Characterization of single wall carbon nanotubes by scanning tunneling and scanning force microscopy

Abstract

In high-resolution scanning tunneling microscopy images of single-wall carbon nanotubes we often find complex superstructures superimposed onto the simple atomic pattern. They can be interpreted as a result of elastic scattering of the Fermi states at defects or impurities. A new combination of scanning tunneling and scanning force microscopy enables near-atomic point resolution in the resulting images. Using the force interaction as a feedback signal, the tubes can be identified without the need of a conducting substrate. This imaging mode is a crucial step for the characterization of electronic devices based on individual single-wall tubes. First results are presented showing that it is possible to obtain current images from tubes which are only locally connected to electrical contacts defined on insulating substrates.