Effect of surface structure of sapphire A-face on directional carbon nanotube growth

Abstract

The surface structure change of sapphire A-face (1 1 -2 0) by heating in air has been investigated from the viewpoint of its influence on the aligned growth of single wall carbon nanotubes (SWCNTs). The step shape was getting regular with an increase of the annealing temperature, and straight step array appeared at 1473 K. A further increase of the temperature to 1523 K resulted in altered region formation on terraces, although the atomic step shape was not changed. A terrace appeared as if it had been divided into two sub-terraces, but the height difference was less than 0.1 nm. Secondary electron images showed different contrasts in two regions, suggesting a compositional difference between them. Aligned SWCNTs were obtained regardless of the annealing temperature up to 1473 K. However, on the 1523 K-annealed surface, SWCNTs grew irregularly. The altered region changed the interaction between SWCNTs and the surface. © 2009 The Surface Science Society of Japan.