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Akhtar F, Dabrowski J, Lukose R, Wenger C, Lukosius M. Chemical Vapor Deposition Growth of Graphene on 200 mm Ge(110)/Si Wafers and Ab Initio Analysis of Differences in Growth Mechanisms on Ge(110) and Ge(001). ACS Appl Mater Interfaces 2023. [PMID: 37479219 PMCID: PMC10401564 DOI: 10.1021/acsami.3c05860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/23/2023]
Abstract
For the fabrication of modern graphene devices, uniform growth of high-quality monolayer graphene on wafer scale is important. This work reports on the growth of large-scale graphene on semiconducting 8 inch Ge(110)/Si wafers by chemical vapor deposition and a DFT analysis of the growth process. Good graphene quality is indicated by the small FWHM (32 cm-1) of the Raman 2D band, low intensity ratio of the Raman D and G bands (0.06), and homogeneous SEM images and is confirmed by Hall measurements: high mobility (2700 cm2/Vs) and low sheet resistance (800 Ω/sq). In contrast to Ge(001), Ge(110) does not undergo faceting during the growth. We argue that Ge(001) roughens as a result of vacancy accumulation at pinned steps, easy motion of bonded graphene edges across (107) facets, and low energy cost to expand Ge area by surface vicinals, but on Ge(110), these mechanisms do not work due to different surface geometries and complex reconstruction.
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Affiliation(s)
- Fatima Akhtar
- IHP - Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - Jaroslaw Dabrowski
- IHP - Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - Rasuole Lukose
- IHP - Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - Christian Wenger
- IHP - Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
- BTU Cottbus Senftenberg, Platz der Deutschen Einheit 1, 03046 Cottbus, Germany
| | - Mindaugas Lukosius
- IHP - Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
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2
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Straumal BB, Konyashin I. Faceting/Roughening of WC/Binder Interfaces in Cemented Carbides: A Review. Materials (Basel) 2023; 16:ma16103696. [PMID: 37241323 DOI: 10.3390/ma16103696] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Revised: 05/08/2023] [Accepted: 05/09/2023] [Indexed: 05/28/2023]
Abstract
Hardmetals (or cemented carbides) were invented a hundred years ago and became one of the most important materials in engineering. The unique conjunction of fracture toughness, abrasion resistance and hardness makes WC-Co cemented carbides irreplaceable for numerous applications. As a rule, the WC crystallites in the sintered WC-Co hardmetals are perfectly faceted and possess a truncated trigonal prism shape. However, the so-called faceting-roughening phase transition can force the flat (faceted) surfaces or interfaces to become curved. In this review, we analyze how different factors can influence the (faceted) shape of WC crystallites in the cemented carbides. Among these factors are the modification of fabrication parameters of usual WC-Co cemented carbides; alloying of conventional cobalt binder using various metals; alloying of cobalt binder using nitrides, borides, carbides, silicides, oxides; and substitution of cobalt with other binders, including high entropy alloys (HEAs). The faceting-roughening phase transition of WC/binder interfaces and its influence on the properties of cemented carbides is also discussed. In particular, the increase in the hardness and fracture toughness of cemented carbides correlates with transition of WC crystallites from a faceted to a rounded shape.
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Affiliation(s)
- Boris B Straumal
- Chernogolovka Scientific Center, Osipyan Institute of Solid State Physics, Russian Academy of Sciences, Ac. Osipyan Str. 2, 142432 Chernogolovka, Russia
| | - Igor Konyashin
- Element Six GmbH, Staedeweg 18-24, 36151 Burghaun, Germany
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3
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Abstract
Particle size disparities suppress crystallization. However, soft deformable nanogels can change the size of the larger particles in suspension and crystallize even at a high initial size-polydispersity. Using neutron scattering with contrast variation, the response of individual nanogels in crowded environments was probed, and an increase of the parameter describing size-polydispersity was found, which is often interpreted as deformation. Here, computer simulations are used to generate deformed nanogels and the corresponding form factor. The data are fitted with the spherical model used to analyze scattering data. The fits show the same qualitative increase of the parameter related to the size-polydispersity with increasing particle deformation. Starting from the simulated deformed spheres, we also reproduce experimental scattering data. A further analysis of the particle shows that the size disparities between nanogels do not increase significantly. In contrast, their shapes strongly vary from one nanogel to the other.
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Affiliation(s)
- Tom Höfken
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - Christian Strauch
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - Stefanie Schneider
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - Andrea Scotti
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
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4
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Chung S, Schober JC, Tober S, Schmidt D, Khadiev A, Novikov DV, Vonk V, Stierle A. Epitaxy and Shape Heterogeneity of a Nanoparticle Ensemble during Redox Cycles. ACS Nano 2021; 15:13267-13278. [PMID: 34350766 DOI: 10.1021/acsnano.1c03002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The role of metal-support epitaxy on shape and size heterogeneity of nanoparticles and their response to gas atmospheres is not very well explored. Here we show that an ensemble of Pd nanoparticles, grown on MgO(001) by deposition under ultrahigh vacuum, mostly consists of two distinctly epitaxially oriented particles, each having a different structural response to redox cycles. X-ray reciprocal space patterns were acquired in situ under oxidizing and reducing environments. Each type of nanoparticle has a truncated octahedral shape, whereby the majority grows with a cube-on-cube epitaxy on the substrate. Less frequently occurring and larger particles have their principal crystal axes rotated ±3.7° with respect to the substrate's. Upon oxidation, the top (001) facets of both types of particles shrink. The relative change of the rotated particles' top facets is much more pronounced. This finding indicates that a larger mass transfer is involved for the rotated particles and that a larger portion of high-index facets forms. On the main facets of the cube-on-cube particles, the oxidation process results in a considerable strain, as concluded from the evolution to largely asymmetric facet scattering signals. The shape and strain responses are reversible upon reduction, either by annealing to 973 K in vacuum or by reducing with hydrogen. The presented results are important for unraveling different elements of heterogeneity and their effect on the performance of real polycrystalline catalysts. It is shown that a correlation can exist between the particle-support epitaxy and redox-cycling-induced shape changes.
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Affiliation(s)
- Simon Chung
- CXNS - Center for X-ray and Nano Science, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
| | - Jan-Christian Schober
- CXNS - Center for X-ray and Nano Science, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
- Fachbereich Physik, Universität Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
| | - Steffen Tober
- CXNS - Center for X-ray and Nano Science, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
- Fachbereich Physik, Universität Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
| | - Daniel Schmidt
- Fachbereich Physik, Universität Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
| | - Azat Khadiev
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
| | - Dmitri V Novikov
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
| | - Vedran Vonk
- CXNS - Center for X-ray and Nano Science, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
| | - Andreas Stierle
- CXNS - Center for X-ray and Nano Science, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
- Fachbereich Physik, Universität Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
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5
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Ren X, Wang X, Jin C. Atomic-Precision Fabrication of Quasi-Full-Space Grain Boundaries in Two-Dimensional Hexagonal Boron Nitride. Nano Lett 2019; 19:8581-8589. [PMID: 31663768 DOI: 10.1021/acs.nanolett.9b03114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Precise control and in-depth understanding of the interfaces are crucial for the functionality-oriented material design with desired properties. Herein, via modifying the long-standing bicrystal strategy, we proposed a novel nanowelding approach to build up interfaces between two-dimensional (2D) materials with atomic precision. This method enabled us, for the first time, to experimentally achieve the quasi-full-parameter-space grain boundaries (GBs) in 2D hexagonal boron nitride (h-BN). It further helps us unravel the long-term controversy and confusion on the registry of GBs in h-BN, including (i) discriminate the relative contribution of the strain and chemical energy on the registry of GBs; (ii) identify a new dislocation core-Frank partial dislocation and four new antiphase boundaries; and (iii) confirm the universal GB faceting. Our work provides a new paradigm to the exploitation of structural-property correlation of interfaces in 2D materials.
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Affiliation(s)
- Xibiao Ren
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering , Zhejiang University , Hangzhou , Zhejiang 310027 , China
| | - Xiaowei Wang
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering , Zhejiang University , Hangzhou , Zhejiang 310027 , China
| | - Chuanhong Jin
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering , Zhejiang University , Hangzhou , Zhejiang 310027 , China
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6
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Sun YL, Matsumura R, Jevasuwan W, Fukata N. Au-Sn Catalyzed Growth of Ge 1-xSn x Nanowires: Growth Direction, Crystallinity, and Sn Incorporation. Nano Lett 2019; 19:6270-6277. [PMID: 31448621 DOI: 10.1021/acs.nanolett.9b02395] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Ge1-xSnx nanowires (NWs) have been a focus of research attention for their potential in realizing next-generation Si-compatible electronic and optoelectronic devices. To control the growth of NWs and increase their Sn content, the growth mechanism needs to be understood. The use of Au-Sn alloy catalysts instead of Au catalysts allows an easier understanding of Ge1-xSnx NW growth, and the effects of Sn at different concentrations in catalysts on growth direction, Sn incorporation, and crystallinity of Ge1-xSnx NWs can be clarified. High Sn content in Au-Sn alloy catalysts favors ⟨110⟩-oriented NW growth and high Sn incorporation in NWs. The higher Sn content in Au-Sn alloy catalysts also improves the crystallinity of NWs.
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Affiliation(s)
- Yong-Lie Sun
- International Center for Materials Nanoarchitectonics , National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
- Institute of Applied Physics , University of Tsukuba , 1-1-1 Tennodai , Tsukuba 305-8573 , Japan
| | - Ryo Matsumura
- International Center for Materials Nanoarchitectonics , National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Wipakorn Jevasuwan
- International Center for Materials Nanoarchitectonics , National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Naoki Fukata
- International Center for Materials Nanoarchitectonics , National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
- Institute of Applied Physics , University of Tsukuba , 1-1-1 Tennodai , Tsukuba 305-8573 , Japan
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7
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Castanet U, Feral-Martin C, Demourgues A, Neale RL, Sayle DC, Caddeo F, Flitcroft JM, Caygill R, Pointon BJ, Molinari M, Majimel J. Controlling the {111}/{110} Surface Ratio of Cuboidal Ceria Nanoparticles. ACS Appl Mater Interfaces 2019; 11:11384-11390. [PMID: 30843391 DOI: 10.1021/acsami.8b21667] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The ability to control the size and morphology is crucial in optimizing nanoceria catalytic activity as this is governed by the atomistic arrangement of species and structural features at the surfaces. Here, we show that cuboidal cerium oxide nanoparticles can be obtained via microwave-assisted hydrothermal synthesis in highly alkaline media. High-resolution transmission electron microscopy (HRTEM) revealed that the cube edges were truncated by CeO2{110} surfaces and the cube corners were truncated by CeO2{111} surfaces. When adjusting synthesis conditions by increasing NaOH concentration, the average particle size increased. Although this was accompanied by an increase of the cube faces, CeO2{100}, the cube edges, CeO2{110}, and cube corners, CeO2{111}, remained of constant size. Molecular dynamics (MD) was used to rationalize this behavior and revealed that energetically, the corners and edges cannot be atomically sharp, rather they are truncated by {111} and {110} surfaces, respectively, to stabilize the nanocube; both the experiment and simulation showed agreement regarding the minimum size of ∼1.6 nm associated with this truncation. Moreover, HRTEM and MD revealed {111}/{110} faceting of the {110} edges, which balances the surface energy associated with the exposed surfaces, which follows {111} > {110} > {100}, although only the {110} surface facets because of the ease of extracting oxygen from its surface and follows {111} > {100} > {110}. Finally, MD revealed that the {100} surfaces are "liquid-like" with a surface oxygen mobility 5 orders of magnitude higher than that on the {111} surfaces; this arises from the flexibility of the surface species network that can access many different surface arrangements because of very small energy differences. This finding has implications for understanding the surface chemistry of nanoceria and provides avenues to rationalize the design of catalytically active materials at the nanoscale.
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Affiliation(s)
- Uli Castanet
- CNRS, Univ. Bordeaux, ICMCB, UPR 9048 , 87 Avenue du Docteur Schweitzer , 33600 Pessac , France
| | | | - Alain Demourgues
- CNRS, Univ. Bordeaux, ICMCB, UPR 9048 , 87 Avenue du Docteur Schweitzer , 33600 Pessac , France
| | - Rachel L Neale
- School of Physical Science , University of Kent , Canterbury , Kent CT2 7NZ , U.K
| | - Dean C Sayle
- School of Physical Science , University of Kent , Canterbury , Kent CT2 7NZ , U.K
| | - Francesco Caddeo
- School of Physical Science , University of Kent , Canterbury , Kent CT2 7NZ , U.K
| | - Joseph M Flitcroft
- Department of Chemistry , University of Huddersfield , Huddersfield HD1 3DH , U.K
| | - Robert Caygill
- Department of Chemistry , University of Huddersfield , Huddersfield HD1 3DH , U.K
| | - Ben J Pointon
- Department of Chemistry , University of Huddersfield , Huddersfield HD1 3DH , U.K
| | - Marco Molinari
- Department of Chemistry , University of Huddersfield , Huddersfield HD1 3DH , U.K
| | - Jerome Majimel
- CNRS, Univ. Bordeaux, ICMCB, UPR 9048 , 87 Avenue du Docteur Schweitzer , 33600 Pessac , France
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8
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Guerra R, Leven I, Vanossi A, Hod O, Tosatti E. Smallest Archimedean Screw: Facet Dynamics and Friction in Multiwalled Nanotubes. Nano Lett 2017; 17:5321-5328. [PMID: 28795813 PMCID: PMC5600185 DOI: 10.1021/acs.nanolett.7b01718] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 08/10/2017] [Indexed: 05/28/2023]
Abstract
We identify a new material phenomenon, where minute mechanical manipulations induce pronounced global structural reconfigurations in faceted multiwalled nanotubes. This behavior has strong implications on the tribological properties of these systems and may be the key to understand the enhanced interwall friction recently measured for boron-nitride nanotubes with respect to their carbon counterparts. Notably, the fast rotation of helical facets in these systems upon coaxial sliding may serve as a nanoscale Archimedean screw for directional transport of physisorbed molecules.
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Affiliation(s)
- Roberto Guerra
- Center
for Complexity and Biosystems, Department of Physics, University of Milan, 20133 Milan, Italy
| | - Itai Leven
- Department
of Physical Chemistry, School of Chemistry, The Raymond and Beverly
Sackler Faculty of Exact Sciences and The Sackler Center for Computational
Molecular and Materials Science, Tel Aviv
University, Tel Aviv 6997801, Israel
| | - Andrea Vanossi
- International
School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy
- CNR-IOM
Democritos National Simulation Center, Via Bonomea 265, 34136 Trieste, Italy
| | - Oded Hod
- Department
of Physical Chemistry, School of Chemistry, The Raymond and Beverly
Sackler Faculty of Exact Sciences and The Sackler Center for Computational
Molecular and Materials Science, Tel Aviv
University, Tel Aviv 6997801, Israel
| | - Erio Tosatti
- International
School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy
- CNR-IOM
Democritos National Simulation Center, Via Bonomea 265, 34136 Trieste, Italy
- The
Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, 34151 Trieste, Italy
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9
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Lukosius M, Dabrowski J, Kitzmann J, Fursenko O, Akhtar F, Lisker M, Lippert G, Schulze S, Yamamoto Y, Schubert MA, Krause HM, Wolff A, Mai A, Schroeder T, Lupina G. Metal-Free CVD Graphene Synthesis on 200 mm Ge/Si(001) Substrates. ACS Appl Mater Interfaces 2016; 8:33786-33793. [PMID: 27960421 DOI: 10.1021/acsami.6b11397] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Good quality, complementary-metal-oxide-semiconductor (CMOS) technology compatible, 200 mm graphene was obtained on Ge(001)/Si(001) wafers in this work. Chemical vapor depositions were carried out at the deposition temperatures of 885 °C using CH4 as carbon source on epitaxial Ge(100) layers, which were grown on Si(100), prior to the graphene synthesis. Graphene layer with the 2D/G ratio ∼3 and low D mode (i.e., low concentration of defects) was measured over the entire 200 mm wafer by Raman spectroscopy. A typical full-width-at-half-maximum value of 39 cm-1 was extracted for the 2D mode, further indicating that graphene of good structural quality was produced. The study also revealed that the lack of interfacial oxide correlates with superior properties of graphene. In order to evaluate electrical properties of graphene, its 2 × 2 cm2 pieces were transferred onto SiO2/Si substrates from Ge/Si wafers. The extracted sheet resistance and mobility values of transferred graphene layers were ∼1500 ± 100 Ω/sq and μ ≈ 400 ± 20 cm2/V s, respectively. The transferred graphene was free of metallic contaminations or mechanical damage. On the basis of results of DFT calculations, we attribute the high structural quality of graphene grown by CVD on Ge to hydrogen-induced reduction of nucleation probability, explain the appearance of graphene-induced facets on Ge(001) as a kinetic effect caused by surface step pinning at linear graphene nuclei, and clarify the orientation of graphene domains on Ge(001) as resulting from good lattice matching between Ge(001) and graphene nucleated on such nuclei.
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Affiliation(s)
- M Lukosius
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - J Dabrowski
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - J Kitzmann
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - O Fursenko
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - F Akhtar
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - M Lisker
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - G Lippert
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - S Schulze
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - Y Yamamoto
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - M A Schubert
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - H M Krause
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - A Wolff
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - A Mai
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - T Schroeder
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
- BTU Cottbus-Senftenberg , Konrad Zuse Str. 1, 03046 Cottbus, Germany
| | - G Lupina
- IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
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10
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Lee HF, Esfarjani K, Dong Z, Xiong G, Pelegri AA, Tse SD. Molecular Dynamics Study of Cubic Boron Nitride Nanoparticles: Decomposition with Phase Segregation during Melting. ACS Nano 2016; 10:10563-10572. [PMID: 27797465 DOI: 10.1021/acsnano.6b06583] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The relative stability and melting of cubic boron nitride (c-BN) nanoparticles of varying shapes and sizes are studied using classical molecular dynamics (MD) simulation. Focusing on the melting of octahedral c-BN nanoparticles, which consist solely of the most stable {111} facets, decomposition is observed to occur during melting, along with the formation of phase segregated boron clusters inside the c-BN nanoparticles, concurrent with vaporization of surface nitrogen atoms. To assess this MD prediction, a laser-heating experiment of c-BN powders is conducted, manifesting boron clusters for the post-treated powders. A general analysis of the geometrical and surface dependence of the nanoparticle ground-state energy using a Stillinger-Weber potential determines the relative stability of cube-shaped, octahedral, cuboctahedral, and truncated-octahedral c-BN nanoparticles. This stability is further examined using transient MD simulations of the melting behavior of the differently shaped nanoparticles, providing insights and revealing the key roles played by corner and edge initiated disorder as well as surface reconstruction from {100} to the more stable {111} facets in the melting process. Finally, the size dependence of the melting point of octahedral c-BN nanoparticles is investigated, showing the well-known qualitative trend of depression of melting temperature with decreasing size, albeit with different quantitative behavior from that predicted by existing analytical models.
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Affiliation(s)
- Hsiao-Fang Lee
- Department of Mechanical and Aerospace Engineering, Rutgers University , Piscataway, New Jersey 08854, United States
| | - Keivan Esfarjani
- Department of Mechanical and Aerospace Engineering, Rutgers University , Piscataway, New Jersey 08854, United States
| | - Zhizhong Dong
- Department of Mechanical and Aerospace Engineering, Rutgers University , Piscataway, New Jersey 08854, United States
| | - Gang Xiong
- Department of Mechanical and Aerospace Engineering, Rutgers University , Piscataway, New Jersey 08854, United States
| | - Assimina A Pelegri
- Department of Mechanical and Aerospace Engineering, Rutgers University , Piscataway, New Jersey 08854, United States
| | - Stephen D Tse
- Department of Mechanical and Aerospace Engineering, Rutgers University , Piscataway, New Jersey 08854, United States
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11
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Kolíbal M, Pejchal T, Vystavěl T, Šikola T. The Synergic Effect of Atomic Hydrogen Adsorption and Catalyst Spreading on Ge Nanowire Growth Orientation and Kinking. Nano Lett 2016; 16:4880-4886. [PMID: 27458789 DOI: 10.1021/acs.nanolett.6b01352] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Hydride precursors are commonly used for semiconductor nanowire growth from the vapor phase and hydrogen is quite often used as a carrier gas. Here, we used in situ scanning electron microscopy and spatially resolved Auger spectroscopy to reveal the essential role of atomic hydrogen in determining the growth direction of Ge nanowires with an Au catalyst. With hydrogen passivating nanowire sidewalls the formation of inclined facets is suppressed, which stabilizes the growth in the ⟨111⟩ direction. By contrast, without hydrogen gold diffuses out of the catalyst and decorates the nanowire sidewalls, which strongly affects the surface free energy of the system and results in the ⟨110⟩ oriented growth. The experiments with intentional nanowire kinking reveal the existence of an energetic barrier, which originates from the kinetic force needed to drive the droplet out of its optimum configuration on top of a nanowire. Our results stress the role of the catalyst material and surface chemistry in determining the nanowire growth direction and provide additional insights into a kinking mechanism, thus allowing to inhibit or to intentionally initiate spontaneous kinking.
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Affiliation(s)
- Miroslav Kolíbal
- Institute of Physical Engineering, Brno University of Technology , Technická 2, 616 69 Brno, Czech Republic
- CEITEC BUT, Brno University of Technology , Purkyňova 123, 616 69 Brno, Czech Republic
| | - Tomáš Pejchal
- CEITEC BUT, Brno University of Technology , Purkyňova 123, 616 69 Brno, Czech Republic
| | - Tomáš Vystavěl
- FEI Company, Vlastimila Pecha 1282/12, 627 00 Brno, Czech Republic
| | - Tomáš Šikola
- Institute of Physical Engineering, Brno University of Technology , Technická 2, 616 69 Brno, Czech Republic
- CEITEC BUT, Brno University of Technology , Purkyňova 123, 616 69 Brno, Czech Republic
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12
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Anjum DH, Sougrat R. Transmission electron microscopy of mercury metal. J Microsc 2016; 263:365-70. [PMID: 27018645 DOI: 10.1111/jmi.12399] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 12/18/2015] [Accepted: 02/14/2016] [Indexed: 11/28/2022]
Abstract
Transmission electron microcopy (TEM) analysis of liquid metals, especially mercury (Hg), is difficult to carry out because their specimen preparation poses a daunting task due to the unique surface properties of these metals. This paper reports a cryoTEM study on Hg using a novel specimen preparation technique. Hg metal is mixed with water using sonication and quenched in liquid ethane cryogen. This technique permits research into the morphological, phase and structural properties of Hg at nanoscale dimensions.
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Affiliation(s)
- Dalaver H Anjum
- Imaging and Characterization Lab King Abdullah University of Science & Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Rachid Sougrat
- Imaging and Characterization Lab King Abdullah University of Science & Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
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Lee HC, Jo SB, Lee E, Yoo MS, Kim HH, Lee SK, Lee WH, Cho K. Facet-Mediated Growth of High-Quality Monolayer Graphene on Arbitrarily Rough Copper Surfaces. Adv Mater 2016; 28:2010-2017. [PMID: 26766210 DOI: 10.1002/adma.201504190] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 11/27/2015] [Indexed: 06/05/2023]
Abstract
A synthetic approach for high-quality graphene on rough Cu surfaces via chemical vapor deposition is proposed. High-quality graphene is synthesized on rough Cu surfaces by inducing surface faceting of Cu surfaces prior to graphene growth. The electron mobility of synthesized graphene on the rough Cu surfaces is enhanced to 10 335 cm(2) V(-1) s(-1).
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Affiliation(s)
- Hyo Chan Lee
- Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, South Korea
| | - Sae Byeok Jo
- Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, South Korea
| | - Eunho Lee
- Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, South Korea
| | - Min Seok Yoo
- Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, South Korea
| | - Hyun Ho Kim
- Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, South Korea
| | - Seong Kyu Lee
- Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, South Korea
| | - Wi Hyoung Lee
- Department of Organic and Nano System Engineering, Konkuk University, Seoul, 143-701, South Korea
| | - Kilwon Cho
- Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, South Korea
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Lukyanchuk I, Sharma P, Nakajima T, Okamura S, Scott JF, Gruverman A. High-symmetry polarization domains in low-symmetry ferroelectrics. Nano Lett 2014; 14:6931-6935. [PMID: 25420186 DOI: 10.1021/nl503070f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present experimental evidence for polygonal domain faceting in the ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) films with the lower orthorhombic crystallographic symmetry. It is proposed that this effect can arise from purely electrostatic depolarizing forces. We show that, in contrast to magnetic bubble shape domains, where such type of deformation instability has a predominantly elliptical character, the emergence of more symmetrical circular harmonics is favored in ferroelectrics with high dielectric constants.
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Affiliation(s)
- I Lukyanchuk
- Laboratory of Condensed Matter Physics, University of Picardie , Amiens, 80000, France
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Abstract
The tetraoctylammonium bromide (TOAB)-stabilized gold nanoparticles have been successfully fabricated. After an annealing of the as-synthesized nanoparticles at 300 degrees C for 30 min, the coalescence behavior of gold nanoparticles has been investigated using high-resolution transmission electron microscopy in detail. Two types of coalescence, one being an ordered combination of two or more particles in appropriate orientations through twinning, and the other being an ordered combination of two small particles with facets through a common lattice plane, have been observed.
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Affiliation(s)
- YQ Wang
- The Cultivation Base for State Key Laboratory, Qingdao University, No. 308 Ningxia Road, Qingdao, 266071, People’s Republic of China
| | - WS Liang
- The Cultivation Base for State Key Laboratory, Qingdao University, No. 308 Ningxia Road, Qingdao, 266071, People’s Republic of China
| | - CY Geng
- The Cultivation Base for State Key Laboratory, Qingdao University, No. 308 Ningxia Road, Qingdao, 266071, People’s Republic of China
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