Computational Studies of Defects in Nanoscale Carbon Materials
The formation and observation of individual vacancies in carbon nanotubes by a focused electron beam
Modern scanning transmission electron microscopes (STEM) with aberration correctors enable us to focus an extremely intense electron beam onto an Angstrom-size spot. The highly focused electron beam gives us the possibility of carrying out in-situ electron irradiation on the atomic scale and to displace ballistically pre-selected atoms in the lattice. This technique is applied to single- and multi-wall carbon nanotubes. Irradiation experiments within a wide temperature range show the particular relaxation behaviour of different types of nanotubes. Single or multiple vacancies are created in desired positions with the focused beam. This gives us, for the first time, the possibility of observing in real time the response of graphitic materials to the creation of individual point defects. It is shown how the reconstruction of the graphitic lattice after the creation of point defects determines the behaviour of carbon nanostructures upon the removal of atoms.