Growth of high-density horizontal SWNT arrays by pre-cracking of carbon source

Obtaining high-density horizontal single-walled carbon nanotube (SWNT) arrays is the key point of developing SWNT-based integrated circuits. However, some catalysts showing good control over SWNT structures possess relatively low activity to grow SWNT, which restricts the density of the grown arrays. Therefore, we developed a rational method to grow high-density SWNT arrays by iron (Fe)-assisted pre-cracking of carbon source in gas phase. A tiny amount of Fe, decomposed from ferrocene, was introduced into the chemical vapor deposition system with the gas flow without forming Fe nanoparticles on the substrates. The density of the SWNT arrays grown from Mo2C, WC and Cu catalysts can be significantly increased by 3–5 times with the help of Fe, reaching 40, 35 and 24 tubes μm−1, respectively. Through gas chromatography and Raman spectrum characterization, it is proved that carbon source decomposed more completely with Fe in the gas phase, which resulted in higher utilization efficiency of carbon source and better quality of the grown SWNTs. This pre-cracking approach is an effective way to improve the density of SWNT arrays with controlled structures.