In situoptical characterization of the alignment and density of carbon nanotubes

Various characteristics of the growth of carbon nanotubes (CNTs) were examined by in situ optical interference patterns. A dc plasma chemical vapour deposition technique was used to grow the CNTs. The optical interference curves provided considerable in situ information such as the length, the alignment and related growth properties of CNTs. Curled CNTs have relatively small numbers of oscillations compared to well-aligned nanotubes during the same growth time. Sparse and short CNTs have shown a high reflectance with no interference oscillations. The alignment of the CNTs was strongly dependent on variations in the NH3 pre-treatment current. The electric field has a large effect on the direction of growth of well-aligned CNTs with high packing density. However, curled CNTs do not appear to be affected by the presence of the electric field. This optical interference method provides an in situ and effective method for monitoring the growth characteristics of CNTs.