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Kamaratos M, Sotiropoulos A, Vlachos D. Ultrathin films of Ge on the Si(100)2 × 1 surface. SURF INTERFACE ANAL 2017. [DOI: 10.1002/sia.6358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- M. Kamaratos
- Department of Physics; University of Ioannina; PO Box 1186 451 10 Ioannina Epirus Greece
| | - A.K. Sotiropoulos
- Department of Physics; University of Ioannina; PO Box 1186 451 10 Ioannina Epirus Greece
| | - D. Vlachos
- Department of Physics; University of Ioannina; PO Box 1186 451 10 Ioannina Epirus Greece
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Fuhrer A, Rueß FJ, Moll N, Curioni A, Widmer D. Atomic structure of Mn wires on Si(001) resolved by scanning tunneling microscopy. Phys Rev Lett 2012; 109:146102. [PMID: 23083259 DOI: 10.1103/physrevlett.109.146102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Indexed: 06/01/2023]
Abstract
At submonolayer coverage, Mn forms atomic wires on the Si(001) surface oriented perpendicular to the underlying Si dimer rows. While many other elements form symmetric dimer wires at room temperature, we show that Mn wires have an asymmetric appearance and pin the Si dimers nearby. We find that an atomic configuration with a Mn trimer unit cell can explain these observations as due to the interplay between the Si dimer buckling phase near the wire and the orientation of the Mn trimer. We study the resulting four wire configurations in detail using high-resolution scanning tunneling microscopy (STM) imaging and compare our findings with the STM images simulated by density functional theory.
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Affiliation(s)
- A Fuhrer
- IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland.
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Lai MY, Chou JP, Utas OA, Denisov NV, Kotlyar VG, Gruznev D, Matetsky A, Zotov AV, Saranin AA, Wei CM, Wang YL. Broken even-odd symmetry in self-selection of distances between nanoclusters due to the presence or absence of topological solitons. Phys Rev Lett 2011; 106:166101. [PMID: 21599388 DOI: 10.1103/physrevlett.106.166101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Indexed: 05/30/2023]
Abstract
Depositing particles randomly on a 1D lattice is expected to result in an equal number of particle pairs separated by even or odd lattice units. Unexpectedly, the even-odd symmetry is broken in the self-selection of distances between indium magic-number clusters on a Si(100)-2×1 reconstructed surface. Cluster pairs separated by even units are less abundant because they are linked by silicon atomic chains carrying topological solitons, which induce local strain and create localized electronic states with higher energy. Our findings reveal a unique particle-particle interaction mediated by the presence or absence of topological solitons on alternate lattices.
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Affiliation(s)
- M Y Lai
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan, Republic of China
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Norman AG, Ahrenkiel SP, Moutinho HR, Ballif C, Al-Jassim MM, Mascarenhas A, Follstaedt DM, Lee SR, Reno JL, Jones ED, Mirecki-Millunchick J, Twesten RD. The Nature and Origin of Lateral Composition Modulations in Short-Period Strained-Layer Superlattices. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-583-297] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractThe nature and origin of lateral composition modulations in (AlAs)m(InAs)n short-period strained-layer superlattices grown by molecular beam epitaxy on InP substrates have been investigated by x-ray diffraction, atomic force microscopy, and transmission electron microscopy. Strong modulations were observed for growth temperatures between ≈ 540 and 560° C. The maximum strength of modulations was found for SPS samples with InAs mole fraction x (= n/(n+m)) close to ≈ 0.50 and when n ≈ m ≈ 2. The modulations were suppressed at both high and low values of x. For x > 0.52 (global compression), the modulations were along the <100> directions in the (001) growth plane. For x < 0.52 (global tension), the modulations were along the two <310> directions rotated ≈ ±27° from [110] in the growth plane. The remarkably constant wavelength of the modulations, between ≈ 20–30 nm, and the different modulation directions observed, suggest that the origin of the modulations is due to surface roughening associated with the high misfit between the individual SPS layers and the InP substrate. Highly uniform unidirectional modulations have been grown by control of the InAs mole fraction and growth on suitably offcut substrates, which show great promise for application in device structures.
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Abstract
Using scanning tunneling microscopy movies, we directly observe individual embedded Ge atoms to be mobile within the Si(100)-(2x1)-Ge surface at temperatures as low as 90 degrees C. We demonstrate that Ge atoms move by exchange diffusion with (1) adsorbed monomers and (2) individual constituent atoms of adsorbed dimers. Our observations are consistent with recent density-functional theory calculations, which give the atomistic pathways and energetic barriers for both exchange mechanisms. We find that neither adsorbed monomers nor dimers can diffuse more than a few nanometers between exchange events, illustrating how Ge diffusion and intermixing are intimately coupled at the nanoscale on the Si(100) surface.
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Affiliation(s)
- E Bussmann
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
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Gerbode SJ, Lee SH, Liddell CM, Cohen I. Restricted dislocation motion in crystals of colloidal dimer particles. Phys Rev Lett 2008; 101:058302. [PMID: 18764434 DOI: 10.1103/physrevlett.101.058302] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2008] [Indexed: 05/26/2023]
Abstract
At high area fractions, monolayers of colloidal dimer particles form a degenerate crystal (DC) structure in which the particle lobes occupy triangular lattice sites while the particles are oriented randomly along any of the three lattice directions. We report that dislocation glide in DCs is blocked by certain particle orientations. The mean number of lattice constants between such obstacles is Z[over](exp)=4.6+/-0.2 in experimentally observed DC grains and Z[over](sim)=6.18+/-0.01 in simulated monocrystalline DCs. Dislocation propagation beyond these obstacles is observed to proceed through dislocation reactions. We estimate that the energetic cost of dislocation pair separation via such reactions in an otherwise defect free DC grows linearly with final separation, hinting that the material properties of DCs may be dramatically different from those of 2-D crystals of spheres.
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Affiliation(s)
- Zhilin Li
- College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China and College of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
| | - Huibin Xu
- College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China and College of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
| | - Shengkai Gong
- College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China and College of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
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da Silva AJ, Dalpian GM, Janotti A, Fazzio A. Two-atom structures of Ge on Si(100): dimers versus adatom pairs. Phys Rev Lett 2001; 87:036104. [PMID: 11461575 DOI: 10.1103/physrevlett.87.036104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2001] [Indexed: 05/23/2023]
Abstract
We present an ab initio study of the properties of structures composed of two and four Ge atoms adsorbed on the troughs of the Si(100) surface, and we conclude that these structures are all composed of dimers, with a chemical bonding between the adatoms. We compare our calculated local density of states with scanning tunneling microscope (STM) images, and we show that these Ge dimers adsorbed on the troughs between the substrate dimer rows can be identified with the adatom pairs observed experimentally. We also show that the local buckling of the substrate dimers can give rise to similar structures with very different STM images.
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Affiliation(s)
- A J da Silva
- Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, SP, Brazil
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Lu ZY, Liu F, Wang CZ, Qin XR, Swartzentruber BS, Lagally MG, Ho KM. Unique dynamic appearance of a Ge-Si ad-dimer on Si(001). Phys Rev Lett 2000; 85:5603-5606. [PMID: 11136057 DOI: 10.1103/physrevlett.85.5603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2000] [Indexed: 05/23/2023]
Abstract
We carry out a comparative study of the energetics and dynamics of Si-Si, Ge-Ge, and Ge-Si ad-dimers on top of a dimer row in the Si(001) surface, using first-principles calculations. The dynamic appearance of a Ge-Si dimer is distinctively different from that of a Si-Si or Ge-Ge dimer, providing a unique way for its identification by scanning tunneling microscopy (STM). Its "rocking" motion, observed in STM, actually reflects a 180 degrees rotation of the dimer, involving a piecewise-rotation mechanism. The calculated energy barrier of 0.74 eV is in good agreement with the experimental value of 0.82 eV.
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Affiliation(s)
- Z Y Lu
- Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
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Zandvliet HJ, Galea TM, Zoethout E, Poelsema B. Diffusion driven concerted motion of surface atoms: Ge on Ge(001). Phys Rev Lett 2000; 84:1523-1526. [PMID: 11017558 DOI: 10.1103/physrevlett.84.1523] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/1999] [Indexed: 05/23/2023]
Abstract
The diffusion of Ge dimers on the Ge(001) surface has been studied with scanning tunneling microscopy. We have identified three different diffusion pathways for the dimers: diffusion of on-top dimers over the substrate rows, diffusion across the substrate rows, and diffusion of dimers in the trough. We report on a heretofore unknown phenomenon, namely, diffusion driven concerted motion of substrate atoms. This concerted motion is a direct consequence of the rearrangement of substrate atoms in the proximity of the trough dimer adsorption site.
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Affiliation(s)
- HJ Zandvliet
- Department of Applied Physics and MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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