Very thin transparent, conductive carbon nanotube films on flexible substrates

We investigate the morphological, electrical, and optical properties of carbon nanotube thin films, focusing on films with transmittance, T > 90%. For films with T approximate to 90% we measure sheet resistance of R(s)<400 Omega/square. However, we show that optoelectrical properties, such as sigma(dc) and sigma(dc)/sigma(Op), degrade with decreasing film thickness, t, for percolating nanotube networks, i.e., those with t < 20 nm and T > 90%. Thus, while reducing t can give T > 99%, the corresponding Rs increases to > 40 k Omega/square. Acid treatment improves the conductivity by doping, giving properties such as T approximate to 98% for R(s) approximate to 10 k Omega/square. (C) 2010 American Institute of Physics. [doi:10.1063/1.3462317]