Preferential Adsorption of Zigzag Single-Walled Carbon Nanotubes on the ST-Cut Surface of Quartz

Synthesis of horizontally aligned single-walled carbon nanotubes (SWCNTs) has achieved high degree of orientation and selectivity when specific cuts of quartz surfaces are used as support In this study we demonstrate that finite length zigzag nanotubes are adsorbed stronger than armchair tubes on the quartz support This is done through density functional theory calculations that evaluate the interaction between SWCNTs and the ST-cut surface of the quartz substrate. Among the nanotubes studied, the (7,0) presents the strongest adsorption energy, found along the [010] direction, which is parallel to the y-axis. Unexpectedly, patterns delineated by silicon and oxygen atoms along the [010] direction established the strongest as well as the weakest adsorption energies. This suggests that the nanotube electronic band structure is a key factor on the preferential adsorption of zigzag tubes. Charge analysis demonstrates the role of oxygen atoms on the partial oxidation of nanotube atoms closest to the substrate. Finally, the analysis of the electronic density of states proves that atomic interactions between substrate and nanotubes induce modifications of the occupied states near to the Fermi level, which can potentially modify the metallic or semiconducting character in adsorbed SWCNTs.