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Ahsan A, Mousavi SF, Nijs T, Nowakowska S, Popova O, Wäckerlin A, Björk J, Gade LH, Jung TA. Phase Transitions in Confinements: Controlling Solid to Fluid Transitions of Xenon Atoms in an On-Surface Network. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1803169. [PMID: 30556276 DOI: 10.1002/smll.201803169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 09/20/2018] [Indexed: 06/09/2023]
Abstract
This study reports on "phase" transitions of Xe condensates in on-surface confinements induced by temperature changes and local probe excitation. The pores of a metal-organic network occupied with 1 up to 9 Xe atoms are investigated in their propensity to undergo "condensed solid" to "confined fluid" transitions. Different transition temperatures are identified, which depend on the number of Xe atoms in the condensate and relate to the stability of the Xe clustering in the condensed "phase." This work reveals the feature-rich behavior of transitions of confined planar condensates, which provide a showcase toward future "phase-transition" storage media patterned by self-assembly. This work is also of fundamental interest as it paves the way to real space investigations of reversible solid to fluid transitions of magic cluster condensates in an array of extremely well-defined quantum confinements.
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Affiliation(s)
- Aisha Ahsan
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - S Fatemeh Mousavi
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Thomas Nijs
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Sylwia Nowakowska
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Olha Popova
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Aneliia Wäckerlin
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Jonas Björk
- Department of Physics, Chemistry and Biology, IFM, Linköping University, Linköping, 58183, Sweden
| | - Lutz H Gade
- Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Thomas A Jung
- Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232, Villigen, PSI, Switzerland
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2
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Mizushima H, Koike H, Kuroda K, Ishida Y, Nakayama M, Mase K, Kondo T, Shin S, Kanai K. Effect of physisorption of inert organic molecules on Au(111) surface electronic states. Phys Chem Chem Phys 2018; 19:18646-18651. [PMID: 28692082 DOI: 10.1039/c7cp04232a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The modification of the Au(111) Shockley surface state (SS) by an n-alkane molecule (n-tetratetracontane) monolayer was observed by angle-resolved ultraviolet photoemission spectroscopy. Although there is little chance of chemical interaction in this ideal physisorption system, the volume of the Fermi surface of the SS was significantly reduced accompanied by the formation of large interface electric dipoles. Moreover, Rashba splitting of the SS by spin-orbit interactions was slightly increased upon n-tetratetracontane adsorption, which arose from the decrease in the symmetry of the wave function around the Au nuclei at the surface. The detailed information about the simple physisorption system presented in this paper provides basic knowledge for understanding the electronic structure at the interface between other organic molecules and metal substrates.
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Affiliation(s)
- Hirotaka Mizushima
- Department of Physics, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
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3
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Kher-Elden M, El-Fattah ZA, Yassin O, El-Okr M. Refraction-reflection of electrons at lateral metallic interfaces. PHYSICA B: CONDENSED MATTER 2017; 524:127-136. [DOI: 10.1016/j.physb.2017.08.068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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Nicoara N, Méndez J, Gómez-Rodríguez JM. Visualizing the interface state of PTCDA on Au(111) by scanning tunneling microscopy. NANOTECHNOLOGY 2016; 27:475707. [PMID: 27782009 DOI: 10.1088/0957-4484/27/47/475707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We have investigated by means of scanning tunneling microscopy (STM) and spectroscopy (STS) the electronic structure of PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) molecular monolayers grown on Au(111). Thanks to our STM/STS measurements, performed under ultra-high vacuum conditions and low temperature, an interface state directly derived from the Shockley-type surface state of pristine Au(111) has been detected. Low bias voltage STM images show the formation of standing wave patterns both on Au(111) and on Au(111) covered by a PTCDA monolayer. These patterns result from the scattering of quasi-free 2D electron surface states with surface defects. By Fourier transforming STM images, the corresponding wavevectors have been extracted. In particular, the simultaneous imaging of both pristine and PTCDA covered Au(111) areas has allowed to measure the Fermi contours and the Fermi wavevectors of both systems. These measurements show that one monolayer PTCDA on Au(111) presents an interface state with an isotropic circular Fermi contour and smaller Fermi wavector ([Formula: see text]) than the corresponding Fermi wavector of pristine Au(111) ([Formula: see text]). This picture is consistent with an upward shift of the Shockley-type surface state due to the presence of the molecular monolayer.
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Affiliation(s)
- N Nicoara
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049-Madrid, Spain. International Iberian Nanotechnology Laboratory, 4715-330 Braga, Portugal
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5
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Nowakowska S, Wäckerlin A, Piquero-Zulaica I, Nowakowski J, Kawai S, Wäckerlin C, Matena M, Nijs T, Fatayer S, Popova O, Ahsan A, Mousavi SF, Ivas T, Meyer E, Stöhr M, Ortega JE, Björk J, Gade LH, Lobo-Checa J, Jung TA. Configuring Electronic States in an Atomically Precise Array of Quantum Boxes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2016; 12:3757-3763. [PMID: 27276517 DOI: 10.1002/smll.201600915] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 04/25/2016] [Indexed: 06/06/2023]
Abstract
A 2D array of electronically coupled quantum boxes is fabricated by means of on-surface self-assembly assuring ultimate precision of each box. The quantum states embedded in the boxes are configured by adsorbates, whose occupancy is controlled with atomic precision. The electronic interbox coupling can be maintained or significantly reduced by proper arrangement of empty and filled boxes.
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Affiliation(s)
- Sylwia Nowakowska
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Aneliia Wäckerlin
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Ignacio Piquero-Zulaica
- Centro de Física de Materiales (CSIC/UPV-EHU)-Materials Physics Center, Manuel Lardizabal 5, 20018, San Sebastián, Spain
| | - Jan Nowakowski
- Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, 5232, Villigen, PSI, Switzerland
| | - Shigeki Kawai
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
- PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Christian Wäckerlin
- Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, 5232, Villigen, PSI, Switzerland
| | - Manfred Matena
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
- Donostia International Physics Center (DIPC), Manuel Lardizabal 4, 20018, San Sebastián, Spain
| | - Thomas Nijs
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Shadi Fatayer
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
- Departamento de Física Aplicada, Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, Campinas, 13083-859, Brazil
| | - Olha Popova
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Aisha Ahsan
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - S Fatemeh Mousavi
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Toni Ivas
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Ernst Meyer
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Meike Stöhr
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands
| | - J Enrique Ortega
- Centro de Física de Materiales (CSIC/UPV-EHU)-Materials Physics Center, Manuel Lardizabal 5, 20018, San Sebastián, Spain
- Donostia International Physics Center (DIPC), Manuel Lardizabal 4, 20018, San Sebastián, Spain
- Departamento Física Aplicada I, Universidad del País Vasco, 20018, San Sebastián, Spain
| | - Jonas Björk
- Department of Physics, Chemistry and Biology, IFM, Linköping University, Linköping, 581 83, Sweden
| | - Lutz H Gade
- Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Jorge Lobo-Checa
- Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, E-50009, Zaragoza, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, E-50009, Zaragoza, Spain
| | - Thomas A Jung
- Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, 5232, Villigen, PSI, Switzerland
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Abstract
Gold surfaces host special electronic states that have been understood as a prototype of Shockley surface states. These surface states are commonly employed to benchmark the capability of angle-resolved photoemission spectroscopy (ARPES) and scanning tunnelling spectroscopy. Here we show that these Shockley surface states can be reinterpreted as topologically derived surface states (TDSSs) of a topological insulator (TI), a recently discovered quantum state. Based on band structure calculations, the Z2-type invariants of gold can be well-defined to characterize a TI. Further, our ARPES measurement validates TDSSs by detecting the dispersion of unoccupied surface states. The same TDSSs are also recognized on surfaces of other well-known noble metals (for example, silver, copper, platinum and palladium), which shines a new light on these long-known surface states. The surfaces of noble metals possess Shockley states which exhibit Rashba-type spin splitting and spin-momentum locking. Here, the authors use ab initio methods and photoemission spectroscopy to demonstrate how such Shockley states may be reinterpreted as topologically protected surface states.
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Crepaldi A, Zhan RR, Moser S, Sheverdyaeva PM, Carbone C, Papagno M, Moras P, Baraldi A, Grioni M. Interplay between electronic and structural properties in the Pb/Ag(1 0 0) interface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:455502. [PMID: 26490303 DOI: 10.1088/0953-8984/27/45/455502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report an investigation of the structural and electronic properties of a Pb monolayer (ML) grown on Ag(1 0 0), by combining x-ray photoelectron diffraction (XPD) and angle resolved photoelectron spectroscopy (ARPES). The Pb atoms are found to arrange in a pseudo-hexagonal adlayer commensurate to the underlying square Ag substrate, resulting in a coincidence cell with c([Formula: see text]) periodicity. The electronic structure of the Pb ML in proximity of the Fermi level consists in three p-derived bands, which show different degrees of hybridization with the substrate for their different orbital characters. In particular, we report that the p xy states disperse without forming energy gap, in contrast to previous ARPES studies of the Pb ML on different metallic substrates. We attribute the absence of energy gap to the commensurability between substrate and adlayer, resulting in a higher two-dimensionality of the Pb ML.
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Affiliation(s)
- A Crepaldi
- Elettra-Sincrotrone Trieste, SCpA, SS 14 km 163.5, 34149 Trieste, Italy. Institut de Physique de la Matière Condensée (ICPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland
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8
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Zhou J, Li Y, Zahl P, Sutter P, Stacchiola DJ, White MG. Characterization of one-dimensional molecular chains of 4,4′-biphenyl diisocyanide on Au(111) by scanning tunneling microscopy. J Chem Phys 2015; 142:101901. [DOI: 10.1063/1.4906046] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Jing Zhou
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
| | - Yan Li
- Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Percy Zahl
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Peter Sutter
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Dario J. Stacchiola
- Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Michael G. White
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
- Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA
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Interplay of weak interactions in the atom-by-atom condensation of xenon within quantum boxes. Nat Commun 2015; 6:6071. [PMID: 25608225 PMCID: PMC4354259 DOI: 10.1038/ncomms7071] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 12/09/2014] [Indexed: 01/24/2023] Open
Abstract
Condensation processes are of key importance in nature and play a fundamental role in chemistry and physics. Owing to size effects at the nanoscale, it is conceptually desired to experimentally probe the dependence of condensate structure on the number of constituents one by one. Here we present an approach to study a condensation process atom-by-atom with the scanning tunnelling microscope, which provides a direct real-space access with atomic precision to the aggregates formed in atomically defined ‘quantum boxes’. Our analysis reveals the subtle interplay of competing directional and nondirectional interactions in the emergence of structure and provides unprecedented input for the structural comparison with quantum mechanical models. This approach focuses on—but is not limited to—the model case of xenon condensation and goes significantly beyond the well-established statistical size analysis of clusters in atomic or molecular beams by mass spectrometry. Condensation in the regime of weakly interactions is of fundamental importance. Here, the authors study the condensation process one atom at a time, showing the forces driving the behaviour of xenon atoms as they condense into aggregate structures in nanoscale pores.
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10
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Jeon C, Hwang HN, Lee WG, Jung YG, Kim KS, Park CY, Hwang CC. Rotated domains in chemical vapor deposition-grown monolayer graphene on Cu(111): an angle-resolved photoemission study. NANOSCALE 2013; 5:8210-8214. [PMID: 23863869 DOI: 10.1039/c3nr01700a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Copper is considered to be the most promising substrate for the growth of high-quality and large area graphene by chemical vapor deposition (CVD), in particular, on the (111) facet. Because the interactions between graphene and Cu substrates influence the orientation, quality, and properties of the synthesized graphene, we studied the interactions using angle-resolved photoemission spectroscopy. The evolution of both the Shockley surface state of the Cu(111) and the π band of the graphene was measured from the initial stage of CVD growth to the formation of a monolayer. Graphene growth was initiated along the Cu(111) lattice, where the Dirac band crossed the Fermi energy (EF) at the K point without hybridization with the d-band of Cu. Then two rotated domains were additionally grown as the area covered with graphene became wider. The Dirac energy was about -0.4 eV and the energy of the Shockley surface state of Cu(111) shifted toward the EF by ~0.15 eV upon graphene formation. These results indicate weak interactions between graphene and Cu, and that the electron transfer is limited to that between the Shockley surface state of Cu(111) and the π band of graphene. This weak interaction and slight lattice mismatch between graphene and Cu resulted in the growth of rotated graphene domains (9.6° and 8.4°), which showed no significant differences in the Dirac band with respect to different orientations. These rotated graphene domains resulted in grain boundaries which would hinder a large-sized single monolayer growth on Cu substrates.
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Affiliation(s)
- Cheolho Jeon
- Division of Materials Science, Korea Basic Science Institute, Daejeon 305-333, Republic of Korea
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11
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Lauwaet K, Schouteden K, Janssens E, Van Haesendonck C, Lievens P. Dependence of the NaCl/Au(111) interface state on the thickness of the NaCl layer. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:475507. [PMID: 23110874 DOI: 10.1088/0953-8984/24/47/475507] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigated the growth and the electronic properties of crystalline NaCl layers on Au(111) surfaces by means of cryogenic scanning tunneling microscopy and spectroscopy under ultra-high vacuum conditions. Deposition of NaCl on Au(111) at room temperature yields bilayer NaCl islands, which can be transformed into trilayer NaCl islands by post-annealing. Upon NaCl adsorption, the Au(111) Shockley surface state becomes an interface state (IS) at the NaCl/Au(111) interface. Using Fourier-transform images of maps of the local density of states, the energy versus wave vector dispersions of the IS and the Au(111) bulk states are determined. The dispersion of both states is found to depend strongly on the thickness of the adsorbed NaCl layer.
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Affiliation(s)
- Koen Lauwaet
- Laboratory of Solid-State Physics and Magnetism, KU Leuven, B-3001 Leuven, Belgium
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12
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Mirhosseini H, Ernst A, Ostanin S, Henk J. Tuning independently the Fermi energy and spin splitting in Rashba systems: ternary surface alloys on Ag(111). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:385501. [PMID: 21386552 DOI: 10.1088/0953-8984/22/38/385501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
By detailed first-principles calculations we show that the Fermi energy and the Rashba splitting in disordered ternary surface alloys Bi(x)Pb(y)Sb(1 - x - y)/Ag(111) can be independently tuned by choosing the concentrations x and y of Bi and Pb, respectively. The findings are explained by three fundamental mechanisms, namely the relaxation of the adatoms, the strength of the atomic spin-orbit coupling, and band filling. By mapping the Rashba characteristics, i.e. the splitting k(R) and the Rashba energy E(R), and the Fermi energy of the surface states in the complete range of concentrations, we find that these quantities depend monotonically on x and y, with a very few exceptions. Our results suggest that we should investigate experimentally effects which rely on the Rashba spin-orbit coupling depending on spin-orbit splitting and band filling.
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Affiliation(s)
- H Mirhosseini
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Saale), Germany.
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13
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Sachs S, Schwalb CH, Marks M, Schöll A, Reinert F, Umbach E, Höfer U. Electronic structure at the perylene-tetracarboxylic acid dianhydride/Ag(111) interface studied with two-photon photoelectron spectroscopy. J Chem Phys 2009; 131:144701. [DOI: 10.1063/1.3243851] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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14
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Frantzeskakis E, Pons S, Mirhosseini H, Henk J, Ast CR, Grioni M. Tunable spin gaps in a quantum-confined geometry. PHYSICAL REVIEW LETTERS 2008; 101:196805. [PMID: 19113296 DOI: 10.1103/physrevlett.101.196805] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Indexed: 05/27/2023]
Abstract
We have studied the interplay of a giant spin-orbit splitting and of quantum confinement in artificial Bi-Ag-Si trilayer structures. Angle-resolved photoelectron spectroscopy reveals the formation of a complex spin-dependent gap structure, which can be tuned by varying the thickness of the Ag buffer layer. This provides a means to tailor the electronic structure at the Fermi energy, with potential applications for silicon-compatible spintronic devices.
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Affiliation(s)
- Emmanouil Frantzeskakis
- Laboratoire de Spectroscopie Electronique, Institut de Physique des Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), station 3, CH-1015 Lausanne-Switzerland
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15
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Schwalb CH, Sachs S, Marks M, Schöll A, Reinert F, Umbach E, Höfer U. Electron lifetime in a Shockley-type metal-organic interface state. PHYSICAL REVIEW LETTERS 2008; 101:146801. [PMID: 18851554 DOI: 10.1103/physrevlett.101.146801] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2008] [Indexed: 05/26/2023]
Abstract
The lifetimes of electrons at the interface between 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) and Ag(111) have been studied by means of time- and angle-resolved two-photon photoemission. We observe a dispersing unoccupied state 0.6 eV above the Fermi level with an effective electron mass of 0.39m{e} at the Gamma[over ] point. The short lifetime of 54 fs is indicative of a large penetration of the wave function into the metal. Supported by model calculations this interface state is interpreted as predominantly arising from an upshift of the occupied Shockley surface state of the clean metal due to the interaction with the PTCDA overlayer.
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Affiliation(s)
- C H Schwalb
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, D-35032 Marburg, Germany
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16
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Ast CR, Henk J, Ernst A, Moreschini L, Falub MC, Pacilé D, Bruno P, Kern K, Grioni M. Giant spin splitting through surface alloying. PHYSICAL REVIEW LETTERS 2007; 98:186807. [PMID: 17501597 DOI: 10.1103/physrevlett.98.186807] [Citation(s) in RCA: 195] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Indexed: 05/15/2023]
Abstract
The long-range ordered surface alloy Bi/Ag(111) is found to exhibit a giant spin splitting of its surface electronic structure due to spin-orbit coupling, as is determined by angle-resolved photoelectron spectroscopy. First-principles electronic structure calculations fully confirm the experimental findings. The effect is brought about by a strong in-plane gradient of the crystal potential in the surface layer, in interplay with the structural asymmetry due to the surface-potential barrier. As a result, the spin polarization of the surface states is considerably rotated out of the surface plane.
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Affiliation(s)
- Christian R Ast
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany.
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Forster RJ, Iqbal J, Hjelm J, Keyes TE. Solvent effects on charge transport through solid deposits of [Os(4,4′-diphenyl-2,2′-dipyridyl)2Cl2]. Analyst 2004; 129:1186-92. [PMID: 15565216 DOI: 10.1039/b414814b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mechanically attached, solid-state films of [Os(4,4'-diphenyl-2,2'-dipyridyl)2Cl2] have been formed on gold macro- and microelectrodes and their voltammetric properties investigated. The voltammetric response of these films associated with the Os(2+/3+) redox reaction is reminiscent of that observed for an ideal reversible, solution phase redox couple only when the contacting electrolyte contains of the order of 40% v/v of acetonitrile (ACN). The origin of this effect appears to involve preferential solvation of the redox centres by acetonitrile which facilitates the incorporation of charge compensating counterions. Scanning electron microscopy reveals that voltammetric cycling in 40:60 ACN-H2O containing 1.0 M LiClO4 as the electrolyte induces the formation of microcrystals. Voltammetry conducted under semi-infinite linear diffusion conditions has been used to determine the apparent diffusion coefficient, Dapp, for homogeneous charge transport through the deposit. The dynamics of charge transport decrease with increasing film thickness but appear to increase with increasing electrolyte concentration. These observations suggest that ion transport rather than the rate of electron self-exchange limit the overall rate of charge transport through these solids. When in contact with 40:60 ACN-H2O containing 1.0 M LiClO4 as electrolyte, Dapp values for oxidation and reduction are identical at 1.7 +/- 0.4 x 10(-12) cm2 s(-1). In the same electrolyte, the standard heterogeneous electron transfer rate constant, k(o), determined by fitting the full voltammogram using the Butler-Volmer formalism, is 8.3 +/- 0.5 x 10(-7) cm s(-1). The importance of these results for the rational design of solid state redox active materials for battery, display and sensor applications is considered.
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Affiliation(s)
- Robert J Forster
- School of Chemical Sciences, National Center for Sensor Research, Dublin City University, Dublin 9, Ireland
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