Imaging surface charge distribution near carbon nanotube device in aqueous environments

In this paper, we demonstrate the scanning photocurrent imaging on carbon nanotube devices in high-purity water environments. We found a streak of photocurrent signals along the nanotube devices; these streaks help in locating individual nanotubes. The photocurrent signals appearing in the middle of the nanotubes are due to the presence of additional ions in the electrical double layer, and as a result, a nanotube device can be used to sense the charge distribution at water-substrate interfaces with nanometer resolution. The gate-dependent photocurrent signals allow us to enumerate the effective charge density influencing nanotube electric potentials. We monitored the dynamical change in the charge distribution, which originates from the dissolution of carbon dioxide from the atmosphere into the solutions. (C) 2014 AIP Publishing LLC.