In situ monitoring of the electrical property of carbon nanotube thin film in floating catalyst chemical vapor deposition

In floating catalyst chemical vapor deposition (FCCVD), when a carbon nanotube (CNT) network film is produced by filter collection, the film thickness is adjusted by controlling the collection time. However, even with consistent synthesis parameters, the synthesis condition in FCCVD changes constantly depending on the carbon and catalyst adhesion to the inner wall of the reaction tube. Thus, the rate of synthesis changes, making it difficult to obtain the target film thickness repeatedly and stably. We propose a method of monitoring CNT film thickness and percolation threshold by the in situ measurement of the electrical impedance during the deposition. The time evolution of the measured impedance is reproducible by an equivalent electrical circuit simulation.