Hokkaido University announced on April 27 2011 that a research group led by Professor Kazutoshi Gohara in cooperation with Hitachi, Ltd. has succeeded in imaging individual atoms in single-walled carbon nanotubes (SWCNT) by using an electron microscope at a resolution of 0.12 nm. Details are published in online version of Applied Physics Letters*.
The demand for atomic-scale analysis without serious damage to the specimen has been increasing due to the spread of applications of light-element three-dimensional (3D) materials. An example of target material is carbon nanotubes (CNT) because its electronic properties will change from semiconducting to metallic with structural difference. Although electron microscope is a promising method, high electron voltage necessary to discriminate individual atoms often causes damage in CNT.
Instead of direct imaging by focusing electron beam, researchers developed diffraction imaging method in which atomic images are reconstructed from diffraction pattern of scattered electrons. However, resolution was limited to 0.34 nm with a low voltage (30kV) electron microscope. Improvement to resolution around 0.1 nm has been achieved by using scanning electron microscope architecture to get wide field of view.
They demonstrated low-voltage (30 kV) electron diffractive imaging of SWCNT at a resolution of 0.12 nm. In the reconstructed pattern, the intensity difference between single carbon atom and two overlapping atoms could be clearly distinguished. That is the imaging of individual carbon atoms in 3D. Researchers noticed that this method can be applied to other materials including biologically important ones.
