Horizontal single-walled carbon nanotubes on MgO(1 1 0) and MgO(0 0 1) substrates

Horizontal single-walled carbon nanotubes (SWNT) on MgO(1 1 0) and MgO(0 0 1) single-crystal substrates were synthesized in a temperature range of 830–910 °C by chemical vapor deposition using Co catalyst particles. SWNTs grow preferentially along the 〈1 1 0〉 directions of the two MgO surface planes. For synthesis at 830 °C, the distribution of the radial breathing mode (RBM) frequencies of SWNTs grown on MgO(1 1 0) is centered at 142 and 168 cm−1, attributed to semi-conducting SWNTs. For the same synthesis time, the RBM distribution of SWNTs grown on MgO(0 0 1) is significantly broader. This difference would be due to the larger surface energy of MgO(1 1 0) which reduces the probability of coalescence between Co particles.