Laser treatment of solution-deposited carbon nanotube thin films for improved conductivity and transparency

Solution-deposited single-walled carbon nanotube (SWCNT) films contain a surfactant material and it should be removed by a post-deposition treatment to improve the conductivity. We here report that the sodium dodecyl sulfate (SDS) surfactant in SWCNT films can be completely removed by a pulsed Nd:YAG laser (wavelength = 1064 nm, pulse width = 99 ms). SWCNT films were spray-coated onto a glass substrate and were scanned by a laser beam of 2 mm size. In this process, individual nanotubes absorb the laser energy and generate heat to vaporize the surrounding surfactant. This mechanism was supported by the fact that the required pulse energy decreased as the SWCNT density increased. An encouraging feature is that unlike typical acid treatments, the laser treatment can improve not only the conductivity but also the transmittance. This might be associated with complete surfactant removal without leaving any particulate debris. For a film, the sheet resistance decreased from 1.07 kΩ/sq to 700 Ω/sq and its visible transmittance simultaneously increased by 4%.