1
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Liu YW, Zhuang YC, Ren YN, Yan C, Zhou XF, Yang Q, Sun QF, He L. Visualizing a single wavefront dislocation induced by orbital angular momentum in graphene. Nat Commun 2024; 15:3546. [PMID: 38670960 PMCID: PMC11053005 DOI: 10.1038/s41467-024-47756-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 04/11/2024] [Indexed: 04/28/2024] Open
Abstract
Phase singularities are phase-indeterminate points where wave amplitudes are zero, which manifest as phase vertices or wavefront dislocations. In the realm of optical and electron beams, the phase singularity has been extensively explored, demonstrating a profound connection to orbital angular momentum. Direct local imaging of the impact of orbital angular momentum on phase singularities at the nanoscale, however, remains challenging. Here, we study the role of orbital angular momentum in phase singularities in graphene, particularly at the atomic level, through scanning tunneling microscopy and spectroscopy. Our experiments demonstrate that the scatterings between different orbital angular momentum states, which are induced by local rotational symmetry-breaking potentials, can generate additional phase singularities, and result in robust single-wavefront dislocations in real space. Our results pave the way for exploring the effects of orbital degree of freedom on quantum phases in quasiparticle interference processes.
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Affiliation(s)
- Yi-Wen Liu
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China
| | - Yu-Chen Zhuang
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
| | - Ya-Ning Ren
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China
| | - Chao Yan
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China
| | - Xiao-Feng Zhou
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China
| | - Qian Yang
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China
| | - Qing-Feng Sun
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China.
- Hefei National Laboratory, Hefei, 230088, China.
| | - Lin He
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China.
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China.
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2
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Söll A, Lopriore E, Ottesen A, Luxa J, Pasquale G, Sturala J, Hájek F, Jarý V, Sedmidubský D, Mosina K, Sokolović I, Rasouli S, Grasser T, Diebold U, Kis A, Sofer Z. High-κ Wide-Gap Layered Dielectric for Two-Dimensional van der Waals Heterostructures. ACS NANO 2024; 18:10397-10406. [PMID: 38557003 PMCID: PMC11025129 DOI: 10.1021/acsnano.3c10411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 03/13/2024] [Accepted: 03/20/2024] [Indexed: 04/04/2024]
Abstract
van der Waals heterostructures of two-dimensional materials have unveiled frontiers in condensed matter physics, unlocking unexplored possibilities in electronic and photonic device applications. However, the investigation of wide-gap, high-κ layered dielectrics for devices based on van der Waals structures has been relatively limited. In this work, we demonstrate an easily reproducible synthesis method for the rare-earth oxyhalide LaOBr, and we exfoliate it as a 2D layered material with a measured static dielectric constant of 9 and a wide bandgap of 5.3 eV. Furthermore, our research demonstrates that LaOBr can be used as a high-κ dielectric in van der Waals field-effect transistors with high performance and low interface defect concentrations. Additionally, it proves to be an attractive choice for electrical gating in excitonic devices based on 2D materials. Our work demonstrates the versatile realization and functionality of 2D systems with wide-gap and high-κ van der Waals dielectric environments.
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Affiliation(s)
- Aljoscha Söll
- Department
of Inorganic Chemistry, University of Chemistry
and Technology Prague, Technicka 5, 166 28, Prague 6, Czech Republic
| | - Edoardo Lopriore
- Institute
of Electrical and Microengineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Institute
of Materials Science and Engineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Asmund Ottesen
- Institute
of Electrical and Microengineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Institute
of Materials Science and Engineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Jan Luxa
- Department
of Inorganic Chemistry, University of Chemistry
and Technology Prague, Technicka 5, 166 28, Prague 6, Czech Republic
| | - Gabriele Pasquale
- Institute
of Electrical and Microengineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Institute
of Materials Science and Engineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Jiri Sturala
- Department
of Inorganic Chemistry, University of Chemistry
and Technology Prague, Technicka 5, 166 28, Prague 6, Czech Republic
| | - František Hájek
- Institute
of Physics of the Czech Academy of Sciences, v.v.i., Cukrovarnická 10, 162 00, Prague 6, Czech Republic
| | - Vítězslav Jarý
- Institute
of Physics of the Czech Academy of Sciences, v.v.i., Cukrovarnická 10, 162 00, Prague 6, Czech Republic
| | - David Sedmidubský
- Department
of Inorganic Chemistry, University of Chemistry
and Technology Prague, Technicka 5, 166 28, Prague 6, Czech Republic
| | - Kseniia Mosina
- Department
of Inorganic Chemistry, University of Chemistry
and Technology Prague, Technicka 5, 166 28, Prague 6, Czech Republic
| | - Igor Sokolović
- Institute
of Microelectronics, TU Wien, Gußhausstraße 27−29, 1040 Vienna, Austria
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8−10, 1040 Vienna, Austria
| | - Saeed Rasouli
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8−10, 1040 Vienna, Austria
| | - Tibor Grasser
- Institute
of Microelectronics, TU Wien, Gußhausstraße 27−29, 1040 Vienna, Austria
| | - Ulrike Diebold
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8−10, 1040 Vienna, Austria
| | - Andras Kis
- Institute
of Electrical and Microengineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Institute
of Materials Science and Engineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Zdeněk Sofer
- Department
of Inorganic Chemistry, University of Chemistry
and Technology Prague, Technicka 5, 166 28, Prague 6, Czech Republic
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3
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Franceschi G, Brandstetter S, Balajka J, Sokolović I, Pavelec J, Setvín M, Schmid M, Diebold U. Interaction of surface cations of cleaved mica with water in vapor and liquid forms. Faraday Discuss 2024; 249:84-97. [PMID: 37791454 PMCID: PMC10845011 DOI: 10.1039/d3fd00093a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 06/08/2023] [Indexed: 10/05/2023]
Abstract
Natural minerals contain ions that become hydrated when they come into contact with water in vapor and liquid forms. Muscovite mica - a common phyllosilicate with perfect cleavage planes - is an ideal system to investigate the details of ion hydration. The cleaved mica surface is decorated by an array of K+ ions that can be easily exchanged with other ions or protons when immersed in an aqueous solution. Despite the vast interest in the atomic-scale hydration processes of these K+ ions, experimental data under controlled conditions have remained elusive. Here, atomically resolved non-contact atomic force microscopy (nc-AFM) is combined with X-ray photoelectron spectroscopy (XPS) to investigate the cation hydration upon dosing water vapor at 100 K in ultra-high vacuum (UHV). The cleaved surface is further exposed to ultra-clean liquid water at room temperature, which promotes ion mobility and partial ion-to-proton substitution. The results offer the first direct experimental views of the interaction of water with muscovite mica under UHV. The findings are in line with previous theoretical predictions.
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Affiliation(s)
- Giada Franceschi
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria.
| | - Sebastian Brandstetter
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria.
| | - Jan Balajka
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria.
| | - Igor Sokolović
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria.
| | - Jiří Pavelec
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria.
| | - Martin Setvín
- Department of Surface and Plasma Science, Charles University in Prague, V Holesovickach 2, 180 00 Praha, Czech Republic
| | - Michael Schmid
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria.
| | - Ulrike Diebold
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria.
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4
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Franceschi G, Kocán P, Conti A, Brandstetter S, Balajka J, Sokolović I, Valtiner M, Mittendorfer F, Schmid M, Setvín M, Diebold U. Resolving the intrinsic short-range ordering of K + ions on cleaved muscovite mica. Nat Commun 2023; 14:208. [PMID: 36639388 PMCID: PMC9839703 DOI: 10.1038/s41467-023-35872-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 01/04/2023] [Indexed: 01/15/2023] Open
Abstract
Muscovite mica, KAl2(Si3Al)O10(OH)2, is a common layered phyllosilicate with perfect cleavage planes. The atomically flat surfaces obtained through cleaving lend themselves to scanning probe techniques with atomic resolution and are ideal to model minerals and clays. Despite the importance of the cleaved mica surfaces, several questions remain unresolved. It is established that K+ ions decorate the cleaved surface, but their intrinsic ordering - unaffected by the interaction with the environment - is not known. This work presents clear images of the K+ distribution of cleaved mica obtained with low-temperature non-contact atomic force microscopy (AFM) under ultra-high vacuum (UHV) conditions. The data unveil the presence of short-range ordering, contrasting previous assumptions of random or fully ordered distributions. Density functional theory (DFT) calculations and Monte Carlo simulations show that the substitutional subsurface Al3+ ions have an important role for the surface K+ ion arrangement.
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Affiliation(s)
- Giada Franceschi
- grid.5329.d0000 0001 2348 4034Institute of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Vienna, Austria
| | - Pavel Kocán
- grid.4491.80000 0004 1937 116XDepartment of Surface and Plasma Science, Charles University, V Holesovickach 2, 180 00 Prague, Czech Republic
| | - Andrea Conti
- grid.5329.d0000 0001 2348 4034Institute of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Vienna, Austria
| | - Sebastian Brandstetter
- grid.5329.d0000 0001 2348 4034Institute of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Vienna, Austria
| | - Jan Balajka
- grid.5329.d0000 0001 2348 4034Institute of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Vienna, Austria
| | - Igor Sokolović
- grid.5329.d0000 0001 2348 4034Institute of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Vienna, Austria
| | - Markus Valtiner
- grid.5329.d0000 0001 2348 4034Institute of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Vienna, Austria
| | - Florian Mittendorfer
- grid.5329.d0000 0001 2348 4034Institute of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Vienna, Austria
| | - Michael Schmid
- grid.5329.d0000 0001 2348 4034Institute of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Vienna, Austria
| | - Martin Setvín
- grid.5329.d0000 0001 2348 4034Institute of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Vienna, Austria ,grid.4491.80000 0004 1937 116XDepartment of Surface and Plasma Science, Charles University, V Holesovickach 2, 180 00 Prague, Czech Republic
| | - Ulrike Diebold
- grid.5329.d0000 0001 2348 4034Institute of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Vienna, Austria
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5
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Wang Z, Reticcioli M, Jakub Z, Sokolović I, Meier M, Boatner LA, Schmid M, Parkinson GS, Diebold U, Franchini C, Setvin M. Surface chemistry on a polarizable surface: Coupling of CO with KTaO 3(001). SCIENCE ADVANCES 2022; 8:eabq1433. [PMID: 35984882 PMCID: PMC9390988 DOI: 10.1126/sciadv.abq1433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 07/06/2022] [Indexed: 06/15/2023]
Abstract
Polarizable materials attract attention in catalysis because they have a free parameter for tuning chemical reactivity. Their surfaces entangle the dielectric polarization with surface polarity, excess charge, and orbital hybridization. How this affects individual adsorbed molecules is shown for the incipient ferroelectric perovskite KTaO3. This intrinsically polar material cleaves along (001) into KO- and TaO2-terminated surface domains. At TaO2 terraces, the polarity-compensating excess electrons form a two-dimensional electron gas and can also localize by coupling to ferroelectric distortions. TaO2 terraces host two distinct types of CO molecules, adsorbed at equivalent lattice sites but charged differently as seen in atomic force microscopy/scanning tunneling microscopy. Temperature-programmed desorption shows substantially stronger binding of the charged CO; in density functional theory calculations, the excess charge favors a bipolaronic configuration coupled to the CO. These results pinpoint how adsorption states couple to ferroelectric polarization.
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Affiliation(s)
- Zhichang Wang
- Institute of Applied Physics, TU Wien, Vienna, Austria
- State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China
| | - Michele Reticcioli
- Faculty of Physics and Center for Computational Materials Science, University of Vienna, Vienna, Austria
| | - Zdenek Jakub
- Institute of Applied Physics, TU Wien, Vienna, Austria
| | | | | | - Lynn A. Boatner
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | | | | | | | - Cesare Franchini
- Faculty of Physics and Center for Computational Materials Science, University of Vienna, Vienna, Austria
- Dipartimento di Fisica e Astronomia, Universita di Bologna, 40127 Bologna, Italy
| | - Martin Setvin
- Institute of Applied Physics, TU Wien, Vienna, Austria
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, 180 00 Prague 8, Czech Republic
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6
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Meier M, Hulva J, Jakub Z, Kraushofer F, Bobić M, Bliem R, Setvin M, Schmid M, Diebold U, Franchini C, Parkinson GS. CO oxidation by Pt 2/Fe 3O 4: Metastable dimer and support configurations facilitate lattice oxygen extraction. SCIENCE ADVANCES 2022; 8:eabn4580. [PMID: 35363523 PMCID: PMC10938578 DOI: 10.1126/sciadv.abn4580] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 02/09/2022] [Indexed: 06/14/2023]
Abstract
Heterogeneous catalysts based on subnanometer metal clusters often exhibit strongly size-dependent properties, and the addition or removal of a single atom can make all the difference. Identifying the most active species and deciphering the reaction mechanism is extremely difficult, however, because it is often not clear how the catalyst evolves in operando. Here, we use a combination of atomically resolved scanning probe microscopies, spectroscopic techniques, and density functional theory (DFT)-based calculations to study CO oxidation by a model Pt/Fe3O4(001) "single-atom" catalyst. We demonstrate that (PtCO)2 dimers, formed dynamically through the agglomeration of mobile Pt-carbonyl species, catalyze a reaction involving the oxide support to form CO2. Pt2 dimers produce one CO2 molecule before falling apart into two adatoms, releasing the second CO. Olattice extraction only becomes facile when both the Pt-dimer and the Fe3O4 support can access metastable configurations, suggesting that substantial, concerted rearrangements of both cluster and support must be considered for reactions occurring at elevated temperature.
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Affiliation(s)
- Matthias Meier
- Institute of Applied Physics, TU Wien, Vienna, Austria
- Computational Materials Physics, University of Vienna, Vienna, Austria
| | - Jan Hulva
- Institute of Applied Physics, TU Wien, Vienna, Austria
| | - Zdenek Jakub
- Institute of Applied Physics, TU Wien, Vienna, Austria
| | | | - Mislav Bobić
- Institute of Applied Physics, TU Wien, Vienna, Austria
| | - Roland Bliem
- Institute of Applied Physics, TU Wien, Vienna, Austria
| | - Martin Setvin
- Institute of Applied Physics, TU Wien, Vienna, Austria
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
| | | | | | - Cesare Franchini
- Computational Materials Physics, University of Vienna, Vienna, Austria
- Alma Mater Studiorum – Università di Bologna, Bologna, Italy
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7
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Sokolović I, Reticcioli M, Čalkovský M, Wagner M, Schmid M, Franchini C, Diebold U, Setvín M. Resolving the adsorption of molecular O 2 on the rutile TiO 2(110) surface by noncontact atomic force microscopy. Proc Natl Acad Sci U S A 2020; 117:14827-14837. [PMID: 32527857 PMCID: PMC7334520 DOI: 10.1073/pnas.1922452117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Interaction of molecular oxygen with semiconducting oxide surfaces plays a key role in many technologies. The topic is difficult to approach both by experiment and in theory, mainly due to multiple stable charge states, adsorption configurations, and reaction channels of adsorbed oxygen species. Here we use a combination of noncontact atomic force microscopy (AFM) and density functional theory (DFT) to resolve [Formula: see text] adsorption on the rutile [Formula: see text](110) surface, which presents a longstanding challenge in the surface chemistry of metal oxides. We show that chemically inert AFM tips terminated by an oxygen adatom provide excellent resolution of both the adsorbed species and the oxygen sublattice of the substrate. Adsorbed [Formula: see text] molecules can accept either one or two electron polarons from the surface, forming superoxo or peroxo species. The peroxo state is energetically preferred under any conditions relevant for applications. The possibility of nonintrusive imaging allows us to explain behavior related to electron/hole injection from the tip, interaction with UV light, and the effect of thermal annealing.
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Affiliation(s)
- Igor Sokolović
- Institute of Applied Physics, Technische Universität Wien, 1040 Vienna, Austria
| | - Michele Reticcioli
- Institute of Applied Physics, Technische Universität Wien, 1040 Vienna, Austria
- Faculty of Physics, University of Vienna, 1090 Vienna, Austria
- Center for Computational Materials Science, University of Vienna, 1090 Vienna, Austria
| | - Martin Čalkovský
- Institute of Applied Physics, Technische Universität Wien, 1040 Vienna, Austria
- Institute of Physical Engineering, Brno University of Technology, 616 69 Brno, Czech Republic
| | - Margareta Wagner
- Institute of Applied Physics, Technische Universität Wien, 1040 Vienna, Austria
- Central European Institute of Technology, Brno University of Technology, 612 00 Brno, Czech Republic
| | - Michael Schmid
- Institute of Applied Physics, Technische Universität Wien, 1040 Vienna, Austria
| | - Cesare Franchini
- Faculty of Physics, University of Vienna, 1090 Vienna, Austria
- Center for Computational Materials Science, University of Vienna, 1090 Vienna, Austria
- Dipartimento di Fisica e Astronomia, Università di Bologna, 40127 Bologna, Italy
| | - Ulrike Diebold
- Institute of Applied Physics, Technische Universität Wien, 1040 Vienna, Austria
| | - Martin Setvín
- Institute of Applied Physics, Technische Universität Wien, 1040 Vienna, Austria;
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, 180 00 Prague 8, Czech Republic
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8
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Local electronic structure of doping defects on Tl/Si(111)1x1. Sci Rep 2019; 9:779. [PMID: 30692592 PMCID: PMC6349925 DOI: 10.1038/s41598-018-37361-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 11/28/2018] [Indexed: 11/26/2022] Open
Abstract
The Tl/Si(111)1 × 1 surface is a representative of a 2D layer with Rashba-type spin-split electronic bands. To utilize the spin polarization, doping of the system should be understood on atomic level. We present a study of two types of atomic defects predicted to dope the considered electronic system – Si-induced vacancies and defects associated with the presence of extra Tl atoms. Structural calculations based on density functional theory (DFT) confirm the stability of the proposed defect structure consisting of an extra Si atom and missing seven Tl atoms as proposed in an earlier experimental study. The calculated spatial charge distributions indicate an enhancement of the charge around the extra Si atom, which correctly reproduces topographies of the corresponding scanning tunneling microscopy images while the calculated local densities of states of this system explain obtained scanning tunneling spectra. The DFT structural calculations let us determine the atomic structure of the defect caused by the presence of an extra Tl atom. The calculated spatial charge distributions show a ring-like feature around the extra Tl atom. The obtained results indicate a charge transfer from the central extra Tl atom to its vicinity in the agreement with earlier photoemission measurements.
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9
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Reticcioli M, Sokolović I, Schmid M, Diebold U, Setvin M, Franchini C. Interplay between Adsorbates and Polarons: CO on Rutile TiO_{2}(110). PHYSICAL REVIEW LETTERS 2019; 122:016805. [PMID: 31012645 DOI: 10.1103/physrevlett.122.016805] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 11/26/2018] [Indexed: 06/09/2023]
Abstract
Polaron formation plays a major role in determining the structural, electrical, and chemical properties of ionic crystals. Using a combination of first-principles calculations, scanning tunneling microscopy, and atomic force microscopy, we analyze the interaction of polarons with CO molecules adsorbed on the reduced rutile TiO_{2}(110) surface. Adsorbed CO shows attractive coupling with polarons in the surface layer, and repulsive interaction with polarons in the subsurface layer. As a result, CO adsorption depends on the reduction state of the sample. For slightly reduced surfaces, many adsorption configurations with comparable adsorption energies exist and polarons reside in the subsurface layer. At strongly reduced surfaces, two adsorption configurations dominate: either inside an oxygen vacancy, or at surface Ti_{5c} sites, coupled with a surface polaron. Similar conclusions are predicted for TiO_{2}(110) surfaces containing near-surface Ti interstitials. These results show that polarons are of primary importance for understanding the performance of polar semiconductors and transition metal oxides in catalysis and energy-related applications.
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Affiliation(s)
- Michele Reticcioli
- University of Vienna, Faculty of Physics and Center for Computational Materials Science, Vienna 1090, Austria
| | - Igor Sokolović
- Institute of Applied Physics, Technische Universität Wien, Vienna 1090, Austria
| | - Michael Schmid
- Institute of Applied Physics, Technische Universität Wien, Vienna 1090, Austria
| | - Ulrike Diebold
- Institute of Applied Physics, Technische Universität Wien, Vienna 1090, Austria
| | - Martin Setvin
- Institute of Applied Physics, Technische Universität Wien, Vienna 1090, Austria
| | - Cesare Franchini
- University of Vienna, Faculty of Physics and Center for Computational Materials Science, Vienna 1090, Austria
- Dipartimento di Fisica e Astronomia, Università di Bologna, 40127 Bologna, Italy
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10
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Wagner M, Hofinger J, Setvín M, Boatner LA, Schmid M, Diebold U. Prototypical Organic-Oxide Interface: Intramolecular Resolution of Sexiphenyl on In 2O 3(111). ACS APPLIED MATERIALS & INTERFACES 2018; 10:14175-14182. [PMID: 29589447 PMCID: PMC5940326 DOI: 10.1021/acsami.8b02177] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 03/28/2018] [Indexed: 05/19/2023]
Abstract
The performance of an organic semiconductor device is critically determined by the geometric alignment, orientation, and ordering of the organic molecules. Although an organic multilayer eventually adopts the crystal structure of the organic material, the alignment and configuration at the interface with the substrate/electrode material are essential for charge injection into the organic layer. This work focuses on the prototypical organic semiconductor para-sexiphenyl (6P) adsorbed on In2O3(111), the thermodynamically most stable surface of the material that the most common transparent conducting oxide, indium tin oxide, is based on. The onset of nucleation and formation of the first monolayer are followed with atomically resolved scanning tunneling microscopy and noncontact atomic force microscopy (nc-AFM). Annealing to 200 °C provides sufficient thermal energy for the molecules to orient themselves along the high-symmetry directions of the surface, leading to a single adsorption site. The AFM data suggests an essentially planar adsorption geometry. With increasing coverage, the 6P molecules first form a loose network with a poor long-range order. Eventually, the molecules reorient into an ordered monolayer. This first monolayer has a densely packed, well-ordered (2 × 1) structure with one 6P per In2O3(111) substrate unit cell, that is, a molecular density of 5.64 × 1013 cm-2.
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Affiliation(s)
- Margareta Wagner
- Institute of Applied
Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Jakob Hofinger
- Institute of Applied
Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Martin Setvín
- Institute of Applied
Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Lynn A. Boatner
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Michael Schmid
- Institute of Applied
Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Ulrike Diebold
- Institute of Applied
Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
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11
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Halwidl D, Mayr-Schmölzer W, Setvin M, Fobes D, Peng J, Mao Z, Schmid M, Mittendorfer F, Redinger J, Diebold U. A full monolayer of superoxide: oxygen activation on the unmodified Ca 3Ru 2O 7(001) surface. JOURNAL OF MATERIALS CHEMISTRY. A 2018; 6:5703-5713. [PMID: 30009023 PMCID: PMC6003542 DOI: 10.1039/c8ta00265g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 03/04/2018] [Indexed: 05/20/2023]
Abstract
Activating the O2 molecule is at the heart of a variety of technological applications, most prominently in energy conversion schemes including solid oxide fuel cells, electrolysis, and catalysis. Perovskite oxides, both traditionally-used and novel formulations, are the prime candidates in established and emerging energy devices. This work shows that the as-cleaved and unmodified CaO-terminated (001) surface of Ca3Ru2O7, a Ruddlesden-Popper perovskite, supports a full monolayer of superoxide ions, O2-, when exposed to molecular O2. The electrons for activating the molecule are transferred from the subsurface RuO2 layer. Theoretical calculations using both, density functional theory (DFT) and more accurate methods (RPA), predict the adsorption of O2- with Eads = 0.72 eV and provide a thorough analysis of the charge transfer. Non-contact atomic force microscopy (nc-AFM) and scanning tunnelling microscopy (STM) are used to resolve single molecules and confirm the predicted adsorption structures. Local contact potential difference (LCPD) and X-ray photoelectron spectroscopy (XPS) measurements on the full monolayer of O2- confirm the negative charge state of the molecules. The present study reports the rare case of an oxide surface without dopants, defects, or low-coordinated sites readily activating molecular O2.
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Affiliation(s)
- Daniel Halwidl
- Institute of Applied Physics , TU Wien , Wiedner Hauptstrasse 8-10/134 , 1040 Vienna , Austria .
| | - Wernfried Mayr-Schmölzer
- Institute of Applied Physics , TU Wien , Wiedner Hauptstrasse 8-10/134 , 1040 Vienna , Austria .
- Center for Computational Materials Science , TU Wien , Wiedner Hauptstrasse 8-10/134 , 1040 Vienna , Austria
| | - Martin Setvin
- Institute of Applied Physics , TU Wien , Wiedner Hauptstrasse 8-10/134 , 1040 Vienna , Austria .
| | - David Fobes
- Department of Physics and Engineering Physics , Tulane University , 2001 Percival Stern Hall , New Orleans , LA 70118 , USA
| | - Jin Peng
- Department of Physics and Engineering Physics , Tulane University , 2001 Percival Stern Hall , New Orleans , LA 70118 , USA
| | - Zhiqiang Mao
- Department of Physics and Engineering Physics , Tulane University , 2001 Percival Stern Hall , New Orleans , LA 70118 , USA
| | - Michael Schmid
- Institute of Applied Physics , TU Wien , Wiedner Hauptstrasse 8-10/134 , 1040 Vienna , Austria .
| | - Florian Mittendorfer
- Institute of Applied Physics , TU Wien , Wiedner Hauptstrasse 8-10/134 , 1040 Vienna , Austria .
- Center for Computational Materials Science , TU Wien , Wiedner Hauptstrasse 8-10/134 , 1040 Vienna , Austria
| | - Josef Redinger
- Institute of Applied Physics , TU Wien , Wiedner Hauptstrasse 8-10/134 , 1040 Vienna , Austria .
- Center for Computational Materials Science , TU Wien , Wiedner Hauptstrasse 8-10/134 , 1040 Vienna , Austria
| | - Ulrike Diebold
- Institute of Applied Physics , TU Wien , Wiedner Hauptstrasse 8-10/134 , 1040 Vienna , Austria .
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12
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Kraushofer F, Jakub Z, Bichler M, Hulva J, Drmota P, Weinold M, Schmid M, Setvin M, Diebold U, Blaha P, Parkinson GS. Atomic-Scale Structure of the Hematite α-Fe 2O 3(11̅02) "R-Cut" Surface. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2018; 122:1657-1669. [PMID: 29492182 PMCID: PMC5823487 DOI: 10.1021/acs.jpcc.7b10515] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 12/08/2017] [Indexed: 05/26/2023]
Abstract
The α-Fe2O3(11̅02) surface (also known as the hematite r-cut or (012) surface) was studied using low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning tunneling microscopy (STM), noncontact atomic force microscopy (nc-AFM), and ab initio density functional theory (DFT)+U calculations. Two surface structures are stable under ultrahigh vacuum (UHV) conditions; a stoichiometric (1 × 1) surface can be prepared by annealing at 450 °C in ≈10-6 mbar O2, and a reduced (2 × 1) reconstruction is formed by UHV annealing at 540 °C. The (1 × 1) surface is close to an ideal bulk termination, and the undercoordinated surface Fe atoms reduce the surface bandgap by ≈0.2 eV with respect to the bulk. The work function is measured to be 5.7 ± 0.2 eV, and the VBM is located 1.5 ± 0.1 eV below EF. The images obtained from the (2 × 1) reconstruction cannot be reconciled with previously proposed models, and a new "alternating trench" structure is proposed based on an ordered removal of lattice oxygen atoms. DFT+U calculations show that this surface is favored in reducing conditions and that 4-fold-coordinated Fe2+ cations at the surface introduce gap states approximately 1 eV below EF. The work function on the (2 × 1) termination is 5.4 ± 0.2 eV.
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Affiliation(s)
- Florian Kraushofer
- Institute
of Applied Physics, Vienna University of
Technology, Vienna, Austria
| | - Zdenek Jakub
- Institute
of Applied Physics, Vienna University of
Technology, Vienna, Austria
| | - Magdalena Bichler
- Institute
of Materials Chemistry, Vienna University
of Technology, Vienna, Austria
| | - Jan Hulva
- Institute
of Applied Physics, Vienna University of
Technology, Vienna, Austria
| | - Peter Drmota
- Institute
of Applied Physics, Vienna University of
Technology, Vienna, Austria
| | - Michael Weinold
- Institute
of Applied Physics, Vienna University of
Technology, Vienna, Austria
| | - Michael Schmid
- Institute
of Applied Physics, Vienna University of
Technology, Vienna, Austria
| | - Martin Setvin
- Institute
of Applied Physics, Vienna University of
Technology, Vienna, Austria
| | - Ulrike Diebold
- Institute
of Applied Physics, Vienna University of
Technology, Vienna, Austria
| | - Peter Blaha
- Institute
of Materials Chemistry, Vienna University
of Technology, Vienna, Austria
| | - Gareth S. Parkinson
- Institute
of Applied Physics, Vienna University of
Technology, Vienna, Austria
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13
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Setvin M, Shi X, Hulva J, Simschitz T, Parkinson GS, Schmid M, Di Valentin C, Selloni A, Diebold U. Methanol on Anatase TiO 2 (101): Mechanistic Insights into Photocatalysis. ACS Catal 2017; 7:7081-7091. [PMID: 29034122 PMCID: PMC5634753 DOI: 10.1021/acscatal.7b02003] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 08/29/2017] [Indexed: 01/06/2023]
Abstract
The photoactivity of methanol adsorbed on the anatase TiO2 (101) surface was studied by a combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), X-ray photoemission spectroscopy (XPS), and density functional theory (DFT) calculations. Isolated methanol molecules adsorbed at the anatase (101) surface show a negligible photoactivity. Two ways of methanol activation were found. First, methoxy groups formed by reaction of methanol with coadsorbed O2 molecules or terminal OH groups are photoactive, and they turn into formaldehyde upon UV illumination. The methoxy species show an unusual C 1s core-level shift of 1.4 eV compared to methanol; their chemical assignment was verified by DFT calculations with inclusion of final-state effects. The second way of methanol activation opens at methanol coverages above 0.5 monolayer (ML), and methyl formate is produced in this reaction pathway. The adsorption of methanol in the coverage regime from 0 to 2 ML is described in detail; it is key for understanding the photocatalytic behavior at high coverages. There, a hydrogen-bonding network is established in the adsorbed methanol layer, and consequently, methanol dissociation becomes energetically more favorable. DFT calculations show that dissociation of the methanol molecule is always the key requirement for hole transfer from the substrate to the adsorbed methanol. We show that the hydrogen-bonding network established in the methanol layer dramatically changes the kinetics of proton transfer during the photoreaction.
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Affiliation(s)
- Martin Setvin
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
| | - Xiao Shi
- Department
of Chemistry, Princeton University, Frick
Laboratory, Princeton, New Jersey 08544, United States
| | - Jan Hulva
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
| | - Thomas Simschitz
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
| | - Gareth S. Parkinson
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
| | - Michael Schmid
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
| | - Cristiana Di Valentin
- Dipartimento
di Scienza dei Materiali, Università
di Milano-Bicocca, Via
Cozzi 55, 20125 Milano, Italy
| | - Annabella Selloni
- Department
of Chemistry, Princeton University, Frick
Laboratory, Princeton, New Jersey 08544, United States
| | - Ulrike Diebold
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
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14
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Setvin M, Hulva J, Parkinson GS, Schmid M, Diebold U. Electron transfer between anatase TiO 2 and an O 2 molecule directly observed by atomic force microscopy. Proc Natl Acad Sci U S A 2017; 114:E2556-E2562. [PMID: 28289217 PMCID: PMC5380104 DOI: 10.1073/pnas.1618723114] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Activation of molecular oxygen is a key step in converting fuels into energy, but there is precious little experimental insight into how the process proceeds at the atomic scale. Here, we show that a combined atomic force microscopy/scanning tunneling microscopy (AFM/STM) experiment can both distinguish neutral O2 molecules in the triplet state from negatively charged (O2)- radicals and charge and discharge the molecules at will. By measuring the chemical forces above the different species adsorbed on an anatase TiO2 surface, we show that the tip-generated (O2)- radicals are identical to those created when (i) an O2 molecule accepts an electron from a near-surface dopant or (ii) when a photo-generated electron is transferred following irradiation of the anatase sample with UV light. Kelvin probe spectroscopy measurements indicate that electron transfer between the TiO2 and the adsorbed molecules is governed by competition between electron affinity of the physisorbed (triplet) O2 and band bending induced by the (O2)- radicals. Temperature-programmed desorption and X-ray photoelectron spectroscopy data provide information about thermal stability of the species, and confirm the chemical identification inferred from AFM/STM.
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Affiliation(s)
- Martin Setvin
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
| | - Jan Hulva
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
| | | | - Michael Schmid
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
| | - Ulrike Diebold
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
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15
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Kim M, Rho J. Metamaterials and imaging. NANO CONVERGENCE 2015; 2:22. [PMID: 28191408 DOI: 10.1186/s40580-014-0034-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 06/22/2015] [Indexed: 05/23/2023]
Abstract
Resolution of the conventional lens is limited to half the wavelength of the light source by diffraction. In the conventional optical system, evanescent waves, which carry sub-diffraction spatial information, has exponentially decaying amplitude and therefore cannot reach to the image plane. New optical materials called metamaterials have provided new ways to overcome diffraction limit in imaging by controlling the evanescent waves. Such extraordinary electromagnetic properties can be achieved and controlled through arranging nanoscale building blocks appropriately. Here, we review metamaterial-based lenses which offer the new types of imaging components and functions. Perfect lens, superlenses, hyperlenses, metalenses, flat lenses based on metasurfaces, and non-optical lenses including acoustic hyperlens are described. Not all of them offer sub-diffraction imaging, but they provide new imaging mechanisms by controlling and manipulating the path of light. The underlying physics, design principles, recent advances, major limitations and challenges for the practical applications are discussed in this review.
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Affiliation(s)
- Minkyung Kim
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784 Republic of Korea
| | - Junsuk Rho
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784 Republic of Korea ; Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784 Republic of Korea
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