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Freiberger EM, Steffen J, Waleska-Wellnhofer NJ, Hemauer F, Schwaab V, Görling A, Steinrück HP, Papp C. Bromination of 2D materials. NANOTECHNOLOGY 2024; 35:145703. [PMID: 38048605 DOI: 10.1088/1361-6528/ad1201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 11/30/2023] [Indexed: 12/06/2023]
Abstract
The adsorption, reaction and thermal stability of bromine on Rh(111)-supported hexagonal boron nitride (h-BN) and graphene were investigated. Synchrotron radiation-based high-resolution x-ray photoelectron spectroscopy (XPS) and temperature-programmed XPS allowed us to follow the adsorption process and the thermal evolutionin situon the molecular scale. Onh-BN/Rh(111), bromine adsorbs exclusively in the pores of the nanomesh while we observe no such selectivity for graphene/Rh(111). Upon heating, bromine undergoes an on-surface reaction onh-BN to form polybromides (170-240 K), which subsequently decompose to bromide (240-640 K). The high thermal stability of Br/h-BN/Rh(111) suggests strong/covalent bonding. Bromine on graphene/Rh(111), on the other hand, reveals no distinct reactivity except for intercalation of small amounts of bromine underneath the 2D layer at high temperatures. In both cases, adsorption is reversible upon heating. Our experiments are supported by a comprehensive theoretical study. DFT calculations were used to describe the nature of theh-BN nanomesh and the graphene moiré in detail and to study the adsorption energetics and substrate interaction of bromine. In addition, the adsorption of bromine onh-BN/Rh(111) was simulated by molecular dynamics using a machine-learning force field.
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Affiliation(s)
- Eva Marie Freiberger
- Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
| | - Julien Steffen
- Theoretische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
| | - Natalie J Waleska-Wellnhofer
- Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
| | - Felix Hemauer
- Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
| | - Valentin Schwaab
- Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
| | - Andreas Görling
- Theoretische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
- Erlangen National High Performance Computing Center (NHR@FAU), Martensstr. 1, D-91058 Erlangen, Germany
| | - Hans-Peter Steinrück
- Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
| | - Christian Papp
- Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
- Physikalische und Theoretische Chemie, Freie Universität Berlin, Arnimallee 22, D-14195 Berlin, Germany
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Park C, Yoon M. Topography inversion in scanning tunneling microscopy of single-atom-thick materials from penetrating substrate states. Sci Rep 2022; 12:7321. [PMID: 35513468 PMCID: PMC9072348 DOI: 10.1038/s41598-022-10870-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 04/12/2022] [Indexed: 11/21/2022] Open
Abstract
Scanning tunneling microscopy (STM) is one of the indispensable tools to characterize surface structures, but the distinction between atomic geometry and electronic effects based on the measured tunneling current is not always straightforward. In particular, for single-atomic-thick materials (graphene or boron nitride) on metallic substrates, counterintuitive phenomena such as a larger tunneling current for insulators than for metal and a topography opposite to the atomic geometry are reported. Using first-principles density functional theory calculations combined with analytical modeling, we reveal the critical role of penetrating states of metallic substrates that surpass 2D material states, hindering the measurement of intrinsic 2D materials states and leading to topography inversion. Our finding should be instrumental in the interpretation of STM topographies of atomic-thick materials and in the development of 2D material for (opto)electronic and various quantum applications.
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Affiliation(s)
- Changwon Park
- School of Computational Sciences, Korea Institute for Advanced Study, Hoegiro 85, Seoul, 02455, Republic of Korea.
| | - Mina Yoon
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
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3
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Marie Freiberger E, Späth F, Bauer U, Düll F, Bachmann P, Steinhauer J, Hemauer F, Waleska NJ, Schwaab V, Steinrück HP, Papp C. Selective Oxygen and Hydrogen Functionalization of the h-BN/Rh(111) Nanomesh. Chemistry 2021; 27:13172-13180. [PMID: 34254706 DOI: 10.1002/chem.202101946] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Indexed: 11/05/2022]
Abstract
We present detailed studies on the covalent adsorption of molecular oxygen and atomic hydrogen on the hexagonal boron nitride (h-BN) nanomesh on Rh(111). The functionalization of this two-dimensional (2D) material was investigated under ultra-high vacuum conditions using synchrotron radiation-based in situ high-resolution X-ray photoelectron spectroscopy, temperature-programmed X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. We are able to provide a deep insight into the adsorption behavior and thermal stability of oxygen and hydrogen on h-BN/Rh(111). Oxygen functionalization was achieved via a supersonic molecular beam while hydrogen functionalization was realized using an atomic hydrogen source. Adsorption of the respective species was observed to occur selectively in the pores of h-BN leading to spatially defined modification of the 2D layer. The adsorption of the observed molecular oxygen species was found to be an activated process that requires high-energy oxygen molecules. Upon heating to 700 K, oxygen functionalization was observed to be almost reversible except for small amounts of boron oxides evolving due to the reaction of oxygen with the 2D material. Hydrogen functionalization of h-BN/Rh(111) was fully reversed upon heating to about 640 K.
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Affiliation(s)
- Eva Marie Freiberger
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Florian Späth
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Udo Bauer
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Fabian Düll
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Philipp Bachmann
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Johann Steinhauer
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Felix Hemauer
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Natalie J Waleska
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Valentin Schwaab
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Hans-Peter Steinrück
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Christian Papp
- Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
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4
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Marks LD. Predictive Mixing for Density Functional Theory (and Other Fixed-Point Problems). J Chem Theory Comput 2021; 17:5715-5732. [PMID: 34398610 DOI: 10.1021/acs.jctc.1c00630] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Density functional theory calculations use a significant fraction of current supercomputing time. The resources required scale with the problem size, the internal workings of the code, and the number of iterations to convergence, with the latter being controlled by what is called "mixing". This paper describes a new approach to handling trust regions within these and other fixed-point problems. Rather than adjusting the trust region based upon improvement, the prior steps are used to estimate what the parameters and trust regions should be, effectively estimating the optimal Polyak step from the prior history. Detailed results are shown for eight structures using both the "good" and "bad" multisecant versions as well as the Anderson method and a hybrid approach, all with the same predictive method. Additional comparisons are made for 36 cases with a fixed algorithm greed. The predictive method works well independent of which method is used for the candidate step, and it is capable of adapting to different problem types particularly when coupled with the hybrid approach.
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Affiliation(s)
- L D Marks
- Department of Materials Science and Engineering Northwestern University Evanston, Illinois 60201, United States
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5
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Szitás Á, Gubó R, Pásztor T, Farkas AP, Ajtai T, Óvári L, Palotás K, Berkó A, Kónya Z. Adsorption of Azobenzene on Hexagonal Boron Nitride Nanomesh Supported by Rh(111). THE JOURNAL OF PHYSICAL CHEMISTRY C 2020; 124:14182-14194. [PMID: 32952773 PMCID: PMC7493209 DOI: 10.1021/acs.jpcc.0c01725] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 06/03/2020] [Indexed: 11/29/2022]
Abstract
![]()
Adsorption
properties of azobenzene, the prototypical molecular
switch, were investigated on a hexagonal boron nitride (h-BN) monolayer
(“nanomesh”) prepared on Rh(111). The h-BN layer was
produced by decomposing borazine (B3N3H6) at 1000–1050 K. Temperature-programmed desorption
(TPD) studies revealed that azobenzene molecules adsorbed on the “wire”
and “pore” regions desorb at slightly different temperatures.
Angle-resolved high-resolution electron energy loss spectroscopy (HREELS)
measurements demonstrated that the first molecular layer is characterized
predominantly by an adsorption geometry with the molecular plane parallel
to the surface. Scanning tunneling microscopy (STM) indicated a clear
preference for adsorption in the pores, manifesting a templating effect,
but in some cases one-dimensional molecular stripes also form, implying
attractive molecule–molecule interaction. Density functional
theory (DFT) calculations provided further details regarding the adsorption
energetics and bonding and confirmed the experimental findings that
the molecules adsorb with the phenyl rings parallel to the surface,
preferentially in the pores, and indicated also the presence of an
attractive molecule–molecule interaction.
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Affiliation(s)
- Á Szitás
- Department of Applied and Environmental Chemistry, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary
| | - R Gubó
- Department of Applied and Environmental Chemistry, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary.,ELI-ALPS, ELI-HU Non-Profit Ltd., Wolfgang Sandner utca 3, H-6728 Szeged, Hungary
| | - T Pásztor
- MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary
| | - A P Farkas
- ELI-ALPS, ELI-HU Non-Profit Ltd., Wolfgang Sandner utca 3, H-6728 Szeged, Hungary.,MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary
| | - T Ajtai
- ELI-ALPS, ELI-HU Non-Profit Ltd., Wolfgang Sandner utca 3, H-6728 Szeged, Hungary.,Department of Optics and Quantum Electronics, University of Szeged, Dóm tér 9, H-6720 Szeged, Hungary
| | - L Óvári
- ELI-ALPS, ELI-HU Non-Profit Ltd., Wolfgang Sandner utca 3, H-6728 Szeged, Hungary.,MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary
| | - K Palotás
- MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary.,Institute for Solid State Physics and Optics, Wigner Research Center for Physics, P. O. Box 49, H-1525 Budapest, Hungary
| | - A Berkó
- MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary
| | - Z Kónya
- Department of Applied and Environmental Chemistry, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary.,MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary
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6
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Farkas AP, Szitás Á, Jurdi D, Palotás K, Kiss J, Kónya Z. Selective transformation of ethanol to acetaldehyde catalyzed by Au/h-BN interface prepared on Rh(111) surface. APPLIED CATALYSIS A-GENERAL 2020. [DOI: 10.1016/j.apcata.2020.117440] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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McKee WC, Patterson MC, Frick JR, Sprunger PT, Xu Y. Adsorption of transition metal adatoms on h-BN/Rh(111): Implications for nanocluster self-assembly. Catal Today 2017. [DOI: 10.1016/j.cattod.2016.09.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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8
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Erler P, Schmitt P, Barth N, Irmler A, Bouvron S, Huhn T, Groth U, Pauly F, Gragnaniello L, Fonin M. Highly Ordered Surface Self-Assembly of Fe₄ Single Molecule Magnets. NANO LETTERS 2015; 15:4546-52. [PMID: 26086677 DOI: 10.1021/acs.nanolett.5b01120] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Single molecule magnets (SMMs) have attracted considerable attention due to low-temperature magnetic hysteresis and fascinating quantum effects. The investigation of these properties requires the possibility to deposit well-defined monolayers or spatially isolated molecules within a well-controlled adsorption geometry. Here we present a successful fabrication of self-organized arrays of Fe4 SMMs on hexagonal boron nitride (h-BN) on Rh(111) as template. Using a rational design of the ligand shell optimized for surface assembly and electrospray as a gentle deposition method, we demonstrate how to obtain ordered arrays of molecules forming perfect hexagonal superlattices of tunable size, from small islands to an almost perfect monolayer. High-resolution low temperature scanning tunneling microscopy (STM) reveals that the Fe4 molecule adsorbs on the substrate in a flat geometry, meaning that its magnetic easy axis is perpendicular to the surface. By scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations, we infer that the majority- and minority-spin components of the spin-split lowest unoccupied molecular orbital (LUMO) can be addressed separately on a submolecular level.
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Affiliation(s)
- Philipp Erler
- †Department of Physics and ‡Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | | | - Nicole Barth
- †Department of Physics and ‡Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Andreas Irmler
- †Department of Physics and ‡Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Samuel Bouvron
- †Department of Physics and ‡Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | | | | | - Fabian Pauly
- †Department of Physics and ‡Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Luca Gragnaniello
- †Department of Physics and ‡Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Mikhail Fonin
- †Department of Physics and ‡Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
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9
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Natterer FD, Patthey F, Brune H. Ring state for single transition metal atoms on boron nitride on Rh(111). PHYSICAL REVIEW LETTERS 2012; 109:066101. [PMID: 23006283 DOI: 10.1103/physrevlett.109.066101] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 06/15/2012] [Indexed: 06/01/2023]
Abstract
The low-temperature adsorption of isolated transition metal adatoms (Mn, Co, and Fe) onto hexagonal boron nitride monolayers on Rh(111) creates a bistable adsorption complex. The first state considerably weakens the hexagonal boron nitride- (h-BN-) substrate bond for 60 BN unit cells, leading to a highly symmetric ring in STM images, while the second state is imaged as a conventional adatom and leaves the BN-substrate interaction intact. We demonstrate reversible switching between the two states and, thus, controlled pinning and unpinning of the h-BN layer from the metal substrate. I(z) and d lnI/dz curves are used to reveal the BN deformation in the ring state.
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Affiliation(s)
- Fabian Donat Natterer
- Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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10
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Koch S, Langer M, Kawai S, Meyer E, Glatzel T. Contrast inversion of the h-BN nanomesh investigated by nc-AFM and Kelvin probe force microscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:314212. [PMID: 22820852 DOI: 10.1088/0953-8984/24/31/314212] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Single sheets of hexagonal boron nitride (h-BN) on transition metals provide a model system for layered insulating materials as well as a functional substrate for molecules and metal clusters. The progress in the understanding of h-BN layers on transition metals was mainly driven by scanning tunnelling microscopy (STM) and photoelectron spectroscopy (PES) measurements within the last decade, while direct measurements of mechanical and electrical properties are still rare. Our investigations of the two-dimensional (2D) h-BN nanomesh on a Rh(111) substrate by high-resolution noncontact atomic force microscopy (nc-AFM) reveal a complex surface structure including a frequently observed contrast inversion. Detailed 2D force spectroscopy measurements are revealing towards a mechanical elastic deformation of the h-BN monolayer caused by the tip-sample interaction. Furthermore, Kelvin probe force microscopy (KPFM) and spectroscopy measurements show local work function variations of the nanomesh, proving the results obtained by PES but additionally providing detailed local information.
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Affiliation(s)
- S Koch
- Department of Physics, University of Basel, Basel, Switzerland.
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11
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Dong G, Fourré EB, Tabak FC, Frenken JWM. How boron nitride forms a regular nanomesh on Rh(111). PHYSICAL REVIEW LETTERS 2010; 104:096102. [PMID: 20366997 DOI: 10.1103/physrevlett.104.096102] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Indexed: 05/29/2023]
Abstract
Boron nitride forms nearly perfectly regular films with a thickness of precisely one atom on various metal surfaces. Here, we follow the formation of boron nitride layers on Rh(111) with scanning tunneling microscopy (STM) under realistic growth conditions, up to 1200 K. Our STM movies demonstrate in detail how the structure grows and how defects are introduced. Based on these observations we arrive at the optimal recipe for a high-quality overlayer.
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Affiliation(s)
- Guocai Dong
- Kamerlingh Onnes Laboratory, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands
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12
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Gruner ME. Core-shell morphologies of FePt and CoPt nanoparticles: Anab initiocomparison. ACTA ACUST UNITED AC 2010. [DOI: 10.1088/1742-6596/200/7/072039] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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13
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Müller F, Sachdev H, Hüfner S, Pollard AJ, Perkins EW, Russell JC, Beton PH, Gsell S, Fischer M, Schreck M, Stritzker B. How does graphene grow? Easy access to well-ordered graphene films. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:2291-2296. [PMID: 19565616 DOI: 10.1002/smll.200900158] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The selective formation of large-scale graphene layers on a Rh-YSZ-Si(111) multilayer substrate by a surface-induced chemical growth mechanism is investigated using low-energy electron diffraction, X-ray photoelectron spectroscopy, X-ray photoelectron diffraction, and scanning tunneling microscopy. It is shown that well-ordered graphene layers can be grown using simple and controllable procedures. In addition, temperature-dependent experiments provide insight into the details of the growth mechanisms. A comparison of different precursors shows that a mobile dicarbon species (e.g., C(2)H(2) or C(2)) acts as a common intermediate for graphene formation. These new approaches offer scalable methods for the large-scale production of high-quality graphene layers on silicon-based multilayer substrates.
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Affiliation(s)
- Frank Müller
- Anorganische und Allgemeine Chemie FR 8.1, Naturwissenschaftlich-Technische Fakultät III Chemie, Pharmazie und Werkstoffwissenschaften, Universität des Saarlandes C4.1, 66041 Saarbrücken, Germany
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14
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Abstract
Abstract
This mini-review focuses on the recently discovered nanomeshes and nanotemplates made from carbon, boron nitride and their mixtures with a thickness of just a single atomic layer. Typically they exist on some transition metal or semiconductor substrate, the interaction with it playing a crucial role in nanopattern formation. We review systems such as graphene/SiC(0001), graphene/Ru(0001), h-BN/Ru(0001), and h-BN/Rh(111), their atomistic models, synthesis routes, as well as possible applications as templates for nanoperiodic arrays of clusters and molecules. Scanning tunneling microscopy (STM), a technique with ultimate resolution in real space, is stressed as an indispensable tool for a comprehensive characterization of the given systems.
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15
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Gruner ME, Entel P. Simulating functional magnetic materials on supercomputers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:293201. [PMID: 21828528 DOI: 10.1088/0953-8984/21/29/293201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The recent passing of the petaflop per second landmark by the Roadrunner project at the Los Alamos National Laboratory marks a preliminary peak of an impressive world-wide development in the high-performance scientific computing sector. Also, purely academic state-of-the-art supercomputers such as the IBM Blue Gene/P at Forschungszentrum Jülich allow us nowadays to investigate large systems of the order of 10(3) spin polarized transition metal atoms by means of density functional theory. Three applications will be presented where large-scale ab initio calculations contribute to the understanding of key properties emerging from a close interrelation between structure and magnetism. The first two examples discuss the size dependent evolution of equilibrium structural motifs in elementary iron and binary Fe-Pt and Co-Pt transition metal nanoparticles, which are currently discussed as promising candidates for ultra-high-density magnetic data storage media. However, the preference for multiply twinned morphologies at smaller cluster sizes counteracts the formation of a single-crystalline L1(0) phase, which alone provides the required hard magnetic properties. The third application is concerned with the magnetic shape memory effect in the Ni-Mn-Ga Heusler alloy, which is a technologically relevant candidate for magnetomechanical actuators and sensors. In this material strains of up to 10% can be induced by external magnetic fields due to the field induced shifting of martensitic twin boundaries, requiring an extremely high mobility of the martensitic twin boundaries, but also the selection of the appropriate martensitic structure from the rich phase diagram.
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Affiliation(s)
- Markus Ernst Gruner
- Physics Department and Centre for Nanointegration CENIDE, University of Duisburg-Essen, Duisburg Campus, 47048 Duisburg, Germany
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16
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Laskowski R, Gallauner T, Blaha P, Schwarz K. Density functional theory simulations of B K and N K NEXAFS spectra of h-BN/transition metal(111) interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:104210. [PMID: 21817430 DOI: 10.1088/0953-8984/21/10/104210] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The electronic structure and the corresponding B K and N K near-edge x-ray fine structure (NEXAFS) spectra of epitaxially grown h-BN on Ni(111), Pt(111), and Rh(111) surfaces are investigated by density functional theory. The calculations are carried out using the WIEN2k program package applying the augmented-plane-wave+local orbitals (APW+lo) method. The NEXAFS spectra are simulated using a 3 × 3 × 1 super cell and considering the final state rule by means of a (partial) core hole for the corresponding atom. The influence of a full or partial core hole is shown for the h-BN/Ni(111) system, for which the best agreement with the experimental spectra is found when half a core hole is assumed. All characteristic features of the experimental spectra are well reproduced by theory, including the angular dependences. The bonding effects are investigated by comparing the spectra of bulk h-BN with those of the h-BN/Ni(111) system. An analysis of both the density of states and charge densities reveals strong N-p(z)-Ni-d(z(2)) bonding/antibonding interactions. In the case of Pt(111) and Rh(111) surfaces, we discuss the effects of the nanomesh structures in terms of simple 1 × 1 commensurate models.
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Affiliation(s)
- R Laskowski
- Vienna University of Technology, A-1060 Vienna, Austria
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17
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Dil H, Lobo-Checa J, Laskowski R, Blaha P, Berner S, Osterwalder J, Greber T. Surface Trapping of Atoms and Molecules with Dipole Rings. Science 2008; 319:1824-6. [DOI: 10.1126/science.1154179] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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