Universidad del País Vasco, Dpto. Física Aplicada, E-20018 San Sebastián, Spain
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2
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Anemone G, Taleb AA, Politano A, Kuo CN, Lue CS, Miranda R, Farías D. Setting the limit for the lateral thermal expansion of layered crystals via helium atom scattering. Phys Chem Chem Phys 2022; 24:13229-13233. [DOI: 10.1039/d2cp00758d] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Helium diffraction provides a direct method for measuring the surface thermal expansion of 2D materials.
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Affiliation(s)
- Gloria Anemone
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Departamento de Matemática Aplicada y Estadística, Universidad San Pablo-CEU, CEU Universities, Madrid 28003, Spain
| | - Amjad Al Taleb
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Antonio Politano
- Dipartimento di Scienze Fisiche e Chimiche (DSFC), Università degli Studi dell'Aquila, Via Vetoio 10, I-67100 L’Aquila, Italy
| | - Chia-Nung Kuo
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
| | - Chin Shan Lue
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
| | - Rodolfo Miranda
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain
- Instituto “Nicolás Cabrera”, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Daniel Farías
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Instituto “Nicolás Cabrera”, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
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3
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Abstract
We have measured high-resolution time-of-flight (TOF) spectra of methane scattered from an Ir(111) surface at an incident energy of 81 meV. The angular distributions of scattered CH4 reveal the presence of a sharp and intense specular peak in addition to sharp features corresponding to rotationally inelastic diffraction (RID) peaks along the two main symmetry directions of Ir(111). TOF spectra have been recorded at several RID positions for the two high-symmetry directions. The data show that the scattering dynamics of CH4 is more complex than the one reported for H2/D2, where energy losses in TOF correspond to the expected excitation/deexcitation RID energy transitions. For CH4, this is the case only for RID peaks showing up far from the specular peak, whereas those appearing close to the specular position present different behaviors, depending on the incident direction. The results are compared with Ne scattering TOF data, which allows to assess the relevance of multiphonon scattering in the energy-exchange process. Finally, we report experimental evidence of selective adsorption resonances detected with CH4 beams. This will allow characterizing the CH4-metal surface physisorption well by measuring angular distributions with CH4 beams.
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Affiliation(s)
- Amjad Al Taleb
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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4
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Holst B, Alexandrowicz G, Avidor N, Benedek G, Bracco G, Ernst WE, Farías D, Jardine AP, Lefmann K, Manson JR, Marquardt R, Artés SM, Sibener SJ, Wells JW, Tamtögl A, Allison W. Material properties particularly suited to be measured with helium scattering: selected examples from 2D materials, van der Waals heterostructures, glassy materials, catalytic substrates, topological insulators and superconducting radio frequency materials. Phys Chem Chem Phys 2021; 23:7653-7672. [PMID: 33625410 DOI: 10.1039/d0cp05833e] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Helium Atom Scattering (HAS) and Helium Spin-Echo scattering (HeSE), together helium scattering, are well established, but non-commercial surface science techniques. They are characterised by the beam inertness and very low beam energy (<0.1 eV) which allows essentially all materials and adsorbates, including fragile and/or insulating materials and light adsorbates such as hydrogen to be investigated on the atomic scale. At present there only exist an estimated less than 15 helium and helium spin-echo scattering instruments in total, spread across the world. This means that up till now the techniques have not been readily available for a broad scientific community. Efforts are ongoing to change this by establishing a central helium scattering facility, possibly in connection with a neutron or synchrotron facility. In this context it is important to clarify what information can be obtained from helium scattering that cannot be obtained with other surface science techniques. Here we present a non-exclusive overview of a range of material properties particularly suited to be measured with helium scattering: (i) high precision, direct measurements of bending rigidity and substrate coupling strength of a range of 2D materials and van der Waals heterostructures as a function of temperature, (ii) direct measurements of the electron-phonon coupling constant λ exclusively in the low energy range (<0.1 eV, tuneable) for 2D materials and van der Waals heterostructures (iii) direct measurements of the surface boson peak in glassy materials, (iv) aspects of polymer chain surface dynamics under nano-confinement (v) certain aspects of nanoscale surface topography, (vi) central properties of surface dynamics and surface diffusion of adsorbates (HeSE) and (vii) two specific science case examples - topological insulators and superconducting radio frequency materials, illustrating how combined HAS and HeSE are necessary to understand the properties of quantum materials. The paper finishes with (viii) examples of molecular surface scattering experiments and other atom surface scattering experiments which can be performed using HAS and HeSE instruments.
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Affiliation(s)
- Bodil Holst
- Department of Physics and Technology, University of Bergen, Allegaten 55, 5007 Bergen, Norway.
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5
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Benedek G, Bernasconi M, Campi D, Silkin IV, Chernov IP, Silkin VM, Chulkov EV, Echenique PM, Toennies JP, Anemone G, Al Taleb A, Miranda R, Farías D. Evidence for a spin acoustic surface plasmon from inelastic atom scattering. Sci Rep 2021; 11:1506. [PMID: 33452337 PMCID: PMC7810840 DOI: 10.1038/s41598-021-81018-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 12/29/2020] [Indexed: 11/09/2022] Open
Abstract
Closed-shell atoms scattered from a metal surface exchange energy and momentum with surface phonons mostly via the interposed surface valence electrons, i.e., via the creation of virtual electron-hole pairs. The latter can then decay into surface phonons via electron-phonon interaction, as well as into acoustic surface plasmons (ASPs). While the first channel is the basis of the current inelastic atom scattering (IAS) surface-phonon spectroscopy, no attempt to observe ASPs with IAS has been made so far. In this study we provide evidence of ASP in Ni(111) with both Ne atom scattering and He atom scattering. While the former measurements confirm and extend so far unexplained data, the latter illustrate the coupling of ASP with phonons inside the surface-projected phonon continuum, leading to a substantial reduction of the ASP velocity and possibly to avoided crossing with the optical surface phonon branches. The analysis is substantiated by a self-consistent calculation of the surface response function to atom collisions and of the first-principle surface-phonon dynamics of Ni(111). It is shown that in Ni(111) ASP originate from the majority-spin Shockley surface state and are therefore collective oscillation of surface electrons with the same spin, i.e. it represents a new kind of collective quasiparticle: a Spin Acoustic Surface Plasmon (SASP).
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Affiliation(s)
- G Benedek
- Dipartimento di Scienza dei Materiali, Universitá di Milano-Bicocca, Via R. Cozzi 55, 20125, Milan, Italy.,Donostia International Physics Center (DIPC), 20018, San Sebastián/Donostia, Basque Country, Spain
| | - M Bernasconi
- Dipartimento di Scienza dei Materiali, Universitá di Milano-Bicocca, Via R. Cozzi 55, 20125, Milan, Italy
| | - D Campi
- Dipartimento di Scienza dei Materiali, Universitá di Milano-Bicocca, Via R. Cozzi 55, 20125, Milan, Italy.,École Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland
| | - I V Silkin
- Tomsk State University, 634050, Tomsk, Russia
| | - I P Chernov
- Engineering School of Nuclear Technology, Tomsk Polytechnic University, 634050, Tomsk, Russia
| | - V M Silkin
- Donostia International Physics Center (DIPC), 20018, San Sebastián/Donostia, Basque Country, Spain.,Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, 20080, San Sebastián/Donostia, Basque Country, Spain.,IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Basque Country, Spain
| | - E V Chulkov
- Donostia International Physics Center (DIPC), 20018, San Sebastián/Donostia, Basque Country, Spain.,Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, 20080, San Sebastián/Donostia, Basque Country, Spain.,Centro de Fisica de Materiales, Centro Mixto CSIC-UPV/EHU, 20018, San Sebastian/Donostia, Basque Country, Spain.,St. Petersburg State University, 198504, St. Petersburg, Russia
| | - P M Echenique
- Donostia International Physics Center (DIPC), 20018, San Sebastián/Donostia, Basque Country, Spain.,Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, 20080, San Sebastián/Donostia, Basque Country, Spain.,Centro de Fisica de Materiales, Centro Mixto CSIC-UPV/EHU, 20018, San Sebastian/Donostia, Basque Country, Spain
| | - J P Toennies
- Max-Planck-Institut für Dynamik und Selbstorganisation, Bunsenstraße 10, 37073, Göttingen, Germany
| | - G Anemone
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - A Al Taleb
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - R Miranda
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049, Madrid, Spain.,Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049, Madrid, Spain.,Instituto "Nicolás Cabrera", Universidad Autónoma de Madrid, 28049, Madrid, Spain.,Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - D Farías
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049, Madrid, Spain. .,Instituto "Nicolás Cabrera", Universidad Autónoma de Madrid, 28049, Madrid, Spain. .,Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049, Madrid, Spain.
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6
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D’Olimpio G, Genuzio F, Menteş TO, Paolucci V, Kuo CN, Al Taleb A, Lue CS, Torelli P, Farías D, Locatelli A, Boukhvalov DW, Cantalini C, Politano A. Charge Redistribution Mechanisms in SnSe 2 Surfaces Exposed to Oxidative and Humid Environments and Their Related Influence on Chemical Sensing. J Phys Chem Lett 2020; 11:9003-9011. [PMID: 33035062 PMCID: PMC8015219 DOI: 10.1021/acs.jpclett.0c02616] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 10/01/2020] [Indexed: 06/11/2023]
Abstract
Tin diselenide (SnSe2) is a van der Waals semiconductor, which spontaneously forms a subnanometric SnO2 skin once exposed to air. Here, by means of surface-science spectroscopies and density functional theory, we have investigated the charge redistribution at the SnO2-SnSe2 heterojunction in both oxidative and humid environments. Explicitly, we find that the work function of the pristine SnSe2 surface increases by 0.23 and 0.40 eV upon exposure to O2 and air, respectively, with a charge transfer reaching 0.56 e-/SnO2 between the underlying SnSe2 and the SnO2 skin. Remarkably, both pristine SnSe2 and defective SnSe2 display chemical inertness toward water, in contrast to other metal chalcogenides. Conversely, the SnO2-SnSe2 interface formed upon surface oxidation is highly reactive toward water, with subsequent implications for SnSe2-based devices working in ambient humidity, including chemical sensors. Our findings also imply that recent reports on humidity sensing with SnSe2 should be reinterpreted, considering the pivotal role of the oxide skin in the interaction with water molecules.
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Affiliation(s)
- Gianluca D’Olimpio
- Department
of Physical and Chemical Sciences, University
of L’Aquila, via Vetoio, 67100 L’Aquila, AQ, Italy
| | - Francesca Genuzio
- Elettra-Sincrotrone
S.C.p.A., S.S. 14-km 163.5 in AREA Science Park, 34149 Trieste, Italy
| | - Tevfik Onur Menteş
- Elettra-Sincrotrone
S.C.p.A., S.S. 14-km 163.5 in AREA Science Park, 34149 Trieste, Italy
| | - Valentina Paolucci
- Department
of Industrial and Information Engineering and Economics, University of L’Aquila, Via G. Gronchi 18, I-67100 L’Aquila, Italy
| | - Chia-Nung Kuo
- Department
of Physics, National Cheng Kung University, 1 Ta-Hsueh Road, 70101 Tainan, Taiwan
| | - Amjad Al Taleb
- Departamento
de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Chin Shan Lue
- Department
of Physics, National Cheng Kung University, 1 Ta-Hsueh Road, 70101 Tainan, Taiwan
| | - Piero Torelli
- Elettra-Sincrotrone
S.C.p.A., S.S. 14-km 163.5 in AREA Science Park, 34149 Trieste, Italy
- Consiglio
Nazionale delle Ricerche (CNR)-Istituto Officina dei Materiali (IOM), Laboratorio TASC in Area Science
Park S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Daniel Farías
- Departamento
de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Instituto
‘Nicolás Cabrera’, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, 28049 Madrid, Spain
| | - Andrea Locatelli
- Elettra-Sincrotrone
S.C.p.A., S.S. 14-km 163.5 in AREA Science Park, 34149 Trieste, Italy
| | - Danil W. Boukhvalov
- College
of Science, Institute of Materials Physics and Chemistry, Nanjing Forestry University, Nanjing 210037, P. R. China
- Theoretical
Physics and Applied Mathematics Department, Ural Federal University, Mira Street 19, 620002 Ekaterinburg, Russia
| | - Carlo Cantalini
- Department
of Industrial and Information Engineering and Economics, University of L’Aquila, Via G. Gronchi 18, I-67100 L’Aquila, Italy
| | - Antonio Politano
- Department
of Physical and Chemical Sciences, University
of L’Aquila, via Vetoio, 67100 L’Aquila, AQ, Italy
- CNR-IMM
Istituto per la Microelettronica e Microsistemi, VIII strada 5, I-95121 Catania, Italy
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7
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Abstract
Diffraction with matter waves has been reported since the beginning of quantum mechanics. In free space, diffraction effects have been observed even with objects as large as C60 molecules. However, in scattering from a solid surface, pure elastic diffraction features have never been observed with molecules larger than D2. Here we report the observation of pure molecular diffraction for CH4 scattered off of an Ir(111) surface. These results prove that quantum coherence is preserved, despite the small separation between rotational levels and the interaction with surface phonons. Density functional theory calculations of the potential energy surface provide some clues to understand the larger corrugation sampled by CH4 molecules in comparison to Ne atoms. Our results show that isotope separation of polyatomic molecules may be possible using gas-surface diffraction.
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Affiliation(s)
- Amjad Al Taleb
- Departamento de Física de la Materia Condensada , Universidad Autónoma de Madrid , 28049 Madrid , Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia) , Cantoblanco, 28049 Madrid , Spain
| | - Gloria Anemone
- Departamento de Física de la Materia Condensada , Universidad Autónoma de Madrid , 28049 Madrid , Spain
| | - Linsen Zhou
- Department of Chemistry and Chemical Biology , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Hua Guo
- Department of Chemistry and Chemical Biology , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Daniel Farías
- Departamento de Física de la Materia Condensada , Universidad Autónoma de Madrid , 28049 Madrid , Spain
- Instituto "Nicolás Cabrera" , Universidad Autónoma de Madrid , 28049 Madrid , Spain
- Condensed Matter Physics Center (IFIMAC) , Universidad Autónoma de Madrid , 28049 Madrid , Spain
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8
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Del Cueto M, Maurer RJ, Al Taleb A, Farías D, Martín F, Díaz C. Performance of van der Waals DFT approaches for helium diffraction on metal surfaces. J Phys Condens Matter 2019; 31:135901. [PMID: 30625425 DOI: 10.1088/1361-648x/aafcfd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The ability of the different approaches proposed to date to include the effects of van der Waals (vdW) dispersion forces in density functional theory (DFT) is currently under debate. Here, we used the diffraction of He on a Ru(0 0 0 1) surface as a challenging benchmark system to analyze the suitability of several representative approaches, from the ones correcting the exchange-correlation generalized gradient approximation (GGA) functional, to the ones correcting the DFT energies through pairwise-based methods. To perform our analysis, we have built seven continuous potential energy surfaces (PESs) and carried out quantum dynamics simulations using a multi-configuration time-dependent Hartree method. Our analysis reveals that standard DFT within the PBE-GGA framework, although it overestimates diffraction probabilities, yields the best results in comparison with available experimental measurements. On the other hand, although several of the existing vdW DFT approaches yield physisorption wells in very good agreement with experiment, they all seem to overestimate the long-distance corrugation of the PES, the region probed by He scattering, resulting in a large overestimation of diffraction probabilities.
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Affiliation(s)
- Marcos Del Cueto
- Departamento de Química Módulo 13, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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9
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Abstract
We have measured the temperature dependence of angular distributions of CH4 from Pt(111) at an incident energy of 109 meV. A broad angular distribution has been observed along the two main symmetry directions, whereby the peak center shifts from the supra-specular position to the sub-specular position when the surface temperature increases from 120 K to 800 K. Different widths have been measured for the scattering patterns along the [ 1¯01 ] and the [ 2¯11 ] azimuthal directions. Based on calculations performed within the binary collision model, these differences have been ascribed to different corrugations of the CH4-Pt(111) interaction potential along the two high-symmetry directions. This corrugation has been estimated from the model calculations to amount ∼0.03 Å, a factor of three larger than the one measured with helium diffraction.
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Affiliation(s)
- Takahiro Kondo
- Department of Materials Science and Tsukuba Research Center for Energy Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan
| | - Amjad Al Taleb
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Gloria Anemone
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Daniel Farías
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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10
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Abstract
The reactivity of a Pd monolayer epitaxially grown on Ru(0001) toward O2 has been investigated by molecular beam techniques. O2 initial sticking coefficients were determined using the King and Wells method in the incident energy range of 40-450 meV and for sample temperatures of 100 K and 300 K, and compared to the corresponding values measured on the clean Ru(0001) and Pd(111) surfaces. In contrast to the high reactivity shown by Ru(0001) at 100 K, the Pd/Ru(0001) system exhibits a monotonic decrease in the sticking probability of O2 as a function of normal incident energy. At room temperature, the system was found to be inert. Thermal desorption measurements show that O2 is adsorbed molecularly at 100 K. A completely different behaviour has been measured for the Pd0.95Ru0.05/Ru(0001) surface alloy. On this surface, the O2 sticking probability increases with incident energy and resembles the one observed on the clean Ru(0001) surface, even at 300 K. Thermal desorption measurements point to dissociative adsorption of O2 in this system. Both the charge transfer from the Pd to the Ru substrate and the compressive strain on the Pd monolayer contribute to decrease in the reactivity of the Pd/Ru(0001) system well below those of both Ru(0001) and Pd(111).
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Affiliation(s)
- D Farías
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - M Minniti
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - R Miranda
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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11
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Abstract
We have measured high-resolution angular distributions of methane scattered from a Ni(111) surface at incident energies between 68.9 meV and 108.6 meV. A sharp and intense specular peak has been observed, in addition to sharp features corresponding to rotationally inelastic diffraction (RID) peaks along the two main symmetry directions of Ni(111). The intensity of the most intense RID peaks is ca. 50% of the specular one. The observation of sharp, coherent elastic peaks at such low incident energies suggests that single scattering dominates over trapping at these energies, and that the depth of the van der Waals well should be lower than 60 meV. In contrast, a broad angular distribution shifted from the specular position is observed from a graphene-covered Ni(111) surface under identical incident conditions. These results open up the possibility of studying the physisorption well between CH4 and a transition metal surface using high-resolution molecular beams.
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Affiliation(s)
- Amjad Al Taleb
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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12
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Politano A, Cattelan M, Boukhvalov DW, Campi D, Cupolillo A, Agnoli S, Apostol NG, Lacovig P, Lizzit S, Farías D, Chiarello G, Granozzi G, Larciprete R. Unveiling the Mechanisms Leading to H2 Production Promoted by Water Decomposition on Epitaxial Graphene at Room Temperature. ACS Nano 2016; 10:4543-9. [PMID: 27054462 DOI: 10.1021/acsnano.6b00554] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
By means of a combination of surface-science spectroscopies and theory, we investigate the mechanisms ruling the catalytic role of epitaxial graphene (Gr) grown on transition-metal substrates for the production of hydrogen from water. Water decomposition at the Gr/metal interface at room temperature provides a hydrogenated Gr sheet, which is buckled and decoupled from the metal substrate. We evaluate the performance of Gr/metal interface as a hydrogen storage medium, with a storage density in the Gr sheet comparable with state-of-the-art materials (1.42 wt %). Moreover, thermal programmed reaction experiments show that molecular hydrogen can be released upon heating the water-exposed Gr/metal interface above 400 K. The Gr hydro/dehydrogenation process might be exploited for an effective and eco-friendly device to produce (and store) hydrogen from water, i.e., starting from an almost unlimited source.
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Affiliation(s)
- Antonio Politano
- Department of Physics, University of Calabria , via ponte Bucci, 31/C, I-87036 Rende, Cosenza, Italy
| | - Mattia Cattelan
- Department of Chemical Sciences and INSTM Research Unit, University of Padova , via Marzolo 1, I-35131 Padova, Italy
| | - Danil W Boukhvalov
- Department of Chemistry, Hanyang University , 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, South Korea
- Theoretical Physics and Applied Mathematics Department, Ural Federal University , Mira Street 19, 620002 Ekaterinburg, Russia
| | - Davide Campi
- Department of Materials Science, University of Milano-Bicocca , via R. Cozzi 55, I-20125 Milano, Italy
| | - Anna Cupolillo
- Department of Physics, University of Calabria , via ponte Bucci, 31/C, I-87036 Rende, Cosenza, Italy
| | - Stefano Agnoli
- Department of Chemical Sciences and INSTM Research Unit, University of Padova , via Marzolo 1, I-35131 Padova, Italy
| | - Nicoleta G Apostol
- Elettra-Sincrotrone Trieste S.C.p.A. , SS 14, km 163.5, I-34149 Trieste, Italy
| | - Paolo Lacovig
- Elettra-Sincrotrone Trieste S.C.p.A. , SS 14, km 163.5, I-34149 Trieste, Italy
| | - Silvano Lizzit
- Elettra-Sincrotrone Trieste S.C.p.A. , SS 14, km 163.5, I-34149 Trieste, Italy
| | - Daniel Farías
- Departamento de Física de la Materia Condensada & Instituto de Ciencia de Materiales "Nicolás Cabrera" & Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid , 28049 Madrid, Spain
| | - Gennaro Chiarello
- Department of Physics, University of Calabria , via ponte Bucci, 31/C, I-87036 Rende, Cosenza, Italy
| | - Gaetano Granozzi
- Department of Chemical Sciences and INSTM Research Unit, University of Padova , via Marzolo 1, I-35131 Padova, Italy
| | - Rosanna Larciprete
- CNR, Institute for Complex Systems , via Fosso del Cavaliere 100, I-00133 Roma, Italy
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Abstract
The study of surface phonon dispersion curves is motivated by the quest for a detailed understanding of the forces between the atoms at the surface and in the bulk. In the case of graphene, additional motivation comes from the fact that thermal conductivity is dominated by contributions from acoustic phonons, while optical phonon properties are essential to understand Raman spectra. In this article, we review recent progress made in the experimental determination of phonon dispersion curves of graphene grown on several single-crystal metal surfaces. The two main experimental techniques usually employed are high-resolution electron energy loss spectroscopy (HREELS) and inelastic helium atom scattering (HAS). The different dispersion branches provide a detailed insight into the graphene-substrate interaction. Softening of optical modes and signatures of the substrate's Rayleigh wave are observed for strong graphene-substrate interactions, while acoustic phonon modes resemble those of free-standing graphene for weakly interacting systems. The latter allows determining the bending rigidity and the graphene-substrate coupling strength. A comparison between theory and experiment is discussed for several illustrative examples. Perspectives for future experiments are discussed.
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Affiliation(s)
- Amjad Al Taleb
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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14
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Maccariello D, Al Taleb A, Calleja F, Vázquez de Parga AL, Perna P, Camarero J, Gnecco E, Farías D, Miranda R. Observation of Localized Vibrational Modes of Graphene Nanodomes by Inelastic Atom Scattering. Nano Lett 2016; 16:2-7. [PMID: 26630565 DOI: 10.1021/acs.nanolett.5b02887] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Inelastic helium atom scattering (HAS) is suitable to determine low-energy (few meV) vibrations spatially localized on structures in the nanometer range. This is illustrated for the nanodomes that appear often on graphene (Gr) epitaxially grown on single crystal metal surfaces. The nature of the inelastic losses observed in Gr/Ru(0001) and Gr/Cu/Ru(0001) has been clarified by intercalation of Cu below the Gr monolayer, which decouples the Gr layer from the Ru substrate and changes substantially the out-of-plane, flexural phonon dispersion of epitaxial Gr, while maintaining the nanodomes and their localized vibrations. He diffraction proves that the Cu-intercalated Gr layer is well ordered structurally, while scanning tunneling microscopy reveals the persistence of the (slightly modified) periodic array of Gr nanodomes. A simple model explains the order of magnitude of the energy losses associated with the Gr nanodomes and their size dependence. The dispersionless, low-energy phonon branches may radically alter the transport of heat in intercalated Gr.
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Affiliation(s)
- D Maccariello
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain
| | | | - F Calleja
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain
| | - A L Vázquez de Parga
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain
| | - P Perna
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain
| | - J Camarero
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain
| | - E Gnecco
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain
| | | | - R Miranda
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain
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15
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Anemone G, Climent-Pascual E, Yu HK, Al Taleb A, Jiménez-Villacorta F, Prieto C, Wodtke AM, De Andrés A, Farías D. Quality of graphene on sapphire: long-range order from helium diffraction versus lattice defects from Raman spectroscopy. RSC Adv 2016. [DOI: 10.1039/c5ra27452d] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We report a new method to produce high-quality, transparent graphene/sapphire samples, using Cu as a catalyst.
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Affiliation(s)
- Gloria Anemone
- Departamento de Física de la Materia Condensada
- Universidad Autónoma de Madrid
- 28049 Madrid
- Spain
| | - Esteban Climent-Pascual
- Instituto de Ciencia de Materiales de Madrid
- Consejo Superior de Investigaciones Científicas
- Spain
| | - Hak Ki Yu
- Institute for Physical Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
- Max Planck Institute for Biophysical Chemistry
| | - Amjad Al Taleb
- Departamento de Física de la Materia Condensada
- Universidad Autónoma de Madrid
- 28049 Madrid
- Spain
| | - Felix Jiménez-Villacorta
- Instituto de Ciencia de Materiales de Madrid
- Consejo Superior de Investigaciones Científicas
- Spain
| | - Carlos Prieto
- Instituto de Ciencia de Materiales de Madrid
- Consejo Superior de Investigaciones Científicas
- Spain
| | - Alec M. Wodtke
- Institute for Physical Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
- Max Planck Institute for Biophysical Chemistry
| | - Alicia De Andrés
- Instituto de Ciencia de Materiales de Madrid
- Consejo Superior de Investigaciones Científicas
- Spain
| | - Daniel Farías
- Departamento de Física de la Materia Condensada
- Universidad Autónoma de Madrid
- 28049 Madrid
- Spain
- Instituto “Nicolás Cabrera”
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16
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Farías D, Minniti M, Al Taleb A, Miranda R. Initial Sticking Coefficient of H2 on the Pd–Cu(111) Surface Alloy at very Low Coverages. Z PHYS CHEM 2013. [DOI: 10.1515/zpch.2013.0392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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17
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Farías D, Minniti M, Al Taleb A, Miranda R. Initial Sticking Coefficient of H2 on the Pd–Cu(111) Surface Alloy at very Low Coverages. Z PHYS CHEM 2013. [DOI: 10.1524/zpch.2013.0392] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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18
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Ramos M, Minniti M, Díaz C, Farías D, Miranda R, Martín F, Martínez AE, Busnengo HF. Environment-driven reactivity of H2 on PdRu surface alloys. Phys Chem Chem Phys 2013; 15:14936-40. [DOI: 10.1039/c3cp52001c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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19
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Minniti M, Díaz C, Fernández Cuñado JL, Politano A, Maccariello D, Martín F, Farías D, Miranda R. Helium, neon and argon diffraction from Ru(0001). J Phys Condens Matter 2012; 24:354002. [PMID: 22898880 DOI: 10.1088/0953-8984/24/35/354002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present an experimental and theoretical study of He, Ne and Ar diffraction from the Ru(0001) surface. Close-coupling calculations were performed to estimate the corrugation function and the potential well depth in the atom-surface interaction in all three cases. DFT (density functional theory) calculations, including van der Waals dispersion forces, were used to validate the close-coupling results and to further analyze the experimental results. Our DFT calculations indicate that, in the incident energy range 20-150 meV, anticorrugating effects are present in the case of He and Ar diffraction, whereas normal corrugation is observed with Ne beams.
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Affiliation(s)
- M Minniti
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, Spain
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20
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Minniti M, Farías D, Perna P, Miranda R. Enhanced selectivity towards O2 and H2 dissociation on ultrathin Cu films on Ru(0001). J Chem Phys 2012; 137:074706. [DOI: 10.1063/1.4746942] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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21
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Affiliation(s)
- Pablo Nieto
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Daniel Barredo
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Daniel Farías
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain
| | - Rodolfo Miranda
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain
- Instituto de Ciencia de Materiales “Nicolás Cabrera”, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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22
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Nieto P, Farías D, Miranda R, Luppi M, Baerends EJ, Somers MF, van der Niet MJTC, Olsen RA, Kroes GJ. Diffractive and reactive scattering of H2 from Ru(0001): experimental and theoretical study. Phys Chem Chem Phys 2011; 13:8583-97. [DOI: 10.1039/c0cp02425b] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Barredo D, Laurent G, Nieto P, Farías D, Miranda R. High-resolution elastic and rotationally inelastic diffraction of D2 from NiAl(110). J Chem Phys 2010; 133:124702. [DOI: 10.1063/1.3479587] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Daniel Barredo
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
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24
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Laurent G, Barredo D, Farías D, Miranda R, Díaz C, Rivière P, Somers MF, Martín F. Experimental and theoretical study of rotationally inelastic diffraction of D2 from NiAl(110). Phys Chem Chem Phys 2010; 12:14501-7. [DOI: 10.1039/c0cp00431f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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Diaconescu B, Pohl K, Vattuone L, Savio L, Hofmann P, Silkin VM, Pitarke JM, Chulkov EV, Echenique PM, Farías D, Rocca M. Low-energy acoustic plasmons at metal surfaces. Nature 2007; 448:57-9. [PMID: 17611537 DOI: 10.1038/nature05975] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2007] [Accepted: 05/29/2007] [Indexed: 11/09/2022]
Abstract
Nearly two-dimensional (2D) metallic systems formed in charge inversion layers and artificial layered materials permit the existence of low-energy collective excitations, called 2D plasmons, which are not found in a three-dimensional (3D) metal. These excitations have caused considerable interest because their low energy allows them to participate in many dynamical processes involving electrons and phonons, and because they might mediate the formation of Cooper pairs in high-transition-temperature superconductors. Metals often support electronic states that are confined to the surface, forming a nearly 2D electron-density layer. However, it was argued that these systems could not support low-energy collective excitations because they would be screened out by the underlying bulk electrons. Rather, metallic surfaces should support only conventional surface plasmons-higher-energy modes that depend only on the electron density. Surface plasmons have important applications in microscopy and sub-wavelength optics, but have no relevance to the low-energy dynamics. Here we show that, in contrast to expectations, a low-energy collective excitation mode can be found on bare metal surfaces. The mode has an acoustic (linear) dispersion, different to the dependence of a 2D plasmon, and was observed on Be(0001) using angle-resolved electron energy loss spectroscopy. First-principles calculations show that it is caused by the coexistence of a partially occupied quasi-2D surface-state band with the underlying 3D bulk electron continuum and also that the non-local character of the dielectric function prevents it from being screened out by the 3D states. The acoustic plasmon reported here has a very general character and should be present on many metal surfaces. Furthermore, its acoustic dispersion allows the confinement of light on small surface areas and in a broad frequency range, which is relevant for nano-optics and photonics applications.
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Affiliation(s)
- Bogdan Diaconescu
- Department of Physics and Material Science Program, University of New Hampshire, Durham, New Hampshire 03824, USA
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26
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Barredo D, Laurent G, Díaz C, Nieto P, Busnengo HF, Salin A, Farías D, Martín F. Experimental evidence of dynamic trapping in the scattering of H2 from Pd(110). J Chem Phys 2006; 125:051101. [PMID: 16942196 DOI: 10.1063/1.2229203] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
We have performed H2(D2) diffraction experiments on a Pd(110) surface using two different high-sensitivity set-ups. We have found that, although the total reflectivity of Pd(110) is comparable to that observed in other reactive systems, the corresponding H2(D2) diffraction patterns are quite different: no diffraction peak, including the specular one, is observed on Pd(110). This unexpected result is the consequence of dynamic trapping. Such interpretation is supported by classical dynamics calculations based on accurate ab initio potential energy surfaces.
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Affiliation(s)
- D Barredo
- Departamento de Física de la Materia Condensada and Instituto Nicolás Cabrera, Universidad Autónoma, 28049 Madrid, Spain
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27
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Nieto P, Pijper E, Barredo D, Laurent G, Olsen RA, Baerends EJ, Kroes GJ, Farías D. Reactive and Nonreactive Scattering of H2 from a Metal Surface Is Electronically Adiabatic. Science 2006; 312:86-9. [PMID: 16469880 DOI: 10.1126/science.1123057] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The Born-Oppenheimer approximation of uncoupled electronic and nuclear motion is a standard tool of the computational chemist. However, its validity for molecule-metal surface reactions, which are important to heterogeneous catalysis, has been questioned because of the possibility of electron-hole pair excitations. We have performed experiments and calculations on the scattering of molecular hydrogen from a catalytically relevant metal surface, obtaining absolute probabilities for changes in the molecule's velocity parallel to the representative Pt(111) surface. The comparison for in-plane and out-of-plane scattering and results for dissociative chemisorption in the same system show that for hydrogen-metal systems, reaction and diffractive scattering can be accurately described using the Born-Oppenheimer approximation.
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Affiliation(s)
- Pablo Nieto
- Departamento de Física de la Materia Condensada C-3 and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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28
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Díaz C, Busnengo HF, Rivière P, Farías D, Nieto P, Somers MF, Kroes GJ, Salin A, Martín F. A classical dynamics method for H2 diffraction from metal surfaces. J Chem Phys 2005; 122:154706. [PMID: 15945655 DOI: 10.1063/1.1878613] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We present a discretization method that allows one to interpret measurements on diffraction of diatomic molecules from solid surfaces using six-dimensional (6D) classical trajectory calculations. It has been applied to the D2NiAl(110) and H2Pd(111) systems (which are models for activated and nonactivated dissociative chemisorption, respectively) using realistic potential energy surfaces obtained from first principles. Comparisons with experimental results and 6D quantum dynamical calculations show that, in general, the method is able to predict the relative intensity of the most important diffraction peaks. We therefore conclude that classical mechanics can be an efficient guide for experimentalists in the search for the most significant diffraction channels.
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Affiliation(s)
- C Díaz
- Departamento de Química, Facultad de Ciencias C-9, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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29
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Farías D, Díaz C, Rivière P, Busnengo HF, Nieto P, Somers MF, Kroes GJ, Salin A, Martín F. In-plane and out-of-plane diffraction of H(2) from metal surfaces. Phys Rev Lett 2004; 93:246104. [PMID: 15697832 DOI: 10.1103/physrevlett.93.246104] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2004] [Indexed: 05/24/2023]
Abstract
We have measured in-plane and out-of-plane diffraction of H2 and D2 molecular beams scattered by reactive Pd(111) and nonreactive NiAl(110) surfaces at 140-150 meV. A comparison with six-dimensional quantum dynamics and classical trajectory calculations shows for the first time that accurate diffraction patterns can be obtained from state-of-the-art potential energy surfaces based on density functional theory. Our measurements show that, at general incidence conditions, out-of-plane diffraction is much more important than was assumed in previous experiments.
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Affiliation(s)
- D Farías
- Departamento de Física de la Materia Condensada and Instituto Nicolás Cabrera, Universidad Autónoma, 28049 Madrid, Spain
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30
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Farías D, Kamiński W, Lobo J, Ortega J, Hulpke E, Pérez R, Flores F, Michel EG. Phonon softening, chaotic motion, and order-disorder transition in Sn/Ge(111). Phys Rev Lett 2003; 91:016103. [PMID: 12906557 DOI: 10.1103/physrevlett.91.016103] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2003] [Indexed: 05/24/2023]
Abstract
The phonon dynamics of the Sn/Ge(111) interface is studied using high-resolution helium atom scattering and first-principles calculations. At room temperature we observe a phonon softening at the Kmacr; point in the (sqrt[3]xsqrt[3])R30 degrees phase, associated with the stabilization of a (3x3) phase at low temperature. That phonon band is split into three branches in the (3x3) phase. We analyze the character of these phonons and find out that the low- and room-temperature modes are connected via a chaotic motion of the Sn atoms. The system is shown to present an order-disorder transition.
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Affiliation(s)
- D Farías
- Departamento de Física de la Materia Condensada and Instituto Nicolás Cabrera, Universidad Autónoma, 28049 Madrid, Spain
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31
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Farías D, Miranda R, Rieder KH. Energy dependence of diffractive and rotationally inelastic scattering of D2 from NiAl(110). J Chem Phys 2002. [DOI: 10.1063/1.1488592] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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32
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Farías D, Siebentritt S, Apel R, Pues R, Rieder K. Helium atom scattering and HREELS investigations of the H/Rh(311) adsorption system. J Chem Phys 1997. [DOI: 10.1063/1.473889] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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33
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