Carbon nanotubes grown on polyimide by chemical vapour deposition

Carbon nanotubes (CNTs) are ideal candidates as electrode materials for neuronal stimulation and monitoring devices, since they provide a high charge injection limit without significant Faradic reactions, and carbon nanotube electrodes have a high surface to volume ratio. CNTs are positioned at desired locations by chemical vapour deposition (CVD) growth from patterned catalysts. However, these processes typically require temperatures above 700 °C, which is unacceptable for many flexible substrate materials like polyimide, which looses its insulating properties around 400 °C and its stability at 600 °C. By proper selection of parameters such as catalyst material, gas composition, processing pressure and time, it is possible to grow CNTs at temperatures as low as 350 °C with a total CNT height of ∼1 µm on silicon. On polyimide additional substrate and catalyst pretreatment is necessary at such low temperatures. This indicates that the substrate may influence the growth process of CNTs.