Study on the law and mechanism of anisotropic conductivity of carbon nanotubes film prepared by floating catalytic chemical vapor deposition method

Carbon nanotubes (CNTs) film has attracted extensive attention in the field of electronics, sensors, and other potential applications due to their excellent electrical conductivity. The conductivity of CNTs film is one of the most important aspects of engineering applications. This study investigates the conductivity of CNTs film with varying areal density, prepared using the floating catalyst chemical vapor deposition (FCCVD) method and densified by rolling. The square resistance of pre- and post-rolling films was measured to characterize the electrical properties. Experimental results indicate that square resistance decreases with increasing areal density and stabilizes eventually. A mathematical formula was derived to explain the relationship between areal density and square resistance, incorporating volume and areal density formulas. Experimental data curves of pre- and post-rolling films were fitted, yielding mathematical relations consistent with the derived formulas. The electrical conductivity of post-rolling CNTs film was superior to pre-rolling in experiment and calculation. The charge carrier transport mechanism in CNTs film was studied by analyzing its internal structure and electrical properties. Surface conductivity was over 1000 times higher than volume conductivity, attributed to the distribution of CNTs bundles in collection and thickness directions. Charge carrier transport capacity decreased with increasing layers in thickness direction due to contact resistance and large resistance at tube-tube junctions. Layers of CNTs near the current application surface significantly contribute to charge carrier transport at high areal density levels.