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Title: Diffusion, Coalescence, and Reconstruction of Vacancy Defects in Graphene Layers

Abstract

Diffusion, coalescence, and reconstruction of vacancy defects in graphene layers are investigated by tight-binding molecular dynamics (TBMD) simulations and by first principles total energy calculations. It is observed in the TBMD simulations that two single vacancies coalesce into a 5-8-5 double vacancy at the temperature of 3000 K, and it is further reconstructed into a new defect structure, the 555-777 defect, by the Stone-Wales type transformation at higher temperatures. First principles calculations confirm that the 555-777 defect is energetically much more stable than two separated single vacancies, and the energy of the 555-777 defect is also slightly lower than that of the 5-8-5 double vacancy. In TBMD simulation, it is also found that the four single vacancies reconstruct into two collective 555-777 defects which is the unit for the hexagonal haeckelite structure proposed by Terrones et al. [Phys. Rev. Lett. 84, 1716 (2000)].

Authors:
;  [1]; ;  [2]; ;  [3]
  1. School of Materials Science and Engineering and Inter-university Semiconductor Research Center (ISRC), Seoul National University, Seoul 151-742 (Korea, Republic of)
  2. Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)
  3. School of Materials Science and Engineering and Center for Microstructure Science of Materials, Seoul National University, Seoul 151-742 (Korea, Republic of)
Publication Date:
OSTI Identifier:
20699569
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 95; Journal Issue: 20; Other Information: DOI: 10.1103/PhysRevLett.95.205501; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBON; COALESCENCE; DIFFUSION; LAYERS; MOLECULAR DYNAMICS METHOD; NANOTUBES; SIMULATION; TEMPERATURE RANGE 1000-4000 K; VACANCIES

Citation Formats

Lee, Gun-Do, Yoon, Euijoon, Wang, C.Z., Ho, K.M., Hwang, Nong-Moon, and Kim, Doh-Yeon. Diffusion, Coalescence, and Reconstruction of Vacancy Defects in Graphene Layers. United States: N. p., 2005. Web. doi:10.1103/PhysRevLett.95.205501.
Lee, Gun-Do, Yoon, Euijoon, Wang, C.Z., Ho, K.M., Hwang, Nong-Moon, & Kim, Doh-Yeon. Diffusion, Coalescence, and Reconstruction of Vacancy Defects in Graphene Layers. United States. doi:10.1103/PhysRevLett.95.205501.
Lee, Gun-Do, Yoon, Euijoon, Wang, C.Z., Ho, K.M., Hwang, Nong-Moon, and Kim, Doh-Yeon. Fri . "Diffusion, Coalescence, and Reconstruction of Vacancy Defects in Graphene Layers". United States. doi:10.1103/PhysRevLett.95.205501.
@article{osti_20699569,
title = {Diffusion, Coalescence, and Reconstruction of Vacancy Defects in Graphene Layers},
author = {Lee, Gun-Do and Yoon, Euijoon and Wang, C.Z. and Ho, K.M. and Hwang, Nong-Moon and Kim, Doh-Yeon},
abstractNote = {Diffusion, coalescence, and reconstruction of vacancy defects in graphene layers are investigated by tight-binding molecular dynamics (TBMD) simulations and by first principles total energy calculations. It is observed in the TBMD simulations that two single vacancies coalesce into a 5-8-5 double vacancy at the temperature of 3000 K, and it is further reconstructed into a new defect structure, the 555-777 defect, by the Stone-Wales type transformation at higher temperatures. First principles calculations confirm that the 555-777 defect is energetically much more stable than two separated single vacancies, and the energy of the 555-777 defect is also slightly lower than that of the 5-8-5 double vacancy. In TBMD simulation, it is also found that the four single vacancies reconstruct into two collective 555-777 defects which is the unit for the hexagonal haeckelite structure proposed by Terrones et al. [Phys. Rev. Lett. 84, 1716 (2000)].},
doi = {10.1103/PhysRevLett.95.205501},
journal = {Physical Review Letters},
number = 20,
volume = 95,
place = {United States},
year = {Fri Nov 11 00:00:00 EST 2005},
month = {Fri Nov 11 00:00:00 EST 2005}
}
  • The reconstruction process of vacancy hole in carbon nanotube is investigated by tight-binding molecular dynamics simulations and by ab initio total energy calculations. In the molecular dynamics simulation, a vacancy hole is found to reconstruct into two separated pentagon-heptagon pair defects. As the result of reconstruction, the radius of the carbon nanotube is reduced and the chirality of the tube is partly changed. During the vacancy hole healing process, the formation of pentagonal and heptagonal rings is proceeded by the subsequent Stone-Wales.
  • The dynamics of multivacancy defects in a graphene layer is investigated by tight-binding molecular dynamics simulations and by first principles calculation. The simulations show that four single vacancies in the graphene layer first coalesce into two double vacancies, each consisting of a pentagon-heptagon-pentagon (5-8-5) defective structure. While one of the 5-8-5 defects further reconstructs into a 555-777 defect, which is composed of three pentagonal rings and three heptagonal rings, another 5-8-5 defect diffuses toward the reconstructed 555-777 defect. During the 5-8-5 defect diffusion process, three interesting mechanisms, i.e., 'dimer diffusion', 'chain diffusion', and 'single atom diffusion', are observed. Finally, themore » four single vacancies reconstruct into two adjacent 555-777 defects, which is a local haeckelite structure.« less
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  • A method for preparing shallow dopant distributions via solid-phase epitaxial growth (SPEG) following amorphization by low-energy Si self-ion implantation leaves defects that can lead to unwanted dopant impurity diffusion. The double implant method for SPEG [O. W. Holland {ital et al.}, J. Electron. Mater. {bold 25}, 99 (1996)] uses both low- and high-energy Si self-ion implantation to remove most of the interstitials. Nevertheless, we find that measurable crystalline imperfections remain following the SPEG annealing step. Measurements of defect profiles using variable-energy positron spectroscopy show that there are divacancy-impurity complexes in the SPEG layer and V{sub 6} and larger vacancy clustersmore » near the SPEG-crystalline interface. These measurements should be useful for modeling the diffusion of dopant atoms and for fine tuning the double implant parameters. {copyright} {ital 1999 American Institute of Physics.}« less