The authors investigated the stable structures of (5, 5), (4, 4), and (3, 3) single-walled carbon nanotubes (SWNTs) on the Ti(0001) surface using first-principles calculations based on the density functional theory. They have found that SWNTs with decreasing radius adsorb greatly and transform into archlike structures on the Ti surface. The sp(2) orbital characteristics of the carbon atoms hybridized to sp(3) orbitals as they bind with Ti atoms and retain their conducting properties. Therefore, they expect that SWNTs with small radii can be used as electronic devices because of its stability on the electrode surface. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3093902]