Infrared absorption coefficients of vertically aligned carbon nanotube films

Vertically aligned carbon nanotube (VACNT) films have promising applications in solar cells, radiometers, and photonic devices. We have fabricated VACNT films with thicknesses of 10, 36, 45, and 120 mu m on silicon substrates. The absorption coefficient of each film is obtained from the measured regular transmittance from 1 to 19 mu m wavelengths, using a ratio method. The degree of alignment of the VACNT films is estimated by comparison of experiments with an analysis based on the effective medium theory. The effect of thickness on the absorption coefficient of the VACNT films is elucidated according to their morphologies. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757395]