Ge-catalyzed Vapour-Liquid-Solid growth of Carbon Nanotubes

The interest in carbon nanotubes (CNTs) for electronic applications is predominantly based on the outstanding properties of single walled CNTs, which include ballistic transport and high thermal conductivity. However, there is a need to avoid the standard metal catalysts used for CNT growth, which act as "lifetime killers" for silicon devices. Here the authors present a Ge catalyst growth method of CNTs based on chemical vapour deposition of CNTs on SiGe and Ge dots on Si substrates. From Raman measurements, the grown CNTs are identified as single walled CNTs (SWNTs) with diameters ranging from 1.6 to 2.1 nm. Extensive scanning electron microscopy and atomic force microscopy characterisation of the effect of each stage in the growth process was presented. The authors believe that pre-growth stages lead to the formation of Ge nanoparticle seeds and propose a vapour-liquid-solid growth mechanism