Electron beam induced current on carbon nanotubes measured through substrate electrodes

We demonstrate substrate electron-beam-induced current (s-EBIC) measurements of individual single-walled carbon nanotubes (SWNTs) by measuring the current collected by the substrate electrode, which penetrates through the insulating oxide layer. We found that s-EBIC provided better image contrast than ordinary secondary electron imaging methods for locating SWNTs that are in contact with metal electrodes. The s-EBIC has been measured for different acceleration voltages and probe currents. We found that s-EBIC did not depend critically on the acceleration voltage when the e-beam irradiated an insulating layer as compared to the case when it irradiated metal electrodes. Importantly, s-EBIC signals were increased by more than 10%, when the SWNT part was irradiated, and this makes s-EBIC imaging a very useful tool for locating individual SWNTs efficiently.