Investigation of CNT growth by substrate temperature control using thermal CVD method.

Influence of metal catalyst (Fe) surface condition was investigated for the growth of carbon nanotubes (CNTs). Surface condition of 5 nm thick Fe coated on Si substrate was changed by varying substrate temperature during the CNTs synthesis in a thermal CVD method. Acetylene and argon were used as precursor and carrier gas, respectively, for the synthesis of CNTs. After the growth, the CNTs were removed from the substrate and the post-growth condition of the substrate surface was studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Unlike the case of untreated Fe-coated Si substrate, XPS analysis shows Si peaks from the thermal treated substrate/samples, which indicates the formation of Fe nanoparticles. AFM results indicate that 750 degrees C is optimum temperature for the nanoparticle formation. Moreover, SEM results show that 700 degrees C is optimum temperature for the CNTs synthesis. The results of this study clarify that the optimum temperature for nanoparticle formation and CNT synthesis are different.