Low-cost and ultra-strong p-type doping of carbon nanotube films by a piranha mixture

Recent studies have demonstrated that single-walled carbon nanotube (SWCNT) films can be doped by a nitric/sulfuric acid treatment to significantly improve its conductivity. However, the sheet resistance is still too high for many applications. Here we report on a simple treatment using a piranha mixture that could further enhance SWCNT film conductivity. The high redox potentials of hydrogen peroxides combined with the acidity of sulfuric acid enabled strong p-doping of the carbon nanotube films. Absorption peak suppression and a G-band shift provided proof of strong p-doping of the SWCNT films.