Web Release Date: July 28,
Defective Structure of BN Nanotubes: From Single Vacancies to Dislocation Lines
and
Laboratoire de Physique des Solides (UMR CNRS 8502), Bât. 510 Université Paris Sud, 91405 Orsay, France, Institüt für Physikalische Chemie und Elektrochemie, Technische Universität Dresden, D-1062 Dresden, Germany, Institute des Materiaux, CNRS UMR6502, 2 rue de la Houssinière, 44322 Nantes, France, ICYS National Institute for Materials Science, Namiki 1-1, Tsukuba 305-0044, Japan, and Department of Physics, Stockholm University, Box 6730, S-113 85 Stockholm, Sweden
Received May 12, 2006
Revised June 19, 2006
Abstract:
A combination of electron microscopy and theoretical calculations provides new insights into the structure, electronics, and energetics of point defects and vacancy lines in BN single-wall nanotubes (SWNT). We show that the point defects forming under electron irradiation in the BN SWNTs are primarily divacancies. Due to the partially ionic character of the BN bonding, divacancies behave like an associated Schottky pair, with a dissociation energy of around 8 eV. Clustering of multiple vacancies is energetically favorable and leads to extended defects which locally change the nanotube diameter and chirality. Nevertheless these defects do not alter significantly the band gap energy, and all of them have electronic structure similar to that of BN divacancies. We thus conclude that under irradiation BN SWNT may have a very stable alteration of its electronic and optical properties.
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