We examined how the addition of different metal buffer layers between the Ni/Fe-alloy-catalyst layer and the silicon substrate affected the growth of nanostructured carbon films; Cr, Ti, Ta, and W were tested as buffer layers. Even when the sputter-deposition of catalytic-metal layers and the hot filament chemical vapor deposition of carbon films were carried out under the identical conditions, different buffer layers resulted in substantially different carbon-film growth. More specifically, carbon-nanoparticle films were produced with the Cr and the W buffer layers, and carbon-nanotube films were produced with the Ti, and the Ta buffer layers. X-ray diffraction (XRD) showed a significant and systematic difference between the carbon-nanoparticle and carbon-nanotube films. In the case of the carbon-nanoparticle films deposited with either the Cr or the W buffer layer, the peaks corresponding to the catalytic metal, the carbide phases of the catalytic metal, and the carbide phases of the respective buffer metal were observed. However, in the case of the carbon-nanotube films deposited with either the Ti or the Ta buffer layer, the peaks corresponding to the carbide phases of the catalytic metal and the silicide phases of the respective buffer metal were observed. Moreover, scanning electron microscopy (SEM) images of the cross sections of the films showed the difference in the interface structure and its deposition-time-dependent change. Based on the XRD and cross-section SEM observations, we proposed a model that could account for the growth of different nanostructured carbon films on the different sets of buffer layers. (C) 2003 American Vacuum Society.