Hydrogen termination for the growth of carbon nanotubes on silicon

Vertically aligned carbon nanotubes (CNTs) are grown on Fe-covered nano-structured Si tip apexes and planar Si substrates. Under the similar condition of a hot wire filament chemical vapor deposition technique, the growth and adhesion behaviors of the CNTs strongly depend on the chemical treatment of the Si surfaces, which determines the predominant chemical terminations. The Si substrates are terminated by hydrogen, or covered by a native oxide layer, or treated with tetramethyl ammonium hydroxide. The former provides an extremely strong adhesion, presumably due to the formation of Si-C direct bonds created in the initial stage of the CNT growth process, whereas the latter adheres poorly, and the third not at all, as revealed by images of scanning and transmission electron microscopy. A related concept of the CNT growth is suggested.