Direct growth of aligned multiwalled carbon nanotubes on treated stainless steel substrates.

Growth of aligned carbon nanotubes (CNTs) on electrically conductive substrates is promising for many applications; however, the lack of complete understanding of the substrate effects on CNT growth poses a lot of technical challenges. Here, we report the direct growth of aligned multiwalled nanotubes (MWNTs) on chemically treated stainless steel (Type 304) using a chemical vapor deposition (CVD) process. A detailed X-ray photoelectron spectroscopy (XPS) analysis has been carried out for the various treated samples in order to better understand the correlation between the surface properties of the substrates and the MWNT growth. The XPS studies revealed that the CNTs prefer to grow on the enriched surface of iron oxides obtained by the chemical treatment rather than on the passive chromium oxide films present on the surface of the as-received stainless steel substrates. The density and alignment of the MWNTs could therefore be controlled by tuning the ratio of the iron oxides to chromium oxides through the chemical treatment on the stainless steel surfaces. On the basis of this method, selective growth of CNT patterns on stainless steel has also been demonstrated.