Examining the structural contribution to the electrical character of single wall carbon nanotube forest by a height dependent study

We report an electrical investigation of single-wall carbon nanotube (SWCNT) forests where we have succeeded in elucidating the electrical contributions of the forest surface (cap) and vertically aligned (body) structures of the assembly. We applied an electrical characterization method to SWCNT forests patterned into a Hall bar-like configuration to reliably evaluate the lateral (i.e. in-plane) resistance for a series of SWCNT forests spanning three orders of magnitude, 0.3-700 μm, in height while avoiding direct mechanical contact to the measurement region. A simple model based on treating the forests as two parallel resistors was used to explain the observed behavior of the lateral resistivity and forest height. Through this approach we showed that the forests could be described electrically by two structural features, the cap and body. In addition, our analysis found that the resistivity of the body was about 22-720 times higher than that of the cap.