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Title: Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy

Abstract

The electronic properties of graphene nano-flakes (GNFs) with different edge passivation are investigated by using density functional theory. Passivation with F and H atoms is considered: C{sub N{sub c}} X{sub N{sub x}} (X = F or H). We studied GNFs with 10 < N{sub c} < 56 and limit ourselves to the lowest energy configurations. We found that: (i) the energy difference Δ between the highest occupied molecular orbital and the lowest unoccupied molecular orbital decreases with N{sub c}, (ii) topological defects (pentagon and heptagon) break the symmetry of the GNFs and enhance the electric polarization, (iii) the mutual interaction of bilayer GNFs can be understood by dipole-dipole interaction which were found sensitive to the relative orientation of the GNFs, (iv) the permanent dipoles depend on the edge terminated atom, while the energy gap is independent of it, and (v) the presence of heptagon and pentagon defects in the GNFs results in the largest difference between the energy of the spin-up and spin-down electrons which is larger for the H-passivated GNFs as compared to F-passivated GNFs. Our study shows clearly the effect of geometry, size, termination, and bilayer on the electronic properties of small GNFs. This study reveals important featuresmore » of graphene nano-flakes which can be detected using Raman spectroscopy.« less

Authors:
;  [1];  [1];  [2]
  1. Department of Physics, University of Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium)
  2. (Iran, Islamic Republic of)
Publication Date:
OSTI Identifier:
22255096
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 140; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DEFECTS; DENSITY FUNCTIONAL METHOD; DIPOLES; ENERGY GAP; GRAPHENE; INTERACTIONS; MOLECULAR ORBITAL METHOD; POLARIZATION; RAMAN SPECTROSCOPY; SPIN

Citation Formats

Singh, Sandeep Kumar, E-mail: SandeepKumar.Singh@uantwerpen.be, Peeters, F. M., E-mail: Francois.Peeters@uantwerpen.be, Neek-Amal, M., E-mail: neekamal@srttu.edu, and Department of Physics, Shahid Rajaee Teacher Training University, Lavizan, Tehran 16788. Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy. United States: N. p., 2014. Web. doi:10.1063/1.4865414.
Singh, Sandeep Kumar, E-mail: SandeepKumar.Singh@uantwerpen.be, Peeters, F. M., E-mail: Francois.Peeters@uantwerpen.be, Neek-Amal, M., E-mail: neekamal@srttu.edu, & Department of Physics, Shahid Rajaee Teacher Training University, Lavizan, Tehran 16788. Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy. United States. https://doi.org/10.1063/1.4865414
Singh, Sandeep Kumar, E-mail: SandeepKumar.Singh@uantwerpen.be, Peeters, F. M., E-mail: Francois.Peeters@uantwerpen.be, Neek-Amal, M., E-mail: neekamal@srttu.edu, and Department of Physics, Shahid Rajaee Teacher Training University, Lavizan, Tehran 16788. 2014. "Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy". United States. https://doi.org/10.1063/1.4865414.
@article{osti_22255096,
title = {Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy},
author = {Singh, Sandeep Kumar, E-mail: SandeepKumar.Singh@uantwerpen.be and Peeters, F. M., E-mail: Francois.Peeters@uantwerpen.be and Neek-Amal, M., E-mail: neekamal@srttu.edu and Department of Physics, Shahid Rajaee Teacher Training University, Lavizan, Tehran 16788},
abstractNote = {The electronic properties of graphene nano-flakes (GNFs) with different edge passivation are investigated by using density functional theory. Passivation with F and H atoms is considered: C{sub N{sub c}} X{sub N{sub x}} (X = F or H). We studied GNFs with 10 < N{sub c} < 56 and limit ourselves to the lowest energy configurations. We found that: (i) the energy difference Δ between the highest occupied molecular orbital and the lowest unoccupied molecular orbital decreases with N{sub c}, (ii) topological defects (pentagon and heptagon) break the symmetry of the GNFs and enhance the electric polarization, (iii) the mutual interaction of bilayer GNFs can be understood by dipole-dipole interaction which were found sensitive to the relative orientation of the GNFs, (iv) the permanent dipoles depend on the edge terminated atom, while the energy gap is independent of it, and (v) the presence of heptagon and pentagon defects in the GNFs results in the largest difference between the energy of the spin-up and spin-down electrons which is larger for the H-passivated GNFs as compared to F-passivated GNFs. Our study shows clearly the effect of geometry, size, termination, and bilayer on the electronic properties of small GNFs. This study reveals important features of graphene nano-flakes which can be detected using Raman spectroscopy.},
doi = {10.1063/1.4865414},
url = {https://www.osti.gov/biblio/22255096}, journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 7,
volume = 140,
place = {United States},
year = {Fri Feb 21 00:00:00 EST 2014},
month = {Fri Feb 21 00:00:00 EST 2014}
}