Direct observation of atomic defects in carbon nanotubes and fullerenes

Abstract

The diversified properties of carbon nano-structures (nanotubes, fullerenes and their derivatives) are related to their polymorphic arrangement of carbon atoms. Therefore the direct observation of carbon network, such as defects or chirality, is of great consequence in both scientific and technological viewpoints in order to predict the physical and chemical properties. In order to identify the local configuration of pentagons and hexagons in carbon nanostructures, an electron microscope with higher spatial resolution and higher sensitivity is definitively required. Since the spatial resolution of the conventional TEM is limited by the spherical aberration coefficient (Cs) of its objective lens and the wave length (λ) of incident electron beam, the Cs must be minimized to achieve the best performance because the reduction of the λ is detrimental to the high sensitivity to visualize individual carbon atoms. A high-resolution transmission electron microscope (HRTEM, JEOL-2010F) equipped with a Cs corrector (CEOS) was operated at a moderate accelerating voltage (120kV). The Cs was set to 0.5 ∼ 10 µm in this work. The HRTEM images were digitally recorded under a slightly under-focus condition (Δf = −2 to −7 nm) where the point resolution of 0.14 nm was achieved at 120kV.