Substrate preparation by magnetron sputtering and CVD growth of carbon nanotube arrays

In this study we explored the use of magnetron sputtering as an alternative to e-beam deposition for preparation of the alumina intermediate layer and of the metal catalyst on an oxidized Si wafer. This approach offers large area deposition of the layered substrate including the intermediate alumina layer and the final catalyst film. The effects of the substrate design on the growth of long multi-wall carbon nanotube (MWCNT) arrays by CVD (Chemical Vapor Deposition) were also explored. The CNT synthesis was carried on in a hydrogen/ethylene/water/argon environment at 750 degrees C for different periods of deposition time. Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA) and Transmission Electron Microscopy (TEM) were employed to characterize the substrates and the CNT arrays. The study showed that for specific processing conditions the length of highly oriented CNTs strongly depends on the thickness of Al2O3 intermediate layer and on the catalyst film. The results obtained confirm that magnetron sputtering can be successfully employed as a tool for substrate preparation to grow 7 nun long CNT arrays with high purity. The aligned nanotubes do not suffer from limitations typical for powdered (spaghetti type) nanotubes which opens up new applications.