In this paper we report the influence of the water vapor on the electrical resistance of a single-walled carbon nanotube mat (SWNTm). Our results show that the sample exhibits a crossover from decreasing to increasing conductance versus water concentration in the surrounding atmosphere. We suggest that the water molecules act as a donor doping the SWNTm which has p-type semiconductor character in the outgassed state. The time dependence of the SWNTm resistance after exposition to humid atmosphere is explained as an abnormal diffusion phenomenon.

• Received 10 April 2000

DOI:https://doi.org/10.1103/PhysRevB.62.10000